[ecasound] Re: ecasound & full duplex (fwd)

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Subject: [ecasound] Re: ecasound & full duplex (fwd)
From: Kai Vehmanen (kaiv@wakkanet.fi)
Date: Thu Jan 20 2000 - 11:55:07 EET

Here's another very common question:

---------- Forwarded message ----------
> Is it, or will it be, possible to record using full duplex. Currently
> (RH Linux 6.0; ecasound 1.6.9r9), I tried the following:
> ecasound -d:10 -a:1 -i Fly1.wav -o /dev/dsp -a:2 -i /dev/dsp -o
> Mix.wav

It has been since ecasound's first public version. ;) What ecasound
doesn't support, is opening soundcard devices in read-write mode. In
other words, ecasound treats each input and output as a separate
device. Because of this, read-write is impossible. But there are better
ways to do this:

1. multi-open

Some soundcard drivers support so called 'multi-open', meaning device
can be opened twice - once for playback, once for recording. This
doesn't seem to work with your card.

2. shadow devices

The other solution is shadow devices. If you use OSS/commercial, you
probably have these. Check your /dev/sndstat. For instance, I have:

-- cut from /proc/sndstat --
Audio devices:
0: GUS MAX (CS4231) (DUPLEX)
1: Shadow of audio device #0 (DUPLEX)
2: Ultrasound (DUPLEX)
3: Creative SB AWE64 Gold (4.16) (DUPLEX)
4: SB secondary device (DUPLEX)

In other words, I have two soundcards, but I can still use five
separate devices, /dev/dsp0, /dev/dsp1 ... /dev/dsp4 ... let's
modify your example:

ecasound -d:10 -b:128 -a:1 -i Fly1.wav -o /dev/dsp0 -a:2 -i /dev/dsp1 -o Mix.wav

3. ALSA drivers

ALSA is an alternative to OSS drivers. They offer OSS-compatibility,
full-duplex, many advanced features like pcm-loopback, multichannel
devices, etc etc... You'll find their home page at

I hope this helps.

Kai Vehmanen <kaiv@wakkanet.fi> -------- CS, University of Turku, Finland
 . http://www.wakkanet.fi/ecasound/ - linux multitrack audio processing
 . http://www.wakkanet.fi/sculpscape/ - ambient-idm-rock-... mp3/ra/wav

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