Grouping bypass coded syntax elements in video coding

1. A method of decoding video data, the method comprising:

receiving an entropy encoded bitstream that includes a first group of syntax elements comprising a plurality of flags and a second group of syntax elements for prediction units (PUs) of a coding unit (CU), wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, and wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples of a respective PU in the CU is based on an index into a list of most probable modes and which syntax element is to be received in the second group of syntax elements for the respective PU in the CU, wherein receiving comprises receiving all syntax elements of the first group of syntax elements for the PUs of the CU before receiving any syntax elements of the second group of syntax elements for the PUs of the CU;

context adaptive binary arithmetic coding (CABAC) decoding all syntax elements of the first group of syntax elements prior to bypass decoding any syntax elements of the second group of syntax elements;

subsequent to CABAC decoding all syntax elements of the first group of syntax elements, bypass decoding the second group of syntax elements, wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes; and

reconstructing the video data based on the decoded first group of syntax elements and the decoded second group of syntax elements.

2. The method of claim 1 , further comprising:

CABAC decoding a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC decoding of the first group of syntax elements; and

bypass decoding a second set of bins used to indicate the chroma intra prediction mode separately from the bypass decoding of the second group of syntax elements.

3. The method of claim 1 , wherein the list of most probable modes identifies one or more intra-prediction modes of one or more neighboring PUs.

4. The method of claim 1 , wherein the first group of syntax elements includes four flags, and wherein each of the four flags is associated with a respective PU of an INTRA N×N PU structure of the CU.

5. The method of claim 1 , wherein reconstructing comprises:

intra-prediction decoding the PUs of the CU based on the first group of syntax elements and the second group of syntax elements.

6. An apparatus for decoding video data, the apparatus comprising:

a memory configured to store the video data; and

one or more processor comprising a video decoder, the video decoder configured to:

receive an entropy encoded bitstream that includes a first group of syntax elements comprising a plurality of flags and a second group of syntax elements for prediction units (PUs) of a coding unit (CU), wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, and wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode luma samples of a respective PU in the CU is based on an index into a list of most probable modes and which syntax element is to be received in the second group of syntax elements for the respective PU in the CU, wherein the video decoder is configured to receive all syntax elements of the first group of syntax elements for the PUs of the CU before receiving any syntax elements of the second group of syntax elements for the PUs of the CU;

context adaptive binary arithmetic coding (CABAC) decode all syntax elements of the first group of syntax elements prior to bypass decoding any syntax elements of the second group of syntax elements;

subsequent to CABAC decoding all syntax elements of the first group of syntax elements, bypass decode the second group of syntax elements, wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes; and

reconstructing the video data based on the decoded first group of syntax elements and the decoded second group of syntax elements that are stored in the memory.

7. The apparatus of claim 6 , wherein the video decoder is configured to:

CABAC decode a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC decoding of the first group of syntax elements; and

bypass decode a second set of bins used to indicate the chroma intra prediction mode separately from the bypass decoding of the second group of syntax elements.

8. The apparatus of claim 6 , wherein the list of most probable modes identifies one or more intra-prediction modes of one or more neighboring PUs.

9. The apparatus of claim 6 , wherein the first group of syntax elements includes four flags, and wherein each of the four flags is associated with a respective PU of an INTRA N×N PU structure of the CU.

10. The apparatus of claim 6 , wherein, to reconstruct, the video decoder is configured to:

intra-prediction decode the PUs of the CU based on the first group of syntax elements and the second group of syntax elements.

11. The apparatus of claim 6 , wherein the apparatus comprises at least one of:

an integrated circuit;

a microprocessor; or

a wireless communication device that includes the video decoder and a display to display the reconstructed video data.

12. A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors of a device for decoding video data to:

receive an entropy encoded bitstream that includes a first group of syntax elements comprising a plurality of flags and a second group of syntax elements for prediction units (PUs) of a coding unit (CU), wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, and wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples of a respective PU in the CU is based on an index into a list of most probable modes and which syntax element is to be received in the second group of syntax elements for the respective PU in the CU, wherein the instructions that cause the one or more processors to receive comprise instructions that cause the one or more processors to receive all syntax elements of the first group of syntax elements for the PUs of the CU before receiving any syntax elements of the second group of syntax elements for the PUs of the CU;

context adaptive binary arithmetic coding (CABAC) decode all syntax elements of the first group of syntax elements prior to bypass decoding any syntax elements of the second group of syntax elements;

subsequent to CABAC decoding all syntax elements the first group of syntax elements, bypass decode the second group of syntax elements, wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes; and

reconstructing the video data based on the decoded first group of syntax elements and the decoded second group of syntax elements.

13. The non-transitory computer-readable storage medium of claim 12 , further comprising instructions that cause the one or more processors to:

CABAC decode a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC decoding of the first group of syntax elements; and

bypass decode a second set of bins used to indicate the chroma intra prediction mode separately from the bypass decoding of the second group of syntax elements.

14. The non-transitory computer-readable storage medium of claim 12 , wherein the list of most probable modes identifies one or more intra-prediction modes of one or more neighboring PUs.

15. The non-transitory computer-readable storage medium of claim 12 , wherein the first group of syntax elements includes four flags, and wherein each of the four flags is associated with a respective PU of an INTRA_N×N PU structure of the CU.

16. The non-transitory computer-readable storage medium of claim 12 , wherein the instructions that cause the one or more processors to reconstruct comprise instructions that cause the one or more processors to:

intra-prediction decode the PUs of the CU based on the first group of syntax elements and the second group of syntax elements.

17. An apparatus for decoding video data, the apparatus comprising:

means for receiving an entropy encoded bitstream that includes a first group of syntax elements comprising a plurality of flags and a second group of syntax elements for prediction units (PUs) of a coding unit (CU), wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, and wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples of a respective PU in the CU is based on an index into a list of most probable modes and which syntax element is to be received in the second group of syntax elements for the respective PU in the CU, wherein the means for receiving comprises means for receiving all syntax elements of the first group of syntax elements for the PUs of the CU before receiving any syntax elements of the second group of syntax elements for the PUs of the CU;

means for context adaptive binary arithmetic coding (CABAC) decoding all syntax elements of the first group of syntax elements prior to bypass decoding any syntax elements of the second group of syntax elements;

means for bypass decoding the second group of syntax elements, subsequent to CABAC decoding all syntax elements of the first group of syntax elements, wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes; and

means for reconstructing the video data based on the decoded first group of syntax elements and the decoded second group of syntax elements.

18. The apparatus of claim 17 , further comprising:

means for CABAC decoding a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC decoding of the first group of syntax elements; and

means for bypass decoding a second set of bins used to indicate the chroma intra prediction mode separately from the bypass decoding of the second group of syntax elements.

19. A method of encoding video data, the method comprising:

generating a first group of syntax elements comprising a plurality of flags, wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples of a respective prediction unit (PU) in a coding unit (CU) is based on an index into a list of most probable modes;

generating a second group of syntax elements, wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, wherein the flag of the plurality of flags of the first group of syntax elements indicates which syntax element is to be outputted in the second group of syntax elements for the respective PU in the CU, and wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes;

context adaptive binary arithmetic coding (CABAC) encoding all syntax elements of the first group of syntax elements prior to bypass encoding any syntax elements of the second group of syntax elements;

subsequent to CABAC encoding all syntax elements of the first group of syntax elements, bypass encoding the second group of syntax elements; and

outputting the video data that includes the encoded first group of syntax elements and the encoded second group of syntax elements, wherein outputting comprises outputting all syntax elements of the first group of syntax elements for the PUs of the CU before outputting any syntax elements of the second group of syntax elements for the PUs of the CU.

20. The method of claim 19 , further comprising:

CABAC encoding a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC encoding of the first group of syntax elements; and

bypass encoding a second set of bins used to indicate the chroma intra prediction mode separately from the bypass encoding of the second group of syntax elements.

21. The method of claim 19 , wherein the list of most probable modes identifies one or more intra-prediction modes of one or more neighboring PUs.

22. The method of claim 19 , wherein the first group of syntax elements includes four flags, and wherein each of the four flags is associated with a respective PU of an INTRA N×N PU structure of the CU.

23. The method of claim 19 , further comprising:

intra-prediction encoding the PUs of the CU based on the first group of syntax elements and the second group of syntax elements.

24. An apparatus for encoding video data, the apparatus comprising:

a memory configured to store the video data;

one or more processor comprising a video encoder, the video encoder configured to:

generate a first group of syntax elements comprising a plurality of flags, wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples of a respective prediction unit (PU) in a coding unit (CU) is based on an index into a list of most probable modes;

generate a second group of syntax elements, wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, wherein the flag of the plurality of flags of the first group of syntax elements indicates which syntax element is to be outputted in the second group of syntax elements for the respective PU in the CU, and wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes;

context adaptive binary arithmetic coding (CABAC) encode all syntax elements of the first group of syntax elements prior to bypass encoding any syntax elements of the second group of syntax elements;

subsequent to CABAC encoding all syntax elements of the first group of syntax elements, bypass encode the second group of syntax elements; and

output the video data that includes the encoded first group of syntax elements and the encoded second group of syntax elements that are stored in the memory, wherein the video encoder is configured to output all syntax elements of the first group of syntax elements for the PUs of the CU before outputting any syntax elements of the second group of syntax elements for the PUs of the CU.

25. The apparatus of claim 24 , wherein the video encoder is configured to:

CABAC encode a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC encoding of the first group of syntax elements; and

bypass encode a second set of bins used to indicate the chroma intra prediction mode separately from the bypass encoding of the second group of syntax elements.

26. The apparatus of claim 24 , wherein the list of most probable modes identifies one or more intra-prediction modes of one or more neighboring PUs.

27. The apparatus of claim 24 , wherein the first group of syntax elements includes four flags, and wherein each of the four flags is associated with a respective PU of an INTRA N×N PU structure of the CU.

28. The apparatus of claim 24 , wherein the video encoder is configured to:

intra-prediction encode the PUs of the CU based on the first group of syntax elements and the second group of syntax elements.

29. The apparatus of claim of claim 24 , further comprising a camera configured to capture the video data.

30. A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors of a device for encoding video data to:

generate a first group of syntax elements comprising a plurality of flags, wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples a respective prediction unit (PU) in a coding unit (CU) is based on an index into a list of most probable modes;

generate a second group of syntax elements, wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, wherein the flag of the plurality of flags of the first group of syntax elements indicates which syntax element is to be outputted in the second group of syntax elements for the respective PU in the CU, wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes;

context adaptive binary arithmetic coding (CABAC) encode all syntax elements of the first group of syntax elements prior to bypass encoding any syntax elements of the second group of syntax elements;

subsequent to CABAC encoding all syntax elements of the first group of syntax elements, bypass encode the second group of syntax elements; and

output the video data that includes the encoded first group of syntax elements and the encoded second group of syntax elements, wherein the instructions that cause the one or more processors to output comprise instructions that cause the one or more processors to output all syntax elements of the first group of syntax elements for the PUs of the CU before outputting any syntax elements of the second group of syntax elements for the PUs of the CU.

31. The non-transitory computer-readable storage medium of claim 30 , further comprising instructions that cause the one or more processors to:

CABAC encode a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC encoding of the first group of syntax elements; and

bypass encode a second set of bins used to indicate the chroma intra prediction mode separately from the bypass encoding of the second group of syntax elements.

32. The non-transitory computer-readable storage medium of claim 30 , wherein the list of most probable modes identifies one or more intra-prediction modes of one or more neighboring PUs.

33. The non-transitory computer-readable storage medium of claim 30 , wherein the first group of syntax elements includes four flags, and wherein each of the four flags is associated with a respective PU of an INTRA_N×N PU structure of the CU.

34. The non-transitory computer-readable storage medium of claim 30 , further comprising instructions that cause the one or more processors to:

intra-prediction encode the PUs of the CU based on the first group of syntax elements and the second group of syntax elements.

35. An apparatus for encoding video data, the apparatus comprising:

means for generating a first group of syntax elements comprising a plurality of flags, wherein a flag of the plurality of flags of the first group of syntax elements indicates whether an intra-prediction mode of luma samples a respective prediction unit (PU) in a coding unit (CU) is based on an index into a list of most probable modes;

means for generating a second group of syntax elements, wherein syntax elements of the second group of syntax elements correspond to respective syntax elements of the first group of syntax elements, wherein the flag of the plurality of flags of the first group of syntax elements indicates which syntax element is to be outputted in the second group of syntax elements for the respective PU in the CU, wherein the second group of syntax elements comprises one of:

a first syntax element that indicates the index into the list of most probable modes if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is based on the index into the list of most probable modes; or

a second syntax element that indicates the intra-prediction mode of the luma samples of the respective PU if the flag in the first group of syntax elements indicates that the intra-prediction mode of the luma samples of the respective PU is not based on the index into the list of most probable modes;

means for context adaptive binary arithmetic coding (CABAC) encoding all syntax elements of the first group of syntax elements prior to bypass encoding any syntax elements of the second group of syntax elements;

means for bypass encoding the second group of syntax elements, subsequent to CABAC encoding all syntax elements of the second group of syntax elements the first group of syntax elements; and

means for outputting the video data that includes the encoded first group of syntax elements and the encoded second group of syntax elements, wherein the means for outputting comprises means for outputting all syntax elements of the first group of syntax elements for the PUs of the CU before outputting any syntax elements of the second group of syntax elements for the PUs of the CU.

36. The apparatus of claim 35 , further comprising:

means for CABAC encoding a first set of bins used to indicate a chroma intra prediction mode separately from the CABAC encoding of the first group of syntax elements; and

means for bypass encoding a second set of bins used to indicate the chroma intra prediction mode separately from the bypass encoding of the second group of syntax elements.