[FFmpeg-devel] [PATCH] avformat: add H264 and HEVC support in IVF muxer

[Michael Niedermayer]

On Sun, Oct 14, 2018 at 01:29:53PM +0300, Jan Ekström wrote:
> On Sun, Oct 14, 2018 at 1:27 PM Jan Ekström <jeebjp at gmail.com> wrote:
> >
> > On Sun, Oct 14, 2018 at 3:17 AM Michael Niedermayer
> > <michael at niedermayer.cc> wrote:
> > >
> > > On Fri, Oct 12, 2018 at 01:13:45AM +0100, Derek Buitenhuis wrote:
> > > > On 11/10/2018 23:39, Alex Sukhanov wrote:
> > > > > The only "spec" I'm aware of:https://wiki.multimedia.cx/index.php/IVF
> > > >
> > > > Yeah, not really a spec.
> > > >
> > > > I have no strong objections, I guess.
> > >
> > > so IIUC noone is against this ?
> > > if so i will apply the last patch in a few days unless i forget or
> > > someone else does before
> > >
> > > thx
> > >
> >
> > As mentioned, since this is nothing should have ever been used outside
> > of one of GOOG's legacy systems, I would only apply this with a
> > warning and strictness requirement of experimental or whatever level
> > matches these sorts of cases.
> >
> 
> For the record, this was regarding the muxer so that unknowing people
> will not generate such files that nothing else can read.

If you choose a random container and store a random codec in it (which you can do)
chances are theres not much that will play it.

for example i just tried muxing a stream of png images into mpeg and FFmpeg
does that without complaining.
./ffmpeg -i matrixbench_mpeg2.mpg -vcodec png test.mpeg

So if we do not check this for a major format that has a proper specification
which i belive nowhere allows png

Why should we add a limitation on a format that has nothing saying that you
cannot put some other codec into it ?
And i mean there IS software that uses that what is asked for here.

If you object because the text at https://wiki.multimedia.cx/index.php/IVF
does not list all codecs. Well its a wiki, the author of the patch could
get an account and update this. In fact independant of this discussion here
it surely wont hurt if the people using the format review and update that
page.

The other concern IIUC (please correct me if i misunderstood)
is that its a legacy format. FFmpeg is full of legacy format support, we suport
some really bizare formats ...

And another concern IIUC ( again please correct me if i misunderstood)
is that someone might unintentionally generate a unsupported file
this is tricky, the default video codec for ivf is AV_CODEC_ID_VP8
to get something else, one would need to manually override this and
as we already saw thats not something we current protect against very
well.

Iam not against disallowing the new codecs by default but it feels 
inconsistent compared to other containers.

what do you say ? did i convince you or should we disallow it and add
a check. Iam happy with whatever people agree on

thanks

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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