Transform method, encoder, decoder, and storage medium
A transform method includes: determining a prediction mode parameter of a current block; determining a MIP parameter when the prediction mode parameter indicates that MIP is used for the current block to determine an intra prediction value; determining the intra prediction value of the current block according to the MIP parameter, and calculating a residual value between the current block and the intra prediction value; performing a first transform on the residual value to obtain a first coefficient matrix; determining a scanning order of LFNST coefficients used for the current block according to the MIP parameter when an LFNST is used for the current block; constructing an input coefficient matrix of the LFNST based on the first coefficient matrix according to the scanning order of LFNST coefficients; and performing an LFNST processing on the input coefficient matrix to obtain a transform coefficient matrix of the current block.
1. A transform method, applied to an encoder, the method comprising:
determining a prediction mode parameter of a current block;
determining a Matrix-based Intra Prediction (MIP) parameter when the prediction mode parameter indicates that MIP is used for the current block to determine an intra prediction value;
determining the intra prediction value of the current block according to the MIP parameter, and calculating a residual value between the current block and the intra prediction value;
performing a first transform on the residual value to obtain a first coefficient matrix; wherein the first transform is a transform different from Low-Frequency Non-Separable Transform (LFNST);
determining a scanning order of LFNST coefficients used for the current block according to the MIP parameter when an LFNST is used for the current block; wherein the scanning order of LFNST coefficients comprises a horizontal scanning order or a vertical scanning order;
constructing an input coefficient matrix of the LFNST based on the obtained first coefficient matrix according to the scanning order of LFNST coefficients, wherein the obtained first coefficient matrix comprises a two-dimensional primary transform coefficient matrix; and
performing an LFNST processing on the constructed input coefficient matrix to obtain a transform coefficient matrix of the current block;
wherein the MIP parameter comprises a MIP mode index, wherein the MIP mode index is used for indicating a MIP mode used for the current block, and the MIP mode is used for indicating a calculation and derivation method of determining the intra prediction value of the current block by using MIP;
wherein the determining the scanning order of LFNST coefficients used for the current block according to the MIP parameter comprises:
setting the scanning order of LFNST coefficients to a preset scanning order of LFNST coefficients corresponding to a value of the MIP mode index.
2. The method according to claim 1 , further comprising:
determining the scanning order of LFNST coefficients corresponding to the value of the MIP mode index by using a second look-up table;
wherein the second look-up table at least contains different scanning orders of LFNST coefficients, each of the different scanning orders of LFNST coefficients corresponding to one or more different MIP mode indices.
3. The method according to claim 1 , further comprising:
setting the scanning order of LFNST coefficients to a horizontal scanning order when the value of the MIP mode index is in a preset range of one or more integers; and
setting the scanning order of LFNST coefficients to a vertical scanning order when the value of the MIP mode index is not in the preset range of one or more integers.
4. A transform method, applied to a decoder, the method comprising:
parsing a bitstream and determining a prediction mode parameter of a current block;
parsing the bitstream and determining a Matrix-based Intra Prediction (MIP) parameter when the prediction mode parameter indicates that MIP is used for the current block to determine an intra prediction value;
parsing the bitstream and determining a transform coefficient matrix and a Low-Frequency Non-Separable Transform (LFNST) index of the current block;
processing the transform coefficient matrix of the current block by using an LFNST to obtain an LFNST output coefficient matrix when the LFNST index indicates that the LFNST is used for the current block;
determining a scanning order of LFNST coefficients used for the current block according to the MIP parameter, wherein the scanning order of LFNST coefficients comprises a vertical scanning order or a horizontal scanning order; and
constructing a first coefficient matrix based on the LFNST output coefficient matrix according to the scanning order of LFNST coefficients; wherein the constructed first coefficient matrix comprises a two-dimensional primary transform coefficient matrix;
wherein the MIP parameter comprises a MIP mode index, wherein the MIP mode index is used for indicating a MIP mode used for the current block, and the MIP mode is used for indicating a calculation and derivation method of determining the intra prediction value of the current block by using MIP;
wherein the determining the scanning order of LFNST coefficients used for the current block according to the MIP parameter comprises:
setting the scanning order of LFNST coefficients to a preset scanning order of LFNST coefficients corresponding to a value of the MIP mode index.
5. The method according to claim 4 , further comprising:
determining the scanning order of LFNST coefficients corresponding to the value of the MIP mode index by using a second look-up table;
wherein the second look-up table at least contains different scanning orders of LFNST coefficients, each of the different scanning orders of LFNST coefficients corresponding to one or more different MIP mode indices.
6. The method according to claim 4 , further comprising:
setting the scanning order of LFNST coefficients to a horizontal scanning order when the value of the MIP mode index is in a preset range of one or more integers; and
setting the scanning order of LFNST coefficients to a vertical scanning order when the value of the MIP mode index is not in the preset range of one or more integers.
7. The method according to claim 4 , further comprising:
determining the intra prediction value of the current block according to the MIP parameter;
performing a transform processing, which is different from the LFNST, on the first coefficient matrix to obtain a residual value of the current block; and
determining a reconstructed value of the current block based on the intra prediction value and the residual value.
8. An encoder comprising a first memory and a first processor, wherein
the first memory is configured to store a computer program runnable on the first processor; and
the first processor is configured to perform the method according to claim 1 when running the computer program.
9. A decoder comprising a second memory and a second processor, wherein
the second memory is configured to store a computer program runnable on the second processor; and
the second processor is configured to perform the method according to claim 4 when running the computer program.
10. A non-transitory computer storage medium having stored therein a computer program, wherein, the method according to claim 4 is implemented when the computer program is executed by a processor.