Video coding using multi-model linear model

A computing device including one or more processors, memory and a plurality of programs stored in the memory, wherein the programs, when executed by the one or more processors, cause the computing device to perform operations including:

• receiving bitstream encoding the chroma block, a corresponding luma block, a plurality of neighboring luma samples surrounding the luma block, and a plurality of neighboring chroma samples surrounding the chroma block;
• decoding the luma block, the plurality of neighboring luma samples, and the plurality of neighboring chroma samples to obtain a plurality of reconstructed luma samples of the luma block, a plurality of reconstructed neighboring luma samples, and a plurality of reconstructed neighboring chroma samples, respectively;
• selecting, from the plurality of reconstructed neighboring luma samples and the plurality of reconstructed neighboring chroma samples, a group of reference luma samples and a group of reference chroma samples, wherein each reference luma sample corresponds to a respective reference chroma sample;
• where selecting the group of reference luma samples and the group of reference chroma samples includes selecting every other luma samples from the plurality of reconstructed neighboring luma samples and every other chroma samples from the plurality of reconstructed neighboring chroma samples;
• computing a threshold luma value from the plurality of reconstructed neighboring luma samples, and a threshold chroma value from the plurality of reconstructed neighboring chroma samples;
• determining a maximum luma value and a minimum luma value from the group of the reference luma samples, wherein the threshold luma value is between the minimum luma value and the maximum luma value;
• generating a multi-model linear model including a first linear model between the minimum luma value and the threshold luma value, and a second linear model between the threshold luma value and the maximum luma value;
• and
• reconstructing the chroma block from the luma block using the multi-model linear model;
• wherein the computing device generates the multi-model linear model by perform operations including:
• determining a first chroma value of a first reference chroma sample corresponding to a first reference luma sample having the maximum luma value, and a second chroma value of a second reference chroma sample corresponding to a second reference luma sample having the minimum luma value;
• and wherein the first linear model connects (minimum luma value, second chroma value) and (threshold luma value, threshold chroma value) and the second linear model connects (threshold luma value, threshold chroma value) and (maximum luma value, first chroma value).

A non-transitory computer readable storage medium storing a plurality of programs for execution by a computing device having one or more processors, wherein the programs, when executed by the one or more processors, cause the computing device to perform operations including:

• receiving bitstream encoding the chroma block, a corresponding luma block, a plurality of neighboring luma samples surrounding the luma block, and a plurality of neighboring chroma samples surrounding the chroma block;
• decoding the luma block, the plurality of neighboring luma samples, and the plurality of neighboring chroma samples to obtain a plurality of reconstructed luma samples of the luma block, a plurality of reconstructed neighboring luma samples, and a plurality of reconstructed neighboring chroma samples, respectively;
• selecting, from the plurality of reconstructed neighboring luma samples and the plurality of reconstructed neighboring chroma samples, a group of reference luma samples and a group of reference chroma samples, wherein each reference luma sample corresponds to a respective reference chroma sample;
• where selecting the group of reference luma samples and the group of reference chroma samples includes selecting every other luma samples from the plurality of reconstructed neighboring luma samples and every other chroma samples from the plurality of reconstructed neighboring chroma samples;
• computing a threshold luma value from the plurality of reconstructed neighboring luma samples, and a threshold chroma value from the plurality of reconstructed neighboring chroma samples;
• determining a maximum luma value and a minimum luma value from the group of the reference luma samples, wherein the threshold luma value is between the minimum luma value and the maximum luma value;
• generating a multi-model linear model including a first linear model between the minimum luma value and the threshold luma value, and a second linear model between the threshold luma value and the maximum luma value;
• and
• reconstructing the chroma block from the luma block using the multi-model linear model;
• wherein generating the multi-model linear model includes:
• determining a first chroma value of a first reference chroma sample corresponding to a first reference luma sample having the maximum luma value, and a second chroma value of a second reference chroma sample corresponding to a second reference luma sample having the minimum luma value;
• and wherein the first linear model connects (minimum luma value, second chroma value) and (threshold luma value, threshold chroma value) and the second linear model connects (threshold luma value, threshold chroma value) and (maximum luma value, first chroma value).