Re: Question about linux sound...

On Saturday 08 April 2006 01:55, Trixx stood up and spoke the following
words to the masses in /comp.os.linux.misc...:/

I've recently installed linux, and so far everything is working great,
I use debian, which makes installing certain things pretty easy,
however one thing I noticed is that anytime I ever want to use sound,
I either have to close any other apps which may use sound, or even
sometimes restart X, otherwise I'll get a /dev/dsp/ is in use error.

I was wondering if this was normal, or if it was actually possible to
have sound come from difference sources simultaneously. I've tried
searching for docs on installing sound modules, with no luck.

PS: I have an AC'97 sound card and use 2.4.27-2-386 kernel on debian.

Sound coming from multiple sources at the same time - either in realtime
or with a slight delay - is called /duplex/ mode. Full duplex means
that your soundcard can actually concurrently process multiple sound
sources - e.g. mouseclicks and an /mp3/ playback.

In order to have full duplex, there are two conditions. First of all,
your soundcard needs to support it - I can't vouch for the AC97 chipset
in this regard, but I'd be surprised if it didn't - and secondly, the
driver used for that soundcard (or chipset) needs to have full duplex
capability compiled in. Chances are that the chipset supports it but
that the binary driver doesn't - the source code may actually support
it but it may have been disabled at compile time.

Debian is a nice and stable distribution, but not quite an up-to-date
one in terms of software packages - at least not if you go for what
Debian marks as the "stable" branch. The use of a 2.4.27 kernel in
your distribution shows this - the current stable /vanilla/ kernel is
at 2.6.16.2 as of yesterday April 7th (with 2.6.17 already in RC1
stage) and most other distributions already do feature a stock
2.6-generation kernel.

Important in this respect is that the 2.4-generation of kernels mostly
used the OSS (Open Sound System) drivers, while the default in Linux
2.6 is to use ALSA (Advanced Linux Sound Architecture) for driving the
soundcard. ALSA does have OSS emulation, but you cannot use both
native ALSA and native OSS concurrently for the same soundcard.

I would advise testing ALSA, preferably with a 2.6 kernel. It's highly
possible that running a 2.6 kernel in a system compiled for 2.4 may
break other things, though. For instance, on my system it broke IP
forwarding and masquerading. That's why it's also important to note
that ALSA *is* also available in the 2.4-generation of kernels.

If the sound issue is really important to you and provided that you
succeed in achieving full duplex functionality with a 2.6 kernel and
ALSA drivers, then I would advise you to switch to a different
distribution, or perhaps one of the "marked less stable" Debian
branches - or maybe even Ubuntu or Kubuntu, which are Debian-based - in
order to avoid conflicts between a 2.4-compiled distribution and a
2.6-generation kernel.

Hope this was helpful... ;-)

--
With kind regards,

*Aragorn*
(Registered GNU/Linux user #223157)
.

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