Method and apparatus of simplified luma-based chroma intra prediction

An apparatus of chroma intra prediction based on reconstructed luma pixels and chroma pixels, the apparatus comprising:

• at least one circuit, the at least one circuit configured for:
• receiving neighboring reconstructed luma pixels and current reconstructed luma pixels of a current luma block from a media or a processor;
• receiving neighboring reconstructed chroma pixels of a current chroma block from the media or the processor, wherein the current chroma block is co-located with the current luma block;
• deriving chroma intra prediction for chroma pixels of the current chroma block based on derived co-located current luma pixels of the current luma block scaled by a scaling factor, wherein the scaling factor comprises a product term of a division factor and a scaled covariance value associated with the neighboring reconstructed luma pixels of the current luma block and the neighboring reconstructed chroma pixels of the current chroma block, wherein the division factor is related to a first data range divided with rounding by a scaled variance value associated with the neighboring reconstructed luma pixels of the current luma block;
• and
• providing the chroma intra prediction for encoding or decoding of the chroma pixels of the current chroma block;
• wherein said scaled covariance value is derived based on a covariance value associated with the neighboring reconstructed luma pixels of the current luma block and the neighboring reconstructed chroma pixels of the current chroma block, wherein said scaled covariance value corresponds to right-shifting said covariance value by a first number of bits related to said covariance value and the internal bit depth with which chroma signal is processed during video coding process, a1s=a1>>Max(0, Log 2(abs(a1))−(BitDepthC−2)), wherein a1s represents said scaled covariance value, a1 represents said covariance value, and BitDepthC represents an internal bit depth with which chroma signal is processed during video coding process.

A method of chroma intra prediction based on reconstructed luma pixels and chroma pixels, the method comprising:

• receiving neighboring reconstructed luma pixels and current reconstructed luma pixels of a current luma block from a media or a processor;
• receiving neighboring reconstructed chroma pixels of a current chroma block from the media or the processor, wherein the current chroma block is co-located with the current luma block;
• deriving chroma intra prediction for chroma pixels of the current chroma block based on derived co-located current luma pixels of the current luma block scaled by a scaling factor, wherein the scaling factor comprises a product term of a division factor and a scaled covariance value associated with the neighboring reconstructed luma pixels of the current luma block and the neighboring reconstructed chroma pixels of the current chroma block, wherein the division factor is related to a first data range divided with rounding by a scaled variance value associated with the neighboring reconstructed luma pixels of the current luma block;
• and
• providing the chroma intra prediction for encoding or decoding of the chroma pixels of the current chroma block;
• wherein said scaled variance value is derived based on a variance value associated with the neighboring reconstructed luma pixels of the current luma block, wherein said scaled variance value corresponds to right-shifting said variance value by a second number of bits related to said variance value, a2s=abs(a2>>Max(0, Log 2(abs(a2))−5)), wherein a2s represents said scaled variance value and a2 represents said variance value.

An apparatus of chroma intra prediction based on reconstructed luma pixels and chroma pixels, the apparatus comprising:

• at least one circuit, the at least one circuit configured for:
• receiving neighboring reconstructed luma pixels and current reconstructed luma pixels of a current luma block from a media or a processor;
• receiving neighboring reconstructed chroma pixels of a current chroma block from the media or the processor, wherein the current chroma block is co-located with the current luma block;
• deriving chroma intra prediction for chroma pixels of the current chroma block based on derived co-located current luma pixels of the current luma block scaled by a scaling factor, wherein the scaling factor comprises a product term of a division factor and a scaled covariance value associated with the neighboring reconstructed luma pixels of the current luma block and the neighboring reconstructed chroma pixels of the current chroma block, wherein the division factor is related to a first data range divided with rounding by a scaled variance value associated with the neighboring reconstructed luma pixels of the current luma block;
• and
• providing the chroma intra prediction for encoding or decoding of the chroma pixels of the current chroma block;
• wherein said scaled variance value is derived based on a variance value associated with the neighboring reconstructed luma pixels of the current luma block, wherein said scaled variance value corresponds to right-shifting said variance value by a second number of bits related to said variance value, a2s=abs(a2>>Max(0, Log 2(abs(a2))−5)), wherein a2s represents said scaled variance value and a2 represents said variance value.