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

Reimar Döffinger Reimar.Doeffinger at gmx.de
Tue Sep 3 21:03:26 CEST 2013

On Sat, Aug 31, 2013 at 06:16:19AM -0400, Don Moir wrote:
> ----- Original Message ----- From: "Reimar Döffinger"
> <Reimar.Doeffinger at gmx.de>
> To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> Sent: Friday, August 30, 2013 2:58 PM
> Subject: Re: [FFmpeg-devel] [PATCH] mpeg4videodec: silence "Invalid and inefficient vfw-avi packed B frames detected" warning
> On Thu, Aug 29, 2013 at 10:07:29PM +0200, wm4 wrote:
> >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.
> >It's not like the message jumps out of your monitor and tries to devour
> >you alive. This is useful information about a video that can have
> >potential issues. And as was pointed out, the way this file
> >was created is very relevant.
> >In part due to performance, in part because for example this
> >format isn't working with the new VDPAU API (I am told).
> >Also, if users are easily annoyed by programs trying to give
> >them useful information, they can set the log level to fatal.
> For me and in rare cases, the warnings are only useful during
> development. The end users I deal with have no interest or would not
> even know what the warnings mean.
> On top of that, since I have multiple videos running at the same
> time, you might not even have a clue what video triggered the
> warning.
> So I set av_set_log_callback but only thing that is useful to me is
> the fatal errors which I can filter. log level is bypassed if you
> set the callback which is the way it should be.
> Outside of fatal errors, I would just compile the rest out for release if I could.

I can't figure out what you are trying to tell me.
That some users are not interested?
I never doubted that.
I am mostly saying that
a) There are good reasons to be quite certain that there _are_ users
that care (which btw. could just be users that need a message to search
for, which does not require understanding it).
b) I currently fail to see how a user getting annoyed by that message
could be considered a reasonable user, especially since it is possible
to disable
c) That I think it might be more correct to have this as "info" message.

Though for some reason this yet again seems to have degenerated into
an IMO fairly pointless back and forth, with no attention
or comments that would allow me to understand the issue and where I
might have misunderstood the problem on the two suggestions I had
1) Making the message less technical and more helpful (for the users that
care, why should users not caring about messages be relevant there?)
2) Possibly adjusting the level, which also makes it easier for users
to filter depending on what they care about, though at some level it's
always going to be just a matter of opinion.

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