KR0180165B1 - An adaptive decimation encoder - Google Patents
An adaptive decimation encoder Download PDFInfo
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- KR0180165B1 KR0180165B1 KR1019950021448A KR19950021448A KR0180165B1 KR 0180165 B1 KR0180165 B1 KR 0180165B1 KR 1019950021448 A KR1019950021448 A KR 1019950021448A KR 19950021448 A KR19950021448 A KR 19950021448A KR 0180165 B1 KR0180165 B1 KR 0180165B1
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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
- H04N19/117—Filters, e.g. for pre-processing or post-processing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—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
- H04N19/124—Quantisation
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- H—ELECTRICITY
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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
- H04N19/176—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 block, e.g. a macroblock
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- H—ELECTRICITY
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- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
- H04N19/86—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving reduction of coding artifacts, e.g. of blockiness
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Abstract
본 발명에 따른 적응 간축 부호기는 입력영상을 필터링하는 필터(21)와; 필터링된 영상입력에서 소정의 블럭을 추출하는 블럭 추출기(22); 상기 추출된 블럭을 서로 다른 간측율로 각각 간축하는 다운 샘플러(24-1~24-3); 상기 추출된 블럭의 분산치를 계산한 후 소정의 기준치와 비교하여 선택신호를 발생하는 분산 계산부(23); 상기 분산 계산부(23)의 출력에 따라 상기 다운 샘플러의 출력 중 하나를 선택하는 선택부(25); 및 상기 선택부(25)의 출력을 양자화하는 양자화기(26)로 구성되어 입력된 영상블럭의 분산특성에 따라 간축율을 달리 하므로써 압축요율을 향상시킬 수 있는 효과가 있다.The adaptive short coder according to the present invention includes: a filter 21 for filtering an input image; A block extractor 22 for extracting a predetermined block from the filtered image input; Down samplers 24-1 to 24-3 each shortening the extracted blocks at different interrogation rates; A dispersion calculator 23 for calculating a dispersion value of the extracted block and generating a selection signal by comparing with a predetermined reference value; A selection unit 25 for selecting one of the outputs of the down sampler according to the output of the dispersion calculation unit 23; And a quantizer 26 for quantizing the output of the selector 25, thereby improving the compression rate by varying the reduction ratio according to the dispersion characteristics of the input image block.
Description
제1도는 종래의 간축 부호기를 도시한 블럭도.1 is a block diagram showing a conventional short code encoder.
제2도는 본 발명에 따른 간축 부호기를 도시한 블럭도.2 is a block diagram showing a shortened encoder according to the present invention.
제3도의 (a) 내지 (c)는 본 발명에 따른 간축기의 동작을 설명하기 위하여 도시한 도면이다.(A) to (c) of FIG. 3 are diagrams for explaining the operation of the compactor according to the present invention.
* 도면의 주요부분에 대한 부호의 설명* Explanation of symbols for main parts of the drawings
11,21 : 필터 12 : 다운 샘플러11,21: Filter 12: Down Sampler
13,26 : 양자화기 22 : 블럭추출기13,26: quantizer 22: block extractor
23 : 분산계산부 24-1~24-3 : 다운 샘플러23: dispersion calculation unit 24-1 ~ 24-3: down sampler
25 : 선택부25: selection unit
본 발명은 영상신호를 간축(decimation 혹은 down sampling)하여 압축 부호화하는 영상압축기술에 관한 것으로, 특히 입력되는 영상의 분산특성에 따라 간축율을 다르게 하여 압축부호화하는 적응 간축부호기에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an image compression technique for compressing and encoding a video signal by deciding or down sampling. In particular, the present invention relates to an adaptive condensation encoder for compressing and encoding a different reduction ratio according to a dispersion characteristic of an input image.
일반적으로, 디지탈 영상부호화 기술로는 변환부호화(transformcoding)와, 벡터양자화(Vector quantization), 대역분할부호화(Subband coding), 예측부호화 및 엔트로피 부호화 등이 널리 알려져 있고, 국제표준화기구에 의해 정지영상 및 동영상의 부호화를 위한 표준을 제정하면서 상기 부호화 기술들을 연구하여 보다 개선된 부호기술을 얻기 위한 노력이 계속되고 있다.In general, digital image coding techniques include transform coding, vector quantization, subband coding, prediction coding, and entropy coding. Efforts have been made to study the coding techniques while obtaining a standard for encoding video, thereby obtaining an improved coding technique.
또한, 영상신호의 수학적 통계 특성을 이용하여 블럭 또는 매크로블럭 단위로 처리하는 기존의 부호화방법에서는 비트율이 낮아질수록 즉, 압축율이 높아질수록 블럭화 현상(blocking artifact), 반점현상(mosquito artifact) 및 경계의 흐름현상(blurring) 등의 문제가 심각해져 시각적으로 거슬리게 된다.In addition, in the conventional coding method which processes the block or macroblock unit by using the mathematical statistical characteristics of the image signal, the lower the bit rate, that is, the higher the compression rate, the more the blocking artifact, the mosquito artifact, and the boundary. Problems such as blurring become serious and visually annoying.
따라서, 고압축율을 필요로 하는 시스템에서 화질평가의 주체인 인간시각에 만족할 만한 영상을 재구성하기 위해서는, 사람이 무엇을 보고 어떻게 느끼는가를 연구하는 인간시각시스템(HVS)을 적극적으로 활용하여 영상신호를 부호화하는 것이 바람직하다. 특히, 국제 표준화인 MPEG4의 활동개시로 객체기반(Object-based) 부호화, 모델기반(Model-based)부호화, 분할기반(Segmenrarion-based) 부호화 그리고 프랙털 부호화 등과 같은 제2세대 부호화방식이 적극적으로 연구되고 있다.Therefore, in order to reconstruct an image that satisfies the human vision, which is the subject of image quality evaluation, in a system requiring high compression ratio, the human visual system (HVS), which studies what a person sees and feels, actively uses an image signal. It is preferable to encode. In particular, the second-generation coding schemes such as object-based coding, model-based coding, segmentation-based coding, and fractal coding are actively researched as the start of the international standard MPEG4. It is becoming.
한편, 블럭부호화기의 일종으로서, 종래의 간축 부호기는 블럭단위로 입력되는 영상 데이타를 소정의 간축율로 간축한 후, 양자화하여 압축부호화하는 부호기로서 제1도에 도시된 바와 같이 입력영상을 필터링하는 필터(11)와; 필터링된 영상 입력을 소정의 고정된 간축율로 간축하는 다운 샘플러(12; 간축기라고도 한다); 상기 간축된 영상데이타를 양자화하는 양자화기(13)로 구성되어 입력영상을 소정의 고정된 간측율로 간축한 후 양자화하여 압축된 영상을 출력하였다.On the other hand, as a type of block encoder, the conventional short coder is a coder that quantizes and compresses and encodes the image data input in units of blocks at a predetermined shrink rate, and filters the input image as shown in FIG. A filter 11; A down sampler 12 (also called a condenser) that condenses the filtered image input at a fixed fixed condensation rate; It consists of a quantizer 13 for quantizing the condensed image data, and condensed the input image at a fixed fixed rate, and then quantized to output a compressed image.
그런데 상기와 같이 고정된 간축율로 간축하는 종래의 간축 부호기에서는 입력되는 영상의 특성을 충분히 반영지 못하므로써 압축효율이 떨어지는 문제점이 있다.However, in the conventional contraction coder which contracts at a fixed contraction rate as described above, there is a problem in that the compression efficiency is lowered because it does not sufficiently reflect the characteristics of the input image.
이에 본 발명은 상기와 같은 문제점을 해소하기 위하여 안출된 것으로, 입력 영상블럭의 분산도에 따라 간축율을 압축부호화할 수 있는 적응 간축부호기를 제공하는데 그 목적이 있다.Accordingly, an object of the present invention is to provide an adaptive condensation encoder capable of compressively encoding a condensation rate according to a dispersion degree of an input image block.
상기와 같은 목적을 달성하기 위하여 본 발명의 장치는 필터링된 영상입력에서 소정의 블럭을 추출하는 블럭 추출기; 상기 추출된 블럭을 서로 다른 간축율로 각각 간축하는 다운 샘플러; 상기 추출된 블럭의 분산치를 계산한 후 소정의 기준치와 비교하여 선택신호를 발생하는 분산 계산부; 상기 분산 계산부의 출력에 따라 상기 다운 샘플러의 출력 중 하나를 선택하는 선택수단; 및 상기 선택수단의 출력을 양자화하는 양자화기로 구성된 것을 특징으로 한다.In order to achieve the above object, an apparatus of the present invention includes a block extractor for extracting a predetermined block from a filtered image input; A down sampler for narrowing the extracted blocks at different contraction rates; A variance calculator for generating a selection signal by calculating a variance of the extracted block and comparing it with a predetermined reference value; Selecting means for selecting one of the outputs of the down sampler according to the output of the dispersion calculator; And a quantizer for quantizing the output of the selection means.
즉, 본 발명은 입력 영상블럭의 분산도에 따라 간축율을 달리 하여 간축한 후 양자화하여 입력영상 데이타를 압축부호화하는 것으로서, 분산 계산부에서 계산된 분산치가 높으면 블럭내에 유효한 데이타가 골고루 분포되어 있기 때문에 간축율을 낮게 하여 가능한한 많은 데이타를 부호화하여 전송하고, 분산치가 낮으면 블럭내에 유효한 데이타가 별로 없기 때문에 간축율을 높게 하여 가능한한 적은 데이타를 부호화하므로써 압축율을 향상시키도록 한 것이다.That is, the present invention compresses and encodes the input image data by reducing and reducing the reduction ratio according to the dispersion degree of the input image block. If the variance calculated by the variance calculation unit is high, effective data is uniformly distributed in the block. Therefore, the reduction rate is reduced, so that as much data as possible is encoded and transmitted. If the variance value is low, since there is not much valid data in the block, the reduction rate is increased so that the compression rate is improved by encoding as little data as possible.
이와 같이 입력된 영상블럭의 분산특성에 따라 간축율을 달리 하므로써 압축효율을 향상시킬 수 있는 효과가 있다.Thus, the compression efficiency can be improved by varying the reduction ratio according to the dispersion characteristics of the input image block.
이하, 첨부된 도면을 참조하여 본 발명을 자세히 설명하기로 한다.Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.
본 발명에 따른 적응 간축 부호기는 제2도에 도시된 바와 같이 입력영상을 필터링하는 필터(21)와; 필터링된 영상입력에서 소정의 블럭을 추출하는 블럭 추출기(22); 상기 추출된 블럭을 서로 다른 간축율로 각각 간축하는 다운 샘플러(24-1~24-3); 상기 추출된 블럭의 분산치를 계산한 후 소정의 기준치와 비교하여 선택신호를 발생하는 분산 계산부(23); 상기 분산 계산부(23)의 출력에 따라 상기 다운 샘플러의 출력 중 하나를 선택하는 선택부(25); 및 상기 선택부(25)의 출력을 양자화하는 양자화기(26)로 구성되어 있다.The adaptive shortened encoder according to the present invention includes a filter 21 for filtering the input image as shown in FIG. 2; A block extractor 22 for extracting a predetermined block from the filtered image input; Down samplers 24-1 to 24-3 each shortening the extracted blocks at different reduction rates; A dispersion calculator 23 for calculating a dispersion value of the extracted block and generating a selection signal by comparing with a predetermined reference value; A selection unit 25 for selecting one of the outputs of the down sampler according to the output of the dispersion calculation unit 23; And a quantizer 26 for quantizing the output of the selector 25.
이어서, 상기와 같이 구성되는 본 발명의 작용 효과를 설명한다.Next, the effect of this invention comprised as mentioned above is demonstrated.
먼저, 본 발명은 입력 영상블럭의 분산도에 따라 간축율을 달리 하여 간축한 후 양자화하여 입력영상 데이타를 압축부호화하는 것으로서, 분산 계산부(23)에서 계산된 분산치가 높으면 블럭내에 유효한 데이타가 골고루 분포되어 있기 때문에 간축율을 낮게 하여 가능한한 많은 데이타를 부호화하여 전송하고, 분산치가 낮으면 블럭내에 유효한 데이타가 별로 없기 때문에 간축율을 높게 하여 가능한한 적을 데이타를 부호화하므로써 압축율을 향상시키도록 한 것이다.First of all, the present invention compresses and encodes input image data by reducing the reduction ratio according to the dispersion degree of the input image block and quantizing it. If the variance calculated by the dispersion calculator 23 is high, the effective data in the block is evenly distributed. Since it is distributed, it reduces the reduction ratio and encodes and transmits as much data as possible. When the distribution value is low, the compression ratio is increased by encoding as little data as possible to increase the compression ratio. .
이와 같이 분산 계산부(23)에서 계산된 분산값(σ)은 다음 식1에 따라 계산한다.In this way, the dispersion value σ calculated by the dispersion calculation unit 23 is calculated according to the following expression (1).
여기서은 NxN 화면 블럭의 픽셀들의 평균값이고,는 NxN 화면 블럭의 픽셀을 나타낸다. 또한, 본 발명에 따른 분산치 계산부(23)는 현재 화면 블럭의 분산값을 미리 설정된 기준치(threshold)와 비교하여 간축율을 선택하기 위한 선택신호를 발생한다.here Is the average of the pixels in the NxN screen block, Represents pixels of an NxN screen block. In addition, the dispersion value calculator 23 according to the present invention generates a selection signal for selecting a reduction ratio by comparing the dispersion value of the current screen block with a preset threshold.
본 발명의 블럭 추출기(22)는 필터링된 영상데이타에서 소정의 블럭을 형성하고, 제1 내지 제3 다운 샘플러(24-1~24-3)는 상기 블럭 추출기(22)의 출력을 입력받아 제3도의 (a) 내지 (c)에 도시된 바와 같이 각각 서로 다른 간축율로 간축한다.The block extractor 22 of the present invention forms a predetermined block from the filtered image data, and the first to third down samplers 24-1 to 24-3 receive an output of the block extractor 22, and receive a predetermined block. As shown in (a) to (c) of FIG. 3, each is shrunk at a different shrinkage rate.
즉, 제3도에 있어서, (a) 내지 (c)는 8 x 8 블럭의 영상데이타를 소정의 간축율로 간축하는 다운 샘플러의 동작을 설명하기 위하여 도시한 것으로, o는 입력된 픽셀 데이타중 선택되어 출력되는 데이타를 나타내고 x는 삭제되는 데이타를 나타낸다.That is, in FIG. 3, (a) to (c) are diagrams for explaining the operation of the down sampler which reduces 8 × 8 blocks of image data at a predetermined reduction ratio, and o denotes input pixel data. Represents data to be selected and output, and x represents data to be deleted.
제3도의 (a)는 간축율이 2:1인 경우로서 8x8 블럭에서 64개의 픽셀 데이타중 32개만 선택되어 데이타량이 1/2로 감소되는 것을 보여주고, (b)는 간축율이 4:1인 경우로서 8x8 블럭에서 64개의 픽셀 데이타중 16개만 선택되어 데이타량이 1/4로 감소되는 것을 보여주고, (c)는 간축율이 16:1인 경우로서 8x8 블럭에서 64개의 픽셀 데이타중 4개만 선택되어 데이타량이 1/16로 감소되는 것을 보여준다.(A) of FIG. 3 shows that the reduction ratio is 2: 1, and only 32 pieces of 64 pixel data are selected in an 8x8 block, and the data amount is reduced to 1/2, and (b) shows the reduction ratio is 4: 1. In this case, only 16 out of 64 pixel data are selected in 8x8 block, and the data amount is reduced to 1/4, and (c) shows that the reduction ratio is 16: 1, and only 4 out of 64 pixel data in 8x8 block are. The selection shows that the data amount is reduced to 1/16.
이와 같이 다운 샘플러에서 서로 다른 간축율로 간축된 영상 데이타 출력은 분산 계산부(23)의 선택신호에 따라 어느 하나가 선택되어 양자화기(26)에서 양자화되어 압축된 영상 데이타를 출력하게 된다.As described above, the image data output reduced at different reduction ratios by the down sampler is selected according to the selection signal of the dispersion calculator 23, and the quantizer 26 outputs the image data which is quantized and compressed.
예컨데, 제1 다운 샘플러(24-1)가 제3도의 (a)와 같이 2:1의 간축율로 다운샘플링하고, 제2 다운 샘플러(24-2)가 제3도의 (b)와 같이 4:1의 간축율로 다운 샘플링하며, 제3 다운 샘플러(24-3)가 제3도의 (c)와 같이 16:1 건축율로 다운 샘플링할 경우에 입력된 블럭의 분산치가 높아 선택부가 제3 다운 샘플러(24-3)의 출력을 선택한다면, 16:1로 간축된 영상을 양자화하여 출력한다.For example, the first down sampler 24-1 downsamples at a reduction ratio of 2: 1 as shown in FIG. 3A, and the second down sampler 24-2 uses 4 as shown in FIG. 3B. When the down-sampler is downsampled at a reduction ratio of 1: 1, and the third down sampler 24-3 downsamples at a 16: 1 construction ratio as shown in (c) of FIG. 3, the selected block has a high dispersion value. If the output of the down sampler 24-3 is selected, the image reduced to 16: 1 is quantized and output.
이상에서 살펴 본 바와같이 본 발명에 따른 적응 간축부호기는 입력된 블럭에 대해 계산된 분산치가 높으면 블럭내에 유효한 데이타가 골고루 분포되어 있기 때문에 간축율을 낮게 하여 가능한한 많은 데이타를 부호화하여 전송하고, 분산치가 낮으면 블럭내에 유효한 데이타가 별로 없기 때문에 간축율을 높게 하여 가능한한 적은 데이타를 부호화하므로써 압축율을 향상시키는 잇점이 있다.As described above, the adaptive condensation encoder according to the present invention encodes and transmits as much data as possible by reducing the condensation rate because the effective data is evenly distributed in the block if the variance calculated for the input block is high. If the value is low, since there is not much valid data in the block, there is an advantage in that the compression ratio is improved by encoding a small amount of data as much as possible by increasing the reduction ratio.
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