Re: [Ekiga-list] openal, virtual box...

[Derek Smithies <derek indranet co nz>]

Hi,

> I've a sound problem, the microphone is stoped when starting an 
> application using OpenAL, or when launching a virtualbox 
> within sound support.
yep. The classic sound problem of linux.

My guess as to what is happening::
When you start an application that uses openal, it takes exclusive
ownership of the sound card. Consequently, no other application on
the box can access the microphone side of that sound card.
Now, Ekiga cannot access the microphone. Sadness.

The problem is that one application on a box should not be able to grab 
exclusive acccess to the sound card, and lock all other applications out 
from the sound card.
Imagine this happening to your desktop apps.
Your mail tool could make a beep with incoming messages, but your IM 
client could not make a beep for events.

Over the years, there have been various attempts to solve this problem.
You have artsd - which had serious flaws.

You have the alsa type approach, of putting lots of sound cards in the 
box. let the system have sound card 0, and Ekiga uses sound card 1.
This actually works quite well. When this approach is used with OSS, the
result is perfect...

You then have cleverer cards/drivers, which let multiple applications 
access the sound card at the same time, provided they use the same sample 
rate. Now, ptlib&opal are based on 8khz, which is a bit lower than the 
desktop rate of 48khz.. I think that Ekiga and your openal app are having 
a problem as they are trying to access the microphone at different rates.

yes, Ekiga can up/down sample the rates to 48khz. At the cost of cpu time.
If it is a USB headset/mic, well, will the usb connection cope with the 
data, and the latency requirements??

Pulse was invented as a sound server that would allow all applications to 
access any sound device at any rate. Pulse is the main approach on ubuntu.

With pulse, there are problems..
  High latency.
  High cpu requirements.
  The control guis are ugly.
  The control guis are not reliable, intuitive or even sensible.
I am forced to conclude that pulse stands for
   "patheticly useless linux sound engineers"

Derek.

On Sat, 19 Sep 2009, Frederic Scherma wrote:

> Hello,
>
> Firstly, thanks for our work on this useful software.
>
> I've a sound problem, the microphone is stoped when starting an 
> application using OpenAL, or when launching a virtualbox 
> within sound support.
>
> Ekiga 3.2.5
> OpenAL 1.1
> Alsa 1.0.21
> Debian SID 2.6.30-1-amd64
> Sound card SB Audigy 2 ZS
> KDE 4.3.1, no pulseaudio, no jackaudio, only artsd, xine, and gstreamer
>
> Regards,
> Frédéric
> _______________________________________________
> ekiga-list mailing list
> ekiga-list gnome org
> http://mail.gnome.org/mailman/listinfo/ekiga-list

--
Derek Smithies Ph.D.
IndraNet Technologies Ltd.
Email: derek indranet co nz
ph +64 3 365 6485
Web: http://www.indranet-technologies.com/