Entropy coding supporting mode switching

Patent metadata

Field	Value
Publication number	US-9918090-B2
Application number	US-201314108173-A
Country	US
Kind code	B2
Filing date	Dec 16, 2013
Priority date	Jun 16, 2011
Publication date	Mar 13, 2018
Grant date	Mar 13, 2018

Abstract

A decoder for decoding a data stream into which media data is coded has a mode switch configured to activate a low-complexity mode or a high-efficiency mode depending on the data stream, an entropy decoding engine configured to retrieve each symbol of a sequence of symbols by entropy decoding using a selected one of a plurality of entropy decoding schemes, a desymbolizer configured to desymbolize the sequence of symbols to obtain a sequence of syntax elements, a reconstructor configured to reconstruct the media data based on the sequence of syntax elements, selection depending on the activated low-complexity mode or the high-efficiency mode. In another aspect, a desymbolizer is configured to perform desymbolization such that the control parameter varies in accordance with the data stream at a first rate in case of the high-efficiency mode being activated and the control parameter is constant irrespective of the data stream or changes depending on the data stream, but at a second lower rate in case of the low-complexity mode being activated.

First claim

The invention claimed is:

1. A decoder for decoding a data stream including encoded data of a video, the decoder comprising:
a mode switch configured to activate a low-complexity mode or a high efficiency mode based on mode information from the data stream;
an entropy decoding engine configured to decode, by entropy decoding, data from the data stream using a selected one of a plurality of entropy decoding schemes to obtain a sequence of symbols;
a desymbolizer configured to desymbolize the sequence of symbols in order to acquire a sequence of syntax elements; and
a reconstructor configured to reconstruct at least a portion of the video based on the sequence of syntax elements,
wherein the selection of the one of the plurality of entropy decoding schemes depends on the activated one of the low complexity mode and the high-efficiency mode,
wherein the entropy decoding engine is configured such that each of the plurality of entropy decoding schemes involves arithmetic decoding of symbols associated with the respective entropy decoding scheme, wherein the plurality of entropy decoding schemes differ from each other in terms of a different probability estimate used in the corresponding arithmetic decoding, and
wherein, for at least one symbol of the sequence of symbols, the entropy decoding engine is configured to:
select a context corresponding to the at least one symbol, the selected context corresponding to a probability model, and
entropy decode the at least one symbol using the selected one of a plurality of entropy decoding schemes based on the selected context, wherein the probability model is updated at a first update rate under the high-efficiency mode, and is updated at a second update rate lower than the first update rate under the low-complexity mode.

2. The decoder according to claim 1 , wherein the selection depends on previously retrieved symbols of the sequence of symbols in case of the high-efficiency mode being activated and independent from any previously retrieved symbols of the sequence of symbols in case of the low-complexity mode being activated.

3. The decoder according to claim 1 , wherein the data stream is structured into consecutive portions and each symbol of the sequence of symbols is associated with a respective one of a plurality of symbol types, wherein, for symbols of a predetermined symbol type within a current portion, the selection varies depending on previously retrieved symbols of the sequence of symbols of the predetermined symbol type within the current portion in case of the high-efficiency mode being activated, and is left constant within the current portion in case of the low-complexity mode being activated.

4. The decoder according to claim 1 , wherein each symbol of the sequence of symbols is associated with a respective one of a plurality of symbol types, wherein the entropy decoding engine is configured to, for a predetermined symbol of a predetermined symbol type,
select one of a plurality of contexts depending on previously retrieved symbols of the sequence of symbols and perform the selection among the entropy decoding schemes depending on a probability model associated with the selected context along with updating the probability model associated with the selected context depending on the predetermined symbol in case of the high-efficiency mode being activated, and
perform selecting the one of the plurality of contexts depending on the previously retrieved symbols of the sequence of symbols and perform the selection among the entropy decoding schemes depending on the probability model associated with the selected context along with leaving the probability model associated with the selected context constant in case of the low-complexity mode being activated.

5. The decoder according to claim 1 , wherein each symbol of the sequence of symbols is associated with a respective one of a plurality of symbol types, wherein
for each symbol of a predetermined symbol type, the selection of the one of the plurality of entropy decoding schemes depends on a probability model associated with the predetermined symbol type.

6. The decoder according to claim 1 wherein, for symbols of a predetermined symbol type,
a probability mode adaptation is performed using a probability state index defined at a first probability state accuracy and the selection depends on the probability state index defined at the first probability state accuracy in case of the high-efficiency mode being activated, and
no probability mode adaptation or a probability mode adaptation using a probability state index defined at a second probability state accuracy lower than the first probability state accuracy is performed and the selection depends on the probability state index defined at the second probability state accuracy in case of the low-complexity mode being activated.

7. The decoder according to claim 1 wherein the reconstructor is configured to operate independent from the high-efficiency mode or the low-complexity mode being activated.

8. The decoder according to claim 1 wherein the reconstructor is configured to reconstruct a transform block of transform coefficient levels based on a portion of the sequence of syntax elements independent from the high-efficiency mode or the low-complexity mode being activated, the portion of the sequence of syntax elements comprising, in an un-interleaved manner,
significance map syntax elements defining a significance map indicating positions of non-zero transform coefficient levels within the transform block; and
level syntax elements defining the non-zero transform coefficient levels.

9. The decoder according to claim 1 wherein the reconstructor is configured to reconstruct a transform block of transform coefficient levels based on a portion of the sequence of syntax elements independent from the high-efficiency mode or the low-complexity mode being activated, the portion of the sequence of syntax elements comprising, in an un-interleaved manner,
end position syntax elements indicating a position of a last non-zero transform coefficient level within the transform block;
first syntax elements together defining a significance map and indicating, for each position along a one-dimensional path leading from a DC position to the position of the last non-zero transform coefficient level within the transform block, as to whether the transform coefficient level at the respective position is non-zero or not;
second syntax elements indicating, for each position of the one-dimensional path where, according to the first binary syntax elements, a non-zero transform coefficient level is positioned, as to whether the transform coefficient level at the respective position is greater than one;
third syntax elements revealing, for each position of the one-dimensional path where, according to the first binary syntax elements, a transform coefficient level greater than one is positioned, an amount by which the respective transform coefficient level at the respective position exceeds one,
wherein an order among the end positions syntax elements, and the first, second and third syntax elements is the same for the high-efficiency mode and the low-complexity mode, and wherein the selection is performed for symbols from which the desymbolizer acquires the end position syntax elements, first syntax elements, second syntax elements and/or the third syntax elements, differently depending on the complexity mode or the high-efficiency mode being activated.

10. The decoder according to claim 9 , wherein the selection is, for symbols of a predetermined symbol type among a subsequence of symbols from which the desymbolizer acquires the first syntax elements and second syntax elements,

Assignees

• Ge Video Compression Llc

Inventors

• George Valeri
• Bross Benjamin
• Kirchhoffer Heiner
• Marpe Detlev
• Nguyen Tung
• Preiss Matthias
• Siekmann Mischa
• Stegemann Jan
• Weigand Thomas
• Bartnik Christian

Classifications

• H04N19/126

  Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers · CPC title

• H04N19/13 Primary

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

• H04N19/52

  by predictive encoding · CPC title

• H03M7/4075 Primary

  Golomb codes · CPC title

• H03M7/42

  using table look-up for the coding or decoding process, e.g. using read-only memory {(H03M7/4006 takes precedence)} · CPC title