Re: Setting sound card for full duplex

Shadow_7 <wwwShadow7@xxxxxxxxxxxxxxx> writes:

You've kindly taken me though some of the elements of sound recording,
but it will be some time before I can absorb it all.

I have been unable to find out if my card supports
full duplex. Assuming that it does, how do I set
it for full duplex?

If you're using alsa drivers.

cat /proc/asound/devices

It should by default. Software for full duplex recording
on the otherhand might be difficult. Most sound cards,
even el cheapo integrated ones have at least two input
channels and two output channels. Granted that that's
just stereo capabilities, stereo in, stereo out.

The result of my cat is:

$ cat /proc/asound/devices
0: [0- 0]: ctl
4: [0- 0]: hardware dependent
9: [0- 1]: raw midi
8: [0- 0]: raw midi
19: [0- 3]: digital audio playback
26: [0- 2]: digital audio capture
25: [0- 1]: digital audio capture
16: [0- 0]: digital audio playback
24: [0- 0]: digital audio capture
33: : timer

If I understand you correctly, two capture and playback channels here
only mean it is stereo. But that leaves open whether there is any
indication of full-duplex support. Can you say my card has or has not
from the information returned? Why the extra capture channel?

For me, I have a few options.

My purpose in trying to do sound recording was primarily to test my
card (I'm using the sound card as a digital/analog modem, and was not
getting any analog out of the card from a computer-generated digital
signal). However, I have reasons to take sound recording seriously
otherwise, and so your advice appreciated for that reason as well.

By "options" here it seems you are saying, options for sound recording
under Linux. I started out with krec (despite my not runing a KDE
desktop), and krec was what got me hung up with the duplex issue. You
seem to offer attractive alternatives to krec. These I'll explore.

But a very elementary question remains: Assuming one has a soundcard
and sound driver that support full-duplex, is there anything you must
do to use it? The reason for the question is because if a person runs
the KDE desktop it offers a place to check full-duplex. So I'd guess
full-duplex is something one must implement. So there ought to be
a command you can issue from command line to do that without the KDE
desktop.

--

Haines Brown, KB1GRM
Dialectical Materialist


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