Method and apparatus for video coding using improved cross-component linear model prediction
A method and an apparatus are disclosed for video coding using improved cross-component linear model (CCLM) prediction. The video coding method and the apparatus generate a first predictor of a current chroma block according to CCLM prediction, and additionally generate a second predictor of the current chroma block based on the neighboring pixels of the current chroma block in intra prediction of the current chroma block. The video coding method and the apparatus perform weighted combination on the first predictor and the second predictor.
1 . An intra prediction method for a current chroma block performed by a video decoding apparatus, the intra prediction method comprising:
determining a cross-component prediction mode for cross-component prediction for the current chroma block, wherein the cross-component prediction includes predicting the current chroma block using pixels in a corresponding luma region of the current chroma block;
generating a first predictor of the current chroma block by performing the cross-component prediction based on the cross-component prediction mode;
inferring, as a representative mode, an intra prediction mode derived from neighboring regions of the current chroma block;
generating a second predictor of the current chroma block by performing intra prediction using neighboring pixels of the current chroma block based on the representative mode;
deriving weights for the first predictor and the second predictor; and
generating an intra predictor of the current chroma block by performing weighted sum on the first predictor and the second predictor using the weights.
2 . The intra prediction method of claim 1 , wherein inferring the representative mode includes setting, as the representative mode, a prediction mode of a block including a neighboring pixel at a specific position among the neighboring pixels of the current chroma block.
3 . The intra prediction method of claim 1 , wherein inferring the representative mode includes setting a most frequent prediction mode derived based on a number of blocks among prediction modes of adjacent blocks of the current chroma block as the representative mode.
4 . The intra prediction method of claim 1 , wherein inferring the representative mode includes setting a most frequent prediction mode derived based on a block area among prediction modes of adjacent blocks of the current chroma block as the representative mode.
5 . The intra prediction method of claim 1 , wherein inferring the representative mode includes setting a most frequent prediction mode derived based on a prediction mode of a block including each neighboring pixel of the current chroma block as the representative mode.
6 . The intra prediction method of claim 1 , wherein inferring the representative mode includes setting, as the representative mode, a prediction mode of a block of which an aspect ratio is the same as or most similar to aspect ratio of the current chroma block among adjacent blocks of the current chroma block.
7 . The intra prediction method of claim 1 , wherein deriving the weights includes generating a neighboring pixel correlation based on a correlation between the current chroma block and adjacent blocks of the current chroma block, setting the neighboring pixel correlation as a weight of the second predictor, and setting a value obtained by subtracting the neighboring pixel correlation from 1 as a weight of the first predictor.
8 . The intra prediction method of claim 7 , wherein deriving the weights includes calculating a ratio of adjacent blocks using the representative mode to the adjacent blocks of the current chroma block based on a number of blocks to derive the neighboring pixel correlation.
9 . The intra prediction method of claim 7 , wherein deriving the weights includes calculating a ratio of the adjacent blocks of the current chroma block using the representative mode to the adjacent blocks based on a block area to derive the neighboring pixel correlation.
10 . The intra prediction method of claim 7 , wherein deriving the weights includes deriving the neighboring pixel correlation based on a ratio of a length of sides of the adjacent blocks of the current chroma block using the representative mode adjacent to the current chroma block to a length of entire side of the current chroma block adjacent to the adjacent blocks.
11 . The intra prediction method of claim 1 , wherein deriving the weights includes grouping the pixels of the intra predictor into a plurality of groups and setting the weight for each group, wherein the weight of the group including the pixels in the second predictor increases as a distance between the pixels in the second predictor and the neighboring pixels used at a time of generation of the second predictor becomes closer.
12 . An intra prediction method for a current chroma block performed by a video encoding apparatus, the intra prediction method comprising:
determining a cross-component prediction mode for cross-component prediction for the current chroma block, wherein the cross-component prediction includes predicting the current chroma block using pixels in a corresponding luma region for the current chroma block;
generating a first predictor of the current chroma block by performing the cross-component prediction based on the cross-component prediction mode;
inferring, as a representative mode, an intra prediction mode derived from neighboring regions of the current chroma block;
generating a second predictor of the current chroma block by performing intra prediction using neighboring pixels of the current chroma block based on the representative mode;
deriving weights for the first predictor and the second predictor; and
generating an intra predictor of the current chroma block by performing weighted sum on the first predictor and the second predictor using the weights.
13 . A method for providing a video decoding apparatus with video data, the method comprising:
encoding the video data into a bitstream; and
transmitting the bitstream to the video decoding device,
wherein encoding the video data comprises:
determining a cross-component prediction mode for cross-component prediction for a current chroma block, wherein the cross-component prediction includes predicting the current chroma block using pixels in a corresponding luma region for the current chroma block;
generating a first predictor of the current chroma block by performing the cross-component prediction based on the cross-component prediction mode;
inferring, as a representative mode from prediction modes of adjacent blocks, an intra prediction mode derived from neighboring regions of the current chroma block;
generating a second predictor of the current chroma block by performing intra prediction using neighboring pixels of the current chroma block based on the representative mode;
deriving weights for the first predictor and the second predictor; and
generating an intra predictor of the current chroma block by performing weighted sum on the first predictor and the second predictor using the weights.