Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

6.1.13Other (7)

JCTVC-O0238 Sign coding for transform skipped blocks [J. Wang, D. He, N. Hu, D. Flynn (BlackBerry)]
JCTVC-O0330 Crosscheck of JCTVC-O0238: Sign coding for transform skipped blocks [C. Pang (Qualcomm)] [late] [miss]
JCTVC-O0230 Chroma Deblocking [Alexis Tourapis (Apple), David Flynn (BlackBerry), David Singer (Apple)] [late]
JCTVC-O0043 Best-effort decoding of 10-bit sequences [D. Flynn (BlackBerry)]

Reviewed Thu 31st am (GJS).

HEVC contains profiles that accommodate the decoding of non-8-bit video sequences. In particular, it contains a 10-bit profile that permits the carriage of 10-bit video sequences. In M0255, it was demonstrated that it is possible to re-purpose an existing 8-bit decoder design to decode 10-bit bitstreams (with some modifications – e.g. CABAC parsing of additional quantized coefficient level LSBs). Moreover, through choice of rounding method, it is reportedly possible to reduce the accumulation of decoder error than might otherwise be expected.

This contribution summarizes the requirements basis, use case information, the previous work, and provides additional information regarding the decoding of 12-bit video sequences with a 10-bit decoder. Specification text is proposed to allow such techniques to be applied in the context of HEVC.

Proposed specification text (brackets for sentence not in current text):

8.1 General decoding process

…

The decoding process is specified such that all decoders will produce numerically identical cropped decoded pictures. Any decoding process that produces identical cropped decoded pictures to those produced by the process described herein (with the correct output order or output timing, as specified) conforms to the decoding process requirements of this Specification. [For the purpose of best effort decoding, a decoder conforming to one profile at a given tier and level that, and without claiming conformance to, decodes a bitstream conforming to a different tier, level or profile without using a decoding process that produces numerically identical cropped decoded pictures to those produced by the process described herein conforms to the decoding process requirement of this Specification.]

Hypothetical edited version from discussion:

8.1 General decoding process

…

The decoding process is specified such that all decoders that conform to a specified profile, tier, and level will produce numerically identical cropped decoded output pictures when decoding bitstreams that meet the characteristics specified for decoding by decoders for that profile, tier and level. Any decoding process that produces identical cropped decoded output pictures to those produced by the process described herein (with the correct output order or output timing, as specified) conforms to the decoding process requirements of this Specification.

NOTE ‒ For the purpose of best-effort decoding, a decoder that conforms to a particular profile at a given tier and level may additionally decode some bitstreams conforming to a different tier, level or profile without necessarily using a decoding process that produces numerically identical cropped decoded output pictures to those produced by the process specified herein (without claiming conformance to the other profile, tier and level).

NOTE – A decoder that conforms to a particular profile at a given tier and level may additionally try to decode some bitstreams that do not conform (e.g., due to channel data losses).

A participant expressed some concern about the possibility of the second note encouraging the generation of non-conforming bitstreams.

Decision (Ed.): Add text as shown in modification discussed above, without the second NOTE.