[FFmpeg-devel] [PATCH v2 4/8] ffmpeg: remove sub-frame warning

Michael Niedermayer michael at niedermayer.cc
Fri Apr 1 17:47:45 CEST 2016

On Fri, Apr 01, 2016 at 05:27:11PM +0200, Michael Niedermayer wrote:
> On Fri, Apr 01, 2016 at 04:53:55PM +0200, wm4 wrote:
> > On Fri, 1 Apr 2016 16:44:42 +0200
> > Paul B Mahol <onemda at gmail.com> wrote:
> > 
> > > It should set it because it is not sane format.
> > 
> > I mean, why do we want to keep this message, if it obviously didn't
> > help with anything?
> it is useful for debuging and to prevent invalid files from being
> created

to elaborate on this
If a demuxer returns an AVPacket with multiple frames in it and that
gets stored in a output file then the output file is invalid with
no indication that it is. Such file would likely play fine on some
players and fail on others. Thats a really serious problem for the
user as even if he tests the output file by playing it he possibly
wont notice a problem

With the multiple subframes message decoding both the original file
with the buggy demuxer as well as playing the newly created output
file would likely show warnings that would point at the problem
(which might be a forgotten needs_parsing in the demuxer)

I belive its important to keep some means to detect this kind of
problem. Also as it is easy to set the parsing stuff up wrongly
a reverse engeneered container might appear to store 1 mp3 frame per
packet but that might then turn out false on analysis of a wider
range of files ...


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you drop bombs on a foreign country and kill a hundred thousand
innocent people, expect your government to call the consequence
"unprovoked inhuman terrorist attacks" and use it to justify dropping
more bombs and killing more people. The technology changed, the idea is old.
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