[LAU] Sound in Linux

Shelagh Manton shelagh.manton at gmail.com
Sun Oct 14 00:27:04 EDT 2007


I have some general questions about sound in linux; the interplay of
pulse/(esd) and gstreamer,jackd and alsa.

Let me state what I think I know.
Alsa provides the drivers that allow sound to be produced and also the
midi subsystem. You can use just the alsa system if you want to use
audio or midi, but if you want to use (possibly) more than one program
that uses sound eg the system sounds that gnome and kde make when alerts
happen and say a music program, you need to use something like pulse or
esd, or dmix in alsa. This is because the program captures the whole use
of the sound card and can't release it for other programmes. If you want
to use midi and audio together as in rosegarden, you need jackd because
that allows more than one program to access the soundcard at a time. It
is also useful because if you have the right kernel and privileges your
audio programme can override the right of other programmes to access the
kernel as well meaning that you don't get glitches when you are
recording a masterpiece. Gstreamer fits in the normal esd/pulse picture
by providing the access to codecs that files come in. Now this is where
my understanding fails: gstreamer has a jack module (so I hear rumoured,
but I can't find it in the ubuntu reps) and so does pulse. How do these
fit in with the jackd stuff? Obviously they both make it so that jack
can work with both or either of the sound servers. 

I welcome corrections in my interpretation of what's happening.

Shelagh 




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