[MPlayer-users] Bug report: ffmpeg creates a better file than mencoder

[Reimar Döffinger]

On Fri, Dec 26, 2008 at 11:37:04AM +0300, Igor Katson wrote:
> I want to extract a png image from lots a videofiles, provided a seek 
> point. In 80% of the cases, -vo png does this successfully.
> The cmd in this case is e.g
>
> mplayer video.avi -frames 1 -ss 1 -vo png
>
> But there are files with broken index or smth (here I can't figure out the 
> reason), like the one attached, and -vo png does not produce any output. 
> Options -idx and -forceidx do not help. The output in this case is e.g. the 
> following (if -v turned on):

That video does not contain enough keyframes so seeking forward will seek to to
the end of the video.
You can use e.g.
-vf framestep=30
and take the file 00000002.png.
Or -vf framestep=I
can be interesting as well since when a good encoder was used this will
result in most pngs being right after a scene change (and possibly also at
better-than-average quality).

> I solve this problem by reencoding the video with ffmpeg (it's quite little 
> in size), but when I do this with mencoder, the video is reencoded, but 
> there is still no out png file.
> The cmd in this case  is e.g.
> mencoder video.3gp -ovc lavc -nosound -o video.avi . The only error output 
> with the sample file is:

-lavcopts vqscale=2:keyint=1