Intra-prediction mode for screen content coding of video coding
An example video decoder is configured to decode a first value for a first syntax element of a current block of video data, the first value indicating that the current block is encoded using an intra-prediction mode; after decoding the first value, decode a second value for a second syntax element of the current block, the second value indicating that the current block is encoded using intra mapping mode. In the intra mapping mode, the video decoder is configured to generate a prediction block for the current block using the intra-prediction mode and decode a residual block. To decode the residual block, the video decoder is configured to determine predictors for quantized residual values of the residual block and map decoded mapping values to the quantized residual values using the predictors. The video decoder combines the prediction block with the residual block to decode the current block.
1. A method of decoding video data, the method comprising:
decoding a first value for a first syntax element of a current block of video data, the first value indicating that the current block is encoded using an intra-prediction mode;
after decoding the first value, decoding a second value for a second syntax element of the current block, the second value indicating that the current block is encoded using intra mapping mode;
generating a prediction block for the current block using the intra-prediction mode;
in response to decoding the second value indicating the current block is encoded using intra mapping mode, decoding a residual block for the current block, comprising, for each quantized residual value for the current block:
determining a predictor for a current quantized residual value from a neighboring quantized residual value to the current quantized residual value, the predictor being separate from the prediction block;
entropy decoding a mapping value for the current quantized residual value;
when the mapping value is equal to one, setting the current quantized residual value equal to the predictor; and
when the mapping value is not equal to one, setting the current quantized residual value equal to the mapping value or the mapping value minus one; and
combining the prediction block with the residual block to decode the current block.
2. The method of claim 1 , wherein when the mapping value is not equal to one, setting the current quantized residual value comprises:
when the mapping value is less than or equal to the predictor, setting the current quantized residual value equal to the mapping value minus one; or
when the mapping value is greater than the predictor, setting the current quantized residual value equal to the mapping value.
3. The method of claim 1 , wherein entropy decoding the mapping value comprises:
entropy decoding a significant coefficient flag for the mapping value;
entropy decoding one or more absolute level greater than N flags, N being a positive integer value, for the mapping value;
entropy decoding a parity flag for the mapping value; and
when each of the absolute level greater than N flags has a value of one, entropy decoding an absolute remainder value for the mapping value.
4. The method of claim 1 , further comprising determining that the first value for the first syntax element indicates that the intra-prediction mode comprises one of a horizontal intra-prediction mode or a vertical intra-prediction mode.
5. The method of claim 1 , wherein decoding the residual block comprises, in response to decoding the second value, avoiding application of residual differential pulse code modulation (RDPCM) mode to the residual block.
6. The method of claim 1 , wherein decoding the residual block comprises, in response to decoding the second value, avoiding residual level prediction for the residual block.
7. The method of claim 1 , wherein generating the prediction block comprises generating the prediction block using unfiltered neighboring pixels to the current block.
8. The method of claim 1 , wherein determining the predictor comprises calculating the predictor as a sum of an absolute value of an above-neighboring quantized residual value to the current quantized residual value and an absolute value of a left-neighboring quantized residual value to the current quantized residual value and bitwise right-shifting the sum.
9. The method of claim 1 , wherein determining the predictor comprises:
when an absolute value of an above-neighboring quantized residual value to the current quantized residual value is greater than an absolute value of a left-neighboring quantized residual value to the current quantized residual value, setting the predictor equal to the absolute value of the above-neighboring quantized residual value; or
when the absolute value of the above-neighboring quantized residual value is not greater than the absolute value of the left-neighboring quantized residual value, setting the predictor equal to the absolute value of the left-neighboring quantized residual value.
10. A device for decoding video data, the device comprising:
a memory configured to store video data; and
one or more processors implemented in circuitry and configured to:
decode a first value for a first syntax element of a current block of the video data, the first value indicating that the current block is encoded using an intra-prediction mode;
after decoding the first value, decode a second value for a second syntax element of the current block, the second value indicating that the current block is encoded using intra mapping mode;
generate a prediction block for the current block using the intra-prediction mode;
in response to decoding the second value, decode a residual block for the current block, wherein to decode the residual block, the one or more processors are configured to, for each quantized residual value for the current block:
determine a predictor for a current quantized residual value from a neighboring quantized residual value to the current quantized residual value, the predictor being separate from the prediction block;
entropy decode a mapping value for the current quantized residual value;
when the mapping value is equal to one, set the current quantized residual value equal to the predictor; and
when the mapping value is not equal to one, set the current quantized residual value equal to the mapping value or the mapping value minus one; and
combine the prediction block with the residual block to decode the current block.
11. The device of claim 10 , wherein when the mapping value is not equal to one, the one or more processors are configured to:
when the mapping value is less than or equal to the predictor, set the current quantized residual value equal to the mapping value minus one; or
when the mapping value is greater than the predictor, set the current quantized residual value equal to the mapping value.
12. The device of claim 10 , wherein to entropy decode the mapping value, the one or more processors are configured to:
entropy decode one or more absolute level greater than N flags, N being a positive integer value, for the mapping value;
entropy decode a parity flag for the mapping value; and
when each of the absolute level greater than N flags has a value of one, entropy decode an absolute remainder value for the mapping value.
13. The device of claim 10 , wherein the one or more processors are further configured to determine that the first value for the first syntax element indicates that the intra-prediction mode comprises one of a horizontal intra-prediction mode or a vertical intra-prediction mode.
14. The device of claim 10 , wherein the one or more processors are configured to, in response to decoding the second value, avoid application of residual differential pulse code modulation (RDPCM) mode to the residual block.
15. The device of claim 10 , wherein the one or more processors are configured to, in response to decoding the second value, avoid residual level prediction for the residual block.
16. The device of claim 10 , the one or more processors are configured to generate the prediction block using unfiltered neighboring pixels to the current block.
17. The device of claim 10 , wherein the one or more processors are configured to calculate the predictor as a sum of an absolute value of an above-neighboring quantized residual value to the current quantized residual value and an absolute value of a left-neighboring quantized residual value to the current quantized residual value and bitwise right-shift the sum.
18. The device of claim 10 , wherein to determine the predictor, the one or more processors are configured to:
when an absolute value of an above-neighboring quantized residual value to the current quantized residual value is greater than an absolute value of a left-neighboring quantized residual value to the current quantized residual value, set the predictor equal to the absolute value of the above-neighboring quantized residual value; or
when the absolute value of the above-neighboring quantized residual value is not greater than the absolute value of the left-neighboring quantized residual value, set the predictor equal to the absolute value of the left-neighboring quantized residual value.
19. The device of claim 10 , further comprising a display configured to display decoded video data.
20. The device of claim 10 , wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.
21. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause a processor to:
decode a first value for a first syntax element of a current block of video data, the first value indicating that the current block is encoded using an intra-prediction mode;
after decoding the first value, decode a second value for a second syntax element of the current block, the second value indicating that the current block is encoded using intra mapping mode;
generate a prediction block for the current block using the intra-prediction mode;
in response to decoding the second value, decode a residual block for the current block, comprising instructions that cause the processor to, for each quantized residual value for the current block:
determine a predictor for a current quantized residual value from a neighboring quantized residual value to the current quantized residual value, the predictor being separate from the prediction block;
entropy decode a mapping value for the current quantized residual value;
when the mapping value is equal to one, set the current quantized residual value equal to the predictor; and
when the mapping value is not equal to one, set the current quantized residual value equal to the mapping value or the mapping value minus one; and
combine the prediction block with the residual block to decode the current block.
22. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to set the current quantized residual value comprise instructions that cause the processor to, when the mapping value is not equal to one:
when the mapping value is less than or equal to the predictor, set the current quantized residual value equal to the mapping value minus one; or
when the mapping value is greater than the predictor, set the current quantized residual value equal to the mapping value.
23. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to entropy decode the mapping value comprise instructions that cause the processor to:
entropy decode a significant coefficient flag for the mapping value;
entropy decode one or more absolute level greater than N flags, N being a positive integer value, for the mapping value;
entropy decode a parity flag for the mapping value; and
when each of the absolute level greater than N flags has a value of one, entropy decode an absolute remainder value for the mapping value.
24. The non-transitory computer-readable storage medium of claim 21 , further comprising instructions that cause the processor to determine that the first value for the first syntax element indicates that the intra-prediction mode comprises one of a horizontal intra-prediction mode or a vertical intra-prediction mode.
25. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to decode the residual block comprise instructions that cause the processor to, in response to decoding the second value, avoid application of residual differential pulse code modulation (RDPCM) mode to the residual block.
26. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to decode the residual block comprise instructions that cause the processor to, in response to decoding the second value, avoid residual level prediction for the residual block.
27. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to generate the prediction block comprise instructions that cause the processor to generate the prediction block using unfiltered neighboring pixels to the current block.
28. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to determine the predictor comprise instructions that cause the processor to calculate the predictor as a sum of an absolute value of an above-neighboring quantized residual value to the current quantized residual value and an absolute value of a left-neighboring quantized residual value to the current quantized residual value and bitwise right-shifting the sum.
29. The non-transitory computer-readable storage medium of claim 21 , wherein the instructions that cause the processor to determine the predictor comprise instructions that cause the processor to:
when an absolute value of an above-neighboring quantized residual value to the current quantized residual value is greater than an absolute value of a left-neighboring quantized residual value to the current quantized residual value, set the predictor equal to the absolute value of the above-neighboring quantized residual value; or
when the absolute value of the above-neighboring quantized residual value is not greater than the absolute value of the left-neighboring quantized residual value, set the predictor equal to the absolute value of the left-neighboring quantized residual value.
30. A device for decoding video data, the device comprising:
means for decoding a first value for a first syntax element of a current block of video data, the first value indicating that the current block is encoded using an intra-prediction mode;
means for decoding a second value for a second syntax element of the current block after decoding the first value, the second value indicating that the current block is encoded using intra mapping mode;
means for generating a prediction block for the current block using the intra-prediction mode;
means for decoding a residual block for the current block in response to decoding the second value, comprising:
means for determining a predictor for a current quantized residual value from a neighboring quantized residual value to the current quantized residual value, the predictor being separate from the prediction block;
means for entropy decoding a mapping value for the current quantized residual value;
means for setting the current quantized residual value equal to the predictor when the mapping value is equal to one; and
means for setting the current quantized residual value equal to the mapping value or the mapping value minus one when the mapping value is not equal to one; and
means for combining the prediction block with the residual block to decode the current block.