Extension data handling
A length indicator associated with an encoded representation of a slice is parsed. The length indicator is indicative of a length of an extension field present in a slice header of the encoded representation. A decoder can then determine to ignore, during decoding of the encoded representation, any value of the extension field in the slice header where these values are identified based on the length indicator. As a consequence, an extension field can be added to slice headers and still enable legacy decoders to correctly decode the encoded representations.
1. A decoding apparatus for decoding an encoded representation of a slice of a picture, said encoded representation comprising a slice header and slice data, said decoding apparatus being configured to:
parse a length indicator associated with said encoded representation and indicative of a length of an extension field in said slice header; and
cause said decoder to ignore, during decoding of said encoded representation, any value of said extension field identified based on said length indicator.
2. The decoding apparatus of claim 1 , wherein the decoding apparatus is further configured to:
determine a length of said extension field based on said length indicator; and
identify an end of said extension field in said slice header based on said length.
3. The decoding apparatus of claim 1 , wherein said decoding apparatus is configured to parse said length indicator present in said slice header.
4. The decoding apparatus of claim 1 , wherein said decoding apparatus is configured to ignore, during decoding of said encoded representation, any value of said extension field directly following said length indicator in said slice header up to an end of said extension field as identified based on said length indicator.
5. The decoding apparatus of claim 1 , wherein said decoding apparatus is configured to parse said length indicator present in a parameter set identified based on a parameter set identifier obtainable based on said slice header.
6. The decoding apparatus of claim 1 , wherein said decoding apparatus is further configured to:
parse a slice header extension present flag associated with said encoded representation;
parse said length indicator;
ignore said any value if said slice header extension present flag has a predefined value.
7. The decoding apparatus of claim 6 , wherein said decoding apparatus is further configured to:
identify a parameter set associated with said encoded representation based on a parameter set identifier obtainable based on said slice header, and
parse said slice header extension present flag present in said parameter set.
8. The decoding apparatus of claim 1 , wherein said decoding apparatus is further configured to:
identify a start of said slice data based on an end of said extension field as identified based on length indicator; and
parse and decode said slice data starting from said start of said slice data.
9. The decoding apparatus of claim 8 , wherein said decoding apparatus is configured to parse and decode said slice data by ignoring said any value of said extension field in said slice header.
10. A communication device comprising:
a receiver; and
the decoding apparatus of claim 1 .
11. A decoding apparatus for decoding an encoded representation of a slice of a picture, said encoded representation comprising a slice header and slice data, said decoding apparatus being configured to:
parse a length indicator associated with said encoded representation and indicative of a length of an extension field in said slice header;
identify said extension field in said slice header based on said length indicator; and
decode said encoded representation of said slice based on at least one value of said extension field identified by said extension field identifying unit.
12. A communication device comprising:
a receiver; and
the decoding apparatus of claim 11 .
13. An encoding apparatus for encoding a slice of a picture, said encoding apparatus being configured to:
generate a length indicator indicative of a length of an extension field present in a slice header of said slice;
encode said slice into an encoded representation of said slice comprising said slice header and slice data; and
associate said length indicator with said encoded representation.
14. The encoding apparatus of claim 13 , further comprising:
a determining unit configured to determine a length of said extension field present in said slice header, wherein said generating unit is configured to generate said length indicator based on said length of said extension field.
15. The encoding apparatus of claim 13 , wherein said associating unit is configured to insert said length indicator into said slice header.
16. The encoding apparatus of claim 15 , wherein said associating unit is configured to insert said length indicator directly preceding said extension field in said slice header.
17. The encoding apparatus of claim 13 , wherein said associating unit is configured to insert said length indicator into a parameter set and associating a parameter set identifier identifying said parameter set with said encoded representation.
18. The encoding apparatus of claim 13 , further comprising:
a setting unit configured to set a slice header extension present flag to a predefined value to indicate presence of said extension field in said slice header, wherein said associating unit is configured to associate said slice header extension present flag with said encoded representation.
19. The encoding apparatus of claim 18 , wherein associating unit is configured to insert said slice header extension present flag into a parameter set and associate a parameter set identifier identifying said parameter set with said encoded representation.
20. A communication device comprising:
a transmitter; and
the encoding apparatus of claim 13 .
21. A decoding apparatus, comprising:
a memory; and
processing circuitry coupled to the memory and being configured to:
obtain an encoded representation of a slice of a picture, said encoded representation comprising a slice header and slice data immediately following the slice header, and said slice header comprising a variable length header extension data field storing extension data;
based on information associated with said encoded representation, determine an ending position of the variable length header extension data field; and
after determining the ending position of the variable length header extension data field, ignore all of the extension data contained within the variable length header extension data field.
22. The decoding apparatus of claim 21 , wherein
said slice header further comprises a variable length header extension length field immediately preceding the variable length header extension data field,
said information associated with said encoded representation comprises an encoded length value stored in the variable length header extension length field, wherein the encoded length value identifies X number of sequential bytes, X>0; and
the decoding apparatus is configured to ignore all of the extension data contained within the variable length header extension data field by ignoring the X number of bytes that immediately follow the header extension length field.