Intra prediction for square and non-square blocks in video compression
A method for video decoding is provided. For a current block, whether an angular intra prediction mode for the current block is a wide angle mode that is in a direction outside of a range of directions that spans a bottom left diagonal direction and a top right diagonal direction of the current block is determined. Based on the angular intra prediction mode being determined as the wide angle mode, an intra smooth filter is enabled, the enabled intra smooth filter is applied to blocks neighboring the current block to generate filtered blocks, and intra prediction is performed based on the filtered blocks to decode the current block.
1. A method for video decoding, comprising:
determining, for a current block that is a non-square block, whether an angular intra prediction mode for the current block is a wide angle mode that is in a direction outside of a range of directions that spans a bottom left diagonal direction and top right diagonal direction of the current block;
in response to determining that the angular intra prediction mode is the wide angle mode, determining whether a block size of the non-square block is greater than 32;
in response to determining that the block size of the non-square block is greater than 32, enabling an intra smoothing filter and applying the enabled intra smoothing filter to blocks neighboring the current block to generate filtered blocks; and
performing intra prediction based on the filtered blocks to obtain a characteristic value for the current block.
2. The method according to claim 1 , wherein the performing the intra prediction based on the filtered blocks further comprises:
determining whether a coding tool that utilizes the filtered blocks for performing the intra prediction supports the wide angle mode, and
in response to determining that the coding tool does not support the wide angle mode, changing the angular intra prediction mode from the wide angle mode to an intra prediction mode included in the range of directions that spans the bottom left diagonal direction and the top right diagonal direction of the current block.
3. The method according to claim 2 , wherein the angular intra prediction mode is changed to the intra prediction mode in the range of directions having a direction that is opposite to a direction of the wide angle mode such that the changed intra prediction mode is 180 degrees from the wide angle mode.
4. The method according to claim 2 , wherein the angular intra prediction mode is changed to the intra prediction mode in the range of directions that is nearest to the wide angle mode.
5. The method according to claim 2 , wherein the coding tool is an intra prediction coding tool.
6. The method according to claim 5 , wherein the intra prediction coding tool is Position Dependent Prediction Combination (PDPC).
7. The method according to claim 1 , wherein the block size of the current block is determined in accordance with a height, a width, or an arithmetic mean of the height and the width of the current block.
8. A video decoder for video decoding, comprising:
processing circuitry configured to:
determine, for a current block that is a non-square block, whether an angular intra prediction mode for the current block is a wide angle mode that is in a direction outside of a range of directions that spans a bottom left diagonal direction and top right diagonal direction of the current block;
in response to the angular intra prediction mode being determined as the wide angle mode, determine whether a block size of the non-square block is greater than 32;
in response to the block size of the non-square block being determined as greater than 32, enable an intra smoothing filter and apply the enabled intra smoothing filter to blocks neighboring the current block to generate filtered blocks; and
perform intra prediction based on the filtered blocks to obtain a characteristic value for the current block.
9. The video decoder according to claim 8 , wherein the processing circuitry is configured to:
determine whether a coding tool that utilizes the filtered blocks for performing the intra prediction supports the wide angle mode, and
in response to the coding tool being determined to not support the wide angle mode, change the angular intra prediction mode from the wide angle mode to an intra prediction mode included in the range of directions that spans the bottom left diagonal direction and the top right diagonal direction of the current block.
10. The video decoder according to claim 9 , wherein the angular intra prediction mode is changed to the intra prediction mode in the range of directions having a direction that is opposite to a direction of the wide angle mode such that the changed intra prediction mode is 180 degrees from the wide angle mode.
11. The video decoder according to claim 9 , wherein the angular intra prediction mode is changed to the intra prediction mode in the range of directions that is nearest to the wide angle mode.
12. The video decoder according to claim 9 , wherein the coding tool is an intra prediction coding tool.
13. The video decoder according to claim 12 , wherein the intra prediction coding tool is Position Dependent Prediction Combination (PDPC).
14. The video decoder according to claim 8 , wherein the block size of the current block is determined in accordance with a height, a width, or an arithmetic mean of the height and the width of the current block.
15. A non-transitory computer readable medium having instructions stored therein, which when executed by a processor in a video decoder causes the video decoder to execute a method comprising:
determining, for a current block that is a non-square block, whether an angular intra prediction mode for the current block is a wide angle mode that is in a direction outside of a range of directions that spans a bottom left diagonal direction and top right diagonal direction of the current block;
in response to determining that the angular intra prediction mode is the wide angle mode, determining whether a block size of the non-square block is greater than 32;
in response to determining that the block size of the non-square block is greater than 32, enabling an intra smoothing filter and applying the enabled intra smoothing filter to blocks neighboring the current block to generate filtered blocks; and
performing intra prediction based on the filtered blocks to obtain a characteristic value for the current block.
16. The non-transitory computer readable medium according to claim 15 , wherein the performing the intra prediction based on the filtered blocks further comprises:
determining whether a coding tool that utilizes the filtered blocks for performing the intra prediction supports the wide angle mode, and
in response to determining that the coding tool does not support the wide angle mode, changing the angular intra prediction mode from the wide angle mode to an intra prediction mode included in the range of directions that spans the bottom left diagonal direction and the top right diagonal direction of the current block.
17. The non-transitory computer readable medium according to claim 16 , wherein the angular intra prediction mode is changed to the intra prediction mode in the range of directions having a direction that is opposite to a direction of the wide angle mode such that the changed intra prediction mode is 180 degrees from the wide angle mode.
18. The non-transitory computer readable medium according to claim 16 , wherein the angular intra prediction mode is changed to the intra prediction mode in the range of directions that is nearest to the wide angle mode.
19. The non-transitory computer readable medium according to claim 16 , wherein the coding tool is one of an intra prediction coding tool and Position Dependent Prediction Combination (PDPC).
20. The non-transitory computer readable medium according to claim 15 , wherein the block size of the current block is determined in accordance with a height, a width, or an arithmetic mean of the height and the width of the current block.