WO2013069306A1 - Context initialization based on decoder picture buffer - Google Patents
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- WO2013069306A1 WO2013069306A1 PCT/JP2012/007220 JP2012007220W WO2013069306A1 WO 2013069306 A1 WO2013069306 A1 WO 2013069306A1 JP 2012007220 W JP2012007220 W JP 2012007220W WO 2013069306 A1 WO2013069306 A1 WO 2013069306A1
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
- H04N19/13—Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
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- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
- H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
- H04N19/159—Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
- H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
- H04N19/172—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a picture, frame or field
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
- H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
- H04N19/174—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a slice, e.g. a line of blocks or a group of blocks
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/42—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation
- H04N19/436—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation using parallelised computational arrangements
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/44—Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/46—Embedding additional information in the video signal during the compression process
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
- H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
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- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
- H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
Definitions
- Embodiments of the present invention relate generally to video coding and, in particular, some embodiments of the present invention relate to techniques for context initialization.
- H.264/MPEG-4 AVC H.264/AVC
- TMC JCT-VC Test Model under Consideration
- Decoders that support parallel decoding may improve decoding speeds and reduce memory requirements. Additionally, advances in multi-core processors may make encoders and decoders that support parallel decoding desirable.
- H.264/MPEG-4 AVC Joint Video Team of ITU-T VCEG and ISO/IEC MPEG, "H.264: Advanced video coding for generic audiovisual services, " ITU-T Rec. H.264 and ISO/IEC 14496-10 (MPEG4 - Part 10), November 2007]
- a video codec coder/decoder
- TMC Test Model under Consideration
- An aspect of the invention provides a method for decoding a video frame of a video sequence comprising:
- Fig. 1 is a picture showing an H.264/AVC video encoder (prior art);
- Fig. 2 is a picture showing an H.264/AVC video decoder (prior art);
- Fig. 3 is a picture showing an exemplary slice structure (prior art);
- Fig. 4 is a picture showing an exemplary slice group structure (prior art);
- Fig. 5 is a picture showing an exemplary slice partition according to embodiments of the present invention, wherein a picture may be partitioned in at least one reconstruction slice and a reconstruction slice may be partitioned into more than one entropy slice;
- Fig. 6 is chart showing exemplary embodiments of the present invention comprising an entropy slice;
- Fig. 1 is a picture showing an H.264/AVC video encoder (prior art)
- Fig. 2 is a picture showing an H.264/AVC video decoder (prior art)
- Fig. 3 is a picture showing an exemplary slice structure (prior art
- FIG. 7 is a chart showing exemplary embodiments of the present invention comprising parallel entropy decoding of multiple entropy slices followed by slice reconstruction;
- Fig. 8 is a chart showing exemplary embodiments of the present invention comprising prediction data / residual data multiplexing at the picture level for entropy slice construction;
- Fig. 9 is a chart showing exemplary embodiments of the present invention comprising color-plane multiplexing at the picture level for entropy slice construction;
- Fig. 10 is a chart showing exemplary embodiments of the present invention comprising trans-coding a bitstream by entropy decoding, forming entropy slices and entropy encoding;
- FIG. 11 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein the number of bins associated with each entropy slice in the plurality of entropy slices does not exceed a predefined number of bins;
- Fig. 12 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein bins may be associated with an entropy slice until the number of bins in the entropy slice exceeds a threshold based on a predefined maximum number of bins; Fig.
- FIG. 13 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein the number of bins associated with each entropy slice in the plurality of entropy slices does not exceed a predefined number of bins and each reconstruction slice contains no more than a predefined number of macroblocks;
- Fig. 14 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein bins may be associated with an entropy slice until the number of bins in the entropy slice exceeds a threshold based on a predefined maximum number of bins and each reconstruction slice contains no more than a predefined number of macroblocks;
- Fig. 14 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein bins may be associated with an entropy slice until the number of bins in the en
- FIG. 15 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein the number of bits associated with each entropy slice in the plurality of entropy slices does not exceed a predefined number of bits;
- Fig. 16 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein bits may be associated with an entropy slice until the number of bits in the entropy slices exceeds a threshold based on a predefined maximum number of bits;
- Fig. 17 is a picture depicting exemplary embodiments of the present invention comprising multiple bin coders; Fig.
- FIG. 18 is a picture depicting exemplary embodiments of the present invention comprising multiple context-adaptation units
- Fig. 19 is a picture depicting exemplary embodiments of the present invention comprising multiple bin coders and multiple context-adaptation units
- Fig. 20 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein the size of an entropy slice is restricted to limit the number of bins operated on, in the entropy slice, by each restricted entropy-coder unit; Fig.
- FIG. 21 is a chart showing exemplary embodiments of the present invention comprising partitioning a reconstruction slice into a plurality of entropy slices, wherein the size of an entropy slice is restricted to limit the number of bins operated on, in the entropy slice, by each restricted entropy-coder unit;
- Fig. 22 is a picture depicting exemplary embodiments of the present invention comprising a plurality of bin decoders;
- Fig. 23 is a picture depicting exemplary embodiments of the present invention comprising a plurality of context-adaptation units;
- Fig. 24 is a picture depicting exemplary embodiments of the present invention comprising multiple bin decoders and multiple context-adaptation units; Fig.
- FIG. 25 is a picture showing an exemplary partition of a reconstruction block into a plurality of entropy slices in which the macroblocks within an entropy slice are contiguous;
- Fig. 26 is a picture showing an exemplary partition of a reconstruction block into a plurality of entropy slices in which the macroblocks within an entropy slice are not contiguous;
- Fig. 27 is a picture illustrating non-contiguous neighboring blocks, used in entropy decoding, for an exemplary partition of a reconstruction block into a plurality of entropy slices in which the macroblocks within an entropy slice are not contiguous;
- Fig. 26 is a picture showing an exemplary partition of a reconstruction block into a plurality of entropy slices in which the macroblocks within an entropy slice are not contiguous;
- Fig. 27 is a picture illustrating non-contiguous neighboring blocks, used in entropy decoding, for an exemplary partition of a
- FIG. 28 is a picture illustrating neighboring blocks used in entropy decoding and reconstruction of a block within an entropy slice for an exemplary partition of a reconstruction block into a plurality of entropy slice in which the macroblocks within an entropy slice are not contiguous;
- Fig. 29 is a pictorial representation of an exemplary portion of an exemplary bitstream depicting entropy-slice header location restrictions;
- Fig. 30 is a pictorial representation of an exemplary portion of an exemplary bitstream depicting entropy-slice header location restrictions;
- Fig. 29 is a pictorial representation of an exemplary portion of an exemplary bitstream depicting entropy-slice header location restrictions;
- Fig. 30 is a pictorial representation of an exemplary portion of an exemplary bitstream depicting entropy-slice header location restrictions;
- FIG. 31 is a chart showing exemplary embodiments of the present invention comprising an entropy decoder processing a restricted portion of a bitstream to identify an entropy-slice header
- Fig. 32 is a chart showing exemplary embodiments of the present invention comprising an entropy decoder processing a restricted portion of a bitstream to identify an entropy-slice header
- Fig. 33 is a chart showing exemplary embodiments of the present invention comprising an entropy decoder processing a restricted portion of a bitstream to identify an entropy-slice header
- Fig. 32 is a chart showing exemplary embodiments of the present invention comprising an entropy decoder processing a restricted portion of a bitstream to identify an entropy-slice header
- Fig. 33 is a chart showing exemplary embodiments of the present invention comprising an entropy decoder processing a restricted portion of a bitstream to identify an entropy-slice header
- FIG. 34 is a picture illustrating an exemplary context table initialization scheme within entropy slices according to embodiments of the present invention
- Fig.34A is a picture illustrating scanning adaptation in exemplary embodiments of the present invention.
- Fig. 35 is a chart showing exemplary embodiments of the present invention comprising an entropy encoder with context fetching decoupled from coefficient scan order;
- Fig. 36 is a chart showing exemplary embodiments of the present invention comprising an entropy decoder with context fetching decoupled from coefficient scan order;
- Fig. 37 is a chart showing exemplary embodiments of the present invention comprising bin-count-based context adaptation;
- Fig. 38 is a picture illustrating an exemplary, disjoint partitioning of a number of bins processed;
- Fig. 38 is a picture illustrating an exemplary, disjoint partitioning of a number of bins processed;
- Fig. 38 is a picture illustrating an exemplary, disjoint partitioning of a number
- FIG. 39 is a chart showing exemplary embodiments of the present invention comprising quantization-parameter-based context adaptation; Fig. 40 illustrates an context initialization technique; Fig. 41 illustrates another context initialization technique; and FIG. 42 illustrates an context initialization technique.
- FIG. 43 illustrates an initialization technique.
- FIG. 44 illustrates an initialization technique.
- FIG. 45 illustrates an initialization technique.
- FIG. 46 illustrates an initialization technique.
- State-of-the-art video-coding methods and standards may provide higher coding efficiency than older methods and standards at the expense of higher complexity.
- Increasing quality requirements and resolution requirements on video coding methods and standards may also increase their complexity.
- Decoders that support parallel decoding may improve decoding speeds and reduce memory requirements. Additionally, advances in multi-core processors may make encoders and decoders that support parallel decoding desirable.
- H.264/AVC and many other video coding standards and methods, are based on a block-based hybrid video-coding approach, wherein the source-coding algorithm is a hybrid of inter-picture, also considered inter-frame, prediction, intra-picture, also considered intra-frame, prediction and transform coding of a prediction residual.
- Inter-frame prediction may exploit temporal redundancies
- intra-frame and transform coding of the prediction residual may exploit spatial redundancies.
- Figure 1 shows a block diagram of an exemplary H.264/AVC video encoder 2.
- An input picture 4, also considered a frame, may be presented for encoding.
- a predicted signal 6 and a residual signal 8 may be produced, wherein the predicted signal 6 may be based on either an inter-frame prediction 10 or an intra-frame prediction 12.
- the inter-frame prediction 10 may be determined by motion compensation section 14 using a stored, reference picture 16, also considered reference frame, and motion information 19 determined by a motion estimation section 18 process between the input frame 4 and the reference frame 16.
- the intra-frame prediction 12 may be determined by an intra-frame prediction section 20 using a decoded signal 22.
- the residual signal 8 may be determined by subtracting the input 4 from the prediction 6.
- the residual signal 8 is transformed, scaled and quantized by a transforming/scaling/quantizing section 24, thereby producing quantized, transform coefficients 26.
- the decoded signal 22 may be generated by adding the predicted signal 6 to a signal 28 generated by an inverse (transforming/scaling/quantizing) section 30 using the quantized, transform coefficients 26.
- the motion information 19 and the quantized, transform coefficients 26 may be entropy coded by an entropy coding section 32 and written to the compressed-video bitstream 34.
- An output image region 38 for example a portion of the reference frame, may be generated at the encoder 2 by a de-blocking filter 36 using the reconstructed, pre-filtered signal 22.
- FIG. 2 shows a block diagram of an exemplary H.264/AVC video decoder 50.
- An input signal 52 also considered a bitstream, may be presented for decoding.
- Received symbols may be entropy decoded by an entropy decoding section 54, thereby producing motion information 56 and quantized, scaled, transform coefficients 58.
- the motion information 56 may be combined by a motion compensation section 60 with a portion of a reference frame 84 which may reside in frame memory 64, and an inter-frame prediction 68 may be generated.
- the quantized, scaled, transform coefficients 58 may be inverse quantized, scaled and inverse transformed by an inverse (transforming/scaling/quantizing) section 62, thereby producing a decoded residual signal 70.
- the residual signal 70 may be added to a prediction signal 78: either the inter-frame prediction signal 68 or an intra-frame prediction signal 76.
- the intra-frame prediction signal 76 may be predicted by an intra-frame prediction section 74 from previously decoded information in the current frame 72.
- the combined signal 72 may be filtered by a de-blocking filter 80 and the filtered signal 82 may be written to frame memory 64.
- H.264/AVC In H.264/AVC, an input picture is partitioned into fixed-size macroblocks, wherein each macroblock covers a rectangular picture area of 16x16 samples of the luma component and 8x8 samples of each of the two chroma components.
- an elementary unit, or basic coding unit, different than a macroblock, for example, a coding tree block, may be used.
- the decoding process of the H.264/AVC standard is specified for processing units which are macroblocks.
- the entropy decoder 54 parses the syntax elements of the compressed-video bitstream 52 and de-multiplexes them.
- H.264/AVC specifies two alternative methods of entropy decoding: a low-complexity technique that is based on the usage of context-adaptively switched sets of variable length codes, referred to as CAVLC, and the computationally more demanding algorithm of context-based adaptively binary arithmetic coding, referred to as CABAC.
- CAVLC context-adaptively switched sets of variable length codes
- CABAC context-based adaptively binary arithmetic coding
- a macroblock may be reconstructed by obtaining: the residual signal through inverse quantization and the inverse transform, and the prediction signal, either the intra-frame prediction signal or the inter-frame prediction signal.
- Blocking distortion may be reduced by applying a de-blocking filter to every decoded macroblock. No processing may begin until the input signal is entropy decoded, thereby making entropy decoding a potential bottleneck in decoding.
- entropy decoding may be requisite prior to all processing at the decoder, thereby making entropy decoding a potential bottleneck.
- an input picture comprising a plurality of macroblocks may be partitioned into one or several slices.
- the values of the samples in the area of the picture that a slice represents may be correctly decoded without the use of data from other slices provided that the reference pictures used at the encoder and the decoder are identical. Therefore, entropy decoding and macroblock reconstruction for a slice do not depend on other slices.
- the entropy coding state is reset at the start of each slice.
- the data in other slices are marked as unavailable when defining neighborhood availability for both entropy decoding and reconstruction.
- slices may be entropy decoded and reconstructed in parallel. No intra prediction and motion-vector prediction are allowed across the slice boundary. De-blocking filtering may use information across slice boundaries.
- Figure 3 shows an exemplary video picture 90 comprising eleven macroblocks in the horizontal direction and nine macroblocks in the vertical direction (nine exemplary macroblocks labeled 91-99).
- Figure 3 shows three exemplary slices: a first slice denoted "SLICE #0" 100, a second slice denoted "SLICE #1” 101 and a third slice denoted "SLICE #2” 102.
- An H.264/AVC decoder may decode and reconstruct the three slices 100, 101, 102 in parallel.
- context models are initialized or reset and macroblocks in other slices are marked as unavailable for both entropy decoding and macroblock reconstruction.
- the macroblock labeled 93, in “SLICE #1, " macroblocks (for example, macroblocks labeled 91 and 92) in “SLICE #0" may not be used for context model selection or reconstruction.
- the macroblock labeled 95, in “SLICE #1, " other macroblocks (for example, macroblocks labeled 93 and 94) in “SLICE #1” may be used for context model selection or reconstruction. Therefore, entropy decoding and macroblock reconstruction must proceed serially within a slice. Unless slices are defined using flexible macroblock ordering (FMO), macroblocks within a slice are processed in the order of a raster scan.
- FMO flexible macroblock ordering
- Flexible macroblock ordering defines a slice group to modify how a picture is partitioned into slices.
- the macroblocks in a slice group are defined by a macroblock-to-slice-group map, which is signaled by the content of the picture parameter set and additional information in the slice headers.
- the macroblock-to-slice-group map consists of a slice-group identification number for each macroblock in the picture.
- the slice-group identification number specifies to which slice group the associated macroblock belongs.
- Each slice group may be partitioned into one or more slices, wherein a slice is a sequence of macroblocks within the same slice group that is processed in the order of a raster scan within the set of macroblocks of a particular slice group. Entropy decoding and macroblock reconstruction must proceed serially within a slice.
- Figure 4 depicts an exemplary macroblock allocation into three slice groups: a first slice group denoted "SLICE GROUP #0" 103, a second slice group denoted “SLICE GROUP #1” 104 and a third slice group denoted "SLICE GROUP #2” 105.
- These slice groups 103, 104, 105 may be associated with two foreground regions and a background region, respectively, in the picture 90.
- Some embodiments of the present invention may comprise partitioning a picture into one or more reconstruction slices, wherein a reconstruction slice may be self-contained in the respect that values of the samples in the area of the picture that the reconstruction slice represents may be correctly reconstructed without use of data from other reconstruction slices, provided that the references pictures used are identical at the encoder and the decoder. All reconstructed macroblocks within a reconstruction slice may be available in the neighborhood definition for reconstruction.
- Some embodiments of the present invention may comprise partitioning a reconstruction slice into more than one entropy slice, wherein an entropy slice may be self-contained in the respect that symbol values in the area of the picture that the entropy slice represents may be correctly entropy decoded without the use of data from other entropy slices.
- the entropy coding state may be reset at the decoding start of each entropy slice.
- the data in other entropy slices may be marked as unavailable when defining neighborhood availability for entropy decoding.
- macroblocks in other entropy slices may not be used in a current block's context model selection.
- the context models may be updated only within an entropy slice. In these embodiments of the present invention, each entropy decoder associated with an entropy slice may maintain its own set of context models.
- CABAC encoding/decoding may comprise CABAC encoding/decoding.
- the CABAC encoding process includes the following four elementary steps: binarization; context model selection; binary arithmetic coding; and probability update.
- binarization A non-binary-valued symbol (for example, a transform coefficient, a motion vector, or other coding data) is converted into a binary code, also referred to as a bin string or a binarized symbol.
- a binary-valued syntax element When a binary-valued syntax element is given, the initial step of binarization may be bypassed.
- a binary-valued syntax element or an element of a binarized symbol may be referred to as a bin.
- a context model is a probability model for one or more bins.
- the context model comprises, for each bin, the probability of the bin being a "1" or a "0. " The model may be chosen for a selection of available models depending on the statistics of recently coded data symbols, usually based on the left and above neighboring symbols, if available.
- [Binary Arithmetic Coding] An arithmetic coder encodes each bin according to the selected probability model and is based on recursive interval subdivision.
- Probability Update The selected context model is updated based on the actual coded value.
- Context adaptation may refer to the process of selecting, based on neighboring symbol values, a context model state, also referred to as a state, associated with a bin and updating a model probability distribution assigned to the given symbols.
- a context model state also referred to as a state
- the location of the neighboring symbols may be defined according to a context template.
- all of the context models may be initialized or reset to predefined models.
- Figure 5 shows an exemplary video frame 110 comprising eleven macroblocks in the horizontal direction and nine macroblocks in the vertical direction (nine exemplary macroblocks labeled 115-123).
- Figure 5 shows three exemplary reconstruction slices: a first reconstruction slice denoted "R_SLICE #0" 111, a second reconstruction slice denoted "R_SLICE #1” 112 and a third reconstruction slice denoted "R_SLICE #2” 113.
- Figure 5 further shows a partitioning of the second reconstruction slice "R_SLICE #1" 112 into three entropy slices: a first entropy slice denoted “E_SLICE #0" shown in cross-hatch 114, a second entropy slice denoted “E_SLICE #1” shown in vertical-hatch 115 and a third entropy slice denoted "E_SLICE #2” shown in angle-hatch 116.
- Each entropy slice 114, 115, 116 may be entropy decoded in parallel.
- only data from macroblocks within an entropy slice may be available for context model selection during entropy decoding of the entropy slice. All other macroblocks may be marked as unavailable.
- macroblocks labeled 117 and 118 are unavailable for context model selection when decoding symbols corresponding to the area of macroblock labeled 119 because macroblocks labeled 117 and 118 are outside of the entropy slice containing macroblock 119.
- these macroblocks 117, 118 are available when macroblock 119 is reconstructed.
- a process determines if a macroblock belongs to the same reconstruction slice as the current macroblock. Some embodiments of the invention determine if the macroblock belongs to the same reconstruction slice as the current macroblock by determining if the macroblock and current macroblock are in the same entropy slice. Some embodiments of the invention determine if the macroblock belongs to the same reconstruction slice as the current macroblock by determining if the current macroblock is in an entropy slice. Some embodiments of the invention determine if the macroblock belongs to the same reconstruction slice as the current macroblock by determining if the information describing the slice containing the macroblock is equal to the information describing the slice containing the current macroblock. In some embodiments of the invention, the macroblock and current macroblock are determined to be in the same reconstruction slice when the three previous embodiments are true.
- an encoder may determine whether or not to partition a reconstruction slice into entropy slices, and the encoder may signal the decision in the bitstream.
- the signal may comprise an entropy-slice flag, which may be denoted "entropy_slice_flag" in some embodiments of the present invention.
- an entropy-slice flag may be examined 130, and if the entropy-slice flag indicates that there are no 132 entropy slices associated with a picture, or a reconstruction slice, then the header may be parsed 134 as a regular slice header.
- the entropy decoder state may be reset 136, and the neighbor information for the entropy decoding and the reconstruction may be defined 138.
- the slice data may then be entropy decoded 140, and the slice may be reconstructed 142.
- the header may be parsed 148 as an entropy-slice header.
- the entropy decoder state may be reset 150, the neighbor information for entropy decoding may be defined 152 and the entropy-slice data may be entropy decoded 154.
- the neighbor information for reconstruction may then be defined 156, and the slice may be reconstructed 142. After slice reconstruction 142, the next slice, or picture, may be examined 158.
- the decoder may be capable of parallel decoding and may define its own degree of parallelism, for example, consider a decoder comprising the capability of decoding N entropy slices in parallel.
- the decoder may identify 170 N entropy slices.
- the decoder may decode entropy slices from subsequent pictures, or reconstruction slices, if they are available.
- the decoder may wait until the current picture, or reconstruction slice, is completely processed before decoding portions of a subsequent picture, or reconstruction slice.
- each of the identified entropy slices may be independently entropy decoded.
- a first entropy slice may be decoded 172-176.
- the decoding 172-176 of the first entropy slice may comprise resetting the decoder state 172.
- the CABAC state may be reset.
- the neighbor information for the entropy decoding of the first entropy slice may be defined 174, and the first entropy slice data may be decoded 176. For each of the up to N entropy slices, these steps may be performed (178-182 for the Nth entropy slice).
- the decoder may reconstruct 184 the entropy slices when all of the entropy slices are entropy decoded. In alternative embodiments of the present invention, the decoder may begin reconstruction 184 after one or more entropy slices are decoded.
- a decode thread may begin entropy decoding a next entropy slice upon the completion of entropy decoding of an entropy slice.
- the thread may commence decoding additional entropy slices without waiting for other threads to finish their decoding.
- an entropy slice may share most of the slice attributes of a regular slice according to the standard or method. Therefore, an entropy slice may require a small header.
- the entropy slice header may allow a decoder to identify the start of an entropy slice and start entropy decoding.
- the entropy slice header may be the regular header, or a reconstruction slice header.
- an entropy slice may be signaled by adding a new bit, "entropy_slice_flag" to the existing slice header.
- Table 1 lists the syntax for an entropy slice header according to embodiments of the present invention, wherein C indicates Category and Descriptor u(1), ue(v) indicate some fixed length or variable length coding methods.
- Embodiments of the present invention comprising an "entropy_slice_flag" may realize improved coding efficiency.
- first_mb_in_slice specifies the address of the first macroblock in the entropy slice associated with the entropy-slice header.
- the entropy slice may comprise a sequence of macroblocks.
- cabac_init_idc specifies the index for determining the initialization table used in the initialization process for the context mode.
- Table 1 Exemplary Syntax Table for Entropy Slice Header
- an entropy slice may be assigned a different network abstraction layer (NAL) unit type from the regular slices.
- NAL network abstraction layer
- a decoder may distinguish between regular slices and entropy slices based on the NAL unit type.
- the bit field "entropy_slice_flag" is not required.
- the bit field "entropy_slice_flag” may not be transmitted in all profiles. In some embodiments of the present invention, the bit field “entropy_slice_flag” may not be transmitted in a baseline profile, but the bit field “entropy_slice_flag” may be transmitted in higher profiles such as a main, an extended or a professional profile. In some embodiments of the present invention, the bit field "entropy_slice_flag” may only be transmitted in bitstreams associated with characteristics greater than a fixed characteristic value. Exemplary characteristics may include spatial resolution, frame rate, bit depth, bit rate and other bitstream characteristics.
- the bit field "entropy_slice_flag" may only be transmitted in bitstreams associated with spatial resolutions greater than 1920x1080 interlaced. In some embodiments of the present invention, the bit field “entropy_slice_flag” may only be transmitted in bitstreams associated with spatial resolutions greater than 1920x1080 progressive. In some embodiments of the present invention, if the bit field "entropy_slice_flag" is not transmitted, a default value may be used.
- an entropy slice may be constructed by altering the data multiplexing.
- the group of symbols contained in an entropy slice may be multiplexed at the macroblock level.
- the group of symbols contained in an entropy slice may be multiplexed at the picture level.
- the group of symbols contained in an entropy slice may be multiplexed by data type.
- the group of symbols contained in an entropy slice may be multiplexed in a combination of the above.
- prediction data 190 and residual data 192 may be entropy encoded by a prediction encoder 194 and a residual encoder 196 separately and the encoded prediction data and the encoded residual data may be multiplexed by a picture-level multiplexer 198 at the picture level.
- the prediction data for a picture 190 may be associated with a first entropy slice
- the residual data for a picture 192 may be associated with a second entropy slice.
- the encoded prediction data and the encoded entropy data may be decoded in parallel.
- each partition comprising prediction data or residual data may be partitioned into entropy slices which may be decoded in parallel.
- the residual of each color plane may be entropy encoded by a Y encoder 206, a U encoder 208, and a V encoder 210 separately and the entropy encoded residuals may be multiplexed by a picture-level multiplexer 212 at the picture level.
- the luma residual for a picture 200 may be associated with a first entropy slice
- the first chroma residual for a picture 202 may be associated with a second entropy slice
- the second residual for a picture 204 may be associated with a third entropy slice.
- each partition comprising color-plane residual data may be partitioned into entropy slices which may be decoded in parallel.
- the luma residual 200 may have relatively more entropy slices compared to the chroma residuals 202, 204.
- an compressed-video bitstream may be trans-coded to comprise entropy slices, thereby allowing for parallel entropy decoding as accommodated by embodiments of the present invention described above.
- Some embodiments of the present invention may be described in relation to Figure 10.
- An input bitstream without entropy slices may be processed picture-by-picture according to Figure 10.
- a picture from the input bitstream may be entropy decoded 220.
- the data which had been coded for example, mode data, motion information, residual information and other data, may be obtained.
- Entropy slices may be constructed 222 one at a time from the data.
- An entropy-slice header corresponding to an entropy slice may be inserted 224 in a new bitstream.
- the encoder state may be reset and the neighbor information defined 226.
- the entropy slice may be entropy encoded 228 and written to the new bitstream. If there is picture data that has not been consumed 232 by the constructed entropy slices, then another entropy slice may be constructed 222, and the process 224-230 may continue until all of the picture data has been consumed 234 by the constructed entropy slices, and then the next picture may be processed.
- an encoder may partition a reconstruction slice into a plurality of entropy slices wherein the size of each entropy slice may be less than, or may not exceed, a fixed number of bins.
- the encoder may restrict the size of each entropy slice, the maximum number of bins may be signaled in the bitstream.
- the encoder may restrict the size of each entropy slice, the maximum number of bins may be defined by the profile and level conformance point of the encoder. For example, Annex A of the H.264/AVC video coding specification may be extended to comprise a definition of the maximum number of bins allowed in an entropy slice.
- the maximum number of bins allowed in an entropy slice may be indicated for each level conformance point of the encoder according to a table, for example, as shown in Table 2, where
- a set of maximum number of bins allowed in an entropy slice may be determined for all levels based on bit rate, image size, number of macroblocks and other encoding parameters. In some embodiments of the present invention the maximum number of bins allowed in an entropy slice may be the set to the same number for all levels. Exemplary values are 38,000 bins and 120,000 bins.
- an encoder may determine a worst case number of bins associated with a macroblock, and the encoder may write the bins associated with:
- the encoder may update the worst case number based on measurements of the sizes of previously processed macroblocks.
- an encoder may, for a reconstruction slice, partition the reconstruction slice into a plurality of entropy slices wherein no entropy slice may be larger in size than a predetermined number of bins.
- the encoder may initialize 240 to zero a counter associated with the number of bins in a current entropy slice. The counter value may be denoted
- the syntax elements for a next macroblock may be obtained 242.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 244 to a string of bins.
- Binary syntax elements may not require conversion.
- the number of bins associated with the macroblock may be determined 246.
- the number of bins associated with the macroblock may include the bins in the strings of bins associated with the non-binary syntax elements in addition to the binary syntax elements, and the number of bins associated with the macroblock may be denoted
- the number of bins associated with the macroblock may be added 248 to the number of already accumulated bins associated with the current entropy slice without 249 exceeding a maximum number of bins allowed for an entropy slice, then the number of accumulated bins associated with the current entropy slice may be updated 250 to include the bins associated with the macroblock, and the bins associated with the macroblock may be written 252, by the entropy encoder, to the bitstream and associated with the current entropy slice.
- the syntax elements for the next macroblock may be obtained 242, and the partitioning process may continue.
- the encoder may start 254 a new entropy slice associated with the current reconstruction slice and may terminate the current entropy slice. Then the counter associated with the number of bins in the new, now current, entropy slice may be initialized 256 to zero. The number of accumulated bins associated with the current entropy slice may be updated 250 to include the bins associated with the macroblock, and the bins associated with the macroblock may be written 252, by the entropy encoder, to the bitstream and associated with the current entropy slice. The syntax elements for the next macroblock may be obtained 242, and the partitioning process may continue.
- an encoder may, for a reconstruction slice, partition the reconstruction slice into a plurality of entropy slices wherein no entropy slice may be larger in size than a predetermined maximum number of bins.
- the encoder may associate macroblock syntax elements with an entropy slice until the size of the entropy slice reaches a threshold associated with the predetermined maximum number of bins allowed in an entropy slice.
- the threshold may be a percentage of the maximum number of bins allowed in an entropy slice.
- the threshold may be 90% of the maximum number of bins allowed in an entropy slice, supposing that the greatest number of bins expected in a macroblock is less than 10% of the maximum number of bins.
- the threshold may be a percentage of the maximum number of bins allowed in an entropy slice wherein the percentage may be based on the greatest number of bins expected in a macroblock.
- the threshold size may be selected to ensure that the entropy slice does not exceed the maximum number of bins allowed in an entropy slice.
- the threshold size may be a function of the maximum number of bins allowed in an entropy slice and an estimate of the maximum number of bins expected for a macroblock.
- the encoder may initialize 270 to zero a counter associated with the number of bins in a current entropy slice.
- the counter value may be denoted
- the syntax elements for a next macroblock may be obtained 272.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 274 to a string of bins. Binary syntax elements may not require conversion.
- the bins associated with the macroblock may be written 276, by the entropy encoder, to the bitstream and associated with the current entropy slice.
- the number of bins associated with the macroblock may be determined 278, and the number of accumulated bins associated with the current entropy slice may be updated 280 to include the bins associated with the macroblock. If 282 the number of accumulated bins associated with the current entropy slice is greater 284 than a threshold, which may be denoted
- the encoder may start 286 a new entropy slice and may terminate the current entropy slice. Then the encoder may initialize 288 to zero the counter associated with the number of bins in the new, now current, entropy slice.
- the syntax elements for the next macroblock may be obtained 272, and the partitioning process may continue. If the number of accumulated bins associated with the current entropy slice is not greater 283 than the threshold based on the maximum number of bins allowed in an entropy slice, then the syntax elements for the next macroblock may be obtained 272, and the partitioning process may continue.
- an encoder may terminate the current reconstruction slice and start a new reconstruction slice when a predetermined number of macroblocks have been assigned to the current reconstruction slice.
- an encoder may terminate the current reconstruction slice and start a new reconstruction slice when a predetermined number of macroblocks have been assigned to the current reconstruction slice.
- the encoder may initialize 300 to zero a counter associated with the number of macroblocks in a current reconstruction slice.
- the counter value may be denoted
- the encoder may initialize 310 to zero a counter associated with the number of bins in a current entropy slice.
- the counter value may be denoted
- a new entropy slice may be started 332 and a new reconstruction slice may be started 334, terminating the current reconstruction slice and current entropy slice.
- the maximum number of macroblocks allowed in a reconstruction slice may be denoted
- the syntax elements for a next macroblock may be obtained 314.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 316 to a string of bins.
- Binary syntax elements may not require conversion.
- the number of bins associated with the macroblock may be determined 318.
- the number of bins associated with the macroblock may include the bins in the strings of bins associated with the non-binary syntax elements in addition to the binary syntax elements, and the number of bins associated with the macroblock may be denoted
- the number of bins associated with the macroblock may be added 320 to the number of already accumulated bins associated with the current entropy slice without 321 exceeding a maximum number of bins allowed for an entropy slice, then the number of accumulated bins associated with the current entropy slice may be updated 322 to include the bins associated with the macroblock, the bins associated with the macroblock may be written 324, by the entropy encoder, to the bitstream and associated with the current entropy slice, and the number of macroblocks associated with the current reconstruction slice may be incremented 326.
- the number of macroblocks associated with the current reconstruction slice may be compared 312 to the predetermined maximum number of macroblocks allowed in a reconstruction slice, and the partitioning process may continue.
- the encoder may start 328 a new, now current, entropy slice associated with the current reconstruction slice, and the counter associated with the number of bins in the current entropy slice may be initialized 330 to zero.
- the number of accumulated bins associated with the current entropy slice may be updated 322 to include the bins associated with the macroblock, the bins associated with the macroblock may be written 324, by the entropy encoder, to the bitstream and associated with the current entropy slice, and the number of macroblocks associated with the current reconstruction slice may be incremented 326.
- the number of macroblocks associated with the current reconstruction slice may be compared 312 to the predetermined maximum number of macroblocks allowed in a reconstruction slice, and the partitioning process may continue.
- an encoder may start a new reconstruction slice when a predetermined number of macroblocks have been assigned to the current reconstruction slice.
- the encoder may associate macroblock syntax elements with an entropy slice until the size of the entropy slice reaches a threshold associated with the predetermined maximum number of bins allowed in an entropy slice.
- the threshold may be a percentage of the maximum number of bins allowed in an entropy slice.
- the threshold may be 90% of the maximum number of bins allowed in an entropy slice, supposing that the greatest number of bins expected in a macroblock is less than 10% of the maximum number of bins.
- the threshold may be a percentage of the maximum number of bins allowed in an entropy slice wherein the percentage may be based on the greatest number of bins expected in a macroblock.
- the threshold size may be selected to ensure that the entropy slice does not exceed the maximum number of bins allowed in an entropy slice.
- the threshold size may be a function of the maximum number of bins allowed in an entropy slice and an estimate of the maximum number of bins expected for a macroblock.
- the encoder may initialize 350 to zero a counter associated with the number of macroblocks in a current reconstruction slice.
- the counter value may be denoted
- the encoder may initialize 352 to zero a counter associated with the number of bins in a current entropy slice.
- the counter value may be denoted
- the syntax elements for a next macroblock may be obtained 356.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 358 to a string of bins. Binary syntax elements may not require conversion.
- the bins associated with the macroblock may be written 360, by the entropy encoder, to the bitstream and associated with the current entropy slice.
- the number of bins associated with the macroblock may be determined 362, and the number of accumulated bins associated with the current entropy slice may be updated 364 to include the bins associated with the macroblock. If 366 the number of accumulated bins associated with the current entropy slice is greater 369 than a threshold, which may be denoted
- the encoder may start 370 a new entropy slice, and initialize 372 to zero the counter associated with the number of bins in a current entropy slice.
- the number of macroblocks associated with the current reconstruction slice may be incremented 368.
- the number of macroblocks associated with the current reconstruction slice may be compared 354 to the predetermined maximum number of macroblocks allowed in a reconstruction slice, and the partitioning process may continue.
- the number of accumulated bins associated with the current entropy slice is not greater 367 than the threshold based on the maximum number of bins allowed in an entropy slice, then the number of macroblocks associated with the current reconstruction slice may be incremented 368, and the number of macroblocks associated with the current reconstruction slice may be compared 354 to the predetermined maximum number of macroblocks allowed in a reconstruction slice, and the partitioning process may continue.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein each entropy slice may be associated with no more than a predefined number of bits.
- an encoder may, for a reconstruction slice, partition the reconstruction slice into a plurality of entropy slices wherein no entropy slice may be larger in size than a predetermined number of bits.
- the encoder may initialize 400 to zero a counter associated with the number of bits in a current entropy slice.
- the counter value may be denoted
- the syntax elements for a next macroblock may be obtained 402.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 404 to a string of bins. Binary syntax elements may not require conversion.
- the bins, converted non-binary elements and binary elements, associated with the macroblock may be presented to the entropy encoder, and the bins may be entropy encoded 406.
- the number of bits associated with the macroblock may be determined 408. The number of bits associated with the macroblock may be denoted
- the number of bits associated with the macroblock may be added 410 to the number of already accumulated bits associated with the current entropy slice without 411 exceeding a maximum number of bits allowed for an entropy slice, then the number of accumulated bits associated with the current entropy slice may be updated 412 to include the bits associated with the macroblock, and the bits associated with the macroblock may be written 414 to the bitstream and associated with the current entropy slice.
- the syntax elements for the next macroblock may be obtained 402, and the partitioning process may continue.
- the encoder may start 416 a new entropy slice associated with the current reconstruction slice, and the counter associated with the number of bits in the current entropy slice may be initialized 418 to zero.
- the number of accumulated bits associated with the current entropy slice may be updated 412 to include the bits associated with the macroblock, and the bits associated with the macroblock may be written 414 to the bitstream and associated with the current entropy slice.
- the syntax elements for the next macroblock may be obtained 402, and the partitioning process may continue.
- an encoder may, for a reconstruction slice, partition the reconstruction slice into a plurality of entropy slices wherein no entropy slice may be larger in size than a predetermined maximum number of bits.
- the encoder may associate macroblock syntax elements with an entropy slice until the size of the entropy slice reaches a threshold associated with the predetermined maximum number of bits allowed in an entropy slice.
- the threshold may be a percentage of the maximum number of bits allowed in an entropy slice.
- the threshold may be 90% of the maximum number of bits allowed in an entropy slice, supposing that the greatest number of bits expected in a macroblock is less than 10% of the maximum number of bits.
- the threshold may be a percentage of the maximum number of bits allowed in an entropy slice wherein the percentage may be based on the greatest number of bits expected in a macroblock.
- the threshold size may be selected to ensure that the entropy slice does not exceed the maximum number of bits allowed in an entropy slice.
- the threshold size may be a function of the maximum number of bits allowed in an entropy slice and an estimate of the maximum number of bits expected for a macroblock.
- the encoder may initialize 440 to zero a counter associated with the number of bits in a current entropy slice.
- the counter value may be denoted
- the syntax elements for a next macroblock may be obtained 442.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 444 to a string of bins. Binary syntax elements may not require conversion.
- the bins associated with the macroblock may be entropy encoded 446, and the number of bins associated with the macroblock may be determined 448.
- the number of accumulated bits associated with the current entropy slice may be updated 450 to include the bins associated with the macroblock, and the entropy encoded bins associated with the macroblock may be written 452 to the bitstream. If 454 the number of accumulated bits associated with the current entropy slice is greater 456 than a threshold based on the maximum number of bits allowed in an entropy slice, then the encoder may start 458 a new entropy slice, and initialize 460 to zero the counter associated with the number of bits in a current entropy slice. The syntax elements for the next macroblock may be obtained 442, and the partitioning process may continue.
- the syntax elements for the next macroblock may be obtained 442, and the partitioning process may continue.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein each entropy slice may be associated with no more than a predefined number of macroblocks.
- a restriction on the maximum number of macroblocks in a reconstruction slice may be imposed in addition to a restriction on the size of an entropy slice.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted to less than a predefined number of macroblocks and to less than a predefined number of bins.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted to less than a predefined number of macroblocks and to less than a predefined number of bits.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted to less than a predefined number of macroblocks, to less than a predefined number of bins and to less than a predefined number of bits.
- bin coding within an entropy coder may be parallelized allowing parallel encoding of more than one bin, which may reduce encoding time.
- the entropy coder 480 may comprise a context-adaptation unit 482, a state-based, bin-coder selector 484 and a plurality of bin coders, also considered bin-coder units, (three shown) 486, 488, 500 that may operate in parallel.
- Bins 502 may be made available to the entropy coder 480 from a binarizer 504 that may generate the bins 502 from input symbols 506.
- the bins 502 may be made available to the context-adaptation unit 482 and the state-based, bin-coder selector 484.
- the context-adaptation unit 482 may perform context adaptation and generate a model state, also referred to as a state, 508 that may be used to select a bin coder to which a bin 502 may be directed among the bin coders 486, 488, 500.
- the state-based, bin-coder selector 484 may select the bin coder associated with the generated model state 508 among the bin coders 486, 488, 500 to encode the bin 502. In some embodiments (not shown), the generated state 508 may be made available to the selected bin coder.
- Output bits 510, 512, 514 may be generated by the bin coders 486, 488, 500, and the output bits 510, 512, 514 may be incorporated into a bitstream.
- the output bits 510, 512, 514 may be buffered and incorporated into the bitstream by concatenation.
- the output bits 510, 512, 514 may be buffered and incorporated into the bitstream according to an interleaving scheme.
- a first bin may be sent to a first bin coder in response to a first model state generated in relation to the first bin.
- the context-adaptation unit 482 upon completion of processing the first bin, may begin processing of a second bin, sending the second bin to a second bin coder in response to a second model state generated in relation to the second bin, thereby allowing substantially parallel processing of more than one bin.
- an entropy coder may comprise a plurality of context-adaptation units that may operate in parallel and a single bin coder.
- a plurality of context-adaptation units operating in parallel may reduce encoding time.
- Bins 544 may be made available to the entropy coder 530 from a binarizer 546 that may generate the bins 544 from input symbols 548.
- the bins 544 may be made available to the context-adaptation-unit selector 538, the state selector 540 and the bin coder 542.
- the context-adaptation-unit selector 538 may be used to select, or to schedule, a context-adaptation unit 532, 534, 536 to which a bin 544 may be directed and from which a state value 550, 552, 554 may be generated.
- the context-adaptation-unit selector 538 may select a context-adaptation unit among the context-adaptation units 532, 534, 536 based on the syntax associated with the bin, for example a context-adaptation unit identifier may be associated with a bin identifying the context-adaptation unit to which the bin may be directed for processing.
- the context-adaptation-unit selector 538 may select a context-adaptation unit among the context-adaptation units 532, 534, 536 based on a scheduling protocol or load-balancing constraint associated with the context-adaptation units 532, 534, 536.
- the generated state value may be selected by the state selector 540, according to the criterion used at the context-adaptation unit selector 538, at the appropriate timing to be passed to the bin coder 542.
- the bin coder 542 may use the state value 556 passed by the state selector 540 in coding the bin 544.
- the state value may not be required by the bin coder and, therefore, not made available to the bin coder.
- Output bits 558 may be generated by the bin coder 542, and the output bits 558 may be incorporated into a bitstream.
- the output bits 558 may be buffered and incorporated into the bitstream by concatenation.
- the output bits 558 may be buffered and incorporated into the bitstream according to an interleaving scheme.
- an entropy coder may comprise a plurality of context-adaptation units that may operate in parallel and a plurality of bin coders that may operate in parallel.
- the entropy coder 570 may comprise a plurality of context-adaptation units (three shown) 572, 574, 576, a context-adaptation-unit selector 578, a state selector 580, a state-based, bin-coder selector 582 and a plurality of bin coders (three shown) 584, 586, 588.
- Bins 590 may be made available to the entropy coder 570 from a binarizer 592 that may generate the bins 590 from input symbols 594.
- the bins 590 may be made available to the context-adaptation-unit selector 578, the state selector 580 and the bin-coder selector 582.
- the context-adaptation-unit selector 578 may be used to select, or to schedule, a context-adaptation unit 572, 574, 576 to which a bin 590 may be directed and from which a state value 596, 598, 600 may be generated.
- the generated state value may be selected by the state selector 580 at the appropriate timing to be passed to the state-based, bin-coder selector 582.
- the state-based, bin-coder selector 582 may use the state value 602 passed by the state selector 580 to select a bin coder among the bin coders 584, 586, 588 to which a bin 590 may be directed.
- the state value 602 may be made available to the selected bin coder.
- the selected bin coder may use the state value 602 in coding the bin 590.
- the state value may not be required by the bin coder and, therefore, not made available to the bin coder.
- Output bits 604, 606, 608 may be generated by the bin coders 584, 586, 588 and the output bits 604, 606, 608 may be incorporated into a bitstream.
- the output bits 604, 606, 608 may be buffered and incorporated into the bitstream by concatenation. In alternative embodiments, the output bits 604, 606, 608 may be buffered and incorporated into the bitstream according to an interleaving scheme
- An exemplary embodiment of the present invention may comprise a plurality of variable length coding codecs that may operate in parallel.
- a bin coder may comprise binary arithmetic coding. In another exemplary embodiment of the present invention, a bin coder may comprise variable length coding. In yet another exemplary embodiment of the present invention, a bin coder may comprise fixed length coding.
- an entropy coder may comprise
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that one, or more, of
- bin-coder units may each operate on no more than a limited number of bins during the processing of the entropy slice. Context-adaptation units and bin-coder units with such a restriction may be referred to as restricted entropy-coder units.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that none of the
- context-adaptation units may operate on more than
- ⁇ may be signaled, for example, in a bitstream, profile constraint, level constraint or other normative mechanism.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that none of the
- bin-coder units may operate on more than
- ⁇ may be signaled, for example, in a bitstream, profile constraint, level constraint or other normative mechanism.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that none of the
- context-adaptation units may operate on more than
- bin-coder units may operate on more than
- ⁇ may be signaled, for example, in a bitstream, profile constraint, level constraint or other normative mechanism.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that the ith
- ⁇ may be signaled, for example, in a bitstream, profile constraint, level constraint or other normative mechanism.
- an encoder may, for a reconstruction slice, partition the reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that one, or more, of
- bin-coder units may operate on no more than a limited number of bins.
- the encoder may initialize 650 to zero a counter, for each restricted entropy-coder unit, associated with the number of bins processed in a current entropy slice.
- the counter value may be denoted
- the syntax elements for a next macroblock may be obtained 652.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 654 to a string of bins. Binary syntax elements may not require conversion.
- the number of bins, associated with the macroblock, processed by each restricted entropy-coder unit may be determined 656.
- the number of bins associated with the macroblock may include the bins in the strings of bins associated with the non-binary syntax elements in addition to the binary syntax elements.
- the number of bins, associated with the macroblock, processed by each restricted entropy-coder unit may be denoted
- the number of bins associated with the macroblock for each restricted entropy-coder unit may be added 658 to the number of already accumulated bins, associated with the current entropy slice, for each restricted entropy-coder unit, without 659 exceeding a maximum number of bins allowed for any restricted entropy-coder unit, then the number of accumulated bins associated with the current entropy slice may be updated 660 to include the bins associated with the macroblock, and the bins associated with the macroblock may be written 662, by the entropy encoder, to the bitstream and associated with the current entropy slice.
- the syntax elements for the next macroblock may be obtained 652, and the partitioning process may continue.
- the encoder may start 664 a new entropy slice associated with the current reconstruction slice, and the counter associated with the number of bins in the current entropy slice may be initialized 666 to zero.
- the number of accumulated bins associated with the current entropy slice may be updated 660 to include the bins associated with the macroblock, and the bins associated with the macroblock may be written 662, by the entropy encoder, to the bitstream and associated with the current entropy slice.
- the syntax elements for the next macroblock may be obtained 652, and the partitioning process may continue.
- an encoder may, for a reconstruction slice, partition the reconstruction slice into a plurality of entropy slices, wherein the size of each entropy slice may be restricted such that one, or more, of
- bin-coder units may operate on no more than a limited number of bins.
- the encoder may initialize 700 to zero a counter, for each restricted entropy-coder unit, associated with the number of bins processed in a current entropy slice by the restricted entropy-coder unit.
- the counter value may be denoted
- the encoder may associate macroblock syntax elements with an entropy slice until the number of bins processed by a restricted entropy-coder unit reaches a threshold associated with the predetermined maximum number of bins allowed to be processed, in an entropy slice, by the restricted entropy-coder unit.
- the threshold may be a percentage of the maximum number of bins allowed to be processed, in an entropy slice, by the restricted entropy-coder unit.
- the threshold may be 90% of the maximum number of bins allowed to be processed, in an entropy slice, by the restricted entropy-coder unit, supposing that the greatest number of bins expected in a macroblock to be processed by the restricted entropy-coder unit is less than 10% of the maximum number of bins allowed to be processed, in an entropy slice, by the restricted entropy-coder unit.
- the threshold may be a percentage of the maximum number of bins allowed to be processed, in an entropy slice, by a restricted entropy-coder unit wherein the percentage may be based on the greatest number of bins expected in a macroblock to be processed by the restricted entropy-coder unit.
- the threshold size may be selected to ensure that the entropy slice does not exceed the maximum number of bins allowed to be processed by any one restricted entropy-coder unit in an entropy slice.
- the threshold size may be a function of the maximum number of bins allowed in an entropy slice and an estimate of the maximum number of bins expected for a macroblock.
- the syntax elements for a next macroblock may be obtained 702.
- the next macroblock may be determined according to a predefined macroblock processing order.
- the macroblock processing order may correspond to a raster-scan ordering.
- Non-binary syntax elements in the macroblock may be converted 704 to a string of bins. Binary syntax elements may not require conversion.
- the bins associated with the macroblock may be written 706, by the entropy encoder, to the bitstream and associated with the current entropy slice.
- the number of bins, associated with the macroblock, processed by each restricted entropy-coder unit may be determined 708.
- the number of bins associated with the macroblock may include the bins in the strings of bins associated with the non-binary syntax elements in addition to the binary syntax elements. For illustrative purposes in the remainder of the description of the embodiments of the present invention described in relation to Figure 21, the number of bins, associated with the macroblock, processed by each restricted entropy-coder unit may be denoted
- the number of accumulated bins, associated with the current entropy slice, processed by each restricted entropy-coder unit may be updated 710 to include the bins associated with the macroblock. If 712 the number of accumulated bins, associated with the current entropy slice, processed by a restricted entropy-coder unit is greater 714 than a threshold, which may be denoted
- the encoder may start 716 a new entropy slice, and initialize 718 to zero the counter associated with the number of bins processed by each restricted entropy-coder unit in a current entropy slice.
- the syntax elements for the next macroblock may be obtained 702, and the partitioning process may continue. If the number of accumulated bins, associated with the current entropy slice, processed by a restricted entropy-coder unit is not greater 713 than the threshold, then the syntax elements for the next macroblock may be obtained 702, and the partitioning process may continue.
- Some embodiments of the present invention may comprise a combination of the above-described criteria for entropy slice partitioning.
- starting a new entropy slice may comprise terminating the current slice and considering the new entropy slice the current entropy slice.
- the decoding of a plurality of bits within an entropy slice may be parallelized within an entropy decoder comprising a plurality of bin decoders, which may reduce decoding time.
- Exemplary embodiments of the present invention may be understood in relation to an exemplary entropy decoder 750, depicted in Figure 22, comprising a plurality (three shown) of bin decoders 762, 764, 766. Bits 752 within an entropy slice and previously decoded symbols 754 may be made available to an entropy decoder 750.
- the bits 752 may be made available to a bin-decoder selector 756 which may select a bin decoder, based on a context state 758 generated from a context-adaptation unit 760, among the bin decoders 762, 764, 766.
- the context-adaptation unit 760 may generate the context state 758 based on the previously decoded symbols 754 made available to the context-adaptation unit 760.
- the bin-decoder selector 756 may assign a bin-decoder 762, 764, 766 based on the context state 758.
- the bit to be decoded 752 may be passed by the bin-decoder selector 756 to the selected bin decoder.
- the bin decoders 762, 764, 766 may generate decoded bins 768, 770, 772 which may be multiplexed by a multiplexer 774 and the multiplexed bins 776 may be sent to a symbolizer 778 which may generate the symbols 754 associated with the bins 776.
- decoding of a plurality of bits within an entropy slice may be parallelized within an entropy decoder comprising a plurality of context-adaptation units, which may reduce decoding time.
- Exemplary embodiments of the present invention may be understood in relation to an exemplary entropy decoder 800, depicted in Figure 23, comprising a plurality (three shown) of context-adaptation units 814, 816, 818.
- Bits 802 within an entropy slice and previously decoded symbols 810 may be made available to an entropy decoder 800.
- the bits 802 may be made available to a context-adaptation unit selector 812 that may select from a plurality of context-adaptation units 814, 816, 818 a context-adaptation unit for the decoding process of an input bit.
- the context-adaptation unit selector 812 may select the Nth context-adaptation unit when receiving every Nth bit.
- the selected context-adaptation unit may generate a context state 820, 822, 824 based on the previously decoded symbols 810 made available to the selected context-adaptation unit.
- a state selector 826 at the appropriate timing, may select the generated context state in associated with an input bit.
- state selector 826 may select the Nth context-adaptation unit when receiving every Nth bit according to the same procedure as the context-adaptation unit selector 812.
- the selected state 828 may be made available to the bin decoder 804.
- the bin decoder 804 may decode the bit 802 and send the decoded bin 806 to a symbolizer 808 which may generate a symbol 810 associated with the decoded bin 806.
- decoding of a plurality of bits within an entropy slice may be parallelized within an entropy decoder comprising a plurality of context-adaptation units and a plurality of bin decoders, which may reduce decoding time.
- Exemplary embodiments of the present invention may be understood in relation to an exemplary entropy decoder 850, depicted in Figure 24, comprising a plurality (three shown) of context-adaptation units 852, 854, 856 and a plurality (three shown) of bin decoders 858, 860, 862.
- Bits 864 within an entropy slice and previously decoded symbols 866 may be made available to an entropy decoder 850.
- the bits 864 may be made available to a context-adaptation unit selector 868 that may select from the plurality of context-adaptation units 852, 854, 856 a context-adaptation unit for the decoding process of an input bit.
- the context-adaptation unit selector 868 may select the Nth context-adaptation unit when receiving every Nth bit.
- the selected context-adaptation unit may generate a context state 870, 872, 874 based on the previously decoded symbols 866 made available to the selected context-adaptation unit.
- a state selector 876 at the appropriate timing, may select the generated context state in associated with an input bit.
- state selector 876 may select the Nth context-adaptation unit when receiving every Nth bit according to the same procedure as the context-adaptation unit selector 868.
- the selected state 878 may be made available to a bin-decoder selector 880, which may select, based on the selected context state 878, a bin decoder 858, 860, 862.
- the bin-decoder selector 880 may assign a bin-decoder 858, 860, 862 based on the context state 878.
- the bit to be decoded 864 may be passed by the bin-decoder selector 880 to the selected bin decoder.
- the bin decoders 858, 860, 862 may generate decoded bins 882, 884, 886 which may be multiplexed by a multiplexer 888 and the multiplexed bins 890 may be sent to a symbolizer 892 which may generate the symbols 866 associated with the bins 890.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the macroblocks within an entropy slice are contiguous.
- Figure 25 depicts an exemplary reconstruction slice 950 partitioned into three entropy slices: entropy slice 0 shown in cross-hatch 952, entropy slice 1 shown in white 954 and entropy slice 2 shown in dot-hatch 956.
- the macroblocks within each entropy slice 952, 954, 956, in this exemplary reconstruction slice 950 are contiguous.
- an encoder may partition a reconstruction slice into a plurality of entropy slices, wherein the macroblocks within an entropy slice may not be contiguous.
- Figure 26 depicts an exemplary reconstruction slice 960 partitioned into three entropy slices: entropy slice 0 shown in cross-hatch 962, entropy slice 1 shown in white 964 and entropy slice 2 shown in dot-hatch 966.
- the macroblocks within each entropy slice 962, 964, 966, in this exemplary reconstruction slice 960 are not contiguous.
- a partition of a reconstruction slice in which the macroblocks within an entropy slice are not contiguous may be referred to as an interleaved partition.
- the decoder may use other blocks from the same entropy slice to predict information related to the entropy decoding of the current block.
- other blocks from the same reconstruction slice may be used to predict information related to the reconstruction of the current block.
- a reconstruction slice comprises an interleaved partition
- neighboring blocks within an entropy slice used in the decoding of a current block within the entropy slice may not be directly neighboring, or contiguous.
- Figure 27 illustrates this situation for the exemplary interleaved partition depicted in Figure 26.
- the left-neighbor block used for entropy decoding of the current block 970 is the contiguous, left-neighbor block 972 within the entropy slice 964.
- the upper-neighbor block used for entropy decoding of the current block 970 is the non-contiguous, upper-neighbor block 974 within the same entropy slice 964.
- the left-neighbor block is the contiguous, left-neighbor block 972 within the reconstruction slice 960
- the upper-neighbor block is the contiguous, upper-neighbor block 976 within the reconstruction slice 960.
- a reconstruction slice comprises an interleaved partition
- Figure 28 illustrates this situation for the exemplary interleaved partition depicted in Figure 26.
- Figure 28 for a current block 980 within an entropy slice 964, there is no left-neighbor block within the entropy slice 964 to be used for entropy decoding of the current block 980.
- the upper-neighbor block used for entropy decoding of the current block 980 is the non-contiguous, upper-neighbor block 982 within the same entropy slice 964.
- the left-neighbor block is the contiguous, left-neighbor block 984 within the reconstruction slice 960
- the upper-neighbor block is the contiguous, upper-neighbor block 986 within the reconstruction slice 960.
- a decoder may pre-process a complete incoming bitstream to identify the locations of the entropy slices. In some embodiments of the present invention, a decoder may pre-process an entire reconstruction slice to identify the locations of the entropy slices within the reconstruction slice. In some embodiments, the locations of the entropy slices may be determined by identifying the locations of the entropy-slice headers. In these embodiments, the decoder may read the bits in the bitstream and pre-defined start-code values may be identified.
- entropy-slice headers may be constrained to a range of bits located at pre-defined positions within an incoming bitstream. In alternative embodiments, entropy-slice headers may be constrained to a range of bytes located at pre-defined positions within an incoming bitstream. In these embodiments, either bit aligned or byte aligned, a decoder need not pre-process significantly large portions of the incoming bitstream to locate the entropy slices.
- an encoder may signal, in the bitstream, entropy-slice-location information, also referred to as entropy-slice-location parameters, for example, offset and range information, that may constrain the locations of the entropy-slice headers.
- entropy-slice-location information may not be signaled in the bitstream, but may be determined from entropy-slice parameters, for example, a fixed number of bins allowed in any given entropy slice, a fixed number of bits allowed in any given entropy slice and other entropy-slice parameters.
- entropy-slice-location information may be defined by other normative means, for example, the information may be specified in a profile constraint, a level constraint, an application constraint, or other constraint, or the information may be signaled as supplemental information or signaled by other out-of-bound means.
- one set of entropy-slice-location parameter values may be used for all entropy slices within a bitstream.
- entropy-slice-location parameter values may be defined for a group of pixels represented by a portion of a sequence.
- entropy-slice-location parameter values may be defined for each picture within a bitstream and may be used for all entropy slices within the associated picture.
- entropy-slice-location parameter values may be defined for each reconstruction slice within a bitstream and may be used for all entropy slices within the associated reconstruction slice.
- multiple sets of entropy-slice-location parameter values may be used by the decoder.
- entropy-slice-location parameter values may be assigned to entropy-slice identifiers, for example, a first entropy-slice header may use a first set of entropy-slice-location parameter values, a second entropy-slice header may use a second set of entropy-slice-location parameter values and, in general, an Nth entropy-slice header may use an Nth set of entropy-slice-location parameter values.
- entropy-slice-parameter values may be assigned to frame identifiers.
- a first picture may use a first set of entropy-slice-parameter values
- a second picture may use a second set of entropy-slice-parameter values and, in general, an Nth picture may use an Nth set of entropy-slice-location parameter values.
- a picture of a first type may use a first set of entropy-slice-location parameter values and a picture of a second type may use a second set of entropy-slice-location parameter values.
- Exemplary types of pictures are intra pictures, predicted pictures and other types of pictures.
- an entropy-slice offset and an entropy-slice range may be signaled in a sequence parameter set Raw Byte Sequence Payload (RBSP) by adding an "entropy_slice_offset” parameter and an "entropy_slice_range” to the sequence parameter set.
- RBSP Raw Byte Sequence Payload
- an entropy-slice offset and an entropy-slice range may be signaled in a picture parameter set Raw Byte Sequence Payload (RBSP) by adding an "entropy_slice_offset" parameter and an "entropy_slice_range” to the picture parameter set.
- RBSP Raw Byte Sequence Payload
- an entropy-slice offset and an entropy-slice range may be signaled in a slice header by adding an "entropy_slice_offset" parameter and an "entropy_slice_range” to the slice header.
- Table 5 lists exemplary slice header syntax according to embodiments of the present invention.
- an entropy-slice offset and an entropy-slice range may be indicated for each level conformance point of the encoder according to a table, for example, as shown in Table 6, where
- Table 3 Exemplary Sequence Parameter Set RBSP Syntax Table
- Table 4 Exemplary Picture Parameter Set RBSP Syntax Table
- entropy-slice-location information may comprise information that may constrain the locations of the entropy-slice headers.
- entropy-slice-location information may comprise an offset, also referred to as a period or base offset, value and a range, also referred to as a deviation or offset for a period, value.
- An entropy-slice-header location may be constrained based on the offset value and the range value.
- an offset value and a range value may be defined explicitly.
- an offset value and a range value may be implicitly defined as a minimum offset value and a maximum offset value.
- an offset value and a range value may be implicitly defined as a maximum offset value and the difference between the maximum offset value and a minimum offset value.
- an offset value and a range value may be implicitly defined as a minimum offset value and the difference between the minimum offset value and a maximum offset value.
- an offset value and a range value may be implicitly defined as a third value and the difference between the third value and a maximum offset value and a minimum offset value.
- an offset value and a range value may be defined through an index into a look-up table that contains the corresponding minimum and maximum bit-values.
- an offset value and a range value may be defined using an offset based look-up tree.
- an offset value and a range value may be defined using cost-minimizing indexing.
- signaling a range value may be optional.
- the range value when a range value is not signaled, then the range value may be set to a pre-defined value.
- the pre-defined value may be zero.
- the pre-defined value may be a non-zero integer value.
- bits may be measured may be referred to as the reference location.
- a reference location may not be associated with a particular reconstruction slice and may be the same fixed location within a bitstream for all entropy slices.
- the entropy-slice header may be byte aligned, and the constraint may be associated with a number of bytes. While the example illustrated in relation to Figure 29 is described in terms of bits, a person having ordinary skill in the art may appreciate the alternative byte-aligned embodiments.
- Figure 29 is a pictorial representation of an exemplary portion 1000 of an exemplary bitstream.
- the bitstream portion 1000 comprises a reconstruction-slice header 1002, represented by a solid black rectangle, four entropy-slice headers (the entropy-slice header corresponding to the zeroth entropy slice 1003, referred to as the zeroth entropy-slice header, the entropy-slice header corresponding to the first entropy slice 1004, referred to as the first entropy-slice header, the entropy-slice header corresponding to the second entropy slice 1005, referred to as the second entropy-slice header, the entropy-slice header corresponding to the third entropy slice 1006, referred to as the third entropy-slice header), represented by solid gray rectangles, and remaining portions of the entropy slices, represented by thin, black-and-white stripes.
- the reference location may be the start 1001 of the reconstruction-slice header 1002.
- the entropy-slice header corresponding to the zeroth entropy slice 1003 may be constrained to be located immediately after the reconstruction-slice header 1002.
- the entropy-slice header corresponding to the zeroth entropy slice may be a part of the reconstruction-slice header. That is to say, the reconstruction-slice header can also serve as the entropy-slice header corresponding to the zeroth entropy slice.
- the reconstruction-slice header may comprise a reconstruction portion and an entropy portion.
- the first entropy-slice header 1004 may be constrained to be located after
- the second entropy-slice header 1005 may be constrained to be located after
- the second entropy-slice header 1006 may be constrained to be located after
- the entropy-slice-location information may not comprise a range parameter.
- an entropy decoder may begin searching for the Nth entropy-slice header after
- the entropy-slice header may further be constrained to be within a
- bits may be measured may be referred to as the reference location.
- a reference location may not be associated with a particular reconstruction slice and may be the same fixed location within a bitstream for all entropy slices.
- the entropy-slice header may be byte aligned, and the constraint may be associated with a number of bytes. While the example illustrated in relation to Figure 30 is described in terms of bits, a person having ordinary skill in the art may appreciate the alternative byte-aligned embodiments.
- Figure 30 is a pictorial representation of an exemplary portion 1020 of an exemplary bitstream.
- the bitstream portion 1020 comprises a reconstruction-slice header 1022, represented by a solid black rectangle, four entropy-slice headers (the entropy-slice header corresponding to the zeroth entropy slice 1023, referred to as the zeroth entropy-slice header, the entropy-slice header corresponding to the first entropy slice 1024, referred to as the first entropy-slice header, the entropy-slice header corresponding to the second entropy slice 1025, referred to as the second entropy-slice header, the entropy-slice header corresponding to the third entropy slice 1026, referred to as the third entropy-slice header), represented by solid gray rectangles, and remaining portions of the entropy slices, represented by thin, black-and-white stripes.
- the reference location may be the start 1021 of the reconstruction-slice header 1022.
- the entropy-slice header corresponding to the zeroth entropy slice 1023 may be constrained to be located immediately after the reconstruction-slice header 1022.
- the entropy-slice header corresponding to the zeroth entropy slice may be a part of the reconstruction-slice header.
- the reconstruction-slice header may comprise a reconstruction portion and an entropy portion.
- the first entropy-slice header 1024 may be constrained to be located within
- the second entropy-slice header 1025 may be constrained to be located within
- the second entropy-slice header 1026 may be constrained to be located within
- bits from the reference location may terminate the search after identifying the entropy-slice header or after searching
- an entropy decoder may receive 1050 an entropy-slice number indicating the number of the entropy slice in the current reconstruction block to entropy decode.
- the entropy decoder may determine 1052 the entropy-slice-location information.
- the entropy-slice-location information also referred to as entropy-slice-location parameters, may be signaled in the bitstream, and the decoder may determine 1052 the entropy-slice information by examining the bitstream.
- the entropy-slice-location information may not be signaled in the bitstream, but may be determined 1052, by the decoder, from entropy-slice parameters, for example, a fixed number of bins allowed in any given entropy slice, a fixed number of bits allowed in any given entropy slice and other entropy-slice parameters.
- the entropy-slice-location information may be defined and determined 1052 by other normative means, for example, the information may be specified in a profile constraint, a level constraint, an application constraint, or other constraint, or the information may be signaled as supplemental information or signaled by other out-of-bound means.
- the entropy decoder may calculate 1054 an entropy-slice-search start location at before which, in the bitstream, the entropy-slice header is restricted from having been written by the encoder.
- the entropy-slice-search start location may be calculated 1054 using an offset value and a range value determined from the entropy-slice-location information.
- the entropy-slice-search start location may be calculated 1054 using an offset value determined from the entropy-slice-location information.
- the entropy decoder may advance 1056, in the bitstream, to the entropy-slice-search start location, and may examine 1058 the bitstream for an entropy-slice header.
- an entropy-slice header may be indicated by a start code.
- an entropy decoder may receive 1070 an entropy-slice number indicating the number of the entropy slice in the current reconstruction block to entropy decode.
- the entropy decoder may determine 1072 the entropy-slice-location information.
- the entropy-slice-location information also referred to as entropy-slice-location parameters, may be signaled in the bitstream, and the decoder may determine 1072 the entropy-slice information by examining the bitstream.
- the entropy-slice-location information may not be signaled in the bitstream, but may be determined 1072, by the decoder, from entropy-slice parameters, for example, a fixed number of bins allowed in any given entropy slice, a fixed number of bits allowed in any given entropy slice and other entropy-slice parameters.
- the entropy-slice-location information may be defined and determined 1072 by other normative means, for example, the information may be specified in a profile constraint, a level constraint, an application constraint, or other constraint, or the information may be signaled as supplemental information or signaled by other out-of-bound means.
- the entropy decoder may calculate 1074 an entropy-slice-search start location before which, in the bitstream, the entropy-slice header is restricted from having been written by the encoder.
- the entropy-slice-search start location may be calculated 1074 using an offset value and a range value determined from the entropy-slice-location information.
- the entropy-slice-search start location may be calculated 1074 using an offset value determined from the entropy-slice-location information.
- the entropy decoder may advance 1076, in the bitstream, to the entropy-slice-search start location and may examine 1078 the bitstream for an entropy-slice header.
- an entropy-slice header may be indicated by a start code.
- the bits, in the bitstream, may be examined 1078 in sequence starting at the entropy-slice-search start location. If 1080 an entropy-slice header is identified 1081, then the entropy decoder may entropy decode 1082 the entropy slice associated with the identified entropy-slice header. If 1080 an entropy-slice header is not identified 1083, then the entropy decoder may terminate 1084 the search. In some embodiments, the entropy decoder may indicate an error when no entropy-slice header is identified 1083.
- an entropy decoder may receive 1100 an entropy-slice number indicating the number of the entropy slice, in the current reconstruction, block to entropy decode.
- the entropy decoder may determine 1102 the entropy-slice-location information.
- the entropy-slice-location information also referred to as entropy-slice-location parameters, may be signaled in the bitstream, and the decoder may determine 1102 the entropy-slice information by examining the bitstream.
- the entropy-slice-location information may not be signaled in the bitstream, but may be determined 1102, by the decoder, from entropy-slice parameters, for example, a fixed number of bins allowed in any given entropy slice, a fixed number of bits allowed in any given entropy slice and other entropy-slice parameters.
- the entropy-slice-location information may be defined and determined 1102 by other normative means, for example, the information may be specified in a profile constraint, a level constraint, an application constraint, or other constraint, or the information may be signaled as supplemental information or signaled by other out-of-bound means.
- the entropy decoder may calculate 1104 an entropy-slice-search start location before which, in the bitstream, the entropy-slice header is restricted from having been written by the encoder.
- the entropy-slice-search start location may be calculated 1104 using an offset value and a range value determined from the entropy-slice-location information.
- the entropy-slice-search start location may be calculated 1104 using an offset value determined from the entropy-slice-location information.
- the entropy decoder may advance 1106, in the bitstream, to the entropy-slice-search start location and may examine 1108 the bitstream for an entropy-slice header.
- an entropy-slice header may be indicated by a start code.
- the bits, in the bitstream, may be examined 1108 in sequence starting at the entropy-slice-search start location. If 1110 an entropy-slice header is identified 1111, then the entropy decoder may entropy decoder 1112 the entropy slice associated with the identified entropy-slice header. If 1110 an entropy-slice header is not identified 1113, then if 1114 a search criterion is satisfied 1115, the entropy decoder may terminate 1116.
- the search criterion may provide a standard by which a determination may be made as to whether, or not, valid locations for the start of entropy-slice header remain to be searched.
- a search criterion may be satisfied if valid locations remain to be examined. In alternative embodiments, a search criterion may be satisfied if there are no valid locations remaining to be examined 1115, and the search may terminate 1116. In some embodiments, the entropy decoder may indicate an error when no entropy-slice header is identified 1115. If 1114 the search criterion is not satisfied 1117, the examination 1108 of the bitstream may continue after advancing 1118, in the bitstream to the next search location.
- the search criterion may be related to a range value, for example, the location of the start of an entropy-slice header may be restricted to a range of
- the location of the start of the entropy-slice header associated with entropy slice is the entropy slice number within a reconstruction slice. In these embodiments, the location of the start of the entropy-slice header associated with entropy slice
- the search criterion may be related to a restriction, or restrictions, on the size of an entropy slice. In some embodiments, the search criterion may be related to a combination of restrictions.
- an encoder may pad an entropy slice in order to meet a restriction on the location of the next entropy-slice header.
- an encoder may terminate an entropy slice prior to other entropy-slice size restrictions being met in order to meet a restriction on the location of the next entropy-slice header.
- an encoder may pad the last entropy slice within the reconstruction slice to satisfy the constraint on the location of the next entropy-slice header.
- an entropy-slice header may comprise a last-entropy-slice flag, wherein the value of the last-entropy-slice flag may indicate whether or not the entropy slice associated with the entropy-slice header is the last entropy slice in a reconstruction slice.
- a last-entropy-slice flag value of zero may be associated with the last entropy slice.
- a last-entropy-slice flag value of one may be associated with the last entropy slice.
- the subsequent entropy-slice header may be located immediately following the current entropy slice without padding.
- Table 7 shows exemplary syntax and semantics for signaling a last-entropy-slice flag, referred to as a "next_entropy_slice_flag. "
- the "next_entropy_slice_flag” flag signals if there are additional entropy slices for a current reconstruction slice. If the "next_entropy_slice_flag" flag indicates that there are no additional entropy slices for the current reconstruction slice, then the location of the next entropy-slice header in the bitstream may not be constrained by the entropy-slice-location parameters.
- the location of entropy-slice headers may be organized in a tree format with the root node pointing to an entropy-slice header location.
- the entropy-slice header location pointed to by the root node may be relative.
- the entropy-slice header location pointed to by the root node may be absolute.
- the remaining nodes of the tree may contain offset distances with respect to their parent node.
- the tree may be designed according to a design constraint, for example, to reduce an average time for determining entropy-slice header location, to bound a worst-case time required for determining entropy-slice header location, to signal a preferred order of entropy slice decoding, to minimize a storage cost for the tree and other design constraints.
- the number of children of each node in the tree may be controlled based on a desired level of parallelism in entropy-slice header location determination.
- Table 7 Exemplary Syntax Table for Last-Entropy-Slice Flag
- the context models may be reset within an entropy slice whenever a context-model-reset condition is met.
- the values to which the context models may be reset may be based on the context model of a neighboring elementary unit within the entropy slice, and if the neighboring elementary unit is not within the entropy slice, then default values may be used.
- the context models may be reset to default values.
- the context models may be reset based on a context model whose identifier may be signaled within the bitstream, the identifier indicating one of a plurality of predefined context models.
- a predefined context model may depend on one, or more, parameters in the bitstream.
- the context models may be reset based on a signaled "cabac_init_idc" value, within the bitstream, indicating one of a plurality of predefined context models.
- a context table may be used to initialize a plurality of context models, wherein a context table refers to a set of context models.
- the set of context models in a context table may undergo adaptation based on one, or more, parameters in the bitstream, for example, a quantization parameter, a slice type parameter or other parameter.
- the context models may be reset, within an entropy slice, when a current macroblock is the first macroblock in a row, in addition to being reset at the starting macroblock in an entropy slice.
- Figure 34 depicts an exemplary reconstruction slice 1200 containing 48 macroblocks 1208-1255 partitioned into three entropy slices: entropy slice "0" (shown in cross-hatch) 1202, entropy slice "1” (shown in white) 1204 and entropy slice “2" (shown in dot-hatch) 1206.
- Entropy slice "0" 1202 contains 15 macroblocks 1208-1222.
- Entropy slice "1" 1204 contains 17 macroblocks 1223-1239, and entropy slice “2" 1206 contains 16 macroblocks 1240-1255.
- the macroblocks at which the context models may be reset are indicated with a thick black edge 1260-1266 and are those macroblocks 1208, 1223, 1240 at the start of each entropy slice and the first macroblock in each row 1216, 1224, 1232, 1240, 1248.
- the elementary unit, for example, the macroblock, at the start of an entropy slice may be referred to as the slice-start elementary unit.
- the respective slice-start elementary units are 1208, 1223 and 1240.
- An elementary unit that is the first elementary unit in a row in an entropy slice may be referred to as a row-start elementary unit, for example, macroblocks 1208, 1216, 1224, 1232, 1240 and 1248 in Figure 34.
- the context models may be reset based on the context models of a neighboring macroblock if the neighboring macroblock is within the entropy slice and default values if the neighboring macroblock is not within the entropy slice.
- the context models may be reset based on the context models of the macroblock above the current macroblock if the macroblock above the current macroblock is in the same entropy slice, but set to default values if the macroblock above the current macroblock is not in the same entropy slice.
- the context models may be reset, within an entropy slice, when a current elementary unit is the first elementary unit in a row.
- the context-model-reset condition may be based on other criteria, for example, the number of bins processed within the entropy slice, the number of bits processed within the slice, the spatial location of the current elementary unit and other criterion.
- a context-model-reset flag may be used to indicate whether or not the context models may be reset within an entropy slice whenever a context-model-reset condition is met.
- the context-model-reset flag may be in the entropy-slice header.
- the context-model-reset flag may be in the reconstruction-slice header.
- the context-model-reset flag may be a binary flag, and the context-model-reset condition may be a default condition.
- the context-model-reset flag may by a multi-valued flag further indicating the context-model-reset condition.
- an "lcu_row_cabac_init_flag" flag may signal if entropy decoding may be initialized at the start of the largest coding unit (LCU) row.
- LCU coding unit
- an LCU is a generalization of the macroblock concept used in H.264 to high efficiency video coding (HEVC), and a picture is divided into slices, wherein a slice is made up of a sequence of LCUs.
- HEVC high efficiency video coding
- an LCU is the largest block of pixel value locations that may be represented with a single, transmitted mode value.
- an LCU is the largest block of pixel value locations that may be represented with a single, transmitted prediction mode value.
- an "lcu_row_cabac_init_flag" flag value of "1" may signal that the entropy coding context is reset.
- An entropy coding context may represent the set of all context models associated with an entropy coder.
- an "lcu_row_cabac_init_flag" flag value of "1" may signal that the entropy coding context is reset and the adaptive scanning is reset.
- Adaptive scanning may refer to a process in which a codec adapts a scan ordering of transform coefficients based on previously transmitted transform coefficient values.
- the adaptive scanning may be reset at the start of every LCU row by choosing a pre-defined scanning order.
- the scan ordering is determined by generating a coefficient significance map, and the transform coefficient values corresponding to coefficient significance values larger than a pre-determined value may be transmitted prior to the transform coefficient values corresponding to coefficient significance values less than or equal to the pre-determined value.
- the coefficient significance values that correspond to transform coefficient values that are greater than a pre-determined value may subsequently be increased.
- the coefficient significance values that correspond to transform coefficient values that are less than or equal to a pre-determined value may subsequently be decreased.
- the adaptive scanning process may be reset by setting the coefficient significant map to a pre-defined value.
- the default value, assumed when the flag is not sent, for the "lcu_row_cabac_init_flag" flag may be "0.
- An "lcu_row_cabac_init_idc_flag” flag may signal if cabac_init_idc values will be transmitted at the start of each LCU row.
- the default value, assumed when the flag is not sent, for the "lcu_row_cabac_init_idc_flag" flag may be "0. "
- a "cabac_init_idc_present_flag” flag may signal if a cabac_init_idc value is transmitted for the LCU.
- the entropy coding context is reset using the preceding value for cabac_init_idc in the bit-stream.
- "lcu_row_cabac_init_flag” and “lcu_row_cabac_init_idc_flag” may be signaled in a regular slice header, for example, when the value of "entropy_slice_flag” is "0".
- Table 8 and Table 9 show exemplary syntax for these embodiments.
- "lcu_row_cabac_init_flag” and “lcu_row_cabac_init_idc_flag” may be signaled in a entropy-slice header, for example, when the value of "entropy_slice_flag" is "1".
- Table 8 shows exemplary slice header syntax
- Table 9 shows exemplary slice data syntax (coding_unit).
- Table 8 Exemplary Syntax Table for Signaling the Initialization of Entropy Coding at the Start of the LCU Row
- Table 9 Exemplary Syntax Table for Signaling the Initial Context for the LCU
- an "mb_row_cabac_init_flag” flag may signal if entropy decoding may be initialized at the first macroblock in a row.
- an "mb_row_cabac_init_flag” flag value of "1” may signal that the entropy coding context is reset at the start of each macroblock row.
- an "mb_row_cabac_init_flag” flag value of "1” may signal that the entropy coding context is reset and the adaptive scanning is reset at the start of each macroblock row.
- the default value, assumed when the flag is not sent, for the "mb_row_cabac_init_flag” flag may be "0.
- An “mb_row_cabac_init_idc_flag” flag may signal if cabac_init_idc values will be transmitted at the start of each macroblock row.
- the default value, assumed when the flag is not sent, for the "mb_row_cabac_init_idc_flag” flag may be "0.
- a "cabac_init_idc_present_flag” flag may signal if a cabac_init_idc value is transmitted for the macroblock. In some embodiments, when a cabac_init_idc value is not transmitted for the macroblock, then the entropy coding context is reset using the preceding value for cabac_init_idc in the bit-stream. In some embodiments of the present invention, the "mb_row_cabac_init_flag" flag and the "mb_row_cabac_init_idc_flag” flag may be signaled in a regular slice header, for example, when the value of "entropy_slice_flag" is "0".
- the "mb_row_cabac_init_flag" flag and the "mb_row_cabac_init_idc_flag” flag may be signaled in a entropy-slice header, for example, when the value of "entropy_slice_flag" is "1".
- Table 10 and Table 11 show exemplary syntax for these embodiments. Table 10 shows exemplary slice header syntax, and Table 11 shows exemplary slice data syntax (coding_unit).
- Table 10 Exemplary Syntax Table for Signaling the Initialization of Entropy Coding at the Start of the Macroblock Row
- Table 11 Exemplary Syntax Table for Signaling the Initial Context for the Macroblock
- the locations, in a bitstream, of the entropy slices may be signaled in the bitstream.
- a flag may be used to signal that the locations, in the bitstream, of the entropy slices are going to be signaled in the bitstream.
- Some exemplary embodiments may comprise an "entropy_slice_locations_flag" that if "true” may indicate that the locations, in the bitstream, of the entropy-slice headers are going to be signaled in the bitstream.
- the location data may be differentially encoded.
- the location data may be sent in each reconstruction slice. In alternative embodiments, the location data may be sent once per picture.
- the locations, in a bitstream, of the LCU rows may be signaled in the bitstream.
- a flag may be used to signal that the location, in the bitstream, of the first LCU in each row is going to be signaled in the bitstream.
- Some exemplary embodiments may comprise an "lcu_row_location_flag" that if "true” may indicate that the location, in the bitstream, of the first LCU in each row is going to be signaled in the bitstream.
- the location data may be differentially encoded.
- the location data may be sent in each entropy slice. In alternative embodiments, the location data may be sent once per reconstruction slice.
- Table 12A-C shows exemplary syntax for signaling the locations, in the bitstream, of the LCU rows and the entropy slices.
- the semantics are:
- entropy_slice_locations_flag signals if entropy slice header location is transmitted. If the value of "entropy_slice_locations_flag” is set to "1", then the entropy slice header location is transmitted, otherwise it is not transmitted. The default value for the "entropy_slice_locations_flag" is "0".
- entropy_slice_offset [i] indicates the offset of the i th entropy slice from the previous entropy slice.
- “lcu” in Table 12A-C may be replaced by “macroblock”.
- “first_lcu_in_slice”, “lcu_row_cabac_init_flag”, “lcu_row_cabac_init_idc_flag”, “lcu_row_locations_flag”, “lcu_row_locations ()", “num_of_lcu_rows_minus1”, and “lcu_row_offset[i]” in Table 12A-C may be replaced by "first_mb_in_slice", “mb_row_cabac_init_flag", “mb_row_cabac_init_idc_flag", “mb_row_locations_flag", “mb_row_locations_flag", “mb_row_locations ()", “num_of_mb_rows_minus1", and “mb_row_offset[i]", respectively.
- Table 12A-C Exemplary Syntax Table for Signaling the Locations, in the Bitstream, of the First LCU in a Row
- the locations in a bitstream of entropy coder initialization may be signaled in the bitstream.
- a flag may be used to signal that the location, in the bitstream, of entropy coder initialization may be signaled in the bitstream.
- the entropy coder initialization defines a location in the bit-stream where an entropy coder is initialized to a predefined state at both the encoder and decoder.
- the entropy coder is initialized using an initialization process that results in any subsequent output from the entropy coder to be aligned with a byte boundary.
- the entropy coder is initialized using an initialization process that results in any subsequent output from the entropy coder to be aligned with a bit boundary.
- bit represents a single binary value in a bitstream
- byte represents a unit that is equal to a multiple of bits. For example, 8 bits typically are equivalent to a byte.
- Some exemplary embodiments may comprise an "entropy_locations_flag" that if "true" may indicate that the location, in the bitstream, of the entropy coder initialization is going to be signaled in the bitstream.
- the location data may be differentially encoded.
- the location data may be sent in each entropy slice.
- the location data may be sent once per reconstruction slice.
- the location data may be sent once per slice.
- Table 18A-B shows exemplary syntax for signaling the locations, in the bitstream, of the entropy coder initialization.
- the semantics are:
- "entropy_entry_point_flag” signals if entropy coder initialization locations are present in the bit-stream. If the value of "entropy_entry_point_flag" is set to "1", then entropy coder initialization locations are present in the bit-stream. In some embodiments, these entropy coder initialization locations correspond to the start of an entropy slice. In some embodiments, these entropy coder entropy coder initialization locations correspond to the start of a tile, which is a rectangular slice. In some embodiments, these entropy coder initialization locations correspond to the start of a LCU row. In some embodiments, these entropy coder initialization locations correspond to the start of a sub-stream, which is defined as a set of LCU rows. The default value for the "entropy_entry_point_flag" is "0".
- entropy_locations_offset [i] indicates the offset of the i th entropy coder initialization location from the previous entropy coder initialization location.
- "entropy_point_locations_flag” signals if entropy coder entry point location information is being transmitted or not. If the value of "entropy_point_locations_flag” is "1", then the entropy coder entry point location information is transmitted, otherwise it is not transmitted. The default value for "entropy_point_locations_flag" is "0".
- Table 18A-B Exemplary Syntax Table for Signaling the Locations, in the Bitstream
- Table 19A-B shows exemplary syntax for signaling the locations, in the bitstream, of the entropy coder initialization.
- the semantics are:
- entropy_entry_point_flag signals if entropy coder initialization locations are present in the bit-stream. If the value of "entropy_entry_ponit_flag" is set to "1", then entropy coder initialization locations are present in the bit-stream. In some embodiments, these entropy coder initialization locations correspond to the start of an entropy slice. In some embodiments, these entropy coder entropy coder initialization locations correspond to the start of a tile, which is a rectangular slice. In some embodiments, these entropy coder initialization locations correspond to the start of a LCU row. In some embodiments, these entropy coder initialization locations correspond to the start of a sub-stream, which is defined as a set of LCU rows. The default value for the "entropy_entry_point_flag" is "0".
- entropy_locations_offset [i] indicates the offset of the i th entropy coder initialization location from the previous entropy coder initialization location.
- entropy_point_locations_flag signals if entropy coder entry point location information is being transmitted or not. If the value of "entropy_point_locations_flag” is "1", then the entropy coder entry point location information is transmitted, otherwise it is not transmitted. The default value for "entropy_point_locations_flag” is "0".
- Table 19A-B Exemplary Syntax Table for Signaling the Locations, in the Bitstream
- entropy_locations_offset [i] is signaled according to the alignment of the first entropy coder initialization process for a set of values for the index i
- entropy_locations_offset [i] is signaled according to the alignment of the second entropy coder initialization process for a second set of values for the index i.
- entropy_locations_offset [i] may be signaled according to the alignment of the first entropy coder initialization process when it is an integer multiple of num_of_second_entropy_locat i ons_minus1+1.
- entropy_locations_offset [i] may be signaled according to the alignment of the first entropy coder initialization process when i+N is an integer multiple of num_of_second_entropy_locations_minus1+1, where N is defined in this embodiment and an integer value.
- entropy_slice_locations_offset[i] when entropy_slice_locations_offset[i] is signaled according to the alignment of the first entropy coder initialization process and entropy_slice_locations_offset[i+1] is signaled according to the alignment of the second entropy coder initialization process, the location identified by entropy_slice_locations_offset[i] is mapped from the alignment of the first entropy coder initialization process to the alignment of the second entropy coder initialization process before derivation of the entropy coder initialization location corresponding to entropy_slice_locations_offset[i+1].
- the byte aligned location is converted to a bit aligned location.
- the byte aligned location may be multiplied by the number of bits in a byte.
- the bit aligned location is converted to a byte aligned location.
- the bit aligned location may be divided by the number of bits in a byte. For this example, division may denote integer division. Alternatively, for this example, division may denote a right shift operation.
- the process may additionally include adding an offset following the division operation described above.
- the representation of entropy_locations_offset[i] may be depend on the entropy coder initialization process corresponding to the entropy coder initialization location entropy_locations_offset[i].
- bit-stream representation when the bit-stream representation is signaled as N bits (where N is an integer for this embodiment) for a first entropy coder initialization process that is byte aligned, a bit-stream representation of M bits (where M is an integer for this embodiment) may be used for the bit-stream representation for a second entropy coder initialization process.
- the ratio between M and N may be equal to the ratio of the alignment of the first initialization process and the second initialization process.
- the ratio between M and N may be the same as the ratio of the number of bits in a byte.
- the efficient transmission of residual data from an encoder to a decoder may be accomplished by signaling the location of zero-valued transform coefficients and the level values of the non-zero transform coefficients for an elementary unit, for example, a macroblock. Many coding systems may attempt to locate the zero-valued transform coefficients at the end of the residual data for the elementary unit, thereby allowing the use of an "end-of-block" code after the last significant transform coefficient to efficiently signal that the remaining transform coefficient values are zero.
- Some coding systems may track the locations of zero-valued transform coefficients in the residual data previously transmitted for a previously processed elementary unit, which may allow the locations with previous zero-valued transform coefficients to be transmitted last in subsequent residual data.
- some coding systems may track the locations of non-zero-valued transform coefficients in the residual data previously transmitted. While this may improve coding efficiency, it makes it necessary to completely decode previous residual data in order to decode current residual data due to the fact that the coding of residual data uses context models, also referred to as probability models, which are determined by a transform coefficient identifier that may only be determined with the knowledge of the locations that are identified to be transmitted at the end of the residual data.
- adaptive scanning in order to allow parallel coding of entropy slices, adaptive scanning may be reset to an entropy slice default scan order at the slice-start elementary unit of each entropy slice, thereby allowing separate entropy slices to be coded in parallel.
- a scan order of an adaptive scan calculation may be set to a known, also referred to as a row default, scan order at the row-start elementary unit of each LCU row within an entropy slice.
- the block transform-coefficient scanning order and the corresponding context model, also referred as context which may be fetched for coding a transform coefficient may be decoupled, thereby allowing parallel coding.
- a transform coefficient located at a first location in the bitstream may be associated, based on its location relative to the other transform coefficients in the bitstream, with a correspondingly located context in a context fetch order.
- a context fetch order which may be denoted
- the coding process may code
- the entropy-coding process may operate independently of the scanning order.
- Some encoder embodiments may be described in relation to Figure 35.
- An encoder may fetch 1280 the next transform coefficient to be encoded and may fetch 1282 the next context, from a predefined fetch list of contexts.
- the fetched transform coefficient may be entropy encoded 1284 using the fetched context, and a determination 1286 may be made as to whether or not there are significant transform coefficients remaining to encode. If there are 1287 significant transform coefficients remaining to be encoded, the next significant transform coefficient may be fetched 1280, and the process may continue. If there are not 1289, then the process may terminate 1290.
- Some decoder embodiments may be described in relation to Figure 36.
- a decoder may fetch 1300 the next context and entropy decode 1302 the next significant transform coefficient from the bitstream using the fetched context.
- the decoded transform coefficient may be stored 1304, and a determination 1306 may be made as to whether or not there are remaining significant transform coefficients to be decoded. If there are 1307, then the next context may be fetched 1300, and the process may continue. If there are not 1309, then the process may terminate 1310.
- a coefficient scanning order may be restricted to a subset of all possible scanning combinations and may be explicitly signaled.
- the scanning order may be set to a signaled scanning order.
- the scanning order may be signaled as a normative syntax.
- the scanning order may be signaled with a non-normative message, for example, an SEI message or other non-normative message.
- a coefficient scanning order may be restricted to a subset of all possible scanning combinations and may be explicitly signaled.
- the scanning order may be set to a signaled scanning order.
- the scanning order may be signaled as a normative syntax.
- the scanning order may be signaled with a non-normative message, for example, an SEI message or other non-normative message.
- the coefficient scanning order may be set to the scanning order of a previously decoded elementary unit.
- the scanning order may be set to the scanning order used in the elementary unit above.
- the scanning order may be set to the scanning order used in the elementary unit above and to the right.
- the coefficient scanning order may be set to the scanning order of a previously decoded elementary unit.
- the scanning order may be set to the scanning order used in the elementary unit above.
- the scanning order may be set to the scanning order used in the elementary unit above and to the right.
- a context initialization method for P-slices may be applied to forward-predicted B-slices, which may result in a higher compression efficiency due to the greater degrees of freedom afforded to B-slices and the multi-hypothesis nature of B-predictions.
- the reference slices used in a forward-predicted B-slice are always from temporally earlier frames/pictures as distinguished from a regular B-slice wherein a reference may be chosen from temporally future and/or past frames/pictures.
- a forward-predicted B-slice may comprise residual data with statistical characteristics differing from those of a regular B-slice. As illustrated in FIG.
- the technique may receive B-slices, P-slices, and I-slices and based upon the type of slice received, a context initialization technique is selected.
- a context initialization technique is selected.
- the context initialization technique for the P-slice is used. More specifically, the following steps are performed:
- a slice type may be decoded from bit steam
- an initial probability distribution used to initialize an entropy coder may be generated by training for forward-predicted B frames only.
- initialization of the context may be adapted based on the quantization parameter, which may be denoted
- an encoder may alternatively apply a context initialization method for P-slices to forward-predicted B-slices and may signal the occurrence of the alternation.
- the signaling may be explicit.
- the signaling may be implicit.
- a flag may be sent to the decoder whenever a P-slice is replaced with a forward-predicted B-slice.
- the flag may be signaled as a normative syntax.
- the flag may be signaled within a non-normative message, for example, an SEI message or other non-normative message.
- a context initialization method for P-slices may be applied to uni-predicted B-slices, which may result in a higher compression efficiency due to the greater degrees of freedom afforded to B-slices.
- the reference slices used in a uni-predicted B-slice are a portion of either temporally earlier frames/pictures or temporally later frames/pictures.
- a uni-predicted B-slice may comprise residual data with statistical characteristics different from those of a bi-directional B-slice.
- Temporally may refer to the display order of the decoded pictures / frames. As illustrated in FIG.
- the technique may receive B-slices, P-slices, and I-slices and based upon the type of slice received, a context initialization technique is selected.
- a context initialization technique is selected.
- the context initialization technique for the P-slice is used. More specifically, the following steps are performed:
- a slice type may be decoded from bit steam
- 4103 If the slice type is B-slice (Yes in 4102), then it is determined whether the slice is forward or backward predicted, but not both. If the slice is forward or backward predicted, but not both, then the context is initialized with a second initialization technique, otherwise the context is initialized with a first initialization technique;
- a forward predicted B-slice may be initialized in a manner different than a backward predicted B-slice and/or a bi-directional predicted B-slice, which, which may result in a higher compression efficiency due to the different degrees of freedom afforded to B-slices.
- the reference slices used in a forward predicted B-slice are a portion of temporally earlier frames/pictures.
- a forward predicted B-slice may comprise residual data with statistical characteristics different from those of a backward and/or bi-directional B-slice.
- Temporally may refer to the display order of the decoded pictures / frames. As illustrated in FIG.
- the technique may receive B-slices, P-slices, and I-slices and based upon the type of slice received, a context initialization technique is selected.
- a context initialization technique different from the B-slices, P-slices, and I-slices may be used. More specifically, the following steps are performed:
- a slice type may be decoded from bit steam
- 4203 If the slice type is B-slice (Yes in 4202), then it is determined whether or not the slice is forward predicted. If the slice is forward predicted, then the context is initialized with a fourth initialization technique, otherwise the context is initialized with a first initialization technique;
- the context initialization method may consist of setting values of an entropy coder that are necessary for operation of the entropy coder. For example, a first probability estimate may be set for an entropy coder that uses probability estimates for coding data, such as in an arithmetic coder.
- the context initialization method may use an initialization technique to determine the values. In one embodiment, a first initialization method corresponds to using a first table of precomputed values to set the values. Similarly, a second initialization method corresponds to using a second table of precomputed values to set the values.
- a first initialization method uses a first table of precomputed values that are designed for frames that use more than one prediction between frames to set the values, where the frame(s) used for prediction both temporally precede and proceed the current frame when ordered in display order.
- a second initialization method uses a second table of precomputed values that are designed from frames that use more than one prediction between frames to set the values, where the frames used for prediction temporally precede or temporally proceed, but do not both temporally precede and temporally proceed, the current frame when ordered in display order.
- a third initialization method uses a third table of precomputed values that are designed for frames that use at most one prediction between frames to set the values.
- a fourth initialization method uses a fourth table of precomputed values that are designed for frames that do not use prediction between frames to set the values.
- RefPicList0 contains a list of previously decoded frames that are displayed prior to display of the current frame followed by a list of previously decoded frames that are displayed subsequent to display of the current frame
- RefPicList1 contains a list of previously decoded frames that are displayed subsequent to the display of the current frame followed by a list of previously decoded frames that are displayed prior to display of the current frame.
- condition (2) above is true for a uni-directional B-slice since the number of previously decoded frames that is displayed subsequent to the display of the current frame is zero, or the number of decoded frames that are displayed prior to the display of the current frame is zero.
- PicOrderCnt denotes the display order of the decoded frames.
- condition (3) above is true for a uni-directional B-slice since the decoded frames are all displayed prior to the display of the current frame or subsequent to the display of the current frame.
- an occurrence of a context initialization method for P-slices applied to forward-predicted B-slice may be inferred at a decoder when the reference slices (frames/pictures) used in prediction are all past slices (frames/pictures) based on the order in which the slices are to be displayed.
- the occurrence of a P-slice replaced by a uni-directional B-slice may be inferred when the following conditions are true: (1) the reference picture list RefPicList1 has one or more entries, (2) the reference picture list RefPicList1 and RefPicList0 contain the same set of pictures, and (3) all frames in reference picture list RefPicList1 and RefPiList0 have PicOrderCnt less than the PicOrderCnt of the current frame, where PicOrderCnt indicates the display order of the frames in ascending order.
- the occurrence of a P-slice replaced by a uni-directional B-slice may be inferred when the following conditions are true: (1) the reference picture list RefPicList1 has one or more entries, (2) the reference picture list RefPicList1 and RefPicList0 contain the same set of pictures, and (3) all frames in reference picture list RefPicList1 and RefPiList0 have PicOrderCnt greater than the PicOrderCnt of the current frame, where PicOrderCnt indicates the display order of the frames in ascending order.
- the occurrence of a P-slice replaced by a uni-directional B-slice may be inferred when the following conditions are true: (1) the reference picture list RefPicList1 has one or more entries, and (2) the first frame in the reference picture list RefPicList1 and the first frame in the RefPicList0 have PicOrderCnt less (or greater) than the PicOrderCnt of the current frame, where PicOrderCnt indicates the display order of the frames in ascending order.
- the occurrence of a P-slice replaced by a uni-directional B-slice may be inferred when the following conditions are true: (1) the reference picture list RefPicList1 has more than one entry, and (2) the frames [0,N] in the reference picture list RefPicList1 and the frames [0,N] in the RefPicList0 have PicOrderCnt less (or greater) than the PicOrderCnt of the current frame, where PicOrderCnt indicates the display order of the frames in ascending order.
- the occurrence of a P-slice replaced by a uni-directional B-slice may be inferred when the following conditions are true: (1) the reference picture list RefPicList1 has one or more entries, (2) the first frame in the reference picture list RefPicList1 is the same as the second frame in the reference picture list RefPicList0, (3) the second frame in the reference picture list RefPicList1 is the same as the first frame in the reference picture list RefPicList0, (4) the frames [0,N] in the reference picture list RefPicList1 and the frames [0,N] in the RefPicList0 have PicOrderCnt less (or greater) than the PicOrderCnt of the current frame, where PicOrderCnt indicates the display order of the frames in ascending order.
- the order in the RefPicList0 and RefPicList1 need not be identical to contain the same set of pictures.
- the reference picture list RefPicList1 has more than one entry and RefPicList1 is identical to the reference picture list RefPicLis0, then the first two entries RefPicList1[0] and RefPicList1[1] may be switched.
- N may refer to less than the total number of frames / pictures in the reference picture list.
- the PicOrderCnt may also refer to a relative display order in a decoder picture buffer.
- the context for an entropy slice may be initialized using a P-slice method.
- the context of a slice may be initialized using a P-slice method.
- Table 13 shows exemplary syntax for explicitly signaling that the initial context of a B-slice is to be initialized using a P-slice method.
- "cabac_init_P_flag” is a flag that indicates, for B-slice entropy encoder initialization, whether a B-slice method or a P-slice method should be chosen. In some embodiments, if the value of the "cabac_init_P_flag" flag is "0, " then a B-slice method is chosen for initialization, and if the value of the "cabac_init_P_flag” flag is "1, " then a P-slice method is chosen for initialization.
- Table 13 Exemplary Syntax Table Showing Explicit Signaling of B-slice Initialization Using a P-slice Method
- Table 17 Exemplary Syntax Table Showing Explicit Signaling of Initialization
- a forward predicted B-slice or a backwards predicted B-slice may be initialized in a manner different from a bi-directional predicted B-slice, and in a manner dependent on an initialization flag. This may result in higher compression efficiency due to the different degrees of freedom afforded to B-slices and P-slices.
- the reference slices used in a forward predicted B-slice are a portion of temporally earlier frames/pictures.
- a forward predicted B-slice may comprise residual data with statistical characteristics different from those of a backward and/or bi-directional B-slice. Temporally may refer to the display order of the decoded pictures/frames.
- the technique may receive B-slices, P-slices, I-slices, and an initialization flag. Based upon the type of slice received and the value of the initialization flag, an initialization technique is selected.
- the initialization flag is the cabac_init_idc flag in Table A.
- cabac_init_idc is a flag that indicates that an alternative initialization method is selected. When “cabac_init_idc” is set equal to a value of 0, then a default initialization method is selected. When “cabac_init_idc” is set equal to a value of 1, then an alternative initialization method is selected.
- cabac_init_idc is a set of binary flags that controls the selection of the initialization method. In this embodiment, one of the flags in this set is used to select between a default initialization method and an alternative initialization method.
- entropy_coding_mode_flag is a flag that indicates the entropy coder.
- entropy_coding_mode_flag is a flag that indicates if the initialization flag is transmitted in the bit-stream and entropy_coding_mode_flag does not indicate the entropy coder. It is anticipated that the entropy_coding_mode_flag may consist of a first flag that indicates the entropy coder and a second flag that indicates if the initialization flag is transmitted in the bit-stream.
- the entropy_coding_mode_flag When the entropy_coding_mode_flag consists of more than a first flag, the entropy_coding_mode_flag is true when the flags associated with the entropy_coding_mode_flag are all true.
- the entropy_coding_mode_flag may be true only for a first entropy coder.
- said first entropy coder may be the CABAC entropy coder.
- a forward predicted B-slice may be initialized in a manner different from a backwards predicted B-slice and/or a bi-directional predicted B-slice, and in a manner dependent on an initialization flag. This may result in higher compression efficiency due to the different degrees of freedom afforded to B-slices and P-slices.
- the reference slices used in a forward predicted B-slice are a portion of temporally earlier frames/pictures.
- a forward predicted B-slice may comprise residual data with statistical characteristics different from those of a backward and/or bi-directional B-slice. Temporally may refer to the display order of the decoded pictures/frames.
- the technique may receive B-slices, P-slices, I-slices and an initialization flag. Based upon the type of slice received and the value of the initialization flag, an initialization technique is selected.
- the initialization flag is the cabac_init_idc flag in Table 17.
- cabac_init_idc is a flag that indicates that an alternative initialization method is selected. When “cabac_init_idc” is set equal to a value of 0, then a default initialization method is selected. When “cabac_init_idc” is set equal to a value of 1, then an alternative initialization method is selected.
- cabac_init_idc is a set of binary flags that controls the selection of the initialization method. In this embodiment, one of the flags is used to select between a default initialization method and an alternative initialization method.
- entropy_coding_mode_flag is a flag that indicates the entropy coder.
- entropy_coding_mode_flag is a flag that indicates if the initialization flag is transmitted in the bit-stream and entropy_coding_mode_flag does not indicate the entropy coder. It is anticipated that the entropy_coding_mode_flag may consist of a first flag that indicates the entropy coder and a second flag that indicates if the initialization flag is transmitted in the bit-stream.
- the entropy_coding_mode_flag When the entropy_coding_mode_flag consists of more than a first flag, the entropy_coding_mode_flag is true when the flags associated with the entropy_coding_mode_flag are all true.
- the entropy_coding_mode_flag may be true only for a first entropy coder.
- said first entropy coder may be the CABAC entropy coder.
- an initialization method for P-slices may be applied to forward-predicted B-slices, and the initialization method may be dependent on an initialization flag. This may result in higher compression efficiency due to the different degrees of freedom afforded to B-slices and the multi-hypothesis nature of B-predictions.
- the reference slices used in a forward predicted B-slice are always from temporally earlier frames/pictures as distinguished from a regular B-slice wherein a reference may be chosen from temporally future and/or past frames/pictures.
- forward predicted B-slice may comprise residual data with statistical characteristics different from those of a backward and/or bi-directional B-slice.
- Temporally may refer to the display order of the decoded pictures/frames.
- the technique may receive B-slices, P-slices, I-slices and an initialization flag. Based upon the type of slice received and the value of the initialization flag, an initialization technique is selected.
- the initialization flag is the cabac_init_idc flag in Table 17.
- cabac_init_idc is a flag that indicates that an alternative initialization method is selected. When “cabac_init_idc” is set equal to a value of 0, then a default initialization method is selected. When “cabac_init_idc” is set equal to a value of 1, then an alternative initialization method is selected.
- cabac_init_idc is a set of binary flags that controls the selection of the initialization method. In this embodiment, one of the flags is used to select between a default initialization method and an alternative initialization method.
- entropy_coding_mode_flag is a flag that indicates the entropy coder.
- entropy_coding_mode_flag is a flag that indicates if the initialization flag is transmitted in the bit-stream and entropy_coding_mode_flag does not indicate the entropy coder. It is anticipated that the entropy_coding_mode_flag may consist of a first flag that indicates the entropy coder and a second flag that indicates if the initialization flag is transmitted in the bit-stream.
- the entropy_coding_mode_flag When the entropy_coding_mode_flag consists of more than a first flag, the entropy_coding_mode_flag is true when the flags associated with the entropy_coding_mode_flag are all true.
- the entropy_coding_mode_flag may be true only for a first entropy coder.
- said first entropy coder may be the CABAC entropy coder.
- an initialization method for P-slices may be applied to B-slices and an initialization method for B-slices may be applied to P-slices, and the initialization method may be dependent on an initialization flag. This may result in higher compression efficiency due to the different degrees of freedom afforded by the initialization flag.
- the technique may receive B-slices, P-slices, I-slices and an initialization flag. Based upon the type of slice received and the value of the initialization flag, an initialization technique is selected.
- a first initialization method is used for P-slices and a second initialization method is used for B-slices.
- the first initialization method is used for B-slices and the second initialization method is used for P-slices.
- the initialization flag is the cabac_init_idc flag in Table 17.
- cabac_init_idc is a flag that indicates that an alternative initialization method is selected. When “cabac_init_idc” is set equal to a value of 0, then a default initialization method is selected. When “cabac_init_idc” is set equal to a value of 1, then an alternative initialization method is selected.
- cabac_init_idc is a set of binary flags that controls the selection of the initialization method. In this embodiment, one of the flags is used to select between a default initialization method and an alternative initialization method.
- entropy_coding_mode_flag is a flag that indicates the entropy coder.
- entropy_coding_mode_flag is a flag that indicates if the initialization flag is transmitted in the bit-stream and entropy_coding_mode_flag does not indicate the entropy coder. It is anticipated that the entropy_coding_mode_flag may consist of a first flag that indicates the entropy coder and a second flag that indicates if the initialization flag is transmitted in the bit-stream.
- the entropy_coding_mode_flag When the entropy_coding_mode_flag consists of more than a first flag, the entropy_coding_mode_flag is true when the flags associated with the entropy_coding_mode_flag are all true.
- the entropy_coding_mode_flag may be true only for a first entropy coder.
- said first entropy coder may be the CABAC entropy coder.
- context initialization states for an entropy slice may be based on the number of bins processed by an entropy coder.
- An entropy encoder may converge more quickly to the source statistics when initialized correctly. Faster convergence may result in fewer bits being wasted and thus higher compression efficiency.
- the number of bins that may be transmitted may be estimated, and when the estimated number of bins meets a first criterion, then a first initialization method may be used. When the estimated number of bins does not meet the first criterion, a second initialization method may be used.
- the number of bins processed may be estimated 1320.
- the estimated number of processed bins denoted Nbins
- Tbins a threshold value
- the predictive accuracy of QP-based context initialization may decrease.
- a higher predictive accuracy for context initialization may lead to better compression efficiency.
- the estimated number of processed bins is 1324 greater than the threshold value, than a single context initialization value may be chosen 1326.
- the context may be initialized adaptively 1330 based on QP.
- the single context initialization value may be selected based on training and optimization of chosen metrics, for example, squared error, relative entropy and other distance metrics.
- An adaptive QP-based initialization may be a affine adaptation of the form
- the number of bins may be estimated based on the number of bins processed in the previous slice. In alternative embodiments, the number of bins may be estimated based on the number of bins process in the previous frame.
- multiple, disjoint ranges (three shown 1342, 1344, 1346) of number of bins processed may be determined and described in relation to a number of thresholds (two shown 1348, 1350), and the context initialization value may be selected based on within which of the ranges 1342, 1344, 1346 the estimated number of bins processed falls, for example, for three ranges 1342, 1344, 1346, when
- the context may be initialized adaptively based on QP, when
- the context may be initialized to a first fixed context value and when
- the context may be initialized to a second, different, fixed context value.
- the value of QP may be determined 1400 and examined 1402 in relation to a threshold value, denoted T QP .
- T QP a threshold value
- the context may be initialized adaptively 1406 based on QP.
- a single context initialization value may be chosen 1410. The single context initialization value may be selected based on training and optimization of chosen metrics, for example, squared error, relative entropy and other distance metrics.
- multiple, disjoint ranges of QP may be determined, and the context initialization value may be selected based on within which of the ranges the QP value falls.
- Table 14 shows a comparison of rate distortion performance for all-intra coding.
- the first comparison shown in the two sub-columns of column three, is a comparison, using the H.264/AVC Joint Model (JM) software, version 13.0, between encoding using multiple slices, wherein entropy decoding and macroblock reconstruction for a slice does not depend on other slices, and encoding using no slices.
- JM Joint Model
- the quality is degraded by -0.3380 dB encoding using multiple slices over using no slices.
- the bit rate is increased by 7% by encoding using multiple slices over using no slices.
- the second comparison is a comparison between encoding using one reconstruction slice partitioned, according to embodiments of the present invention, into multiple entropy slices (two rows of macroblocks per entropy slice) and encoding using JM 13.0 with no slices.
- the quality is degraded by -0.0860 dB using one reconstruction slice with multiple entropy slices over encoding using no slices.
- the bit rate is increased by 1.83% by encoding using one reconstruction slice with multiple entropy slices over encoding using no slices.
- Table 15 shows a comparison of rate distortion performance for IBBP coding.
- the first comparison shown in the two sub-columns of column three, is a comparison, using the H.264/AVC Joint Model (JM) software, version 13.0, between encoding using multiple slices, wherein entropy decoding and macroblock reconstruction for a slice does not depend on other slices, and encoding using no slices.
- JM Joint Model
- the quality is degraded by -0.5460 dB encoding using multiple slices.
- the bit rate is increased by 21.41% by encoding using multiple slices over using no slices.
- the second comparison is a comparison between encoding using one reconstruction slice partitioned, according to embodiments of the present invention, into multiple entropy slices (two rows of macroblocks per entropy slice) and encoding using JM 13.0 with no slices.
- the quality is degraded by -0.31 dB using one reconstruction slice with multiple entropy slices over encoding using no slices.
- the bit rate is increased by 11.45% by encoding using one reconstruction slice with multiple entropy slices over encoding using no slices.
- encoding using multiple entropy slices in one reconstruction slice provides a bit rate savings of 5.17% and 9.96% for all-intra and IBBP coding, respectively, over encoding using slices, wherein entropy decoding and macroblock reconstruction for a slice does not depend on other slices, although both allow for parallel decoding.
- Table 16 shows a comparison of rate distortion performance for all-intra and IBBP coding.
- the comparison is a comparison between encoding using no slices and encoding using one reconstruction slice partitioned into entropy slices, according to embodiments of the present invention, of maximum size 26k bins per entropy slice.
- the first comparison shown in the two sub-columns of column two, is a comparison using all-intra coding.
- the quality is degraded by -0.062 dB by encoding using a reconstruction slice with multiple entropy slices.
- the bit rate is increased by 1.86% by encoding using a reconstruction slice with multiple entropy slices.
- there is an average bit rate savings of approximately 0.64 % over that of fixed entropy slice sizes of two rows of macroblocks.
- the second comparison is a comparison using IBBP coding.
- the quality is degraded by -0.022 dB using one reconstruction slice with multiple entropy slices over encoding using no slices.
- the bit rate is increased by 0.787% by encoding using one reconstruction slice with multiple entropy slices over encoding using no slices.
- Table 16 Comparison of rate distortion performance - all-intra and IBBP encoding using entropy slices with less than 26k bins per entropy slice
- entropy slices allows for parallel decoding, and encoder partitioning of a reconstruction slice into entropy slices, wherein each entropy slice is less than a maximum number of bins may provide considerable bit rate savings over entropy slices of a fixed number of macroblocks.
- Some embodiments of the present invention may comprise a computer program product comprising a computer-readable storage medium having instructions stored thereon/in which may be used to program a computing system to perform any of the features and methods described herein.
- Exemplary computer-readable storage media may include, but are not limited to, flash memory devices, disk storage media, for example, floppy disks, optical disks, magneto-optical disks, Digital Versatile Discs (DVDs), Compact Discs (CDs), micro-drives and other disk storage media, Read-Only Memory (ROMs), Programmable Read-Only Memory (PROMs), Erasable Programmable Read-Only Memory (EPROMS), Electrically Erasable Programmable Read-Only Memory (EEPROMs), Random-Access Memory (RAMS), Video Random-Access Memory (VRAMs), Dynamic Random-Access Memory (DRAMs) and any type of media or device suitable for storing instructions and/or data.
- ROMs Read-Only Memory
- PROMs Programmable Read-Only Memory
- Some embodiments of the present invention comprise methods and systems for parallel entropy encoding. Some embodiments of the present invention comprise methods and systems for parallel entropy decoding.
- a scan pattern may be initialized at the start of an entropy slice.
- a scan pattern may be initialized at a starting elementary unit in a row in an entropy slice.
- a state associated with an adaptive scan calculation may be initialized at the start of an entropy slice.
- a state associated with an adaptive scan calculation may be initialized at a starting elementary unit in a row in an entropy slice.
- a coefficient scanning order may be decoupled from a context fetch order.
- a forward-predicted B-slice may be detected and a context associated with entropy coding the forward-predicted B-slice may be initialized according to a P-slice method.
- a context may be initialized based on bin count.
- a context may be initialized based on quantization parameter value.
- An aspect of the invention provides a method for decoding a video frame of a video sequence comprising:
- said identifying comprises only said backward predicted B-slice.
- said identifying is based upon: (1) a first list identifying reference pictures has at least one entry, (2) said first list and a second list identifying reference pictures contain the same set of said pictures, (3) all pictures in said first list and said second list are to be displayed prior to a current slice.
- said identifying is based upon: (1) a first list identifying reference pictures has at least one entry, (2) said first list and a second list identifying reference pictures contain the same set of picture, (3) all pictures in said first list and said second list are to be displayed after a current slice.
- said identifying is based upon: (1) a first list identifying reference pictures has at least one entry, (2) said first list and a second list identifying reference pictures contain a non-coextensive set of pictures, and said non-coextensive set of pictures are to be displayed prior to a current slice.
- said identifying is based upon: (1) a first list identifying reference pictures has at least one entry, (2) said first list and a second list identifying reference pictures contain a non-coextensive set of pictures, and said non-coextensive set of pictures are to be displayed after a current slice.
- said identifying is based upon: (1) a first list identifying reference pictures has at least one entry, (2) a first reference picture in said first list is the same as a second reference picture in a second list, (3) a first reference picture in said second list is the same as a second reference picture in said first list, (4) said first list and a second list identifying reference pictures contain a non-coextensive set of pictures, and said non-coextensive set of pictures are to be displayed prior to a current slice.
- Another aspect of the invention provides a method for decoding a video frame in a video sequence comprising:
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Abstract
Description
[Binarization]: A non-binary-valued symbol (for example, a transform coefficient, a motion vector, or other coding data) is converted into a binary code, also referred to as a bin string or a binarized symbol. When a binary-valued syntax element is given, the initial step of binarization may be bypassed. A binary-valued syntax element or an element of a binarized symbol may be referred to as a bin.
[Context Model Selection]: A context model is a probability model for one or more bins. The context model comprises, for each bin, the probability of the bin being a "1" or a "0. " The model may be chosen for a selection of available models depending on the statistics of recently coded data symbols, usually based on the left and above neighboring symbols, if available.
[Binary Arithmetic Coding]: An arithmetic coder encodes each bin according to the selected probability model and is based on recursive interval subdivision.
[Probability Update]: The selected context model is updated based on the actual coded value.
In some embodiments of the present invention comprising an H.264/AVC codec, an entropy slice may be signaled by adding a new bit, "entropy_slice_flag" to the existing slice header. Table 1 lists the syntax for an entropy slice header according to embodiments of the present invention, wherein C indicates Category and Descriptor u(1), ue(v) indicate some fixed length or variable length coding methods. Embodiments of the present invention comprising an "entropy_slice_flag" may realize improved coding efficiency.
Claims (17)
- A method for decoding a video frame of a video sequence comprising:
(a) receiving a slice header;
(b) identifying a slice type;
(c) receiving a first flag indicating a initialization method used to initialize a context; and
(d) initializing said context associated with said slice type using one of a first initialization method, second initialization method and third initialization method. - The method of claim 1 wherein said first initialization method is used in the case that said slice type indicates P-slice and a value of said first flag is false or in the case that said slice type indicates B-slice and a value of said first flag is true.
- The method of claim 1 wherein said second initialization method is used in case that said slice type indicates B-slice and a value of said first flag is false or in case that said slice type indicates P-slice and a value of said first flag is true.
- The method of claim 1 wherein said third initialization method is used in case that said slice type indicates I-slice.
- The method of claim4 wherein said first flag is not transmitted.
- The method of claim1, further comprising:
(a) receiving a picture parameter set;
(b) identifying a second flag; and
(c) determining a value of said first flag based on a value of said second flag. - The method of claim 6 wherein said first flag is determined to be false in the case that a value of said second flag is false.
- The method of claim 6 wherein said first flag is not received in the bit-stream in the case that said a value of said second flag is false.
- The method of claim 6 wherein said first initialization method is used in the case that said slice type indicates P-slice and a value of said first flag is false or in the case that said slice type indicates B-slice and a value of said first flag is true.
- The method of claim 6 wherein said second initialization method is used in case that said slice type indicates B-slice and a value of said first flag is false or in case that said slice type indicates P-slice and a value of said first flag is true.
- The method of claim 6 wherein said third initialization method is used in case that said slice type indicates I-slice.
- The method of claim 1, further comprising:
(a) receiving a region in a video decoder, said slice consists of one or more said region;
(b) receiving first information indicating whether at least two regions is transmitted within said slice; and
(c) receiving second information in the case that said slice contains at least two regions, said second information indicating at least a location of the second region and number of said at least one region minus one. - The method of claim 12 wherein said location of the second region indicates a distance between one of a plurality of regions being currently decoded and another one of the plurality of regions having been previously decoded.
- The method of claim 12 wherein said first information is identified by a flag.
- The method of claim 12 wherein said second information is provided in said slice header.
- The method of claim 12 wherein said at least one region indicates one of a tile and/or LCU row.
- A method for decoding a video frame of a video sequence comprising:
(a) receiving a slice header;
(b) identifying a type of a slice including at least first slice type and second slice type; and
(c) initializing context associated with said first slice type and said second slice type using one of a first initialization method and a second initialization method based upon said first slice type and second slice type.
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BR112014011334A2 (en) | 2017-05-02 |
EP2777280B1 (en) | 2019-03-20 |
EP2777280A4 (en) | 2015-12-16 |
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US20160212431A1 (en) | 2016-07-21 |
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US20200162740A1 (en) | 2020-05-21 |
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IN2014CN03605A (en) | 2015-10-16 |
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