[FFmpeg-user] fast video codec for screen casting

Carl Eugen Hoyos cehoyos at ag.or.at
Thu Jan 5 12:36:08 CET 2012

dE . <de.techno <at> gmail.com> writes:

> >>> ffmpeg -f x11grab -s 1280x800 -i :0.0 -f null -
> >> 30 FPS
> >
> > I get approximately the same performance with -vcodec mpeg1video, isn't that
> > also true for you?
> No. I tend to think this's cause of bad ati drivers, X takes too much
> CPU cause drivers are incapable of offloading load to the GPU.

As said, I get (approximately) the same performance with -f null and -vcodec
mpeg1video -threads 1, so I don't think this is likely

> I've another PC with a Nvidia GPU and a single core processor. Using
> x264, I get 24 FPS easily.

I also think it is not unlikely that the GPU (and drivers) do play an important
role. But that does not explain a large difference between -f null and using a
"light" codec.

> >> I also tried ffmpeg -f x11grab -s 1280x800 -i :0.0 -f null -qscale 2
> >> -threads 1 -b 20000k -vcodec mpeg1video -an out.avi
> >
> > (-b makes no sense with -qscale)
> > That is great.
> >
> > If you provide us with output / results (or say if the problem still exists
> > with this command line), somebody may be able to help you.
> >
> The mailing list appears to have rejected my attachment (output video).

Attachments are nearly always useless (they are at least much more often useless
than useful so it makes sense not allow them).
What I meant was that you neither provided complete, uncut console output (which
contains all necessary information as you know) or at least told us the speed
(fps) of above command.

Carl Eugen

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