Method and apparatus of non-square intra prediction for chroma components in coding system with quad-tree and binary-tree partition

A method of video coding using Intra prediction video data, comprising:

• receiving input data for a current block;
• partitioning the current block into one or more final sub-blocks including at least one non-square final sub-block using block partition recursively, wherein the block partition either splits each given block into intermediate sub-blocks using one or more split modes including one binary split mode or applies no splitting to each given block, the current block is treated as an initial given block, each intermediate sub-block is treated as one given block in a next recursion, and any one given block not further split becomes one final sub-block;
• and
• applying non-square Intra prediction to each non-square final sub-block by including X additional neighboring reconstructed samples or excluding X neighboring reconstructed samples for deriving DC predictor associated with DC Intra predictor mode, and/or including Y additional neighboring reconstructed samples or excluding Y neighboring reconstructed samples for deriving Intra prediction parameters associated with LM (luma-predict-chroma) Intra prediction mode, wherein X and Y are positive integers,
• wherein each non-square final sub-block has neighboring reconstructed samples along a short side and a long side of each non-square final sub-block, wherein at least one of a first length of the long side of each non-square final sub-block and a second length of the short side of each non-square final sub-block is a power-of-2 integer, wherein X or Y equals the first length of the long side of each non-square final sub-block minus the second length of the short side of each non-square final sub-block, wherein said applying non-square Intra prediction to each non-square final sub-block comprises deriving DC predictor associated with DC Intra predictor mode based only on neighboring reconstructed samples of the long side of each non-square final sub-block, and wherein the DC predictor is a value that is an average of the neighboring reconstructed samples of the long side.

An apparatus for video decoding using Intra prediction for video data, comprising one or more electronic circuitries arranged to:

• receive a video bitstream including coded data for a current block;
• derive, from the video bitstream, a block partitioning structure for partitioning the current block into one or more final sub-blocks including at least one non-square final sub-block using block partition recursively, wherein the block partition either splits each given block into intermediate sub-blocks using one or more split modes including one binary split mode or applies no splitting to each given block, the current block is treated as an initial given block, each intermediate sub-block is treated as one given block in a next recursion, and any one given block not further split becomes one final sub-block;
• and
• reconstruct each non-square final sub-block using non-square Intra prediction by including X additional neighboring reconstructed samples or excluding X neighboring reconstructed samples for deriving DC predictor associated with DC Intra predictor mode, and/or including Y additional neighboring reconstructed samples or excluding Y neighboring reconstructed samples for deriving Intra prediction parameters associated with LM (luma-predict-chroma) Intra prediction mode, wherein X and Y are positive integers,
• wherein each non-square final sub-block has neighboring reconstructed samples along a short side and a long side of each non-square final sub-block, wherein at least one of a first length of the long side of each non-square final sub-block and a second length of the short side of each non-square final sub-block is a power-of-2 integer, wherein X or Y equals the first length of the long side of each non-square final sub-block minus the second length of the short side of each non-square final sub-block, wherein said reconstructing each non-square final sub-block using non-square Intra prediction comprises deriving DC predictor associated with DC Intra predictor mode based only on neighboring reconstructed samples of the long side of each non-square final sub-block, and wherein the DC predictor is a value that is an average of the neighboring reconstructed samples of the long side.