Re: [FFmpeg-devel] [PATCH] lavc/vvc: Invalidate PPSs which refer to a changed SPS

[Nuo Mi <nuomi2021@gmail.com>]

On Sat, Jun 15, 2024 at 2:35 PM Christophe Gisquet <
christophe.gisquet@gmail.com> wrote:

> Le ven. 14 juin 2024, 11:39, Frank Plowman <post@frankplowman.com> a
> écrit :
>
> > When the SPS associated with a particular SPS ID changes, invalidate all
> > the PPSs which use that SPS ID.  Fixes crashes with illegal bitstreams.
> > This is done in the CBS, rather than in libavcodec/vvc/ps.c like the SPS
> > ID reuse validation, as parts of the CBS parsing process for PPSs
> > depend on the SPS being referred to.
> >
>
> I am uncertain about this. I have no definite knowledge nor proof, but I
> would have thought these are persistent, IE it's legal to update some of
> them, their validity depending on something else.
>

> Wondering if the tested streams are thus conformant.
>
> But I don't know the actual rule. Maybe finding an EOB/EOS NUT? Related to
> some particular shape of a clean random access point, that would require
> retransmitting VPS/SPS/PPS/APS/... ?
>
> Asking Benjamin Bross might be a better option here.
>
Hi Chris,
spec said sps should not change in a CVS.  Frank has some patches to fix a
similar issue.
https://github.com/FFmpeg/FFmpeg/commit/2d79ae3f8a3306d24afe43ba505693a8dbefd21b


Hi Frank,
Did it crash before your error hand code in ps.c?
Could you send me the clip?

Thank you


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