Coding of significance maps and transform coefficient blocks

• US 9,357,217 B2
• Filed: 11/17/2015
• Issued: 05/31/2016
• Est. Priority Date: 04/13/2010
• Status: Active Grant

• Current Assignee: GE Video Compression, LLC (General Electric Company)
• Original Assignee: GE Video Compression, LLC (General Electric Company)
• Inventors: Kirchhoffer, Heiner, Schwarz, Heiko, Nguyen, Tung, Marpe, Detlev, Wiegand, Thomas
• Primary Examiner(s): Patel, Jay
• Assistant Examiner(s): SUH, JOSEPH JINWOO
• Application Number:
  US14/944,012
• Publication Number:
  US 20160080742A1
• Time in Patent Office: 196 Days
• US Class Current: 1/1
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/129 Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Abstract

A higher coding efficiency for coding a significance map indicating positions of significant transform coefficients within a transform coefficient block is achieved by the scan order by which the sequentially extracted syntax elements indicating, for associated positions within the transform coefficient block, as to whether at the respective position a significant or insignificant transform coefficient is situated, are sequentially associated to the positions of the transform coefficient block, among the positions of the transform coefficient block depends on the positions of the significant transform coefficients indicated by previously associated syntax elements. Alternatively, the first-type elements may be context-adaptively entropy decoded using contexts which are individually selected for each of the syntax elements dependent on a number of significant transform coefficients in a neighborhood of the respective syntax element, indicated as being significant by any of the preceding syntax elements.

Claims

1. An apparatus for decoding a transform coefficient block, the apparatus comprising:

a decoder configured to extract, from a data stream, a significance map indicating positions of significant transform coefficients within the transform coefficient block, and the significant transform coefficients within the transform coefficient block; and

an associator configured to associate the extracted significant transform coefficients with their respective positions in the transform coefficient block in a coefficient scan order, wherein according to the coefficient scan order, a plurality of sub-blocks of the transform coefficient block are scanned in a sub-block scan order, wherein each sub-block includes more than one pixel, and the transform coefficients within each sub-block are scanned in a position sub-scan order, wherein the position sub-scan order is adaptively selected from a plurality of scan orders including a diagonal scan order,

wherein the decoder is configured to use, in extracting the significant transform coefficients, context-adaptive entropy decoding wherein, for each sub-block, a selected set of contexts from a plurality of sets of contexts is determined based on a statistic of the transform coefficients within a previously traversed sub-block of the transform coefficient block, or a statistic of the transform coefficients of a co-located sub-block in a previously decoded transform coefficient block.

2. The apparatus according to claim 1, wherein the selected set of contexts is selected from the plurality of sets of contexts, wherein the number of contexts of the plurality of sets of contexts is greater than one, and the decoder is configured to, in context-adapted entropy decoding the significant transform coefficients within a sub-block using the selected set of contexts for the respective sub-block, assign the selected set of contexts to the positions within the respective sub-block.

3. The apparatus according to claim 1, wherein the associator is configured such that the sub-block scan order leads zigzag-wise from a sub-block including a position of a lowest frequency in a vertical direction and a horizontal direction to a sub-block including a position of a highest frequency in both the vertical and horizontal directions, while the position sub-scan order leads, in each sub-block, zigzag-wise from a position within the respective sub-block, relating to a highest frequency in a vertical direction and a horizontal direction to a position of the respective sub-block relating to a lowest frequency in both the vertical and horizontal directions.

4. The apparatus according to claim 1, wherein the apparatus is at least a portion of a programmable logic device, programmable gate array, microprocessor, computer or hardware apparatus.

5. The apparatus according to claim 1, wherein the data stream comprises at least a portion associated with color samples.

6. The apparatus according to claim 1, wherein the data stream comprises at least a portion associated with depth values related to a depth map.

7. An apparatus for encoding a transform coefficient block, wherein the apparatus is configured to code, using context-adaptive entropy encoding, significant transform coefficients within the transform coefficient block into a data stream, wherein the apparatus is configured to code the significant transform coefficients in a coefficient scan order, wherein, according to the coefficient scan order, a plurality of sub-blocks of the transform coefficient block are scanned in a sub-block scan order, wherein each sub-block includes more than one pixel, and the transform coefficients within each sub-block are scanned in a position sub-scan order, wherein the position sub-scan order is adaptively selected from a plurality of scan orders including a diagonal scan order,

wherein the apparatus is further configured to use, in context-adaptive entropy encoding, a selected set of contexts from a plurality of sets of contexts, wherein, for each sub-block, the selected set of contexts is based on a statistic of the transform coefficients within a previously traversed sub-block of the transform coefficient block, or a statistic of the transform coefficients of a co-located sub-block in a previously encoded transform coefficient block.

8. The apparatus according to claim 7, wherein the selected set of contexts is selected from the plurality of sets of contexts, wherein the number of contexts of the plurality of sets of contexts is greater than one, and the apparatus is configured to, in context-adapted entropy encoding the significant transform coefficients within a sub-block using the selected set of contexts for the respective sub-block, assign the selected set of contexts to the positions within the respective sub-block.

9. The apparatus according to claim 7, wherein the sub-block scan order leads zigzag-wise from a sub-block including a position of a lowest frequency in a vertical direction and a horizontal direction to a sub-block including a position of a highest frequency in both the vertical and horizontal directions, while the position sub-scan order leads, in each sub-block, zigzag-wise from a position within the respective sub-block, relating to a highest frequency in a vertical direction and a horizontal direction to a position of the respective sub-block relating to a lowest frequency in both the vertical and horizontal directions.

10. The apparatus according to claim 7, wherein the apparatus is at least a portion of a programmable logic device, programmable gate array, microprocessor, computer or hardware apparatus.

11. The apparatus according to claim 7, wherein the data stream comprises at least a portion associated with color samples.

12. The apparatus according to claim 7, wherein the data stream comprises at least a portion associated with depth values related to a depth map.

13. A non-transitory computer readable digital storage medium comprising stored thereon a computer program comprising a program code for performing, when running on a computer, a method for decoding a transform coefficient block, the method comprising:

extracting, from a data stream, a significance map indicating positions of significant transform coefficients within the transform coefficient block, and the significant transform coefficients; and

associating the extracted significant transform coefficients with their respective positions in the transform coefficient block in a coefficient scan order, wherein, according to the coefficient scan order, a plurality of sub-blocks of the transform coefficient block are scanned in a sub-block scan order, wherein each sub-block includes more than one pixel, and the transform coefficients within each sub-block are scanned in a position sub-scan order, wherein the position sub-scan order is adaptively selected from a plurality of scan orders including a diagonal scan order,

wherein, in extracting the significant transform coefficients based on context-adaptive entropy decoding, a selected set of contexts from a plurality of sets of contexts is used, wherein, for each sub-block, the selected set of contexts is determined based on a statistic of the transform coefficients within a previously traversed sub-block of the transform coefficient block, or a statistic of the transform coefficients of a co-located sub-block in a previously decoded transform coefficient block.

14. The non-transitory computer readable digital storage medium according to claim 13, wherein the selected set of contexts is selected from the plurality of sets of contexts, wherein the number of contexts of the plurality of sets of contexts is greater than one, and the method further comprising, in context-adapted entropy decoding the significant transform coefficients within a sub-block using the selected set of contexts for the respective sub-block, assigning the selected set of contexts to the positions within the respective sub-block.

15. The non-transitory computer readable digital storage medium according to claim 13, wherein the sub-block scan order leads zigzag-wise from a sub-block including a position of a lowest frequency in a vertical direction and a horizontal direction to a sub-block including a position of a highest frequency in both the vertical and horizontal directions, while the position sub-scan order leads, in each sub-block, zigzag-wise from a position within the respective sub-block, relating to a highest frequency in a vertical direction and a horizontal direction to a position of the respective sub-block relating to a lowest frequency in both the vertical and horizontal directions.

16. The non-transitory computer readable digital storage medium according to claim 13, wherein the medium is a DVD, Blue-Ray, CD, ROM, PROM, EPROM, EEPROM or FLASH memory.

17. A method for decoding a transform coefficient block, the method comprising:

extracting, from a data stream, a significance map indicating positions of significant transform coefficients within the transform coefficient block, and the significant transform coefficients; and

associating the extracted significant transform coefficients with their respective positions in the transform coefficient block in a coefficient scan order, wherein, according to the coefficient scan order, a plurality of sub-blocks of the transform coefficient block are scanned in a sub-block scan order, wherein each sub-block includes more than one pixel, and the transform coefficients within each sub-block are scanned in a position sub-scan order, wherein the position sub-scan order is adaptively selected from a plurality of scan orders including a diagonal scan order,

wherein, in extracting the significant transform coefficients based on context-adaptive entropy decoding, a selected set of contexts from a plurality of sets of contexts is used, wherein, for each sub-block, the selected set of contexts is determined based on a statistic of the transform coefficients within a previously traversed sub-block of the transform coefficient block, or a statistic of the transform coefficients of a co-located sub-block in a previously decoded transform coefficient block.

18. The method according to claim 17, wherein the selected set of contexts is selected from the plurality of sets of contexts, wherein the number of contexts of the plurality of sets of contexts is greater than one, and the method further comprising, in context-adapted entropy decoding the significant transform coefficients within a sub-block using the selected set of contexts for the respective sub-block, assigning the selected set of contexts to the positions within the respective sub-block.

19. The method according to claim 17, wherein the sub-block scan order leads zigzag-wise from a sub-block including a position of a lowest frequency in a vertical direction and a horizontal direction to a sub-block including a position of a highest frequency in both the vertical and horizontal directions, while the position sub-scan order leads, in each sub-block, zigzag-wise from a position within the respective sub-block, relating to a highest frequency in a vertical direction and a horizontal direction to a position of the respective sub-block relating to a lowest frequency in both the vertical and horizontal directions.

20. The method according to claim 17, wherein the data stream comprises at least a portion associated with color samples.

21. The method according to claim 17, wherein the data stream comprises at least a portion associated with depth values related to a depth map.