Simplified parameter derivation for intra prediction
A method for video processing is provided. The method includes determining, for a conversion between a current video block of a video that is a chroma block and a coded representation of the video, parameters of a cross-component linear model that are completely determinable by two chroma samples and corresponding two luma samples; and performing the conversion based on the determining.
1. A method of video processing, comprising:
determining, for a conversion between a current video block of a video that is a chroma block and a coded representation of the video, parameters of a cross-component linear model that are determinable by two chroma values and two luma values; and
performing the conversion based on the determining;
wherein the two chroma values are denoted as C0 and C1, and the two luma values are denoted as L0 and L1, and wherein the parameters of a cross-component linear model are derived based on a difference between C1 and C0, and a difference between L1 and L0;
wherein predicted samples of the current video block are derived based on reconstructed samples of a luma block corresponding to the current video block and the parameters of the cross-component linear model, and
wherein if L1 is equal to L0, then the predicted samples of the current video block are based on C0 and not based on L0, L1 and C1.
2. The method of claim 1 , wherein if L1 is equal to L0, then the predicted samples of the current video block are set to the C0.
3. The method of claim 1 , wherein if L1 is equal to L0, other intra prediction mode than the cross-component linear model mode is used.
4. The method of claim 1 , wherein the parameters of the cross-component linear model are derived by excluding a division operation.
5. The method of claim 1 , wherein the parameters of the cross-component linear model are derived by using an operation without a look up table, the operation excluding a division operation.
6. The method of claim 1 , wherein the parameters of the cross-component linear model are derived by using Logarithmic operation.
7. The method of claim 6 , wherein the parameters of the cross-component linear model are derived based on a value of Floor(Log 2(L1−L0)), and wherein Floor(x) is a floor function that outputs an integer portion of x.
8. The method of claim 1 , wherein the performing of the conversion includes generating the coded representation from the current video block.
9. The method of claim 1 , wherein the performing of the conversion includes generating the current video block from the coded representation.
10. An apparatus in a video system comprising a processor and a non-transitory memory with instructions that cause the processor to:
determine, for a conversion between a current video block of a video that is a chroma block and a coded representation of the video, parameters of a cross-component linear model that are determinable by two chroma values and two luma values; and
perform the conversion based on the determining;
wherein the two chroma values are denoted as C0 and C1, and the two luma values are denoted as L0 and L1, and wherein the parameters of a cross-component linear model are derived based on a difference between C1 and C0, and a difference between L1 and L0;
wherein predicted samples of the current video block are derived based on reconstructed samples of a luma block corresponding to the current video block and the parameters of the cross-component linear model, and
wherein if L1 is equal to L0, then the predicted samples of the current video block are based on C0 and not based on L0, L1 and C1.
11. The apparatus of claim 10 , wherein if L1 is equal to L0, then the predicted samples of the current video block are set to the C0.
12. The apparatus of claim 10 , wherein the parameters of the cross-component linear model are derived by excluding a division operation.
13. The apparatus of claim 10 , wherein the parameters of the cross-component linear model are derived by using an operation without a look up table, the operation excluding a division operation.
14. The apparatus of claim 10 , wherein the parameters of the cross-component linear model are derived by using Logarithmic operation.
15. The apparatus of claim 14 , wherein the parameters of the cross-component linear model are derived based on a value of Floor(Log 2(L1−L0)), and wherein Floor(x) is a floor function that outputs an integer portion of x.
16. The apparatus of claim 10 , wherein the performing of the conversion includes generating the coded representation from the current video block.
17. The apparatus of claim 10 , wherein the performing of the conversion includes generating the current video block from the coded representation.
18. A computer program product stored on a non-transitory computer readable media, the computer program product including program codes that cause a processor to:
determine, for a conversion between a current video block of a video that is a chroma block and a coded representation of the video, parameters of a cross-component linear model that are determinable by two chroma values and two luma values; and
perform the conversion based on the determining;
wherein the two chroma values are denoted as C0 and C1, and the two luma values are denoted as L0 and L1, and wherein the parameters of a cross-component linear model are derived based on a difference between C1 and C0, and a difference between L1 and L0;
wherein predicted samples of the current video block are derived based on reconstructed samples of a luma block corresponding to the current video block and the parameters of the cross-component linear model, and
wherein if L1 is equal to L0, then the predicted samples of the current video block are based on C0 and not based on L0, L1 and C1.