Conditionally parsed extension syntax for HEVC extension processing
A system for signaling extension functions used in decoding a sequence including a plurality of pictures, each picture processed at least in part according to a picture parameter set is disclosed. An extension presence signaling flag is read and used to determine whether flags signaling the performance of extension functions are to be read. The flags are only read if indicated by the extension presence signaling flag.
1. A method of decoding a plurality of pictures, each picture processed at least in part according to a picture parameter set, the method comprising:
receiving a bitstream comprising the plurality of pictures and a picture parameter set;
parsing the picture parameter set to determine for a picture in the plurality of pictures whether a pps_extension_present_flag signaling flag specifies presence of syntax structure pps_extension_Xbits at a picture level for the picture,
wherein the pps_extension_present_flag and pps_extension_Xbits signaling flags, when present, are adaptable per picture in the plurality of pictures, and
wherein the pps_extension_Xbits signaling flag is represented in the picture parameter set by multiple bits, where X=the number of said bits;
parsing the pps_extension_Xbits syntax structure to determine if any pps_extension_data_flag syntax structures are present in the picture parameter set;
wherein pps_extension_Xbits shall be equal to 0 for bitstreams conforming to High Efficiency Video Coding (HEVC) profiles, and
wherein pps_extension_4 bits not equal to 0 causes pps_extension_data_flag syntax structures in a picture parameter set NAL unit to be ignored during decoding.
2. The method of claim 1 , further comprising:
reading a first extension function signaling flag signaled in the picture parameter set and signaling a first extension function for decoding the picture;
reading a second extension function signaling flag signaled in the picture parameter set and signaling a second extension independently of a value of the read first extension function signaling flag for decoding the picture;
performing decode processing at the picture level in accordance with a syntax structure in the picture parameter set according to the first extension function and the second extension function at the picture level in accordance with a syntax structure in the picture parameter set;
for each picture, reading a further extension presence signaling flag after processing the first extension function and the second extension function without processing further extension functions; and
for each picture, determining from the further extension presence signaling flag that the read extension presence signaling flag indicates that there is no extensions to follow, and upon determining no extensions follow, the decoding for the respective picture proceeds without checking or executing further syntax logic to handle processing of extensions,
wherein the second extension function is independent from the first extension function.
3. The method of claim 2 , further comprising:
(d) determining if the first extension function signaling flag indicates that the picture is to be processed at least in part according to the first extension function.
4. The method of claim 3 , wherein (d) is performed only if the read extension presence signaling flag indicates that the picture is to be processed at least in part according to the at least one extension function.
5. The method of claim 3 , wherein (d) is performed subsequent to (a)-(c).
6. The method of claim 4 , further comprising:
(e) performing the first extension function only if the first extension function signaling flag indicates that the picture is to be processed at least in part according to the first extension function.
7. The method of claim 6 , further comprising:
(f) determining if the second extension function signaling flag indicates that the picture is to be processed at least in part according to the second extension function, and performing the second extension function only if the second extension function signaling flag indicates that the picture is to be processed at least in part according to the second extension function.
8. The method of claim 2 , wherein the first extension function signaling flag is uniquely associated with a first value of an index, and the second extension function signaling flag is uniquely associated with a second value of the index, and wherein:
the reading the first extension function signaling flag and the second extension function signaling flag comprises:
reading the first extension function signaling flag value according to a the index;
incrementing the index; and
reading the second extension function signaling flag value according to the incremented index.
9. The method of claim 8 , wherein:
the first extension function comprises a range extension function; and
the second extension function comprises a high efficiency video coding (HEVC) multilayer or multiview extension function.
10. An apparatus for decoding a plurality of pictures, each picture processed at least in part according to a picture parameter set, the apparatus, comprising:
a processor;
a memory, communicatively coupled to the processor, the memory storing a plurality of instructions comprising instructions for:
receiving a bitstream comprising the plurality of pictures and a picture parameter set;
parsing the picture parameter set to determine for a picture in the plurality of pictures whether a pps_extension_present_flag signaling flag specifies presence of syntax structure pps_extension_Xbits at a picture level for the picture,
wherein the pps_extension_present_flag and pps_extension_Xbits signaling flags, when present, are adaptable per picture in the plurality of pictures, and
wherein the pps_extension_Xbits signaling flag is represented in the picture parameter set by multiple bits, where X=the number of said bits;
parsing the pps_extension_Xbits syntax structure to determine if any pps_extension_data_flag syntax structures are present in the picture parameter set;
wherein pps_extension_Xbits shall be equal to 0 for bitstreams conforming to High Efficiency Video Coding (HEVC) profiles, and
wherein pps_extension_4 bits not equal to 0 causes pps_extension_data_flag syntax structures in a picture parameter set NAL unit to be ignored during decoding.
11. The apparatus of claim 10 , further comprising:
reading a first extension function signaling flag signaled in the picture parameter set and signaling a first extension function for decoding the picture;
reading a second extension function signaling flag signaled in the picture parameter set and signaling a second extension independently of a value of the read first extension function signaling flag for decoding the picture;
performing decode processing at the picture level in accordance with a syntax structure in the picture parameter set according to the first extension function and the second extension function at the picture level in accordance with a syntax structure in the picture parameter set;
(c1) for each picture, reading a further extension presence signaling flag after processing the first extension function and the second extension function without processing further extension functions; and
(c2) for each picture, determining from the further extension presence signaling flag that the read extension presence signaling flag indicates that there is no extensions to follow, and upon determining no extensions follow, the decoding for the respective picture proceeds without checking or executing further syntax logic to handle processing of extensions, and
wherein the second extension function is independent from the first extension function.
12. The apparatus of claim 11 , wherein the instructions further comprise instructions for:
(d) determining if the first extension function signaling flag indicates that the picture is to be processed at least in part according to the first extension function.
13. The apparatus of claim 12 , wherein (d) is performed only if the read extension presence signaling flag indicates that the picture is to be processed at least in part according to the at least one extension function.
14. The apparatus of claim 12 , wherein (d) is performed subsequent to (a)-(c).
15. The apparatus of claim 13 , wherein the instructions further comprise instructions for:
(e) performing the first extension function only if the first extension function signaling flag indicates that the picture is to be processed at least in part according to the first extension function.
16. The apparatus of claim 15 , wherein the instructions further comprise instructions for:
(f) determining if the second extension function signaling flag indicates that the picture is to be processed at least in part according to the second extension function, and performing the second extension function only if the second extension function signaling flag indicates that the picture is to be processed at least in part according to the second extension function.
17. The apparatus of claim 11 , wherein the first extension function signaling flag is uniquely associated with a first value of an index, and the second extension function signaling flag is uniquely associated with a second value of the index, and wherein:
the instructions for reading the first extension function signaling flag and the second extension function signaling flag comprises instructions for:
reading the first extension function signaling flag value according to a the index;
incrementing the index; and
reading the second extension function signaling flag value according to the incremented index.
18. The apparatus of claim 17 , wherein:
the first extension function comprises a range extension function; and
the second extension function comprises a high efficiency video coding (HEVC) multilayer or multiview extension function.