Encoding method, decoding method, and decoder

A decoding method, for a decoder and comprising:

• parsing a bitstream to obtain a prediction parameter and a low-frequency non-separable transform (LFNST) index of a current block, the prediction parameter comprising a prediction mode parameter;
• obtaining neighbouring sample values of the current block and determining matrix-based intra prediction (MIP) input sample values of the current block according to the neighbouring sample values of the current block, when the prediction mode parameter indicates that an MIP mode is used to determine intra prediction values of a colour component of the current block;
• determining MIP prediction values of the colour component of the current block according to the MIP input sample values, an MIP weighting matrix, a shifting offset parameter and a shifting number parameter, wherein the MIP prediction values are prediction values of partial samples of the colour component of the current block, a value of the shifting offset parameter is equal to 32, and a value of the shifting number parameter is equal to 6;
• determining the intra prediction values of the colour component of the current block by filtering the MIP prediction values;
• determining reconstructed transform coefficients of the current block;
• determining second transform coefficients by performing an LFNST on at least partial reconstructed transform coefficients of the reconstructed transform coefficients, when the LFNST index indicates that the LFNST is to be performed on the current block;
• determining reconstructed residual values of the colour component of the current block by performing a first transform on the second transform coefficients;
• and
• determining reconstructed values of the colour component of the current block according to the intra prediction values of the colour component of the current block and the reconstructed residual values.

A non-transitory computer readable storage medium, storing computer programs and a bitstream, wherein when executed by a processor, the computer programs cause the processor to implement an encoding method to generate the bitstream, and the encoding method comprises:

• determining a prediction parameter of a current block, the prediction parameter comprising a prediction mode parameter;
• obtaining neighbouring sample values of the current block and determining matrix-based intra prediction (MIP) input sample values of the current block according to the neighbouring sample values of the current block, when the prediction mode parameter indicates that an MIP mode is used to determine intra prediction values of a colour component of the current block;
• determining MIP prediction values of the colour component of the current block according to the MIP input sample values, an MIP weighting matrix, a shifting offset parameter and a shifting number parameter, wherein the MIP prediction values are prediction values of partial samples of the colour component of the current block, a value of the shifting offset parameter is equal to 32, and a value of the shifting number parameter is equal to 6;
• determining the intra prediction values of the colour component of the current block by filtering the MIP prediction values;
• determining prediction residual values of the colour component of the current block according to the intra prediction values of the colour component of the current block;
• determining first transform coefficients by performing a first transform on the prediction residual values;
• determining low-frequency non-separable transform (LFNST) coefficients by performing LFNST on at least partial transform coefficients of the first transform coefficients, based on a determination that the LFNST is determined to be performed on the at least partial transform coefficients;
• determining a value of an LFNST index;
• and
• encoding the LFNST index and the LFNST coefficients and signalling the encoded LFNST index and the encoded LFNST coefficients into a bitstream.