C[omp]ute

From: "andrew cooke" <andrew@...>

Date: Sat, 23 Jun 2007 18:06:20 -0400 (CLT)

Jack (Linux Audio) promises to be the solution to getting streaming audio
working from any source.  These are notes on my attempts to get it
working.

- To start Jack use qjackctl.  This is a KDE GUI app.  It will start and
stop jack for you (the start and stop buttons).  When Jack doesn't start,
click the Message button to see why.

- My first error was about a missing libportaudio18.  While it was
present, it turned out I had the 32 bit library installed (with 64 bit
Jack).  The SUSE dependencies didn't pick this up - you need to look very
carefully at the installed version (click on the tabs bottom right in
YAST).

- Next error was about /dev/shm/jack-0 already existing.  This seems to be
a permissions thing related to running as root.  So don't run as root.

- Next error was a problem with access rights to /dev/shm (btw /dev/shm
seems to be some kind of dynamic memory thing - don't mess with it, it's
started automatically by SUSE.  If you delete the shm directory the best
way to get it back is reboot; mkdir doesn't seem to do the right thing). 
I fixed that with chmod 666 /dev/shm/jack-shm-registry (as root)

- Next error indicated that realtime play wasn't possible.  You can
disable this in qjackctl's "setup" menu.  However, jack.play seemed to
want to set it (I was using jack.play to test if anything was working). 
Fix here is to add the following lines to /etc/security/limits.conf:
@audio          -       rtprio          90
@audio          -       nice            -10
@audio          -       memlock         4000000
and then add the user to that group (YAST group management - select the
audio tickbox).  Finally log out and in again (type "groups" on the
command line to check you are a member of the audio group).

- Oh, and earlier I had disabled ARTS (the KDE sound thing) by clicking in
the appropriate checkbox of the KDE "Configure Desktop" GUI.  I did this
because the qjackctl message box was scrolling lots of ARTS related
messages.  I also restarted alsa with /etc/init.d/alsasound restart (Jack
uses ALSA to talk to hardware).

- So with those fixes jack.play works (it gives a misleading error on ogg
files, saying they are corrupted, but works fine with flac).  However
there was no sound.  Clicking on the "Connect" button of qjackctl you can
drag the jack.play thing on the left to the soundcard thing on the right. 
This connects them and you hear something!

- To add volume control, start jackmix, delete the connections you made
earlier, and instead connect jack.play to the mixer input.  Then connect
the mixer output to the sound card.  Finally twiddle knobs on the mixer
until you hear something.

That gets basic files to play.  That's it so far.  Amarok crashes.

Andrew