MIP for all channels in the case of 4:4:4-chroma format and of single tree

A video decoding method comprising:

• determining that a picture is in a 4:4:4 color sampling format;
• determining, based at least in part on an index signaled in a data stream, a matrix-based intra prediction (MIP) mode;
• decoding a luma block of the picture using the MIP mode;
• determining, for a chroma block of the picture, whether a coding tree of the chroma block is a single tree;
• selecting an intra prediction mode for decoding the chroma block;
• wherein:
• the selected intra prediction mode is the MIP mode in response to the determination that the coding tree of the chroma block is the single tree;
• and
• the selected intra prediction mode is a planar intra prediction mode in response to the determination that the coding tree of the chroma block is not the single tree;
• and
• decoding the chroma block using the selected intra prediction mode.

A video encoder comprising one or more processors, the one or more processors configured to:

• determine that a picture is in a 4:4:4 color sampling format;
• signal, in a data stream, an index indicating a matrix-based intra prediction (MIP) mode for encoding a luma block of the picture;
• encode the luma block using the MIP mode;
• determine, for a chroma block of the picture, whether a coding tree of the chroma block is a single tree;
• select an intra prediction mode for encoding the chroma block;
• wherein:
• the selected intra prediction mode is the MIP mode in response to the determination that the coding tree of the chroma block is the single tree;
• and
• the selected intra prediction mode is a planar intra prediction mode in response to the determination that the coding tree of the chroma block is not the single tree;
• and
• encode the chroma block using the selected intra prediction mode.

A video encoding method comprising:

• determining that a picture is in a 4:4:4 color sampling format;
• signaling, in a data stream, an index indicating a matrix-based intra prediction (MIP) mode for encoding a luma block of the picture;
• encoding the luma block using the MIP mode;
• determining, for a chroma block of the picture, whether a coding tree of the chroma block is a single tree;
• selecting an intra prediction mode for encoding the chroma block;
• wherein:
• the selected intra prediction mode is the MIP mode in response to the determination that the coding tree of the chroma block is the single tree;
• and
• the selected intra prediction mode is a planar intra prediction mode in response to the determination that the coding tree of the chroma block is not the single tree;
• and
• encoding the chroma block using the selected intra prediction mode.