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US 12,750,524 B2Granted
Transform-based image decoding/encoding apparatus and apparatus for transmitting therefor
AssigneeLG Electronics Inc.
InventorsMoonmo Koo, Seunghwan Kim, Jaehyun Lim
Life of this patent
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Abstract
An image decoding method according to the present document may comprise: a step of deriving transform coefficients for a current block by performing inverse quantization on the basis of residual information; and a step of deriving modified transform coefficients by applying LFNST to the transform coefficients, wherein the step of deriving the transform coefficients comprises a step of parsing position information of a last non-zero transform coefficient, an LFNST index related to application of the LFNST is parsed after parsing a position of the last non-zero transform coefficient, and the transform coefficients are derived after parsing the LFNST index.
Claims13
A decoding apparatus for decoding an image, the apparatus comprising:
- a memory configured to store the image;
- and
- a processor coupled with the memory,
- wherein the processor is configured to:
- obtain residual information from a bitstream;
- derive transform coefficients for a current block by performing inverse quantization based on the residual information;
- and
- derive modified transform coefficients by applying low-frequency non-separable transform (LFNST) to the transform coefficients,
- wherein the processor is further configured to parse information on a position of a last non-zero transform coefficient,
- wherein an LFNST index related to application of the LFNST is parsed after the parsing of the information on the position of the last non-zero transform coefficient,
- wherein the transform coefficients are derived after the parsing of the LFNST index,
- wherein an LFNST index parsing variable indicates whether the LFNST index is parsed, and is initialized in a coding unit level for syntax elements configuring a coding unit syntax table signaled ahead of a residual coding level,
- wherein the LFNST index parsing variable is updated in the residual coding level for a first transform block that satisfies a parsing condition of the LFNST index among transform blocks included in the current block, and
- wherein the updated LFNST index parsing variable is not changed in the residual coding level for other transform block thereafter.
11 more elements
An encoding apparatus for encoding an image, the apparatus comprising:
- a memory configured to store the image;
- and
- a processor coupled with the memory,
- wherein the processor is configured to:
- derive residual samples for a current block based on a prediction sample for the current block;
- derive transform coefficients for the current block based on primary transform for the residual samples;
- derive modified transform coefficients from the transform coefficients by applying low-frequency non-separable transform (LFNST);
- and
- encode and output image information including residual information on the modified transform coefficients and an LFNST index related to application of the LFNST,
- wherein the residual information includes information on a position of a last non-zero transform coefficient,
- wherein the LFNST index is encoded to be signaled after signaling the information on the position of the last non-zero transform coefficient,
- wherein the image information is configured so that the modified transform coefficients are derived after parsing the LFNST index,
- wherein the image information is configured so that an LFNST index parsing variable indicates whether the LFNST index is signaled, and is initialized in a coding unit level for syntax elements configuring a coding unit syntax table signaled ahead of a residual coding level,
- wherein the LFNST index parsing variable is updated in the residual coding level for a first transform block that satisfies a signaling condition of the LFNST index among transform blocks included in the current block, and
- wherein the updated LFNST index parsing variable is not changed in the residual coding level for other transform block thereafter.
12 more elements
An apparatus for transmitting data for image information, the apparatus comprising:
- a processor configured to obtain a bitstream of the image information;
- and
- a transmitter configured to transmit the data comprising the bitstream of the image information,
- wherein the processor is configured to:
- derive residual samples for a current block based on a prediction sample for the current block;
- derive transform coefficients for the current block based on primary transform for the residual samples;
- derive modified transform coefficients from the transform coefficients by applying low-frequency non-separable transform (LFNST);
- and
- encode and output the image information including residual information on the modified transform coefficients and an LFNST index related to application of the LFNST,
- wherein the residual information includes information on a position of a last non-zero transform coefficient,
- wherein the LFNST index is encoded to be signaled after signaling the information on the position of the last non-zero transform coefficient,
- wherein the image information is configured so that the modified transform coefficients are derived after parsing the LFNST index,
- wherein the image information is configured so that an LFNST index parsing variable indicates whether the LFNST index is signaled, and is initialized in a coding unit level for syntax elements configuring a coding unit syntax table signaled ahead of a residual coding level,
- wherein the LFNST index parsing variable is updated in the residual coding level for a first transform block that satisfies a signaling condition of the LFNST index among transform blocks included in the current block, and
- wherein the updated LFNST index parsing variable is not changed in the residual coding level for other transform block thereafter.
12 more elements
Dependencies are inferred from the claim text.