how to have /dev/audio on ubuntu?

Russell Reiter rreiter91-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
Tue Sep 25 17:43:04 UTC 2012 

Sound has traditionally been one of the more confusing issues in
setting up linux. I would have sent this earlier but I don't use
pulseaudio at home. Here's how it is set up on the computer I'm at
today. Newer hardware and running Fedora 17 3.3.4-5.fc17.i686.

# which pulseaudio
/bin/pulseaudio

In the following "by-id" and "by-path" are directories which contain
symlink connections to the hardware links in their parent /dev/snd
directory;

# ls -la /dev/snd
total 0
drwxr-xr-x   4 root root      480 Sep 23 16:17 .
drwxr-xr-x  24 root root     4060 Sep 24 11:23 ..
drwxr-xr-x   2 root root       60 Sep 23 16:17 by-id
drwxr-xr-x   2 root root      100 Sep 23 16:17 by-path
crw-rw----+  1 root audio 116,  8 Sep 23 16:17 controlC0
crw-rw----+  1 root audio 116, 17 Sep 23 16:17 controlC1
crw-rw----+  1 root audio 116, 19 Sep 23 16:17 controlC2
crw-rw----+  1 root audio 116,  7 Sep 23 16:17 hwC0D2
crw-rw----+  1 root audio 116, 16 Sep 23 16:17 hwC1D0
crw-rw----+  1 root audio 116, 15 Sep 23 16:17 hwC1D1
crw-rw----+  1 root audio 116, 14 Sep 23 16:17 hwC1D2
crw-rw----+  1 root audio 116, 13 Sep 23 16:17 hwC1D3
crw-rw----+  1 root audio 116,  6 Sep 25 10:20 pcmC0D0c
crw-rw----+  1 root audio 116,  5 Sep 25 10:15 pcmC0D0p
crw-rw----+  1 root audio 116,  4 Sep 25 08:43 pcmC0D1c
crw-rw----+  1 root audio 116,  3 Sep 25 08:43 pcmC0D1p
crw-rw----+  1 root audio 116,  2 Sep 23 16:17 pcmC0D2c
crw-rw----+  1 root audio 116, 12 Sep 25 08:43 pcmC1D3p
crw-rw----+  1 root audio 116, 11 Sep 23 16:17 pcmC1D7p
crw-rw----+  1 root audio 116, 10 Sep 23 16:17 pcmC1D8p
crw-rw----+  1 root audio 116,  9 Sep 23 16:17 pcmC1D9p
crw-rw----+  1 root audio 116, 18 Sep 25 10:20 pcmC2D0c
crw-rw----   1 root audio 116,  1 Sep 23 16:17 seq
crw-rw----+  1 root audio 116, 33 Sep 23 16:17 timer

controlC0, C1 and C2 are the three cards detected by the os.
In this case cat  /proc/asound/cards - shows C0 is the onboard sound
card, C1 is the Tv tuner and C2 is the mic on the USB camera.

# cat /proc/asound/cards
 0 [Intel          ]: HDA-Intel - HDA Intel
                      HDA Intel at 0xfbff4000 irq 42
 1 [NVidia         ]: HDA-Intel - HDA NVidia
                      HDA NVidia at 0xfaffc000 irq 17
 2 [USB20Camera    ]: USB-Audio - USB2.0_Camera
                      PixArt Imaging Inc. USB2.0_Camera at usb-0000:00:1a

The other detected bits of hardware in /dev/snd are: the several
hwCoD* which link the four HDMI sound output channels of the Tv tuner
card and the primary sound card's third subsystem device (pcmC0D2c)
for HDMI input. The pcmC0D0* are standard computer audio capture and
playback devices. (mic, line in, line out, etc) The ones ending with
"c" are capture and the ones ending in "p" are playback. C0 = three
input and two output channels C1 = four output channels C2 = one
output channel. Historically the joy and the sorrow of setting up a
sound system under linux has been linking a sound source to an output
sink.

It is sometimes desirable to access the sound hardware directly from a
command line. This following would use ALSA (arecord) to capture the
audio from an analogue tv-card by piping that signal to the first
subsystem of the second audio card (hw: 1,0), at an appropriate
playback, quality in Hertz (-r 32000) and in stereo over two channels
(-c 2), further this command defines the signal is appropriate for a
Sound Blaster type card (-f S16_LE).

tvtime | arecord -D hw:1,0 -r 32000 -c 2 -f S16_LE | aplay

This machine using arecord with the above string would try to link the
first subsystem on the second card to a default output
sink [controlC0:pcmC0D0p], and not work because on the other machine
another sound device was enumerated before the primary sound card.
(udev burp) This machine would use hw:0,0 if it had to be done this
way.

This shell snippet was for one of those tv cards which had an external
1/8in pin connector to connect the sound output from the tv card to
the line in of the sound card, so sound would work for Windows. I
could never get that hardware configuration to work in linux. So we
grabbed the signal from the bus in a more traditional way.

Your solution may be as simple as configuring siggen to use the
directory /dev/snd instead of /dev/audio. (assuming Ubuntu puts stuff
in /dev/snd) If your system is set up with OSS, these symlinks might
be placed in /dev/pcm.

If you find the directory holding these hardware links you could try
symlinking that directory to /dev/audio

As root #ln -s <path-to-your-sound-directory> /dev/audio
- might work and siggen will figure out which sink is where.

I know this probably isn't any clearer than anything else you've read
on setting up sound but don't be afraid of breaking software, fixing
it again is half the fun :-)

Russell

On Fri, Sep 21, 2012 at 11:20 AM, Zbigniew Koziol <softquake-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
>
> I remain confused. But I want to thank for responses, Russell and Mel.
>
> It seems that if I do not want to risk damaging the existing sound system I
> should not play too deep with what is there already.
>
> Fortunately, I have another box with Centos, and /dev/audio is still there.
>
> zb.
>
> On 09/21/2012 12:59 AM, Russell Reiter wrote:
>>
>> Ubuntu did not do a very good job of integrating pulseaudio. It's got
>> a lot of features but demands complete control over the sound hardware
>> and it looks like the Ubuntu folks rolled it out too quickly.
>>
>> If your hardware is older it might be better to go back to ALSA/OSS. I
>> haven't seen many problems with pulseaudio in newer equipment with
>> newer installs.
>>
>> I think ALSA still present in Ubuntu
>>
>> On the command line
>> $speaker-test (plays white noise)
>> $aplay - l (lists playback devices)
>> $arecord -l (lists record devices)
>>
>> $alsamixer (make sure PCM volume is not muted.)
>>
>> or $pavucontrol (under pulse for the same reason.)
>>
>> This site may be helpful.
>>
>> http://www.hecticgeek.com/2012/01/how-to-remove-pulseaudio-use-alsa-ubuntu-linux/
>>
>> Hope this helps
>> Russell
>>
>>
>>
>> On Thu, Sep 20, 2012 at 2:39 PM, Zbigniew Koziol<softquake-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org>
>> wrote:
>>>
>>> I am so much confused by reading web, and I swear I never understood how
>>> sound works (except of the times of DOS).
>>>
>>> My program reports:
>>>
>>> [siggen] No such file or directory : /dev/audio
>>>
>>> "siggen" is the name of the program I want to use, but the error message,
>>> I
>>> guess, is not related to the program itself.
>>>
>>> So, how can I make siggen not reporting that silly error message but just
>>> working right away?
>>>
>>> My Ubuntu version is one of the latest ones.
>>>
>>> zb.
>>> http://nanolab.gu-unpk.ru/
>>>
>>> --
>>> The Toronto Linux Users Group.      Meetings: http://gtalug.org/
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>>
>> --
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>
>
> --
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