[PlanetCCRMA] Playing catch-up: Pulseaudio + ALSA + Rhythmbox + Crackling + Module loading.

Kyrian kyrian at ore.org
Wed Apr 22 02:25:21 PDT 2009


Just been catching up on a hell of a lot of email, and I thought it 
would be useful to add some points about various topics I've seen.

I've written this quite quickly so please forgive any excessive brevity, 
or errors.

- Module loading at boot (Firewire sound card guy)

It's a hack, but it'll work if you add the modprobe line to /etc/rc.local

- Pulseaudio and ALSA.

As I understand it, ALSA is implemented in pulseaudio via compatibility 
libraries in the pulseaudio system. A simple "rpm -qa | grep -i pulse" 
should prove enlightening for most.
I think the previous statements about it being bad to try and remove 
pulseaudio are pretty much correct, although I don't hate pulseaudio, 
and I would not recommend trying to remove it unless you have no other 

You can run into all sorts of issues with ALSA compatibility because the 
pulseaudio mixer & utils don't present all of the alsa controls, such as 
'mic select', 'mic boost' etc. so you need (in addition to the 
pulseaudio ones) to find a mixer that will allow it, 
'gnome-volume-control' is IIRC the one I tend to use. Note that using 
gnome-volume-control you have to go into the preferences and select the 
options you want displayed, otherwise you may still find you are unable 
to access them. Lots of people seem to swear by alsamixer/aumix but I 
like my GUI's for this.

A useful strategy is to use alsactl store/restore from the command line 
to save and reload presets from the commandline. "man alsactl" to find 
out more.

List posts on 11/04/2009 also cover this sort of thing, I noted after 
writing the above.

- Crackling, and pulseaudio.

Just my opinion, but while pulseaudio is a great idea in principle 
(although I don't know that it does anything that Jackd doesn't already 
allow for?), the implementation is really quite lacking.

It seems to have a hell of a memory leak problem, and you might have to 
restart the daemon periodically to claw back RAM for other purposes.

It also does crash out quite a lot, maybe due to RAM usage, maybe due to 
something else, and when it does crash out, then you will find that 
various applications (I think ALSA ones primarily) will give you a lot 
of cracking and become virtually unusable because of it.

Doing "ps fwaux | grep pulseaudio" should show up a "pulseaudio -D" 
process if it is actually running.

To stop pulseaudio's server, "killall pulseaudio". If the above ps/grep 
doesn't show it as dead, try "killall -9 pulseaudio". It's an ugly way 
to do so, but it's the best I have come up with so far.

To start it again, as your standard user (non-root) just run "pulseaudio 
-D", it will give you some blurb about permissions and users, probably, 
but it should be alright.

- Devices producing no sound under PulseAudio/ALSA emulation.

With regards the thread where you're using eg. "alsamixer -D hw:0", to 
try and resolve issues of cards being silent, first I'd look at the 
mixer settings as I mentioned above, then you might like to try 
'plughw:0' instead of just 'hw:0' etc.

Also I had more success with 'alsactl -c <card number>' rather than 
trying to control the device through its ID/name.

I can't be arsed to read through the masses of notes I have on this to 
find the exact solution, but don't just try pot luck to work out 
card/interface numbers, use one of the following to work it out for sure:

pactl list
arecord -l

There is the slight problem that with my SB Live I found that the device 
numbers seemed to be 'off by one', so you might have to account for that 
with your setup. Even so, it's still better than just guessing ;-)

- Rhythmbox slowness and crashes.

There is/was another issue in that part of the accessibility systems in 
Fedora dies sometimes, and that makes Rhythmbox run dog slow, chew up 
CPU cycles, and occasionally die totally.

The quick fix was to run this as your regular (non-root) user:

/usr/libexec/at-spi-registryd &

It is not always necessary, but there is a correlation between a hell of 
a lot of repeated warnings in your ~/.xsession-errors file and the 
slowness. Sorry, I can't remember more than that, Google for 
'at-spi-registryd rhythmbox' should find you the buggzilla entries about it?

Even when it's working properly, it's hardly nippy with a >30Gb music 


Kev Green, aka Kyrian. E: kyrian&#64;ore.org WWW: http://kyrian.ore.org/
Linux/Security Contractor/LAMP Coder/ISP, via http://www.orenet.co.uk/
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