| CPC H04N 19/132 (2014.11) [H04N 19/105 (2014.11); H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/186 (2014.11)] | 16 Claims |
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1. An encoding method, for an encoder and comprising:
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 an intra prediction value of a chroma component of the current block;
determining a product of a value of a shifting offset parameter and a sum of the MIP input sample values;
setting a value of a first offset to be a difference between a first constant value and the product;
determining an MIP weighting matrix of the current block according to the prediction parameter; and
calculating a first weighted sum of the MIP weighting matrix and the MIP input sample values;
calculating a first sum of the first weighted sum and the first offset;
determining a first right-shift value by binary right-shifting of the first sum, wherein the number of right shifted bits is equal to a value of a shifting number parameter; and
setting an MIP prediction value of the chroma component of the current block to be a sum of the first right-shift value and a value corresponding to index 0 in first temporal reference values, wherein the first temporal reference values are obtained by downsampling the neighbouring sample values of the current block, and the MIP prediction value is prediction values of partial samples in the chroma component of the current block;
determining the intra prediction value of the chroma component of the current block by filtering the MIP prediction value;
determining a prediction residual value of the chroma component of the current block according to the intra prediction value of the chroma component of the current block;
determining first transform coefficients by performing a first transform on prediction residual values of the current block;
determining whether to perform a low-frequency non-separable transform (LFNST) on at least partial transform coefficients of the first transform coefficients; and
based on a determination that the LFNST is determined to be performed on the at least partial transform coefficients, determining LFNST coefficients by performing the LFNST on the at least partial transform coefficients of the first transform coefficients, and setting a value of an LFNST index to be greater than zero;
based on a determination that the LFNST is determined not to be performed on the at least partial transform coefficients, setting the value of the LFNST index to be zero; and
encoding the LFNST index and signalling the encoded LFNST index into a bitstream, wherein
determining whether to perform the LFNST on the at least partial transform coefficients of the first transform coefficients comprises:
determining a minimum value among size parameters of the current block, when the MIP mode is used to determine the intra prediction value of the chroma component of the current block; and
determining to perform the LFNST on the at least partial transform coefficients of the first transform coefficients, when the minimum value is greater than or equal to a first preset threshold.
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