ENTROPY CODING OF MOTION VECTOR DIFFERENCES

• US 20140177707A1
• Filed: 12/16/2013
• Published: 06/26/2014
• Est. Priority Date: 06/16/2011
• Status: Active Grant

• Current Assignee: GE Video Compression, LLC (General Electric Company)
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: GEORGE, Valeri, BROSS, Benjamin, KIRCHHOFFER, Heiner, MARPE, Detlev, NGUYEN, Tung, PREISS, Matthias, SIEKMANN, Mischa, STEGEMANN, Jan, WIEGAND, Thomas
• Granted Patent: US 9,473,170 B2
• Time in Patent Office: Days
• US Class Current: 375/240.03
• CPC Class Codes: H03M 7/42 using table look-up for the coding or decoding process, e.g. using read-only memory H03M7/4006 takes precedence
• CPC Class Codes: H04N 19/124 Quantisation
• 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 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/174 the region being a slice, e.g. a line of blocks or a group of blocks
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/52 by predictive encoding
• 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

An entropy decoder is configured to, for horizontal and vertical components of motion vector differences, derive a truncated unary code from the data stream using context-adaptive binary entropy decoding with exactly one context per bin position of the truncated unary code, which is common for horizontal and vertical components of the motion vector differences, and an Exp-Golomb code using a constant equi-probability bypass mode to obtain the binarizations of the motion vector differences. A desymbolizer is configured to debinarize the binarizations of the motion vector difference syntax elements to obtain integer values of the horizontal and vertical components of the motion vector differences; A reconstructor is configured to reconstruct a video based on the integer values of the horizontal and vertical components of the motion vector differences.

Claims

1. Decoder for decoding a video from a data stream into which horizontal and vertical components of motion vector differences are coded using binarizations of the horizontal and vertical components, the binarizations equaling a truncated unary code of the horizontal and vertical components, respectively, within a first interval of the domain of the horizontal and vertical components below a cutoff value, and a combination of a prefix in form of the truncated unary code for the cutoff value and a suffix in form of a Exp-Golomb code of the horizontal and vertical components, respectively, within a second interval of the domain of the horizontal and vertical components inclusive and above the cutoff value, wherein the cutoff value is two and the Exp-Golomb code has order one, comprising

an entropy decoder configured to, for the horizontal and vertical components of the motion vector differences, derive the truncated unary code from the data stream using context-adaptive binary entropy decoding with exactly one context per bin position of the truncated unary code, which is common for the horizontal and vertical components of the motion vector differences, and the Exp-Golomb code using a constant equi-probability bypass mode to acquire the binarizations of the motion vector differences;

a desymbolizer configured to debinarize the binarizations of the motion vector difference syntax elements to acquire integer values of the horizontal and vertical components of the motion vector differences;

a reconstructor configured to reconstruct the video based on the integer values of the horizontal and vertical components of the motion vector differences.

2. Decoder according to claim 1, wherein the entropy decoder is configured to derive the truncated unary code from the data stream using binary arithmetic decoding or binary PIPE decoding.

3. Decoder according to claim 1, wherein the entropy decoder is configured to use different contexts for the two bin positions of the truncated unary code.

4. Decoder according to claim 1, wherein the entropy decoder is configured to perform a probability state update by, for a bin currently derived out of the truncated unary code, transitioning from a current probability state associated with the context selected for the bin currently derived, to a new probability state depending on the bin currently derived.

5. Decoder according to claim 1, wherein the entropy decoder is configured to binary arithmetic decode a bin currently to be derived out of the truncated unary code by quantizing a current probability interval width value representing a current probability interval to acquire a probability interval index and performing an interval subdivision by indexing a table entry among table entries using the probability interval index and a probability state index depending on a current probability state associated with the context selected for the bin currently to be derived, to acquire a sub-division of the current probability interval into two partial intervals.

6. Decoder according to claim 5, wherein the entropy decoder is configured to use an 8 bit representation for the current probability interval width value and to grab-out 2 or 3 most significant bits of the 8 bit representation in quantizing the current probability interval width value.

7. Decoder according to claim 5, wherein the entropy decoder is configured to select among the two partial intervals based on an offset state value from an interior of the current probability interval, update the probability interval width value and the offset state value, and infer a value of the bin currently to be derived, using the selected partial interval and perform a renormalization of the updated probability interval width value and the offset state value comprising a continuation of reading bits from the data stream.

8. Decoder according to claim 5, wherein the entropy decoder is configured to, in the constant equi-probability bypass mode, binary arithmetic decode a bin out of the Exp-Golomb code by halving the current probability interval width value to acquire a sub-division of the current probability interval into two partial intervals.

9. Decoder according to claim 1, wherein the entropy decoder is configured to, for each motion vector difference, derive the truncated unary code of the horizontal and vertical components of the respective motion vector difference from the data stream, prior to the Exp-Golomb code of the horizontal and vertical components of the respective motion vector difference.

10. Decoder according to claim 1, wherein the reconstructor is configured to spatially and/or temporally predict the horizontal and vertical components of motion vectors so as to acquire predictors for the horizontal and vertical components of the motion vectors and reconstruct the horizontal and vertical components of the motion vectors by refining the predictors 826 using the horizontal and vertical components of the motion vector differences.

11. Decoder according to claim 1, wherein the reconstructor is configured to predict the horizontal and vertical components of motion vectors in different manners so as to obtain an ordered list of predictors for the horizontal and vertical components of motion vectors, obtain an list index from the data stream and reconstruct the horizontal and vertical components of motion vectors by refining the predictor to which a predictor of the list to which the list index points using the horizontal and vertical components of the motion vector differences.

12. Decoder according to claim 10, wherein the reconstructor is configured to reconstruct the video using motion-compensated prediction by use of the horizontal and vertical components of motion vectors.

13. Decoder according to claim 12, wherein the reconstructor is configured to reconstruct the video using the motion-compensated prediction by applying the horizontal and vertical components of motion vectors at a spatial granularity defined by a sub-division of the video'"'"'s pictures in blocks, wherein the reconstructor uses merging syntax elements present in the data stream so as to group the blocks into merge groups and apply the integer values of the horizontal and vertical components of the motion vector differences obtained by the debinarizer, in units of merge groups.

14. Decoder according to claim 13, wherein the reconstructor is configured to derive the sub-division of the video'"'"'s pictures in blocks from a portion of the datastream excluding the merging syntax elements.

15. Decoder according to claim 13, wherein the reconstructor is configured to adopt the horizontal and vertical components of a predetermined motion vector for all blocks of an associated merge group, or refine same by the horizontal and vertical components of the motion vector differences associated with the blocks of the merge group.

16. Encoder for encoding a video into a data stream, comprising

a constructor configured to predictively code the video by motion compensated prediction using motion vectors and predictively coding the motion vectors by predicting the motion vectors and setting integer values of horizontal and vertical components of motion vector differences to represent a prediction error of the predicted motion vectors;

a symbolizer configured to binarize the integer values to obtain binarizations of the horizontal and vertical components of the motion vector differences, the binarizations equaling a truncated unary code of the horizontal and vertical components, respectively, within a first interval of the domain of the horizontal and vertical components below a cutoff value, and a combination of a prefix in form of the truncated unary code for the cutoff value and a suffix in form of a Exp-Golomb code of the horizontal and vertical components, respectively, within a second interval of the domain of the horizontal and vertical components inclusive and above the cutoff value, wherein the cutoff value is two and the Exp-Golomb code has order one; and

an entropy encoder configured to, for the horizontal and vertical components of the motion vector differences, encode the truncated unary code into the data stream using context-adaptive binary entropy encoding with exactly one context per bin position of the truncated unary code, which is common for the horizontal and vertical components of the motion vector differences, and the Exp-Golomb code using a constant equi-probability bypass mode.

17. Encoder according to claim 16, wherein the entropy encoder is configured to encode the truncated unary code into the data stream using binary arithmetic encoding or binary PIPE encoding.

18. Encoder according to claim 16, wherein the entropy encoder is configured to use different contexts for the two bin positions of the truncated unary code.

19. Encoder according to claim 16, wherein the entropy encoder is configured to perform a probability state update by, for a bin currently encoded out of the truncated unary code, transitioning from a current probability state associated with the context selected for the bin currently encoded, to a new probability state depending on the bin currently derived.

20. Encoder according to claim 16, wherein the entropy encoder is configured to binary arithmetic encode a bin currently to be encoded out of the truncated unary code by quantizing a current probability interval width value representing a current probability interval to obtain a probability interval index and performing an interval subdivision by indexing a table entry among tables entries using the probability interval index and a probability state index depending on a current probability state associated with the context selected for the bin currently to be derived, to obtain a sub-division of the current probability interval into two partial intervals.

21. Encoder according to claim 20, wherein the entropy encoder is configured to use an 8 bit representation for the current probability interval width value and to grab-out 2 or 3 most significant bits of the 8 bit representation in quantizing the current probability interval width value.

22. Encoder according to claim 20, wherein the entropy encoder is configured to select among the two partial intervals based on the integer value of the bin currently to be encoded, update the probability interval width value and a probability interval offset using the selected partial interval and perform a renormalization of the probability interval width value and the probability interval offset comprising a continuation of writing bits to the datastream.

23. Encoder according to claim 20, wherein the entropy encoder is configured to binary arithmetic encode a bin out of the Exp-Golomb code by halving the current probability interval width value to obtain a sub-division of the current probability interval into two partial intervals.

24. Encoder according to claim 16, wherein the entropy encoder is configured to, for each motion vector difference, encode the truncated unary code of the horizontal and vertical components of the respective motion vector difference into the data stream, prior to the Exp-Golomb code of the horizontal and vertical components of the respective motion vector difference.

25. Encoder according to claim 16, wherein the constructor is configured to spatially and/or temporally predict the horizontal and vertical components of the motion vectors so as to obtain predictors for the horizontal and vertical components of motion vectors and determine the horizontal and vertical components of the motion vector differences so as to refine the predictors towards the horizontal and vertical components of motion vectors.

26. Encoder according to claim 16, wherein the constructor is configured to predict the horizontal and vertical components of the motion vectors in different manners so as to obtain a ordered list of predictors for the horizontal and vertical components of motion vectors, determine an list index and insert information revealing same into the data stream and determine the horizontal and vertical components of the motion vector differences so as to refine the predictor to which a predictor of the list to which the list index points towards the horizontal and vertical components of motion vectors.

27. Encoder according to claim 16, wherein the constructor is configured to code the video using the motion-compensated prediction by applying the horizontal and vertical components of motion vectors at a spatial granularity defined by a sub-division of the video'"'"'s pictures in blocks, wherein the constructor determines, and inserts into the datastream, merging syntax elements so as to group the blocks into merge groups and apply the integer values of the horizontal and vertical components of the motion vector differences subject to binarization by the debinarizer, in units of merge groups.

28. Encoder according to claim 27, wherein the constructor is configured to code the sub-division of the video'"'"'s pictures in blocks into a portion of the datastream excluding the merging syntax elements.

29. Encoder according to claim 27, wherein the constructor is configured to adopt the horizontal and vertical components of a predetermined motion vector for all blocks of an associated merge group, or refine same by the horizontal and vertical components of the motion vector differences associated with the blocks of the merge group.

30. Method for decoding a video from a data stream into which horizontal and vertical components of motion vector differences are coded using binarizations of the horizontal and vertical components, the binarizations equaling a truncated unary code of the horizontal and vertical components, respectively, within a first interval of the domain of the horizontal and vertical components below a cutoff value, and a combination of a prefix in form of the truncated unary code for the cutoff value and a suffix in form of a Exp-Golomb code of the horizontal and vertical components, respectively, within a second interval of the domain of the horizontal and vertical components inclusive and above the cutoff value, wherein the cutoff value is two and the Exp-Golomb code has order one, comprising

for the horizontal and vertical components of the motion vector differences, deriving the truncated unary code from the data stream using context-adaptive binary entropy decoding with exactly one context per bin position of the truncated unary code, which is common for the horizontal and vertical components of the motion vector differences, and the Exp-Golomb code using a constant equi-probability bypass mode to obtain the binarizations of the motion vector differences;

debinarizing the binarizations of the motion vector difference syntax elements to obtain integer values of the horizontal and vertical components of the motion vector differences;

reconstructing the video based on the integer values of the horizontal and vertical components of the motion vector differences.

32. Computer program comprising a program code for performing, when running on a computer, a method according to claim 30.

31. Method for encoding a video into a data stream, comprising

predictively coding the video by motion compensated prediction using motion vectors and predictively coding the motion vectors by predicting the motion vectors and setting integer values of horizontal and vertical components of motion vector differences to represent a prediction error of the predicted motion vectors;

binarizing the integer values to obtain binarizations of the horizontal and vertical components of the motion vector differences, the binarizations equaling a truncated unary code of the horizontal and vertical components, respectively, within a first interval of the domain of the horizontal and vertical components below a cutoff value, and a combination of a prefix in form of the truncated unary code for the cutoff value and a suffix in form of a Exp-Golomb code of the horizontal and vertical components, respectively, within a second interval of the domain of the horizontal and vertical components inclusive and above the cutoff value, wherein the cutoff value is two and the Exp-Golomb code has order one; and

for the horizontal and vertical components of the motion vector differences, encoding the truncated unary code into the data stream using context-adaptive binary entropy encoding with exactly one context per bin position of the truncated unary code, which is common for the horizontal and vertical components of the motion vector differences, and the Exp-Golomb code using a constant equi-probability bypass mode.

33. Computer program comprising a program code for performing, when running on a computer, a method according to claim 31.