[FFmpeg-user] Screenrecording, audio is sped up when other process starts

Tarjei Bærland tarjeibaerland at gmail.com
Tue Mar 24 23:24:26 EET 2020

> > With the risk of sounding ignorant ... how would I "grab hardware device
> > exclusively"?
> To use an account part of the audio group and specifying an actual
> hardware device should be enough to do this. I am not sure what the
> difference between cards and devices are to alsa tbh, but I think using hw
> and index to specify the device makes it clear its not a mixer or other.
> Also, does the card have 4 separate streams? If you have no particular
> reason to get all 4 channels maybe there is a way to only record one.

It's an external sound card with 4 separate inputs, yes. The reason for my
not specifying hardware numbers is that those tend to reset when I unplug
the card.

> > I can't with my limiting googling capabilities find out how to not enable
> > the sound mixer in pygame.
> >
> > However, the "glitch" persists even after completely closing the python
> > process.
> But maybe I was wrong in assuming that the contention in controlling the
> device was the problem; iirc, the way to not enable the sound mixer in
> pygame is to not enable it… So if there’s no sound I don’t think that is
> the issue.
It seems Pygame runs a check or something at pygame.init. But setting
"dummy" for the environment variable SDL_AUDIODRIVER did the trick.

> I thought the glitch was the short high pitched noise in the video at 13
> seconds in, is it observable anywhere else in that clip?

There's that, and the raise in pitch in my voice throughout the rest of the

Either way, I have something that works now, so many thanks!


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