[FFmpeg-devel] [WIP] XComposite window capture demuxer (Linux)

[Marton Balint]

On Wed, 20 May 2020, Emanuele Oriani wrote:

>> If that was the only concern against it, then I'd say it is acceptable.
> > But there are some other concerns, also it seems to me xcbgrab can be
> > improved to reach the same smoothness as this attempt, and that was the
> > main distinctive feature of it. With that advantage lost, I'd say fixing
> > xcbgrab is the better bet.
>
> I would think yes - that would be a good outcome - but please note 
> xcbgrab doesn't seem to work when a window is borderless and/or full 
> screen - which sorts of defeat the purpose of capturing 3d apps running 
> full screen?

Hmm, that is strange, because I always tested xcbgrab with full screen 
(not a specific window) capture and it never had any problems.

>
> Do you have a patch for xcbgrab? I will try and capture similar video.

Actually it turned out that the main reason of the jerkyness was that 
ffmpeg is processing the input and feeding the encoders in a single 
thread. However you can trick ffmpeg to use a separate input thread by 
specifying more than one input:

E.g:

ffmpeg -y -f x11grab -video_size hd1080 -framerate 60 -i ":1.0" -f lavfi -i testsrc=d=0.1 -preset ultrafast -map 0 out.mp4 -map 1 -f null none

Regards,
Marton