Methods and apparatus on transform and coefficient signaling
A method for video encoding includes determining whether any coding group of a transform block located within a zero-out region has a non-zero coefficient. The transform block comprises a non-zero region and the zero-out region. Further, in accordance with a determination that no coding group of the transform block located within the zero-out region has a non-zero coefficient, the method includes applying respective inverse transforms to transform coefficients of the transform block in both horizontal and vertical directions.
1. A method for video encoding, comprising:
determining whether any coding group of a transform block located within a zero-out region has a non-zero coefficient, wherein the transform block comprises a non-zero region and the zero-out region; and
in accordance with a determination that no coding group of the transform block located within the zero-out region has a non-zero coefficient:
applying respective inverse transforms to transform coefficients of the transform block in both horizontal and vertical directions.
2. The method of claim 1 , further comprising:
in accordance with a determination that a coding group of the transform block located within the zero-out region has a non-zero coefficient:
applying a predefined default inverse transform to the transform coefficients of the transform block in both the horizontal and vertical directions.
3. The method of claim 2 , wherein the predefined default inverse transform is inverse DCT-2 transform and the respective inverse transforms comprise inverse DST-7 transform and inverse DCT-8 transform.
4. The method of claim 1 , wherein chroma residuals of the transform block are coded in joint coding of chroma residuals (JCCR) mode and a transform skip mode is enabled for a corresponding chroma transform block.
5. The method of claim 1 , wherein the non-zero region is a top-left 16×16 region of the transform block.
6. The method of claim 1 , wherein a scan order of the coefficients of the transform block is a diagonal scan order.
7. An electronic apparatus comprising:
one or more processing units;
memory coupled to the one or more processing units; and
a plurality of programs stored in the memory that, when executed by the one or more processing units, cause the electronic apparatus to perform a method for video encoding, the method including:
determining whether any coding group of a transform block located within a zero-out region has a non-zero coefficient, wherein the transform block comprises a non-zero region and the zero-out region; and
in accordance with a determination that no coding group of the transform block located within the zero-out region has a non-zero coefficient:
applying respective inverse transforms to transform coefficients of the transform block in both horizontal and vertical directions.
8. The electronic apparatus of claim 7 , wherein the method further comprises:
in accordance with a determination that a coding group of the transform block located within the zero-out region has a non-zero coefficient:
applying a predefined default inverse transform to the transform coefficients of the transform block in both the horizontal and vertical directions.
9. The electronic apparatus of claim 8 , wherein the predefined default inverse transform is inverse DCT-2 transform and the respective inverse transforms comprise inverse DST-7 transform and inverse DCT-8 transform.
10. The electronic apparatus of claim 8 , wherein chroma residuals of the transform block are coded in joint coding of chroma residuals (JCCR) mode and a transform skip mode is enabled for a corresponding chroma transform block.
11. The electronic apparatus of claim 8 , wherein the non-zero region is a top-left 16×16 region of the transform block.
12. The electronic apparatus of claim 8 , wherein a scan order of the coefficients of the transform block is a diagonal scan order.
13. A non-transitory computer readable storage medium storing a bitstream generated by a method for video encoding, the method including:
determining whether any coding group of a transform block located within a zero-out region has a non-zero coefficient, wherein the transform block comprises a non-zero region and the zero-out region; and
in accordance with a determination that no coding group of the transform block located within the zero-out region has a non-zero coefficient:
applying respective inverse transforms to transform coefficients of the transform block in both horizontal and vertical directions.
14. The non-transitory computer readable storage medium of claim 13 , wherein the method further comprises:
in accordance with a determination that a coding group of the transform block located within the zero-out region has a non-zero coefficient:
applying a predefined default inverse transform to the transform coefficients of the transform block in both the horizontal and vertical directions.
15. The non-transitory computer readable storage medium of claim 14 , wherein the predefined default inverse transform is inverse DCT-2 transform and the respective inverse transforms comprise inverse DST-7 transform and inverse DCT-8 transform.
16. The non-transitory computer readable storage medium of claim 13 , wherein chroma residuals of the transform block are coded in joint coding of chroma residuals (JCCR) mode and a transform skip mode is enabled for a corresponding chroma transform block.
17. The non-transitory computer readable storage medium of claim 13 , wherein the non-zero region is a top-left 16×16 region of the transform block.
18. The non-transitory computer readable storage medium of claim 13 , wherein a scan order of the coefficients of the transform block is a diagonal scan order.