[FFmpeg-user] Question about x11grab and mkv files

[Giorgio Vazzana]

Carl Eugen Hoyos <cehoyos <at> ag.or.at> writes:

> 
> 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?

I didn't check because ffplay is usually enough for me (I use it for a quick
view, and then I transcode the huge file after the acquisition with ffmpeg), but
I think MPlayer was able to read some of these files in the past.
 
> > 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"), 

Ok.

> please try -vcodec rawvideo -pix_fmt bgr24.

Ok, done.

> The ljpeg encoder claims to encode transparency, but it 
> actually does not...

Ok.
 
> 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 applied your patches and recompiled ffmpeg. Now "-vcodec copy", "-vcodec
rawvideo", "-vcodec -pix_fmt xxx" and "-vcodec ljpeg" all work. I can watch the
resulting video with ffplay. These are the commands I tested:

1. ffmpeg -y -t 5 -f x11grab -video_size 640x480 -framerate 10 -i :0.0 -vcodec
copy qcopy.mkv
2. ffmpeg -y -t 5 -f x11grab -video_size 640x480 -framerate 10 -i :0.0 -vcodec
rawvideo qrawvideo.mkv
3. ffmpeg -y -t 5 -f x11grab -video_size 640x480 -framerate 10 -i :0.0 -vcodec
rawvideo -pix_fmt bgr24 qrawvideobgr24.mkv
4. ffmpeg -y -t 5 -f x11grab -video_size 640x480 -framerate 10 -i :0.0 -vcodec
rawvideo -pix_fmt rgb24 qrawvideorgb24.mkv

> I wonder if any other application reads the resulting files.

I tried MPlayer on those output files and this were the results:

1. it doesn't play, log:

holden at rye:~/tmp2$ mplayer qcopy.mkv 
MPlayer SVN-r34661-4.4.3 (C) 2000-2012 MPlayer Team

Playing qcopy.mkv.
libavformat version 54.0.100 (internal)
libavformat file format detected.
[lavf] stream 0: video (rawvideo), -vid 0
VIDEO:  [BGR0]  640x480  0bpp  10.000 fps    0.0 kbps ( 0.0 kbyte/s)
Clip info:
 ENCODER: Lavf54.0.100
Load subtitles in ./
==========================================================================
Cannot find codec matching selected -vo and video format 0x30524742.
==========================================================================


Exiting... (End of file)

2. it doesn't play, log:

holden at rye:~/tmp2$ mplayer qrawvideo.mkv 
MPlayer SVN-r34661-4.4.3 (C) 2000-2012 MPlayer Team

Playing qrawvideo.mkv.
libavformat version 54.0.100 (internal)
libavformat file format detected.
[lavf] stream 0: video (rawvideo), -vid 0
VIDEO:  [BGR0]  640x480  0bpp  10.000 fps    0.0 kbps ( 0.0 kbyte/s)
Clip info:
 ENCODER: Lavf54.0.100
Load subtitles in ./
==========================================================================
Cannot find codec matching selected -vo and video format 0x30524742.
==========================================================================


Exiting... (End of file)

3. yes it works.

4. yes it works, but it shows strange colors.
 
> > Logs are here: http://mywing.altervista.org/tmp/ffmpeg-x11grab
> 
> Please always post complete, uncut console output here, external 
> resources may disappear.

Ok.

Thanks,

Giorgio Vazzana