[LAU] PulseAudio and Alsa
stephen.doonan at gmail.com
Sun Aug 31 14:19:13 EDT 2008
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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