Simplified signaling method for affine linear weighted intra prediction mode

1. A method for video encoding in an encoder, comprising:

responsive to a current block in a current picture being coded in matrix based intra prediction (MIP),

determining an MIP mode index for the current block, the MIP mode index indicating one of a plurality of MIP modes;

responsive to the current block not being coded in MIP and a first neighboring block of the current block being coded in MIP,

determining an intra prediction candidate mode for the current block to be a Planar intra prediction mode; and

encoding the current block according to (i) the one of the plurality of MIP modes in response to the current block being coded in MIP and (ii) the Planar intra prediction mode in response to the current block not being coded in MIP and the first neighboring block of the current block being coded in MIP.

2. The method of claim 1 , wherein the MIP mode index is one of a truncated binary codeword, a fixed length codeword, and a truncated unary codeword.

3. The method of claim 1 , further comprising:

responsive to the current block being coded in MIP,

constructing a mode candidate list including at least one fixed mode candidate, the at least one fixed mode candidate being a predetermined subset of the plurality of MIP modes.

4. The method of claim 1 , wherein a total number of the plurality of MIP modes is a power of two.

5. The method of claim 1 , further comprising:

responsive to the current block not being coded in MIP and the first neighboring block of the current block being coded in MIP,

constructing a mode candidate list for the current block based on one of (i) a preset intra prediction mode and (ii) an intra prediction mode of a second neighboring block of the current block, the mode candidate list including the Planar intra prediction mode.

6. The method of claim 5 , wherein the preset intra prediction mode is one of the Planar intra prediction mode, a DC intra prediction mode, a Horizontal intra prediction mode, and a Vertical intra prediction mode.

7. The method of claim 5 , wherein the constructing further comprises:

setting the first neighboring block of the current block as unavailable.

8. The method of claim 1 , further comprising:

responsive to the current block being coded in MIP and a derived mode being used for an associated chroma block of the current block,

setting a prediction mode of the associated chroma block to be a preset intra prediction mode.

9. A method for video encoding in an encoder, comprising:

determining that a current block in a current picture is coded in matrix based intra prediction (MIP);

determining whether a first neighboring block of the current block is coded in MIP;

responsive to the first neighboring block not being coded in MIP,

constructing a mode candidate list for the current block based on one of (i) a preset MIP mode and (ii) an MIP mode of a second neighboring block of the current block; and

encoding the current block based on the mode candidate list.

10. The method of claim 9 , wherein the encoding further comprises:

responsive to the first neighboring block not being coded in MIP,

setting the first neighboring block as unavailable.

11. The method of claim 9 , wherein the first neighboring block is adjacent to a top-right corner or a bottom-left corner of the current block.

12. The method of claim 9 , wherein a size of the mode candidate list is based on coded information of the first neighboring block.

13. The method of claim 9 , wherein a chroma block of the current block is associated with multiple luma blocks, and the method further comprises:

determining whether a luma block of the multiple luma blocks is coded in a non-MIP intra prediction mode; and

responsive to the luma block being coded in the non-MIP intra prediction mode,

determining a prediction mode of the chroma block of the current block to be the non-ALWIP intra prediction mode of the luma block.

14. The method of claim 13 , further comprising:

responsive to each of the multiple luma blocks being coded in MIP,

determining the prediction mode of the chroma block of the current block to be a preset intra prediction mode.

15. An apparatus, comprising a processing circuitry configured to:

responsive to a current block in a current picture being coded in matrix based intra prediction (MIP),

determine an MIP mode index for the current block, the MIP mode index indicating one of a plurality of MIP modes;

responsive to the current block not being coded in MIP and a neighboring block of the current block being coded in MIP,

determine an intra prediction candidate mode for the current block to be a Planar intra prediction mode; and

encode the current block according to (i) the one of the plurality of MIP modes in response to the current block being coded in MIP and (ii) the Planar intra prediction mode in response to the current block being not coded in MIP and the neighboring block of the current block being coded in MIP.

16. The apparatus of claim 15 , wherein the MIP mode index is one of a truncated binary codeword, a fixed length codeword, and a truncated unary codeword.

17. An apparatus, comprising a processing circuitry configured to:

determine that a current block in a current picture is coded in matrix based intra prediction (MIP);

determine whether a first neighboring block of the current block is coded in MIP;

responsive to the first neighboring block not being coded in MIP,

construct a mode candidate list for the current block based on one of (i) a preset MIP mode and (ii) an MIP mode of a second neighboring block of the current block; and

encode the current block based on the mode candidate list.

18. The apparatus of claim 17 , wherein the processing circuitry is further configured to:

responsive to the neighboring block not being coded in MIP,

set the neighboring block as unavailable.

19. A non-transitory computer-readable storage medium storing a program executable by at least one processor to perform:

responsive to a current block in a current picture being coded in matrix based intra prediction (MIP),

determining an MIP mode index for the current block, the MIP mode index indicating one of a plurality of MIP modes;

responsive to the current block not being coded in MIP and a neighboring block of the current block being coded in MIP,

determining an intra prediction candidate mode for the current block to be a Planar intra prediction mode; and

encoding the current block according to (i) the one of the plurality of MIP modes in response to the current block being coded in MIP and (ii) the Planar intra prediction mode in response to the current block not being coded in MIP and the neighboring block of the current block being coded in MIP.

20. A non-transitory computer-readable storage medium storing a program executable by at least one processor to perform:

determining that a current block in a current picture is coded in matrix based intra prediction (MIP);

determining whether a first neighboring block of the current block is coded in MIP;

responsive to the first neighboring block not being coded in MIP,

constructing a mode candidate list for the current block based on one of (i) a preset MIP mode and (ii) an MIP mode of a second neighboring block of the current block; and

encoding the current block based on the mode candidate list.