Re: [linux-audio-user] jack and alsa

From: Matt Price <matt.price@email-addr-hidden>
Date: Thu Feb 08 2007 - 19:57:56 EET

On Fri, 2007-02-02 at 17:37 -0500, Paul Davis wrote:
> On Fri, 2007-02-02 at 17:32 -0500, Matt Price wrote:
>
> > playing tunes. would be nice not to have to start and stop jack every
> > time I want to use amarok... but that's more of a wishlist item really.
> > thanks again,
>
> amarok has an experimental gstreamer output engine. gstreamer has a
> properly written JACK audio sink. its only a matter of time and
> energy ...
>
paul and others, haven't gotten amarok working with gstreamer, but I did
find out what most folks on the list doubtless know, that one can set
alsa to actually play through jack using the jack plug-in for alsa. for
me this is an adequate workaround and I am not having the snags that
other people often complain of, at least not with audio apps -- vlc and
mplayer freeze pretty bad, though totem seems to be working ok.

I did htis on ubuntu, where the jack plugin is not enabled by default,
so I had to ocmpile my own libasound2-plugins package. steps:

sudo apt-get build-dep libasound2-plugins
sudo apt-get source libasound2-plugins
cd libasound2-plugins-xxx/
(uncomment jack-related lines in debian-rules)
fakeroot debian/rules binary
sudo dpkg -i ../libasound2-plugins-xxxxx.deb

To get tthe jack plug in working I followed the instructions on the alsa
wiki (http://www.alsa-project.org/alsa-doc/doc-php/asoundrc.php#jackplug
and somewhere I lost track of), and created a .asoundrc :

pcm.!default {
                type plug
                slave { pcm "jack" }
        }

        pcm.jack {
                type jack
                playback_ports {
                        0 alsa_pcm:playback_1
                        1 alsa_pcm:playback_2
                }
                        capture_ports {
                        0 alsa_pcm:capture_1
                        1 alsa_pcm:capture_2
                }
        }

It's great not to have to quit amarok just to use ardour -- this is good
for me because I may want to quickly run through some music to listen to
it for background, and amarok is where my music is actually ORGANIZED.

  It would be nice to be able to specify the alsa plugin at the command
line for these apps (is there some kind of an alsa wrapper on the lines
of aoss that can supercede the setting in .asoundrc ? that would be
great). Failing a better way, I created little wrapper scripts for vlc
and jack:

vlcw:
~$ cat /usr/local/scripts/vlcw
#!/bin/bash
ln -s -f ~/.asoundrc-direct ~/.asoundrc
killall jackd
vlc $1

jackw:
~$ cat /usr/local/scripts/jackw
#!/bin/bash
ln -s -f ~/.asoundrc-jack ~/.asoundrc
/usr/bin/jackd -d alsa -dhw:0 -r 44100 -n3

.asound-direct is an empty file
.asound-jack is the file I quoted above.

so far so good! If I happen on an improvement (e.g. a working jack sink
in gstreamer, and a working gstreamer sink in amarok, vlc, mplayer) I
will let y'all know. and comments welcome of course.

m

>

-- 
Matt Price
History Dept
University of Toronto
matt.price@email-addr-hidden

Received on Thu Feb 8 20:15:04 2007

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