[FFmpeg-user] Question about x11grab and mkv files

Carl Eugen Hoyos cehoyos at ag.or.at
Thu Feb 9 10:38:46 CET 2012

Giorgio Vazzana <mywing81 <at> gmail.com> writes:

> ffmpeg -t 5 -f x11grab -video_size 640x480 -framerate 10 -i :0.0
> -vcodec copy  output-master-copy.mkv

Is there any application except FFmpeg that read the resulting 
(good) files?

> ffmpeg -t 5 -f x11grab -video_size 640x480 -framerate 10 -i :0.0
> -vcodec ljpeg output-master-ljpeg.mkv
> Note the the same commands work fine with ffmpeg-0.10.

Yes, but in the case of -vcodec copy the resulting video 
used "room" (disc space) for transparency information 
that is not there (x11 does not export opaqueness but "0"), 
please try -vcodec rawvideo -pix_fmt bgr24.
The ljpeg encoder claims to encode transparency, but it 
actually does not...

I sent two patches to ffmpeg-devel:
The first makes ljpegenc support BGR0 and BGR24 (but removes 
BGRA which never was really supported).
The second adds tags for BGR0 etc (and RGB64), but see above, 
I wonder if any other application reads the resulting files.

> Logs are here: http://mywing.altervista.org/tmp/ffmpeg-x11grab

Please always post complete, uncut console output here, external 
resources may disappear.

Carl Eugen

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