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Thu Aug 20 06:46:28 UTC 2009

| Stock lenny system.  jackd started with "jackd -d alsa -d hw:0 -r
| 44100" ALSA set up to use jack output as in
| <>.  mplayer defaults
| to using ALSA to output.  After a few seconds of playback (of a WAV
| file, though it does the same with FLAC and MP3 files), it hangs (does
| not respond to 'q' to quit), and jackd produces the following message
| on its terminal:
| 	subgraph starting at alsa-jack.jackP.8292.0 timed out (subgraph_wait_f=
d=3D7, status =3D 0, state =3D Running)
| With 'mplayer -ao jack', on the other hand, everything works fine.

After a little investigation, it looks like this is a known problem in
ALSA's jack backend.  Any pointers for fixing this?

Perhaps it shouldn't be fixed, since the pulseaudio plugin takes
care of most use cases already (with pulseaudio's jack backend as an
added step of indirection).  In that case, we should probably add
notices to the package description and NEWS.Debian to discourage use
of the jack plugin.

Tested with recent packages this time.

| $ COLUMNS=3D120 dpkg -l jackd libasound2-plugins mplayer
| ||/ Name                     Version                  Description
| +++-=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| ii  jackd                    0.118+svn3796-1          JACK Audio Connec=
| ii  libasound2-plugins       1.0.21-3                 ALSA library addi=
| ii  mplayer                  1.0~rc3+svn20090405-1    movie player for =

A little context on the use case is included below.

Adrian Knoth wrote:

>> With 'mplayer -ao jack', on the other hand, everything works fine.
>> Ideas?
> Yeah, don't use mplayer with ao alsa when you really want ao jack. jack=
> is for pro-audio, think of recording studios, and the alsa-jackd-bridge
> is just a little hack to enable non-jackified apps to output in these
> environments.
> In general, update jackd, run it with realtime prios, update the
> alsa-jackd bridge or replace it by pulseaudio. (I see exactly the same
> problems with the alsa-jackd bridge, that's why I switched to
> pulseaudio)

My friend has been working on getting some real-time audio processing
done, investigating various APIs for doing that.  JACK looks like a
nice one.  But unfortunately, if jackd is running, he could not play
movies through Flash.  Adobe=E2=80=99s Flash plugin uses ALSA, so the
alsa-jackd bridge seemed like a natural fix.

mplayer was just a demo program to make sure the bridge was working.

Pulseaudio has plenty of advantages anyway, so I do think I=E2=80=99ll
switch to that.

> In current Debian unstable, we have all these things, jackd operates
> the pro-audio gear and pulseaudio-module-jack bridges between "consumer
> apps" and the pro-audio jackd.

Maybe jackd could Suggests: pulseaudio-module-jack for this.  (But
if you'd like to discuss this more, we should probably take it to
pkg-multimedia-maintainers or a new bug report.)

> To quote jackd author Paul Davis: jackd is not intended to be a generic
> desktop sound server.

This was clear from the home page already, but maybe the package
description should mention it too.


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