Sunday, January 4, 2009

Ubuntu, Pulseaudio, Small Addendum.

I've tended to use this howto to tweak audio configurations whenever I install a new Ubuntu box for someone -- it makes everything from laptop speakers to Skype work much better, shockwave flash videos work (Youtube, etc) and it makes audio a much better experience all-round.

Today, a user who was having audio stuttering issues in Skype mentioned that when running it in verbose mode (with -vv), the following error occurred:

I: main.c: Called SUID root and real-time/high-priority scheduling was requested in the configuration. However, we lack the necessary priviliges:
I: main.c: We are not in group 'pulse-rt' and PolicyKit refuse to grant us priviliges. Dropping SUID again.
I: main.c: For enabling real-time scheduling please acquire the appropriate PolicyKit priviliges, or become a member of 'pulse-rt', or increase the RLIMIT_NICE/RLIMIT_RTPRIO resource limits for this user.
I: main.c: Note that real-time/high-priority scheduling is NOT normally required. If you experience crackling or other sound anomalies, consider one or more of the above solutions.

The easiest way to fix that, is to open a terminal window and run:

sudo usermod -G pulse-rt -a [username] (where of course, [username] is your desktop username.

(note: it needs to be a capital -G and a little -a to add your user to the pulse-rt group and leave your existing groups untouched, one of those check twice, then check again, then press enter moments)

If you re-run Pulseaudio now, you'll get:

I: main.c: PolicyKit refuses acquire-high-priority privilige.
I: main.c: We're in the group 'pulse-rt', allowing real-time and high-priority scheduling.
I: core-util.c: Successfully gained nice level -11.

Which tends to make Skype and WINE (the two applications the user in question was having stuttering audio issues with) behave more normally.