Chroma block prediction method and apparatus

A chroma block prediction apparatus, comprising:

• one or more processors;
• and
• a non-transitory computer-readable storage medium coupled to the one or more processors and storing instructions for execution by the one or more processors, wherein the instructions, when executed by the one or more processors, cause the apparatus to:
• determine preset locations based on an intra prediction mode corresponding to a chroma block;
• obtain four chroma values of chroma samples at the preset locations;
• and
• obtain, based on neighboring samples of a luma block corresponding to a chroma block, four luma values of luma samples corresponding to the four chroma values of the chroma samples at the preset locations;
• classify the four luma values into two smaller luma values and two larger luma values by sorting the four luma values;
• group the two smaller luma values into a first luma set, and group the two larger luma values into a second luma set;
• group chroma values of chroma samples corresponding to luma samples associated with luma values in the first luma set into a first chroma set, and group chroma values of chroma samples corresponding to luma samples associated with luma values in the second luma set into a second chroma set;
• and
• determine a scaling coefficient in a linear model corresponding to the chroma block based on an average value of the luma values in the first luma set, an average value of the luma values in the second luma set, an average value of the chroma values in the first chroma set, and an average value of the chroma values in the second chroma set;
• determine, based on the scaling coefficient, an offset factor in the linear model corresponding to the chroma block;
• determine prediction information of the chroma block based on the scaling coefficient, the offset factor, and luma reconstruction information corresponding to the chroma block, wherein the luma reconstruction information corresponding to the chroma block comprises downsampling information of a luma reconstructed block corresponding to the chroma block;
• encode indication information into a bitstream, wherein the indication information is used to indicate the intra prediction mode corresponding to the chroma block, wherein the intra prediction mode is a linear mode above (LMA) mode.

A non-transitory computer-readable storage medium storing an instruction and a bitstream that is generated by a video encoding method, wherein the bitstream comprises encoded video data and indication information, wherein the indication information is used to indicate an intra prediction mode corresponding to a chroma block, wherein the intra prediction mode is a linear mode above (LMA) mode, which when the instruction is performed by a processor, cause the processor to perform operations of:

• determining preset locations based on an intra prediction mode corresponding to a chroma block;
• obtaining four chroma values of chroma samples at the preset locations;
• obtaining, based on neighboring samples of a luma block corresponding to a chroma block, four luma values of luma samples corresponding to the four chroma values of the chroma samples at the preset locations;
• classifying the four luma values into two smaller luma values and two larger luma values by sorting the four luma values;
• grouping the two smaller luma values into a first luma set, and grouping the two larger luma values into a second luma set;
• grouping chroma values of chroma samples corresponding to luma samples associated with luma values in the first luma set into a first chroma set, and grouping chroma values of chroma samples corresponding to luma samples associated with luma values in the second luma set into a second chroma set;
• determining a scaling coefficient in a linear model corresponding to the chroma block based on an average value of the luma values in the first luma set, an average value of the luma values in the second luma set, an average value of the chroma values in the first chroma set, and an in average value of the chroma values in the second chroma set;
• determining, based on the scaling coefficient, an offset factor in the linear model corresponding to the chroma block;
• and
• determining prediction information of the chroma block based on the scaling coefficient, the offset factor, and luma reconstruction information corresponding to the chroma block, wherein the luma reconstruction information corresponding to the chroma block comprises downsampling information of a luma reconstructed block corresponding to the chroma block;
• encoding indication information into a bitstream, wherein the indication information is used to indicate the intra prediction mode corresponding to the chroma block, wherein the intra prediction mode is a linear mode above (LMA) mode.