Subject: Re: [ecasound] Multi-input Problem
From: Kai Vehmanen (k_AT_eca.cx)
Date: Fri Jul 12 2002 - 00:54:31 EEST
On Thu, 11 Jul 2002, gianni corrado wrote:
> I'am an italian user of ecasound with a multi-input problem.
Welcome to the list!
> I have two sound card: one ice1712 (8 input) and one emu10k1 (2 input).
> I would like to record in one 10 channels file the 8+2 input from the
> two different card.
First, be sure to check
Or http://www.eca.cx/ecasound -> Documentation -> User's guide -> "Can I
use multiple soundcards? "
As a general rule, it's not possible to use multiple physical soundcards
to get more channels for simultaneous recording. The problem is that
soundcards run at slightly different clocks speeds and this caused timing
errors. This is not always a problem (you don't need to playback the
recorded channels in sync or you are lucky and your soundcards happen
to run at exactly the same speed, or you can tolerate the timing drift).
Anyways, now that we got that out of the way...
> ecasound -a:1,2,3,4,5,6,7,8 -f 32,12,44100 -i alsahw,0,0 -a:9,10 -f
> 16,2,44100 -i /dev/dsp -a:1,2,3,4,5,6,7,8,9,10 -o 10ch.wav -z:db
Hmm, you've used both an ALSA device (alsahw,0,0) and an OSS device
(/dev/dsp) at the same time. Is this on purpose?
Anyways, the correct command-line would be:
ecasound -a:rec1 -f:32,12,44100 -i alsahw,0 \
-a:rec2 -f:16,2,44100 -i /dev/dsp \
-a:rec2 -erc:1,9 -erc:2,10 -ea:200 \
-a:rec2 -eac:0,1 -eac:0,2 -ea:200 \
-a:rec1,rec2 -f:32,10,44100 -o 10ch.wav
You don't actually have to repeat '-a:rec2' on every line, but I wanted to
emphasize what is happening. With the two -erc (channel-copy) ops we copy
data from the first two channels to channels 9 and 10. After copying we
must 1 and 2 channels with -eac (channel-amplify). In the last phase we
mix the two chains taking 10 channels of audio from both chains.
The "-ea:200" are not strictly necessary, but help to retain the volume
level.
You can find more info about channel mixing from ecasound user's guide
(see the address above) - check for instance "Problems with panning mono
files".
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