[FFmpeg-devel] [PATCH] mpeg4videodec: silence "Invalid and inefficient vfw-avi packed B frames detected" warning

wm4 nfxjfg at googlemail.com
Thu Aug 29 22:07:29 CEST 2013

On Thu, 29 Aug 2013 21:55:17 +0200
Reimar Döffinger <Reimar.Doeffinger at gmx.de> wrote:

> On Thu, Aug 29, 2013 at 07:48:32PM +0000, Paul B Mahol wrote:
> > On 8/29/13, wm4 <nfxjfg at googlemail.com> wrote:
> > > On Thu, 29 Aug 2013 21:31:54 +0200
> > > Nicolas George <nicolas.george at normalesup.org> wrote:
> > >
> > >> Le duodi 12 fructidor, an CCXXI, wm4 a ecrit :
> > >> > Seeking (resetting the decoder) causes the warning to be printed again.
> > >> > Disabling warnings is not an option, because warnings are supposed to
> > >> > signal that something might be wrong.
> > >>
> > >> So it is printed once after each seek. How is that a problem?
> > >>
> > >> It informs about a problem that can have practical consequences (try
> > >> playing
> > >> this kind of files with a limited CPU) and can be fixed (although not with
> > >> ffmpeg for now). That is exactly what a warning is made for. Simply
> > >> removing
> > >> it would be idiotic.
> > >
> > > The warning is completely meaningless and confusing.
> > 
> > Perhaps warning can be printed only if error recognition is set to
> > some reasonable value?
> One of the reasons for the warning is to make people stop using the
> tools that create these broken files.
> Ideally also to fix them.

This doesn't work, you'll just annoy your users because you want to make
a point. Most people who want to play (or transcode) a video couldn't
care less how the original video was created.

> However I think it is badly worded for that purpose.
> In the link I gave I suggested at least pointing to tools
> to fix it.
> What would be a reasonable way?
> 'Video uses a non-standard and wasteful way to store B-frames ("packed
> B-frames"). Consider using a tool like VirtualDub or avidemux to fix
> it.'

Well, at least one file that prints the warning actually shows
VirtualDub as creator, so that'd be confusing too. And again, users
couldn't care less.

> Is it really a problem if it's printed always when seeking?
> I don't see the big deal with warning messages for files that definitely
> are badly done.

This warning seems to be printed relatively often, and it would be nice
if warnings would be printed only in cases there is an actual problem.

Yes, ffmpeg has to tolerate broken tools and files by still being able
decoding them. That's stupid, but hey, it's its job.

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