[FFmpeg-user] ffmpeg screencapture from a virtual xserver larger than the physical screen

Zenny garbytrash at gmail.com
Thu Nov 19 11:36:12 CET 2015

Thanks Nicolas for the pointer.

I am trying to use xvfb with xpra for forwarding. However there I am
experiencing a bottleneck. The capture is 4k, but the content ran via
xpra is only 1/4th of the screen. Xpra client is at FullHD.

Discussed over the xpra bugtracker at
http://xpra.org/trac/ticket/1036#comment:11, something is going wrong,
but cannot say where?!

To screencapture the virtual x instance, I used:

$ ffmpeg  -f x11grab -s 3840x2160 -i :99 -r 24 -deadline realtime -b:v
1M -threads 5 -qmin 0 -qmax 50 -crf 5 -preset ultrafast -f matroska

The capture looks like: http://picpaste.com/IgV8eLMl.jpg

Any inputs appreciated.


On 11/12/15, Nicolas George <george at nsup.org> wrote:
> Le duodi 22 brumaire, an CCXXIV, Zenny a écrit :
>> 1. create a virtual xserver of 4k resolution without any physical
>> display, and pipe to the physical screen (downsizing to FullHD ).
> http://www.x.org/archive/X11R7.6/doc/man/man1/Xvfb.1.xhtml
> Regards,
> --
>   Nicolas George

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