For our today's agenda, especially the question about pulseaudio

At least suggesting pulseaudio-module-jack in jackd sounds reasonable to

----- Forwarded message from Jonathan Nieder <jrnie...@gmail.com> -----

Date: Tue, 12 Jan 2010 05:16:31 -0600
From: Jonathan Nieder <jrnie...@gmail.com>
To: cont...@bugs.debian.org, libasound2-plug...@packages.debian.org
Cc: 564...@bugs.debian.org, Adrian Knoth <a...@drcomp.erfurt.thur.de>,
        Edward Ruggeri <smallh...@crawblog.com>
Subject: Re: Bug#564828: "subgraph starting at ... timed out" after about
        five seconds of audio playback in mplayer

found 564828 jackd/0.118+svn3796-1
reassign 564828 libasound2-plugins 1.0.21-3

Hi ALSA maintainers,

I reported this bug earlier today.  Basically, mplayer locks up
after some seconds of playback using the ALSA jack plugin, and
even ^C will not kill it.

| $ mplayer -ao alsa 69550__dataka__mu_eca_piano.wav 
| MPlayer SVN-r29142-4.3.3 (C) 2000-2009 MPlayer Team
| mplayer: could not connect to socket
| mplayer: No such file or directory
| Failed to open LIRC support. You will not be able to use your remote control.
| Playing /home/jrn/web/69550__dataka__mu_eca_piano.wav.
| Audio only file format detected.
| ==========================================================================
| Opening audio decoder: [pcm] Uncompressed PCM audio decoder
| AUDIO: 44100 Hz, 2 ch, s16le, 1411.2 kbit/100.00% (ratio: 176400->176400)
| Selected audio codec: [pcm] afm: pcm (Uncompressed PCM)
| ==========================================================================
| AO: [alsa] 44100Hz 2ch s16le (2 bytes per sample)
| Video: no video
| Starting playback...
| A:  25.8 (25.8) of 42.0 (42.0)  0.4% 
| MPlayer interrupted by signal 2 in module: play_audio
| MPlayer interrupted by signal 2 in module: play_audio

From the original report (though the above transcript is from a
sid/experimental hybrid, not lenny):

| Stock lenny system.  jackd started with "jackd -d alsa -d hw:0 -r
| 44100" ALSA set up to use jack output as in
| <http://alsa.opensrc.org/index.php/Jack_(plugin)>.  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_fd=7, status = 0, state = 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=120 dpkg -l jackd libasound2-plugins mplayer
| ||/ Name                     Version                  Description
| +++-========================-========================-==================
| ii  jackd                    0.118+svn3796-1          JACK Audio Connect
| ii  libasound2-plugins       1.0.21-3                 ALSA library addit
| ii  mplayer                  1.0~rc3+svn20090405-1    movie player for U

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. jackd
> 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’s 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’ll
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.


----- End forwarded message -----

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