[LAU] Tutorial on sidechain compression in Qtractor and a question about screencasting

Philipp Überbacher hollunder at lavabit.com
Tue Aug 24 11:34:27 UTC 2010

Excerpts from Jeremy Jongepier's message of 2010-08-24 10:22:57 +0200:
> Hello all,
> I've uploaded a new tutorial to YouTube: 
> http://www.youtube.com/watch?v=pnAqk054g7E
> So using sidechain compression in Qtractor with the SC3 LADSPA plugin.
> Concerning screencasting, anybody any experience with this? For this 
> tutorial I used recordMyDesktop, but it captures video to Theora, so 
> after editing and uploading the quality degrades considerably. The big 
> advantage of recordMyDesktop though is that it has JACK support and that 
> the overhead is pretty small so I can still run my setup at a decent 
> latency.
> I've also started playing around with FFmpeg. The video quality is 
> waaaaay better if you capture to a lossless format but I'm having my 
> thoughts on the audio part. I compiled FFmpeg myself with libjack-dev so 
> it has JACK support. But FFmpeg apparently has troubles to keep up with 
> latencies below 20ms, lots of xruns on the FFmpeg side (JACK doesn't 
> complain though). And I have the feeling FFmpeg lags on the audio side.
> So I'm thinking about capturing the video part with ffmpeg and the audio 
> part with jack_capture and mux the stuff later. But if anyone has any 
> other suggestions, let me know.
> Best,
> Jeremy

Hi Jeremy.
I know little about screencasting, but I do know that recordmydesktop
can either encode on the fly or afterwards. Maybe it's possible to use
and convert its raw data, whatever format that may be, to something else?

The tutorial seems quite nice. I do have a little trouble with it
because you seem to have a really high resolution screen, and my biggest
screen has 1280x800. I'm also not sure it's a good thing that you can't
see the mouse, recordmydesktop has an option for that.

Seems to be quite a hassle to set sidechain compression up. The essence
being: know which sc3 port corresponds to what and what to route where.
I sadly couldn't get that from the video because of aforementioned


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und alle Fragen offen." Bertolt Brecht, Der gute Mensch von Sezuan

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