CN113079373A

CN113079373A - Video coding method based on HEVC-SCC

Info

Publication number: CN113079373A
Application number: CN202110358459.9A
Authority: CN
Inventors: 曹俊
Original assignee: Beijing Yunbo Ruijie Information Technology Co ltd
Current assignee: Beijing Yunbo Ruijie Information Technology Co ltd
Priority date: 2021-04-01
Filing date: 2021-04-01
Publication date: 2021-07-06

Abstract

The invention relates to the technical field of video coding, and discloses a video coding method based on HEVC-SCC, which comprises coding CU mode division, wherein the coding CU mode division comprises rough classification CU, secondary division, tertiary division and intra-frame coding, the rough classification CU can be basically divided into three types: and reading image video information from the smooth video CU, the natural video CU and the mixed video CU, classifying the video coding unit CU by calculating a smooth numerical value S, performing secondary division, performing further division on the CU with S not equal to 0, calculating DCT texture dispersion degree PS, and performing further division according to a PS dispersion degree numerical value. According to the video coding method based on HEVC-SCC, the PSNR and the delta T of the algorithm are designed to be compared, the designed algorithm is used for coding the screen recording video under the conditions of improving the CU partition rate and selectively skipping part of PU prediction models, and the time consumption of video coding can be reduced under the condition of effectively ensuring the coding quality.

Description

Video coding method based on HEVC-SCC

Technical Field

The invention relates to the technical field of video coding, in particular to a video coding method based on HEVC-SCC.

Background

With the continuous development of multimedia digital video application and the continuous improvement of the demand of people on video cloud computing, the data volume of an original video information source can not bear the bandwidth and the storage resource of the existing transmission network. Therefore, compression of video signals has become one of the hot spots for academic research and industrial application at home and abroad. In recent ten years, high-definition videos and ultra-high-definition videos are widely popularized, and the huge information amount of the high-definition videos brings rapidly increased data transmission pressure to a communication network and also causes adverse effects to the continuous development of the high-definition videos.

JCT-VC composed of VCEG and MPEG organizations formally collects the proposal (CFP) of the next generation video coding standard in 1 month 2010, and develops a new video coding standard on the basis of H.264, and the new video coding standard is called high efficiency video coding standard HEVC/H.265. Compared with the current standard H.264, HEVC/H.265 can reduce the coding bit rate by 50% on the premise of the same image quality, so that the method can better adapt to various different network environments.

The video coding process is mainly divided into four steps of prediction, transformation, quantization and entropy coding, wherein the prediction is mainly divided into intra-frame prediction and inter-frame prediction, as shown in fig. 1. The intra-frame prediction of video coding refers to that the current pixel block is predicted by using the pixel block coded by the current image by utilizing the correlation of a video spatial domain so as to achieve the aim of removing the video spatial domain redundancy.

To further improve intra prediction coding efficiency, h.265/HEVC employs more intra prediction modes and larger coding units than h.264. The coding structure of h.265 defines 3 blocks: a coding block CU, a prediction block PU and a transform block TU. HEVC uses a flexible quadtree partition structure to partition a current CU in a recursive manner, the partition depth of the CU is 4 depth levels, which are 0-3, and the partition size of the CU also changes from 64 × 64 to 8 × 8, as shown in fig. 2.

In the CU recursive partitioning process, a CU of one size needs to perform multiple iterative partitioning and rate distortion Cost (RD Cost) calculation to obtain the optimal partitioning depth of the current CU, so the intra-frame prediction encoding complexity is increased in the CU recursive partitioning process, and usually an area with flat image texture is encoded by using a large size to save transmission overhead; and the region with rich image texture is encoded in a small size to realize more accurate prediction.

The efficiency of intra prediction coding is further improved due to the flexible block division structure of h.265. In addition to the difference in block partition structure, h.265/HEVC provides 35 intra prediction modes compared to the h.264 standard with only 9 intra prediction modes, including 33 angular prediction modes and 2 special modes, namely Planar mode and DC mode, these 2 modes being commonly used for predicting smooth pixel blocks. For the current CU, in order to obtain the optimal prediction mode of the current CU, rate-distortion costs under 35 prediction modes need to be calculated respectively, and then a mode with the smallest rate-distortion cost is selected as the optimal prediction mode of the current CU. If the current block size is larger than 8 multiplied by 8, the current block size needs to be further divided into 4 sub-blocks, then the 4 sub-blocks are respectively predicted, finally, the sum of the rate-distortion costs of the 4 sub-blocks is compared with the rate-distortion cost of the large block, and a division structure corresponding to a smaller rate-distortion cost is selected as the optimal division. By analogy, the traversal of the whole division level is completed, and finally the optimal combination of the division structure and the prediction mode is obtained.

The 2016 International standards organization ITU-T moving Picture experts group and the ISO/IEC video coding experts group set forth the high efficiency video coding standard (HEVC) extension standard HEVC-SCC (Screen Content coding). Unlike traditional Camera-Captured Video (CCV), SCV is typically computer-generated content, such as text, computer graphics, graphical user interfaces, or a combination of Camera-Captured content and computer-generated content. Image blocks in screen content video are usually dominated by several primary colors, have few complex textures, have many or repeated patterns and text, are high in contrast, and have sharp edges. In consideration of these characteristics of screen content video, an HEVC-SCC Test Model (SCM) can reduce a code rate by 55% under the condition that the video quality is equivalent to that of HEVC, and in order to improve the coding performance of screen content video, the HEVC-SCC adds various coding tools, i.e., Intra Block Copy (IBC), Palette Mode (PLT). These new coding tools significantly improve coding efficiency, but also place a significant burden on the encoder. The general method of screen content coding is to determine whether to use a video screen content tool based on the traditional video coding for each video sequence or each image frame in each video sequence, and then select an optimal coding tool suitable for the image frame or suitable for the whole video sequence in the rate distortion decision.

The calculation complexity of intra-frame prediction mode selection in the whole video coding process is extremely high, obviously, the calculation complexity of a coding end is very high in the traversal calculation process, the coding time consumed by video compression is long, and the ever-increasing real-time video compression requirement cannot be met. Therefore, a large amount of operation complexity is introduced in the intra-frame prediction process of HEVC, and how to effectively reduce the operation amount of the encoder becomes a problem to be solved urgently at present.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a video coding method based on HEVC-SCC.

(II) technical scheme

In order to realize the purposes of adapting to various network environments, removing video spatial domain redundancy, further improving the efficiency of intra-frame prediction coding, more accurately predicting, further improving the efficiency of intra-frame prediction coding, effectively reducing the operation amount of a coder and reducing the time consumption of video coding under the condition of effectively ensuring the coding quality, the invention provides the following technical scheme: a video coding method based on HEVC-SCC comprises coding CU mode division, wherein the coding CU mode division comprises primary classification CU, secondary division, tertiary division and intra-frame coding.

The rough classification CU, the screen video coding CU can be basically classified into three categories: 1. and the smooth video CU 2, the natural video CU 3 and the mixed video CU read image video information and classify the video coding units CU by calculating a smooth numerical value S.

And the secondary division is used for further dividing the CU with S not equal to 0, calculating the DCT texture dispersity PS and further dividing the CU according to the PS dispersity value.

And for T1 < PS < T2, the three-time division is adopted to carry out edge detection by using a Roberts operator, and classification is carried out by using the approximate gradient of the difference between two adjacent pixels in the diagonal direction.

And the intra-frame coding skips IBC and PLT modes for a natural screen CU, enters a traditional intra-frame coding module, stops downward division for a completely smooth CU, selects the current depth as the optimal division depth, selects DC, Planar, vertical and horizontal modes for entering, enters IBC and PLT modes for a complex screen CU, and skips other intra-frame prediction models.

Preferably, the completely smoothed CU holds the stopping of the downward partition and selects DC, Planar, vertical, horizontal mode entry.

Preferably, the screen complex CU stands into IBC, PLT mode, skipping other intra prediction models.

Preferably, the IBC and PLT modes are skipped when the natural content CU is established, and the conventional intra coding mode is entered.

(III) advantageous effects

Compared with the prior art, the invention provides a video coding method based on HEVC-SCC, which has the following beneficial effects:

1. according to the invention, by designing the algorithm PSNR and comparing the two parameters of the time variation ratio delta T, the designed algorithm is used for coding the screen recording video under the conditions of increasing the CU partition rate and selectively skipping part of PU prediction models, and the time consumption of video coding can be reduced under the condition of effectively ensuring the coding quality.

2. The invention is suitable for various network environments, removes video airspace redundancy, further improves the intra-frame prediction coding efficiency, predicts more accurately, further improves the intra-frame prediction coding efficiency, effectively reduces the computation amount of a coder, reduces the time consumption of video coding under the condition of effectively ensuring the coding quality, reduces the computation complexity and reduces the problem of longer coding time consumed by video compression.

Drawings

FIG. 1 is a flow chart of the algorithm of the present invention;

fig. 2 is a diagram of the HEVC/h.265 video coding framework of the present invention;

fig. 3 is a block diagram of an HEVC quadtree structure according to the present invention;

FIG. 4 is a diagram of 35 intra prediction angles according to the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1-4, a method for video coding based on HEVC-SCC includes coding CU mode partitioning, which includes primary classification CU, secondary classification CU, tertiary classification CU, and intra-frame coding.

Definition of S:

S＝min[S_x,S_y]

and f (x, y) represents the pixel value with the (x, y) pixel point, and the value is 0-255. Sx and Sy represent the sum of differences of pixel points of the coding CU in the Y direction and the X direction. If Sx or Sy is 0, it indicates that the pixel values in the corresponding direction of the CU are equal, and the CU is the encoded video CU

Wherein D (x, y) is the DCT coefficient value with the position (x, y), and N is the CU side length. Setting thresholds T1 and T2, if PS is less than or equal to T1, the region can be considered to be a completely smooth CU, PS is greater than or equal to T2, DCT texture complexity is considered to be high, and the region is judged to be a natural screen CU.

The calculation formula is as follows:

wherein f (x, y) is the pixel value of the pixel point at the position (x, y), N is the side length of the coding CU, a threshold value T3 is set, SR is more than T3, the coding CU is judged to be a natural video CU, SR is less than or equal to T3, and the coding CU is judged to be a complex screen CU

The intra-coding is for a natural screen CU.

And if the natural content CU is established, skipping the IBC and PLT modes and entering a traditional intra-frame coding mode.

Skipping IBC and PLT modes, entering a traditional intra-frame coding module, stopping downward division for a completely smooth CU, selecting the current depth as the optimal division depth, and entering in DC, Planar, vertical and horizontal modes for a complex screen CU.

And enabling the screen complex CU to enter IBC and PLT modes, and skipping other intra-frame prediction models.

And entering IBC and PLT modes, and skipping other intra-frame prediction models.

When the video compression algorithm is used, three types of courseware teaching recorded videos, animation videos and shared desktop collaboration videos are compared to serve as experimental contents, the video compression software Hnew after the algorithm is designed is compared with HEVC-SCC, and the algorithm performance is achieved through PSNR (peak signal-to-noise ratio, a parameter for objectively evaluating video coding quality) and a time variation ratio delta T (delta T ═ T [ ((T ═ T [) ]_HM-T_new)/T_HMX 100%) are compared with one another,

while there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A video coding method based on HEVC-SCC comprises coding CU mode division, and is characterized in that: the coding CU mode division comprises primary classification CU, secondary division, tertiary division and intra-frame coding;

the rough classification CU, the screen video coding CU can be basically classified into three categories: 1. smoothing videos CU, 2, natural videos CU and 3, mixing the videos CU, reading image video information, and classifying video coding units CU by calculating a smoothing value S;

the secondary division is to further divide the CU with S not equal to 0, calculate the DCT texture dispersity PS and further distinguish the CU according to the PS dispersity value;

for the third division, for T1 < PS < T2, a Roberts operator is adopted for edge detection, and the difference approximate gradient between two adjacent pixels in the diagonal direction is used for classification;

2. The method of claim 1, wherein the video coding method based on HEVC-SCC is as follows: the full smoothing UC is established to stop dividing down and to select DC, Planar, vertical, horizontal mode entry.

3. The method of claim 1, wherein the video coding method based on HEVC-SCC is as follows: and enabling the screen complex CU to enter IBC and PLT modes, and skipping other intra-frame prediction models.

4. The method of claim 1, wherein the video coding method based on HEVC-SCC is as follows: and if the natural content CU is established, skipping IBC and PLT modes and entering a traditional intra-frame coding mode.