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Date:      Wed, 13 Nov 2002 12:03:32 -0500
From:      The Anarcat <anarcat@anarcat.ath.cx>
To:        Jim Durham <durham@jcdurham.com>
Cc:        FreeBSD-multimedia@freebsd.org
Subject:   Re: Simultaneous Record/Playback on FreeBSD
Message-ID:  <20021113170331.GA9829@xtanbul.studio.espresso-com.com>
In-Reply-To: <3DD277D3.8050007@jcdurham.com>
References:  <3DD277D3.8050007@jcdurham.com>

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[This is FAQ material, but it's already documented in the handbook]

Q. How can I play and record sound simultaneously under FreeBSD?

A. FreeBSD supports some sound cards multiple channels. This is also
known as half or full-duplex. The way the kernel deals with it is that
it uses virtual channels. Technically, the kernel can handle any
number of channels, read or write, as long as there is duplex
capability on the sound card. The sound driver just mixes the virtual
channels inputs and outputs into the proper physical channels.

The problem with -stable is that it has no devfs. Normally, under
-current, devices are created on the fly, as needed by the sound
applications. Under -stable, you must create them manually and use a
sysctl to tell the system the number of vchans you want available.

More details at:

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/sound-setup.html

A.

On Wed Nov 13, 2002 at 11:03:31AM -0500, Jim Durham wrote:
> I use Audacity from ports to record and edit sound. I noticed that there 
> is a warning message that says "Playing back while recording will not 
> work on most unix systems". Sure enough, at least with my old 
> SoundBlaster16, it doens't work on 4.7. BTW, I'm using KDE3.03.
> 
> Can someone explain what the issue is? This is something that really 
> limits what you can do in creating new tracks simultaneous to already 
> layed-down tracks.
> 
> -Jim
> 
> 
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> 

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