[linux-audio-dev] I need help! I can't handle the problem about full-duplex (playback & record) programming

Frank Neumann Frank.Neumann at st.com
Mon Dec 16 07:07:46 UTC 2002


Hi,
Josh Green wrote:

[..]

> You may want to look into ALSA (http://www.alsa-project.org) which is
> the new Linux sound architecture. Also, it would probably be good to
> make sure your audio card is actually capable of full duplex and that
> this feature really does work in Linux (with the drivers you decide to
> code for). I can't think of any quick and easy programs to test full
> duplex (anyone else have any ideas?). Good luck.

I think what you could do in ALSA is to make a "loopback" connection
from your soundcard's Line Out back into its Line In, then playback some
.wav or .mp3 with e.g. aplay and simultaneously (try to) use arecord(*)
to record whatever comes back in on Line In. This way it should be
possible to detect if there is some cheating going on (like, I think,
these old Soundblaster cards where "Duplex" meant 16Bit stereo playback
and at the same time 8bit stereo recording..can anyone confirm?).

(*) For those who don't know: Both aplay and arecord are part of the
alsa-utils package.

Frank



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