[Gllug] What's a sound server?

[salsaman at xs4all.nl]

On Thu, June 12, 2008 02:13, - Tethys wrote:
> Apparently, pulseaudio is a sound server. So is esd (although that
> claims to be a sound mixing server, which gives some clue). But what
> do they actually *do*?
>
> This question prompted by the fact that the Intel 82801G produces
> precisely zero sound on my new box. Apparently I need to have
> pulseaudio running (which I do), but I don't know why. I'm sure Linux
> userland has got unnecessarily complex while I haven't been looking...
>
> Tet
>
> --
> Perl is like vise grips. You can do anything with it but it is the
> wrong tool for every job. -- Bruce Eckel
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>

I am not overly familiar with pulseaudio, but I know a little about sound
servers. Their purpose is mainly to take audio in from various inputs, mix
them, and then route the result to various outputs. Usually they also
provide sync to the various inputs and outputs - letting these programs
know when they can send or receive another audio buffer. Generally having
a sound server running makes life easier for application programmers
because it also abstracts away a lot of the low level stuff.

I am more familiar with jack:
http://jackaudio.org/
since I have been developing jack for video (a similar idea, but it routes
around video instead of audio).

There are a lot of cool tools for jack (qjackctl, jack-rack, netjack,
jack-eq, etc).

I believe pulseaudio is similar to jack but intended more for desktop
users (the jack developers are aiming for high-end audio).

Regarding your soundcard not working, I doubt it has anything to do with
lack of a sound server. You should be able to play back audio using alsa -
the sound server will use normally use alsa itself for output.

I would suggest the following steps:

- make sure you are running a recent kernel (for example, I am using
2.6.22, and my soundcard works pretty well with this; older kernels gave
problems)

- make sure the sound card is recognised (dmesg) and note down the details
of it

- make sure you have loaded any modules which might be used by it : for
example on my laptop I also have an Intel soundcard, and I have the
following modules

snd, sndcore, snd_hda_intel, snd_pcm, snd_timer, snd_page_alloc,
snd_hwdep, snd_seq_dummy, snd_seq_oss, snd_seq_midi_event, snd_seq,
snd_seq_device, snd_pcm_oss, snd_mixer_oss

(you might need to tweak snd_hda_intel, do a search on google for it)

- make sure you have alsa and alsa-tools installed, and run alsaconfig

- try playing back audio without the desktop running (for example using
mpg123 or ogg123)

Gabriel.
http://lives.sourceforge.net


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