Entropy encoding and decoding scheme

Patent metadata

Field	Value
Publication number	US-10855309-B2
Application number	US-202016836191-A
Country	US
Kind code	B2
Filing date	Mar 31, 2020
Priority date	Jan 14, 2011
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

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 si 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 si yields z, and, if n>1, for all i=1 . . . n−1, the value of si corresponds to a range of the ith partition.

First claim

The invention claimed is:

1. An apparatus for decoding comprising:
a symbol decoder configured to:
obtain, based on codewords from a data stream, a first sequence of source symbols and a second sequence of source symbols by obtaining each source symbol of the first sequence using a first coding scheme including context-based entropy coding and each source symbol of the second sequence using a second coding scheme, which is different from the first coding scheme, wherein the source symbols of the first and second sequences are related to level values of transform coefficients of a transform coefficient block; and
a composer configured to:
compose a sequence of syntax elements having a value range sub-divided into a plurality of portions by, with respect to each syntax element: obtaining a set of source symbols from the first and second sequences based on a portion of the plurality of portions associated with the syntax element, and
combining values of the source symbols of the set to determine the value of the syntax element.

2. The apparatus of claim 1 , wherein the symbol decoder comprises:
a first decoder configured to:
receive a first portion of the data stream, and
reconstruct, using the context-based entropy coding, source symbols of the first sequence of source symbols from codewords of the first portion of the data stream; and
a second decoder configured to:
receive a second portion of the data stream, and
reconstruct, using the second coding scheme including Exp-Golomb coding, source symbols of the second sequence of source symbols from codewords of the second portion of the data stream.

3. The apparatus of claim 1 , wherein a source symbol in the first sequence of source symbols corresponds to a first portion of the plurality of portions, and the plurality of portions is arranged such that the first portion covers lower values of the value range than a second portion of the plurality of portions.

4. The apparatus of claim 1 , wherein the source symbols from the first sequence and the source symbols from the second sequence correspond to different portions.

5. The apparatus of claim 1 , wherein the plurality of portions includes a maximum of three portions.

6. The apparatus of claim 1 , wherein a third portion of the data stream represents at least one scaling factor.

7. The apparatus of claim 1 , wherein the apparatus is at least a portion of a programmable logic device, a programmable gate array, a microprocessor, a computer or an electronic circuit.

8. The apparatus of claim 1 , wherein the composer is configured to adapt at least one limit between the portions during composing absolute transform coefficient levels of the transform coefficients of the transform coefficient block based on at least one of:
a previously reconstructed absolute transform coefficient level of a transform coefficient preceding in a scan order,
a position of a current absolute transform coefficient level to be composed in the scan order,
an evaluation of previously reconstructed absolute transform coefficient levels of transform coefficients spatially neighboring the position of the current absolute transform coefficient level to be composed, and
an evaluation of previously reconstructed absolute transform coefficient levels of transform coefficients neighboring according to the scan order the position of the current absolute transform coefficient level to be composed.

9. A method for decoding comprising:
obtaining, based on codewords from a data stream, a first sequence of source symbols and a second sequence of source symbols by obtaining each source symbol of the first sequence using a first coding scheme including context-based entropy coding and each source symbol of the second sequence using a second coding scheme, which is different from the first coding scheme, wherein the source symbols of the first and second sequences are related to level values of transform coefficients of aa transform coefficient block; and
composing a sequence of syntax elements having a value range sub-divided into a plurality of portions by, with respect to each syntax element:
obtaining a set of source symbols from the first and second sequences based on a portion of the plurality of portions associated with the syntax element, and
combining values of the source symbols of the set to determine the value of the syntax element.

10. The method of claim 9 , further comprising:
receiving a first portion of the data stream;
reconstructing, using the context-based entropy coding, source symbols of the first sequence of source symbols from codewords of the first portion of the data stream;
receiving a second portion of the data stream; and
reconstructing, using the second coding scheme including Exp-Golomb coding, source symbols of the second sequence of source symbols from codewords of the second portion of the data stream.

11. The method of claim 9 , wherein a source symbol in the first sequence of source symbols corresponds to a first portion of the plurality of portions, and the plurality of portions is arranged such that the first portion covers lower values of the value range than a second portion of the plurality of portions.

12. The method of claim 9 , wherein the source symbols from the first sequence and the source symbols from the second sequence correspond to different portions.

13. The method of claim 9 , wherein the plurality of portions includes a maximum of three portions.

14. The method of claim 9 , wherein a third portion of the data stream represents at least one scaling factor.

15. The method of claim 9 , wherein the method is implemented using a programmable logic device, a programmable gate array, a microprocessor, a computer or an electronic circuit.

16. The method of claim 9 , further comprising:
adapting at least one limit between the portions during composing absolute transform coefficient levels of the transform coefficients of the transform coefficient block based on at least one of:
a previously reconstructed absolute transform coefficient level of a transform coefficient preceding in a scan order,
a position of a current absolute transform coefficient level to be composed in the scan order,
an evaluation of previously reconstructed absolute transform coefficient levels of transform coefficients spatially neighboring the position of the current absolute transform coefficient level to be composed, and
an evaluation of previously reconstructed absolute transform coefficient levels of transform coefficients neighboring according to the scan order the position of the current absolute transform coefficient level to be composed.

17. An apparatus for encoding comprising:
a decomposer configured to:
receive a sequence of syntax elements having a value range sub-divided into a plurality of portions, related to level values of transform coefficients of a transform coefficient block, and
obtain a sequence of source symbols based on the sequence of syntax elements by decomposing each syntax element into a corresponding set of source symbols based on a portion of the plurality of portions associated with the syntax element, such that a combination of values of the source symbols of the set yields the value of the syntax element; and
a symbol encoder configured to:
receive the sequence of source symbols,
sub-divide the sequence of source symbols into a first sequence of source symbols and a second sequence of source symbols, and
encode a source symbol of the first sequence using a first coding scheme including context-based entropy coding and a source symbo

Assignees

• Ge Video Compression Llc

Inventors

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

Classifications

• H04N19/13 Primary

  Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC] · CPC title

• H04N19/70

  characterised by syntax aspects related to video coding, e.g. related to compression standards · CPC title

• H03M7/40 Primary

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

• H03M7/4006

  Conversion to or from arithmetic code · CPC title

• H03M7/55

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