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22nd Meeting: by teleconference, April 2021 2021-04-13 18:14
AHG9: On the MAI, DRI, and ACI SEI messages and their interactions with the SDI SEI message
Authors: Ye-Kui Wang ByteDance Yifan Wang ByteDance Li Zhang ByteDance
Abstract
This contribution proposes the following changes on the multiview acquisition information (MAI), depth representation information (DRI), and alpha channel information (ACI) SEI messages and their interactions with the scalability dimension information (SDI) SEI message:
Meeting Notes
JVET-V0064 AHG9: On the MAI, DRI, and ACI SEI messages and their interactions with the SDI SEI message [Y.-K. Wang, Y. Wang, L. Zhang (Bytedance)]

This contribution was discussed in sesssion 9 at 1335 on Thursday 22 April (chaired by GJS).

This contribution proposes the following changes on the multiview acquisition information (MAI), depth representation information (DRI), and alpha channel information (ACI) SEI messages and their interactions with the scalability dimension information (SDI) SEI message:

  1. It is specified that the MAI SEI message persists in decoding order from the current AU until the next AU containing an MAI SEI message for which the content differs from the current MAI SEI message or the end of the bitstream.

The following constraints are further specified:

    1. When an MAI SEI message is present in any AU of a CVS, an MAI SEI message shall be present for the first AU of the CVS.
    2. All MAI SEI messages that apply to the same CVS shall have the same content.
    3. An MAI SEI message shall not be scalable-nested.

Similar as with JVET-V0063, it was agreed that there should be no persistence beyond the CVS.

It was remarked that HEVC already has these SEI messages, and should be checked for persistence issues. This was further discussed in sesssion 18b at 1730 on Monday 26 April 2021 (chaired by GJS) and it was concluded that no action is needed for HEVC.

It was remarked that nesting is allowed in HEVC. The idea was said to be to make the message parsable without the VPS. Another suggested reason was to support pruning of views. Thus no change should be made that affects HEVC in this regard. However, the changes remained proposed for the VVC context.

Discussion stopped here in session 9 at 1400 and resumed at 1525 (chaired by GJS).

  1. Add following constraints on the presence of the MAI, DRI, and ACI SEI messages depending on the SDI SEI message, which seemed straightforward:
    1. When a CVS does not contain an SDI SEI message, the CVS shall not contain an MAI SEI message.
    2. When a CVS does not contain an SDI SEI message with sdi_aux_id[ i ] equal to 2 for at least one value of i, no picture in the CVS shall be associated with a DRI SEI message.
    3. When a CVS does not contain an SDI SEI message with sdi_aux_id[ i ] equal to 1 for at least one value of i, no picture in the CVS shall be associated with an ACI SEI message.
  2. Add following constraints on the decoding order of the MAI, DRI, and ACI SEI messages relative to the SDI SEI message, which seemed straightforward:
    1. When an AU contains both an SDI SEI message and an MAI SEI message, the SDI SEI message shall precede the MAI SEI message in decoding order.
    2. When an AU contains both an SDI SEI message with sdi_aux_id[ i ] equal to 2 for at least one value of i and a DRI SEI message, the SDI SEI message shall precede the DRI SEI message in decoding order.
    3. When an AU contains both an SDI SEI message with sdi_aux_id[ i ] equal to 1 for at least one value of i and an ACI SEI message, the SDI SEI message shall precede the ACI SEI message in decoding order.
  3. The variable NumViews is derived in the semantics of the SDI SEI message and used in the MAI SEI message syntax and semantics, and the use of the array nestingLayerIdList is removed from the semantics of the MAI SEI message.

It was commented that this could create a parsing dependency between SEI messages. There was discussion of whether that is a problem or not. Picture timing depends on buffering period, for example. However, it was agreed to instead simply signal the number of views and constrain it to match the other message content. This is whole-CVS level info, so not so critical for data overhead.

  1. The associated primary layers for an auxiliary layer are signalled in the SDI SEI message syntax and specified in the SDI SEI semantics, and the related texts in the semantics of the DRI and ACI SEI messages are changed accordingly based on the established association. This includes enabling an association of an aux layer to multiple non-aux (primary) layers.

The text changes for the proposals in JVET-V0064 (this contribution) are included in the attachment to JVET-V0063.

Decision (cleanup): Adopt with MAI persistence scope modified to only the containing CVS and to signal the number of views in the MAI SEI message.

References:
JVET-V0063
Cited:
JVET-V0009 JVET-V2006 JVET-W0002 JVET-W0003 JVET-W0083 JVET-W2006 JVET-X2006 JVET-Y2006
PATENTS:
20240040157 1.00 WO/2022/214063 1.00 20240040140 1.00 WO/2022/214056 1.00 20240048749 1.00 WO/2022/214047 1.00 20260012647 0.34 20240040139 0.28
ARCHIVE v1 :
JVET-V0064-v1.docx
Decisions
adopted
Decision (cleanup): Adopt with MAI persistence scope modified to only the containing CVS and to signal the number of views in the MAI SEI message.
Citation