JVET-AP0179 AHG9: Historical Information SEI message [J. Pardo, A. Karabutov, H. You, A. Boev, J. Sauer, T. Solovyev, E. Alshina (Huawei), X. Xu, S. Liu (Tencent)]

Following CfE and CfP sequences selection we can see that user generated content (UGC) plays a bigger role into the elaboration of the next video codec standard. It is proposed that UGC sequences characteristics should be also considered in the VSEI tracks. One of these characteristics that is proposed is to add transcoding information.

Aspect 1 proposes nesting of TDI SEI messages.

Aspect 2 proposes nesting of QM SEI messages.

Aspect 3 proposes nesting of EOI SEI messages.

Aspect 4 proposes nesting of user data unregistered SEI messages.

Aspect 5 proposes nesting of vui_parameters.

Aspect 6 proposes digitally_signed_content_initialization

Aspect 7 proposes multiple nested SEI messages.

It is noted that the scalable nesting and PON messages apply to the current bitstream and not to transcoding history.

It was suggested that the proposed syntax is lacking the payload size which would be needed.

For a new transcoder stage, additional nested SEI messages would be added at the end of this SEI message.

For aspect 7, it might be better to code nb_of_transcoding_minus1 using fixed length coding instead of ue(v) to make it easier to append messages without having to shift. u(7) would be byte aligned.

It was suggested to use the VVC payload type for the indicator value.

It was suggested to use the approach used in PON for indication of payload type.

It was questioned if there is demonstrated benefit for providing historical information. Some proponents considered there to be benefit for quality metrics.

It was suggested that having transcoding information might be useful for debugging purposes.

Further study encouraged.