Transform-based image coding method and apparatus therefor
AssigneeLG Electronics Inc.
InventorsMoonmo KOO, Jaehyun LIM, Seunghwan KIM
Life of this patent
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Abstract
An image decoding method according to the present document comprises the steps of: deriving a transform coefficient for a current block on the basis of residual information; deriving a residual sample by applying, to the transform coefficient, at least one of LFNST and MTS; and generating a reconstructed picture on the basis of the residual samples, wherein the LFNST is performed on the basis of an LFNST index indicating an LFNST kernel, the MTS is performed on the basis of an MTS index indicating an MTS kernel, and the LFNST index may be parsed before the MTS index.
Claims11
An image decoding method performed by a decoding apparatus, the method comprising:
- obtaining prediction related information for a current block from a bitstream;
- deriving prediction samples for a current block based on the prediction related information;
- obtaining residual information from the bitstream;
- deriving transform coefficients for the current block based on the residual information;
- deriving residual samples by applying at least one of a low frequency non-separable transform (LFNST) kernel derived from an LFNST index or a primary transform kernel derived from a multiple transform selection (MTS) index to the transform coefficients;
- and
- generating a reconstructed picture based on the prediction samples and the residual samples,
- wherein the LFNST index is parsed before the MTS index, and
- wherein the MTS index is signaled based on a value of the LFNST index.
An image encoding method performed by an encoding apparatus, the method comprising:
- deriving prediction samples for a current block;
- deriving residual samples for the current block based on the prediction sample;
- deriving transform coefficients by applying at least one of a low frequency non-separable transform (LFNST) kernel or a primary transform kernel to the residual samples;
- and
- encoding i) prediction related information, ii) residual information related to the transform coefficients and iii) at least one of an LFNST index related to the LFNST kernel and an MTS index related to the primary transform kernel,
- wherein the LFNST index is encoded before the MTS index, and
- wherein the MTS index is encoded based on a value of the LFNST index.
A transmitting method comprising obtaining a bitstream, wherein the bitstream is generated by deriving prediction samples for a current block;
- deriving residual samples for the current block based on the prediction sample;
- deriving transform coefficients by applying at least one of a low frequency non-separable transform (LFNST) kernel or a primary transform kernel to the residual samples;
- and encoding i) prediction related information, ii) residual information related to the transform coefficients and iii) at least one of an LFNST index related to the LFNST kernel and an MTS index related to the primary transform kernel to generate the bitstream,
- wherein the LFNST index is encoded before the MTS index, and
- wherein the MTS index is encoded based on a value of the LFNST index.
Dependencies are inferred from the claim text.