Comments on: lsof |grep snd — how to free a linux sound device

By: question

question — Sun, 15 Jan 2012 10:51:43 +0000

yeah… and for getting answer, one must simply ask the question…
mine was provided here: http://www.realitysend.com/kirbj/devlog/linuxsound
and, after following procedures - i ended up with working system sound from java based chess program and listen music from rhythmbox.

By: question

question — Sun, 15 Jan 2012 10:24:17 +0000

Well, article is well written indeed, but…
i wish to have solution, that java program would work with gstreamer apllications simuntaneously.

by default, ubuntu and gnome tend to provide pulseaudio. pulseaudio may be good idea in theory, but in practice pure alsa works better (doeas not glich).
so i get rid pulse by removing it by default.
but java issue remains.

now question, how to setup linux sound in way, that there is provided hardware sound device + at least one virtual hardware device, mixer controls to playback sound from both, for simultaneous play (java program +some other program playback)

By: Sander

Sander — Mon, 09 Jan 2012 12:51:01 +0000

Great how to! This showed me what my problem is.
Unfortunately, I still can't solve it. Here is my problem:

When in Matlab I play a sound, either with 'sound', 'soundsc' or another matlab function it plays it fine, but afterwards I cannot play any other sound. The error is the following:

Unable to open the audio device for playback: javax.sound.sampled.LineUnavailableException: line with format PCM_SIGNED 8192.0 Hz, 16 bit, mono, 2 bytes/frame, big-endian not supported.

I followed some this how to and discovered that matlab does not close the file used for writing the sound. Sometimes it closes eventually and sometimes I cannot listen to anything unless I close matlab first.
When I execute the 'lsof | grep snd' command in a console I get the following output:

gnome-set 1506 sander mem REG 8,5 409528 134483 /usr/lib/libsndfile.so.1.0.23
pulseaudi 1521 sander mem REG 8,5 409528 134483 /usr/lib/libsndfile.so.1.0.23
pulseaudi 1521 sander 28u CHR 116,8 0t0 7782 /dev/snd/controlC0
pulseaudi 1521 sander 35u CHR 116,8 0t0 7782 /dev/snd/controlC0
gconf-hel 1544 sander mem REG 8,5 409528 134483 /usr/lib/libsndfile.so.1.0.23
indicator 1635 sander mem REG 8,5 409528 134483 /usr/lib/libsndfile.so.1.0.23
firefox 2178 sander mem REG 8,5 409528 134483 /usr/lib/libsndfile.so.1.0.23
MATLAB 3704 sander mem REG 8,5 409528 134483 /usr/lib/libsndfile.so.1.0.23
MATLAB 3704 sander mem CHR 116,5 7777 /dev/snd/pcmC0D0p
MATLAB 3704 sander 318u CHR 116,5 0t0 7777 /dev/snd/pcmC0D0p

There are some other processes which have opened a/some sound filedescriptors (I don't fully understand it), but these did not prevent matlab from executing the sound the first time.

So my question is: Does anyone know what is going on? Are these processes perhaps causing deadlock on the soundcard? Is there a way to forcefully close a filedescriptor or make a process release a resource? Or another more permanent solution?

Any help would be very welcome.

By: Audio issues: What do I delete to make a clean start in alsa?

Audio issues: What do I delete to make a clean start in alsa? — Sat, 05 Nov 2011 20:11:41 +0000

[…] Read this http://linux.dsplabs.com.au/lsof-gre…nd-device-p25/ […]

By: Gato

Gato — Fri, 11 Feb 2011 03:58:18 +0000

Thanks very much.

Very good learning!

By: Suhrid Karthik

Suhrid Karthik — Tue, 05 Oct 2010 06:59:52 +0000

Great write up. Really Useful. Thanks.

By: Stasy

Stasy — Thu, 22 Jul 2010 07:03:33 +0000

Thanks a lot!

By: portableRIOT

portableRIOT — Wed, 21 Jul 2010 14:38:37 +0000

so… I'm having the same troubles, I'm attempting to video chat, and I finally got my webcam to work in unbuntu, but now my mic and sound aren't accessable by aMSN. I've tried your fix in the terminal, and It's not working. Could it be because I have an older version of linux, seriously updated? (I installed it on my windows laptop because windows kept crashing on me, and I have no other options.)

PLEASE HELP!!

and thanks

By: Charlie

Charlie — Sun, 09 May 2010 03:50:11 +0000

This is a very well written article - I like that it comes with an explanation as well as the commands.

By: Aistis

Aistis — Thu, 25 Feb 2010 16:57:58 +0000

I luv this tutorial.. OneMegaThanksToYou !!!

By: theme

theme — Thu, 18 Jun 2009 14:28:21 +0000

Kamil: completely agree with you, that is a so dirty solution, but as you point it works. The pitty is that Matlab/java and/or Alsa team doen't manage to fix it. Let's hope they get any solution. Linux is for work and have fun and multitasking system so, we should be able to do both, working with matlab while enjoying great music.

Anyway thanks for the tip, i liked itvery much, sorry for the absence but i've been working in other issues, and now i've already focused again in matlab : )

THNX again

By: Kamil

Kamil — Sat, 09 May 2009 02:07:25 +0000

Hi Dimitris, in all likelihood your sound card can play and record at the same time, f.e. I can use, at the same time, mplayer for playback and gnome-sound-recorder for recording, without errors. The only thing that can get tricky are the mixer settings. Try un-muting all devices using alsamixer and set all the volumes to maximum to get started.

By: Dimitris

Dimitris — Fri, 08 May 2009 20:49:33 +0000

Any solution for me?

By: Kamil

Kamil — Fri, 01 May 2009 11:44:16 +0000

Good question, lets try a few things… if I play music using mplayer and then use say play (a sox based playback script) to play another audio file. Both play fine.

If I play music using mplayer and the start matlab and try to play any audio (even after mplayer finished) it fails like so:

>> x=wavread('sp10.wav');
Warning: The playback thread did not start within one second.
> In audioplayer.playblocking at 35
In audiovideo/private/playsnd at 16
In sound at 46
In soundsc at 48
>> Unable to open the audio device for playback: javax.sound.sampled.LineUnavailableException: Audio Device Unavailable

To get it to work, I have to quit matlab and start it again. On the other hand, if I start matlab first and then try to play audio using mplayer, then mplayer fails to play — it simply sits there with the following prompt: Starting playback…

Ok, so as mentioned previously it is matlab's java based playback libs that simply requires exclusive access to the audio device. A bit of googling confirms that this is a common problem, and that java and/or alsa are at fault for not handling these things nicely.

Alright, if I had to do it, then my hack would be as follows. I would create a matlab wrapper function file called play.m somewhere in matlab's path. The content of play.m would be something like this:

% Saves audio data to a wav file before playback.
%
% audio - audio samples
% fs - sampling rate (Hz) [default: 8000]
% nbits - precision (bits) [default: 16]
% wavfile - filename for the wav file [default: '/tmp/tmp.wav']
%
% usage: play(audio, fs, nbits, wavfile)

function play(audio, fs, nbits, wavfile)

% parse input arguments or use defaults
switch(nargin)
case 1, wavfile='/tmp/tmp.wav'; nbits=16; fs=8000;
case 2, wavfile='/tmp/tmp.wav'; nbits=16;
case 3, wavfile='/tmp/tmp.wav';
case 4,
otherwise, error(sprintf('usage: play(audio, 8000, 16, "/tmp/tmp.wav"\ntype: help play for further details…'));
end

% save audio to file, scale prior to writing to avoid clipping
audio = 0.999*audio/max(abs(audio));
wavwrite(audio, fs, nbits, wavfile);

% playback the audio
if(exist(wavfile, 'file'))
syscmd = sprintf('mplayer %s', wavfile); % uses mplayer for playback
%syscmd = sprintf('play %s', wavfile); % uses sox play for playback
system(syscmd);
else
error(sprintf('%s: file not found.', wavfile));
end

% EOF

In matlab, help play gives the following:

>> help play
Saves audio data to a wav file before playback.

audio - audio samples
fs - sampling rate (Hz) [default: 8000]
nbits - precision (bits) [default: 16]
wavfile - filename for the wav file [default: '/tmp/tmp.wav']

usage: play(audio, fs, nbits, wavfile)
Overloaded methods:
audiorecorder/play
audioplayer/play

So make sure that your play.m is in the path before the other ones, or call it something else…

Ok, it is not pretty, but it works.

Kamil

By: theme

theme — Fri, 01 May 2009 09:36:08 +0000

First of all,this post is awsome and i've learned great and useful things but, i wonder if there's any way to be able to work with matlab (playing sounds) and listening music with another program (f.i. firefox and streaming) without having to kill one of both.

By: Dimitris

Dimitris — Thu, 23 Apr 2009 17:10:36 +0000

Indeed it worked!
This means that i can't hear music at the same time that
i want to speak with the microphone?

I had this problem for a long time, and after i used the commands above
for the first time my aMSN closed alone, and when i reopened it (without music)
the recording and the camera, worked properly. But when i re opened music
i had again the same error " Could not gain access to /dev/dsp for writing." .
Do i have to follow this procedure every time that i open the music?

PLz answer to my mail or here…
Thanks in advance

By: Kamil

Kamil — Wed, 21 Jan 2009 03:00:02 +0000

Kim, take a look at: http://linux.dsplabs.com.au/no-volume-control-gstreamer-plugins-and-or-devices-found-no-sound-or-voume-control-bug-on-ubuntu-p31/

By: Kim

Kim — Tue, 20 Jan 2009 22:32:12 +0000

I have no idea what Im doing here, I keep getting "no volume control gstreamer plugins and or devices found" as an error message when I click on my speaker icon!! Can anyone explain in LAYMEN terms how I fix this pleeeease????

By: Wallace Silva

Wallace Silva — Thu, 04 Dec 2008 15:43:51 +0000

solution in my pc
i did have to install libsnack to alsa

# apt-get install libsnack2-alsa

and solved.

tks.

By: cynthia

cynthia — Tue, 28 Oct 2008 12:23:11 +0000

wow! I've been searching the net to find solution to this problem. My transcription software sometimes runs and sometimes not. A hassle when transcription assignment arrives; but this article saved me! Thanks a lot and more power for giving this support!

By: craig

craig — Fri, 17 Oct 2008 17:40:05 +0000

Thanks a bunch, I always resorted to closing down every program, or even rebooting. More uptime for me now!

By: Miguel

Miguel — Tue, 01 Jul 2008 22:11:02 +0000

Excellent!… It worked!…
I had to do one step more: locating the program lsof using the command: whereis.

By: Kamil

Kamil — Fri, 25 Apr 2008 03:20:47 +0000

what is the laptop model number and what is the sound card type? since your audio device is does not get detected by default it will be a fair bit trickier to get it to work… where I would start is googling to see if others have done it… for example I would search for "linux audio dell 9300 audigy sound blaster".

By: Anonymous

Anonymous — Fri, 25 Apr 2008 01:03:02 +0000

when i run this command:

cat /proc/asound/cards

the output is:

no soundcars

But i belive that i have sound card coz my laptop sound is working when i use windows

help me