Re: USB soundbar as default audio device

[deloptes <deloptes@yahoo.com>]

Chris Jones wrote:

> I am trying to set up a USB sound bar on someone else's laptop running
> ubuntu 10.10 with a gnome desktop.

what is this sound bar? something to eat :-)?

> 
> Since it did not work out of the box, I thought I'd first enhance my
> non-existent skills in this area by first practicising on my machine
> with debian ‘lenny’ and no DE environment.
> 
> I discovered rather quickly that what goes on behind the scenes is that
> said sound bar is (emulates?) an additional sound card.

usb sound devices _are_ additional sound cards (actually anything with a
supported soundchip in linux would be a card)

> 
> As a result, I have to direct each program that produces some form or
> other of sound output to use the second audio device rather than the
> default builtin sound card.

not necessary if you configure the second one to be default ;-)

> 
> I am able to get ‘mplayer’ to do this but I have no idea how I could
> convince the flash plugin behind my web browser to do this, for
> instance.
> 
> Is there any way I can make the sound bar the system's default and be
> done with it?

you can read ALSA docs - they are weired but very good. I usually do few
steps to setup a card. You have two options - to setup system wide or user
specific

> 
> While testing, I tried redirection when launching programs from the bash
> prompt -- i.e. adding ‘/dev/dsp > /dev/dsp1’ -- with unsatisfactory
> results: below par sound quality, loud cracks, the speakers go silent
> for brief periods of time, etc.

dsp is OSS (not ALSA) and it works only with additional modules (loaded and
configured)

> 
> I do not have access to the other laptop right now, but I would assume
> gnome has some sort of GUI that lets you specify your default device
> ‘system-wide’?

check if there is pulse audio installed and running - this might be what you
are looking for (there is something pactrl or alike or gui for this - I'm
not using it but it's the future, so possibly you can use it)

> 
> Another thing I noticed is that the volume button on the sound bar does
> not work: I have to start alsamixer to control the volume, which is not
> optimal.
> 
> Does this mean that I am using a default generic audio USB driver for
> this device and that I should look for something a bit more specific
> that might support additional hardware features?

I would say this was the configuration for the default card (built in)

> 
> While I am at it I thought I might as well learn how these things work
> and stop guessing :-)

then start reading at
http://www.alsa-project.org/main/index.php/Documentation

> 
> Is there a reliable up-to-date document that you would recommend
> reading?
> 
> Thanks,
> 
> cj
> 
> P.S. I refrained from posting the 3 pages output by ‘lsusb -vs’. Not
> sure if that would help at this point.
> 

thanks, but it would help though to mention what kind of chip your usb card
has (or vendor + model)

I usually setup my notebook following way

*) Add the user to the audio(+video) group

*) create a file /etc/modprobe.d/sound  with following

   ## ALSA portion
   alias char-major-116 snd
   alias snd-card-0 snd-hda-intel
   alias snd-card-1 snd-usb-audio
   
   ## module options should go here
   #options snd-hda-intel index=0 model=dell-m6,ref,auto
   #options snd-hda-intel index=0 model=ref enable_msi=1
   options snd-hda-intel index=0 model=ref
   #options snd-hda-intel index=0 model=hp-dv5 enable_msi=1 position_fix=1
   options snd-usb-audio index=1

This way I have always the built in card configured as "0" which means first
and the usb as second

The options you'll find in the kernel version /Documentation

*) For user specific configuration and experimenting with alsa you can use

  $HOME/.asoundrc

example


  # from http://alsa.opensrc.org/index.php/Dmix
  pcm.headset { # playback only on frontpanel headset
   type route
   slave.pcm dmixer
   slave.channels 8
   ttable.0.0 1 # headphones front L
   ttable.1.1 1 # headphones front R
  }

  pcm.speakers { # playback only on desktop speakers
   type route
   slave.pcm dmixer
   slave.channels 8
   ttable.0.4 1 # speakers L
   ttable.1.5 1 # speakers R
  }



regards