[LAU] PulseAudio and Alsa

Stephen Doonan stephen.doonan at gmail.com
Sun Aug 31 14:19:13 EDT 2008

Regarding PulseAudio
Miscellaneous quotes from the 'net

   At an Audacity forum
   For many professional level audio applications, high performance and 
low latency are key features, which is something that JACK is 
specifically designed to do.

   On the other side of the coin, Pulseaudio hogs the sound system, 
making it difficult for high performance music applications to achieve 
the performance levels that they require. With Amarok, you are usually 
only trying to read one stereo file from the hard drive and play it, but 
with Audacity you may need to write a stereo stream to the hard drive, 
while simultaneously playing another 30 tracks from the hard drive.

   At the Fedora project Summer Coding, 2008 ideas webpage
   We use PulseAudio by default in Fedora, and I don't really see the 
point of using Jack if we use PulseAudio for "normal" users (most users 
won't be changing that default).

   At at discussion at KDE.org
   In an interview with the Fedora man responsible 
(http://fedoraproject.org/wiki/Interviews/LennartPoettering), he talked 
about it being all about "ear candy" and a "compiz for sound" e.g. 
active window has sound at 100%, other window's sounds are at 20%; 
clicking left button makes sound come out of left speaker and same with 
right. Will Phonon offer similar features or will it need PulseAudio to 
offer this functionality?

My current impression of PulseAudio--

PulseAudio is an attempt to make various audio needs and desires "just 
work" for "normal users" of a computer. It tries to hide the 
complexities of both audio routing and the various needs of various 
audio-needing programs by doing as much as it (PulseAudio) can by itself 
without user interaction nor (importantly for linux audio users) user 

I currently use Ubuntu Hardy Heron with the default Gnome desktop 
environment and most of the UbuntuStudio packages installed. I have an 
M-Audio Delta 1010 soundcard and various outboard gear (MIDI tone 
generators, keyboards, electronic drums, mixers, etc.) The audio and 
MIDI programs I normally use are Ardour, Rosegarden, Muse (and now 
learning Qtractor), Jamin, Qjackctl, Audacity. With my new installation 
of Ubuntu Hardy Heron and PulseAudio, in all its parts and pieces, 
installed and enabled by default, I have experienced numerous problems, 
crashed, UN-interoperability between programs, unavailability of the 
sound card to many applications including Gnomes own 
System-->Preferences-->Sound configurator--a whole heck of a lot of 
frustrating issues. For example, Audacity's preferences for Audio I/O 
offered no devices to use for recording or playback with PulseAudio 
running in the background. Perhaps PulseAudio could be configured, or 
has a module or plugin, to remedy this problem. But PulseAudio is 
protected from the user (with little easy user configuration) just at is 
tries to protect the user from the complexities of audio. It's like 
PulseAudio is saying to the user: "I'll do what I can to make audio easy 
for you, but you have to keep away from me and leave me alone." This 
might sound good to an "average or 'normal' user," but it sure does 
scare me as a person who likes to do more with audio than Skype, live 
streaming radio, etc.

What can I do about it?--

Well, I think I may have found a simple solution, a way to keep 
PulseAudio from taking over my audio-related resources. In Gnome, it's this:

* In System-->Preferences-->Sound, in the Devices tab, change all Sound 
playback and Sound capture options so that something _other_than_ 
"Autodetect" or "PulseAudio Sound Server" is selected. I changed all of 
mine to "ALSA - Advanced Linux Sound Architecture."

* In System-->Preferences-->Sessons, disable (UNcheckmark) "PuleAudio 
Device Chooser" and "PulseAudio Session Management."

* Log out of Gnome, then log back in for the changes above to take 
effect. Those settings are persistent from login to login and bootup to 
bootup unless and until you change them again.

Yippee! Now Audacity, though it still uses PortAudio, offers and allows 
me to choose from various devices (OSS, ALSA, etc.) for recording and 
playback in its Audio I/O preferences, Jamin doesn't hang and then offer 
no ports for IN or OUT, Ardour and Jamin can both be launched after I 
launch Qjackctl without crashing or hanging, I can launch Qjackctl 
without it having weird interactions with PulseAudio that make some 
things not work, and which requires an additional module to be installed 
so that PulseAudio will work with jack, when neither PulseAudio nor that 
module are really needed, etc.

Anyway, so far, so good--things seem to be working again. :-)


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