[FFmpeg-devel] [PATCH v6 4/9] avcodec: add cbs for h266/vvc

[Jan Ekström]

On Fri, Feb 19, 2021 at 3:52 PM Nuo Mi <nuomi2021 at gmail.com> wrote:
> > >>
> > >> The current logic is that we are writing an AU, so the first NAL unit in
> > >> it is necessarily an AU start and subsequent NAL units are not?
> > >>
> > > H.266 AU contains one or more PU(3.105). One PU contains one coded
> > picture.
> > > Only the first NAL unit of an AU needs the zero_byte(B.2.2)
> > > H.265 has no PU, each AU has one coded picture(3.1)
> > > H.266's PU is the H.265's AU. In vvc_parser, we split bitstream to PU.
> >
> > Er, I don't think this is right: an AVPacket should contain all of the
> > pictures for a single timestamp - a decoder can then output at most one
> > picture from it, for the selected spatial layer.
> >
> This will make parser code very complicate :).
>
>
> > Though I don't know how the container formats are defined here, for other
> > codecs having multiple packets with the same timestamps causes ugly
> > problems in muxing/demuxing which we avoid by saying you aren't allowed to
> > do that.
> >
> We do not have container format spec for vvc yet. The codec is not register
> on http://mp4ra.org/#/codecs. How we handle svc in H.265? It will have same
> timestamp for diffrent AU.
>

FYI, there are already drafts for 14496-15 (Carriage of NAL unit based
video in ISOBMFF aka MP4) with VVC such as document N18825 .
https://isotc.iso.org/livelink/livelink?func=ll&objId=21196449&objAction=Open&viewType=1

Jan