Encoder, decoder, encoding method, and decoding method

Patent metadata

Field	Value
Publication number	US-2021195197-A1
Application number	US-202117173024-A
Country	US
Kind code	A1
Filing date	Feb 10, 2021
Priority date	Sep 28, 2018
Publication date	Jun 24, 2021
Grant date	—

Abstract

An encoder includes circuitry and memory coupled to the circuitry. The circuitry, in operation, for each coefficient of a plurality of coefficients included in a block, determines a base level relating to Context-Based Adaptive Binary Arithmetic Coding (CABAC) for the coefficient, and encodes an absolute value of the coefficient. In determining the base level, when one or more flags are used in encoding the absolute value of the coefficient, the base level is determined to be a first value, and when one or more flags are not used in the encoding, the base level is determined to be a second value that is smaller than the first value. In encoding the absolute value of the coefficient, when one or more flags are not used, a rice parameter is determined based on the base level which is equal to the second value, and the coefficient is binarized using the rice parameter.

First claim

1 . An encoder, comprising:
circuitry; and memory coupled to the circuitry, wherein:
for each coefficient of a plurality of coefficients included in a block, the circuitry, in operation:
determines a base level relating to Context-Based Adaptive Binary Arithmetic Coding (CABAC) for the coefficient; and
encodes an absolute value of the coefficient, wherein

in determining the base level:
when one or more flags are used in encoding the absolute value of the coefficient, the base level is determined to be a first value; and
when one or more flags are not used in encoding the absolute value of the coefficient, the base level is determined to be a second value, the second value being smaller than the first value; and

in encoding the absolute value of the coefficient, when one or more flags are not used:
a rice parameter is determined based on the base level which is equal to the second value; and
the coefficient is binarized using the rice parameter.

2 . The encoder according to claim 1 , wherein whether to use a flag of the one or more flags is determined based on a first condition and a second condition, wherein:
the first condition is based on the absolute value of the coefficient; and the second condition is for limiting a total number of flags used in the block.

3 . The encoder according to claim 2 , wherein in the encoding of the absolute value, the circuitry:
every time the flag is encoded, counts a total number of the flags encoded; when the second condition is not satisfied, determines that the flag is not to be used in encoding the coefficient, even when the first condition is satisfied; and the second condition is that a total number of the flags encoded is less than a limit.

4 . The encoder according to claim 2 , wherein the first condition is one of a condition that the absolute value of the coefficient is not a third value and a condition that the absolute value of the coefficient is greater than a fourth value, the fourth value being greater than the third value.

5 . The encoder according to claim 3 , wherein the first value is zero, and the second value is three.

6 . The encoder according to claim 1 , wherein the one or more flags include flags of mutually different types.

7 . The encoder according to claim 1 , wherein the circuitry, in determining the rice parameter of a first coefficient in the block, uses second to sixth coefficients in the block, the second to the sixth coefficients being located around the first coefficient.

8 . An encoder, comprising:
memory; and a processor coupled to the memory and configured to perform Context-Based Adaptive Binary Arithmetic Coding (CABAC) of H.266/VVC (Versatile Video Coding) standard, wherein the CABAC includes:
obtaining a base level corresponding to a first quantized coefficient in a block;
calculating absolute values of second to sixth quantized coefficients in the block, the second to the sixth quantized coefficients being provided around the first quantized coefficient in the block;
calculating a rice parameter based on the base level and the absolute values; and
binarizing the first quantized coefficient based on the rice parameter.

9 . The encoder according to claim 8 , wherein the processor is configured to calculate the rice parameter based on a difference between each of the absolute values and the base level.

10 . A decoder, comprising:
circuitry; and memory coupled to the circuitry, wherein for each coefficient of a plurality of coefficients included in a block, the circuitry, in operation:
determines a base level relating to Context-Based Adaptive Binary Arithmetic Coding (CABAC) for the coefficient; and
decodes an absolute value of the coefficient, wherein:
in determining the base level:
when one or more flags are used in decoding the absolute value of the coefficient, the base level is determined to be a first value; and
when one or more flags are not used in decoding the absolute value of the coefficient, the base level is determined to be a second value, the second value being smaller than the first value; and

in decoding the absolute value of the coefficient, when one or more flags are not used:
a rice parameter is determined based on the base level which is equal to the second value; and
the coefficient is debinarized using the rice parameter.

11 . The decoder according to claim 10 , wherein when each coefficient of the plurality of coefficients included in the block is encoded, whether to use a flag of the one or more flags is determined based on a first condition and a second condition, wherein:
the first condition is based on the absolute value of the coefficient; and the second condition is for limiting a total number of flags used in the block.

12 . The decoder according to claim 11 , wherein in the decoding of the absolute value, the circuitry:
every time the flag is decoded, counts a total number of the flags decoded; when each coefficient of the plurality of coefficients included in the block is encoded; when the second condition is not satisfied, determines that the flag is not to be used in encoding the coefficient, even when the first condition is satisfied; and the second condition is that a total number of the flags encoded is less than a limit.

13 . The decoder according to claim 11 , wherein the first condition is one of a condition that the absolute value of the coefficient is not a third value and a condition that the absolute value of the coefficient is greater than a fourth value, the fourth value being greater than the third value.

14 . The decoder according to claim 12 , wherein the first value is zero, and the second value is three.

15 . The decoder according to claim 10 , wherein the one or more flags include flags of mutually different types.

16 . The decoder according to claim 10 , wherein the circuitry, in determining the rice parameter of a first coefficient in the block, uses second to sixth coefficients in the block, the second to the sixth coefficients being located around the first coefficient.

17 . A decoder, comprising:
memory; and a processor coupled to the memory and configured to perform decoding by Context-Based Adaptive Binary Arithmetic Coding (CABAC) of H.266/VVC (Versatile Video Coding) standard, wherein the decoding by the CABAC includes:
obtaining a base level corresponding to a first quantized coefficient in a block;
calculating absolute values of second to sixth quantized coefficients in the block, the second to the sixth quantized coefficients being provided around the first quantized coefficient in the block;
calculating a rice parameter based on the base level and the absolute values; and
debinarizing the first quantized coefficient based on the rice parameter.

18 . The decoder according to claim 17 , wherein the processor is configured to calculate the rice parameter based on a difference between each of the absolute values and the base level.

19 . An encoding method, comprising:
for each coefficient of a plurality of coefficients included in a block:
determining a base level relating to Context-Based Adaptive Binary Arithmetic Coding (CABAC) for the coefficient; and
encoding an absolute value of the coefficient, wherein:
in the determining:
when one or more flags are used in the encoding, the base level is determined to be a first value; and
when one or more flags are not used in the encoding, the base level is determined to be a second value, the second value being smaller than the first value; and

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Assignees

• Panasonic Ip Corp America

Inventors

• Kato Yusuke
• Abe Kiyofumi
• Nishi Takahiro
• Toma Tadamasa

Classifications

• H04N19/42

  characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation (H04N19/635 takes precedence) · CPC title

• H04N19/176 Primary

  the region being a block, e.g. a macroblock · CPC title

• H04N19/70 Primary

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

• H04N19/126

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

• H04N19/46

  Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence) · CPC title