[FFmpeg-user] Ignoring errors in transcoding

Alexander Borghgraef alexander.borghgraef.rma at gmail.com
Wed Jun 11 12:15:58 CEST 2014

On Sun, Jun 8, 2014 at 7:57 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> Alexander Borghgraef <alexander.borghgraef.rma <at> gmail.com> writes:
> > > What's wrong with:
> > > $ ffmpeg -i crapfile.mpg -qscale 2 -mbd 2 out.mpg
> > > ?
> >
> > Me not knowing what they do?
> This is the same as
> $ ffmpeg -i crapfile.mpg out.mpg
> but with maximum video quality (-qscale 2) and an
> option that allows to use maximum quality in mpeg
> streams (you can get many warnings without -mbd 2).
> The reason I asked was that I did not understand
> what your usecase is and that I hoped if you
> explain what's wrong with above line I would
> understand it.

My usecase is that I have a few hours of mpeg4 video recorded via packet
capture over a dodgy LAN (I wasn't allowed to interfere with
the system in any other way, so I'm stuck with that). I need to extract
interesting sequences from these videos for my video analysis
research, but the video drops frames all over the place and my usual tools
like vlc, kdenlinve, avidemux etc. either crash or refuse to
play it. Only ffplay gave me useable video, but it's not that userfriendly
to scroll back an forth to find my sequences of interest.

So my first approach was to transcode it to any other codec, hoping that
this would result in something manageable, but the problem
remains. Transcoding to numbered jpeg frame files using '-f image2', and
then back again to video works, but it's pretty wasteful and
takes a long time on longer sequences. So I was looking for a saner way,
and apparently, transcoding with '-mbd 2' results in something
which will play in the usual video players, so I guess it's the solution I
was looking for. Still not entirely certain what '-mbd 2' does exactly,
the documentation seems a bit cryptic, but if it works, it works.

Alex Borghgraef

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