JVET-AG0082 AHG9: On Source Picture Timing SEI message [J. Samuelsson-Allendes, S. Deshpande (Sharp)]

This input document relates to the Source Picture Timing Information (SPTI) SEI message included in the Technology under Consideration for future extensions of VSEI (draft 2). It is proposed to modify how TemporalId is used to derive SourcePictureInterval. It is asserted that the proposed modification makes the SPTI signalling more robust and able to handle more usage scenarios.

The source picture timing information SEI message offers content providers the means for providing receivers with information about the source picture timing, which may be different from the output picture timing. In the current version of the SPTI SEI message draft the source picture interval is defined for “consecutive pictures” and mentions “the previous decoded output picture”. It is asserted that it might not always be clear to the receiver which picture is meant by “the previous decoded output picture”, in particular in cases that involve temporal scalability, step-wise temporal access and/or dropping of individual pictures due to congestion.

It is proposed to specify the previous picture as the one in temporal layer zero, as this is always present. It is pointed out in the discussion tha the proposed approach would deviate from the original intent. If it was always referring to TId zero, it might be necessary to also introduce a scale factor.

It is agreed that there is an issue in case that temporal layers are removed, but another solution would be necessary. After offline consideration, un update was made available in JVET-AG0082v2 (green highlighted text)

Decision: Agreed to include the modification from JVET-AG0082v2 in the SPTI SEI (which is to be included in prelim. WD of VSEIv4)