Entropy encoding and decoding scheme

Patent metadata

Field	Value
Publication number	US-9252806-B2
Application number	US-201514734407-A
Country	US
Kind code	B2
Filing date	Jun 9, 2015
Priority date	Jan 14, 2011
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

Decomposing a value range of the respective syntax elements into a sequence of n partitions with coding the components of z laying within the respective partitions separately with at least one by VLC coding and with at least one by PIPE or entropy coding is used to greatly increase the compression efficiency at a moderate coding overhead since the coding scheme used may be better adapted to the syntax element statistics. Accordingly, syntax elements are decomposed into a respective number n of source symbols s i with i=1 . . . n, the respective number n of source symbols depending on as to which of a sequence of n partitions into which a value range of the respective syntax elements is sub-divided, a value z of the respective syntax elements falls into, so that a sum of values of the respective number of source symbols s i yields z, and, if n>1, for all i=1 . . . n−1, the value of s i corresponds to a range of the i th partition.

First claim

The invention claimed is:

1. A method for decoding comprising:
receiving, by a VLC decoder, a first portion of a bitstream;
reconstructing, by the VLC decoder, source symbols of a first subsequence of source symbols from codewords of the first portion of a bitstream;
receiving, by an arithmetic decoder, a second portion of a bitstream;
reconstructing, by the arithmetic decoder, source symbols of a second subsequence of source symbols from codewords of the second portion of a bitstream;
retrieving, by a composer, source symbols from the first subsequence and source symbols from the second subsequence; and
composing, by the composer, a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions from the first subsequence of source symbols and the second subsequence of source symbols by individually composing each syntax element from a respective number of source symbols by, for at least a subgroup of the syntax elements, determining the respective number of source symbols based on a value of the respective syntax elements and a partition of the sequence of partitions, and by summing-up the values of the respective number of source symbols, as long as the value of at least one source symbol corresponds to a range of a corresponding partition, so as to obtain the value of the syntax element;
wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks and;
wherein the composer is configured to adapt at least one limit between the partitions during composing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform block.

2. The method of claim 1 , wherein the values of the subgroup of the syntax elements are absolute values.

3. The method of claim 2 , wherein a source symbol in the second subsequence of source symbols corresponds to the first-ordered partition in the sequence of partitions; and
wherein the sequence of partitions is arranged such that a first partition covers higher values of the value range than a second partition.

4. The method of claim 1 , wherein the source symbols from the first subsequence and the source symbols from the second subsequence correspond to different partitions.

5. The method of claim 4 , wherein a source symbol in the second subsequence of source symbols corresponds to the first-ordered partition in the sequence of partitions; and
wherein the sequence of partitions is arranged such that a first partition covers higher values of the value range than a second partition.

6. The method of claim 1 , wherein the number of partitions equals three.

7. The method of claim 3 , wherein a source symbol in the first subsequence of source symbols corresponds to the second-ordered partition and wherein the VLC decoder is configured to use a Golomb-Rice code to decode the source symbol in the first subsequence of source symbols.

8. The method of claim 1 , further comprising a step of recombining, by a recombiner, the first subsequence of source symbols and the second subsequence of source symbols to obtain the sequence of source symbols.

9. The method of claim 1 , wherein the step of reconstructing, by the VLC decoder, is performed by reconstructing the source symbols of the first subsequence of source symbols from codewords of the first portion of a bitstream.

10. The method of claim 1 , wherein the composer is configured to adapt at least one limit between the partitions during composing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform block depending on at least one of reconstructed absolute transform coefficient levels of absolute transform coefficients of the respective transform blocks preceding in the scan order, a position of the absolute transform coefficient level to be composed in the scan order, an evaluation of the reconstructed absolute transform coefficient levels of transform coefficients neighboring spatially the position of the absolute transform coefficient level to be composed, and an evaluation of the reconstructed absolute transform coefficient levels of transform coefficients neighboring in scan order the position of the absolute transform coefficient level to be composed.

11. An apparatus for decoding comprising:
a VLC decoder configured to:
receive a first portion of a bitstream; and
reconstruct source symbols of a first subsequence of source symbols from codewords of the first portion of a bitstream;

an arithmetic decoder configured to:
receive a second portion of a bitstream; and
reconstruct a second subsequence of source symbols from codewords of the second portion of a bitstream;

a composer configured to:
retrieve all source symbols from the first subsequence and all source symbols from the second subsequence; and
compose a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions from the first subsequence of source symbols and the second subsequence of source symbols by individually composing each syntax element from a respective number of source symbols by, for at least a subgroup of the syntax elements, determining the respective number of source symbols based on a value of the respective syntax elements and a partition of the sequence of partitions, and by summing-up the values of the respective number of source symbols, as long as the value of at least one source symbol corresponds to a range of a corresponding partition, so as to obtain the value of the syntax element;

wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks;
wherein the composer is configured to adapt at least one limit between the partitions during composing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform.

12. The apparatus of claim 11 , wherein the values of the subgroup of the syntax elements are absolute values.

13. The apparatus of claim 12 , wherein a source symbol in the second subsequence of source symbols corresponds to the first-ordered partition in the sequence of partitions; and
wherein the sequence of partitions is arranged such that a first partition covers higher values of the value range than a second partition.

14. The apparatus of claim 11 , wherein the source symbols from the first subsequence and the source symbols from the second subsequence correspond to different partitions.

15. The apparatus of claim 14 , wherein a source symbol in the second subsequence of source symbols corresponds to the first-ordered partition in the sequence of partitions; and
wherein the sequence of partitions is arranged such that a first partition covers higher values of the value range than a second partition.

16. The apparatus of claim 11 , wherein the number of partitions equals three.

17. The apparatus of claim 11 , wherein a source symbol in the first subsequence of source symbols corresponds to

Assignees

• Ge Video Compression Llc

Inventors

• Marpe Detlev
• Nguyen Tung
• Schwarz Heiko
• Wiegand Thomas

Classifications

• H03M7/4037

  Prefix coding · CPC title

• H03M7/55

  Compression Theory, e.g. compression of random number, repeated compression · CPC title

• H03M7/40 Primary

  Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code · CPC title

• H04N19/91

  Entropy coding, e.g. variable length coding [VLC] or arithmetic coding · CPC title

• H03M7/00 Primary

  Conversion of a code where information is represented by a given sequence or number of digits to a code where the same {, similar or subset of} information is represented by a different sequence or number of digits · CPC title