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

[yannick <sevmek free fr>]

Derek Smithies a écrit :
> 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"
> 

Hi Derek :),

Even if I find your points valid ones, fact is Pulse Audio is setup "by
default" on e.g. Ubuntu and Fedora. I'm myself an Ubuntu user, and
testing the Ekiga stable branch on Ubuntu 9.04 (latest stable release)
Ekiga suffer of a very large delay using the default ubuntu setup
(especially when using video). By very large delay I mean at least 5
seconds, which makes Ekiga pretty useless. I tryed various setup and the
only solution I found was to remove the pulse audio package; all other
setups failed (like using pasuspender or explicitly killing the pulse
audio deamon failed as pulse audio still startup when starting Ekiga).
When removing the pulse audio package Ekiga perform well, but the
desktop is broken, e.g. the default audio/video player (totem) is silent
(probably because it tries to use pulse audio be default). Thus the "by
default" ubuntu setup turns into a nightmare to reconfigure properly the
desktop when removing pulse audio. It is not a big deal for an old timer
like me, but it is not a pratical solution to advice removing pulse
audio for the "average" ubuntu user.

Generaly speacking, it is probably an issue with distros trying to be
cutting edge like Ubuntu or Fedora as they want to inlcude new
technologies pretty fast even if those tehcnologies are not mature
enough. Still IMHO the real issue here is the Linux audio stack still
sucks, i.e. ALSA. The ALSA API is overbloated, the ALSA team is not
really responsive to bug reports and probably the code base is hard to
modify. That would explain why sound server deamons keeps coming back
years after years (like arts, esd, pulse audio, phonon etc.) as a
practical workaround for ALSA deficiencies.

Thinking of the forseeable future, new sound deamons like pulse audio
might be a good thing as it will help ALSA to fix its issues; it is
better to deal with 1 deamon than with several applications directly
using the whole ALSA API. IMHO this work has to be done, we cannot
counter it by saying it was working well enough before the pulse audio
introduction. Still the actual situation is pretty bad...

As some major actors of the GNU/Linux VoIP are following the pulse audio
trend, like gstreamer/empathy or even skype (which seems to have a pulse
audio plugin now), and e.g. nokia is giving cash for its mobile platform
(maemo and the N900 hardware) we have to compete...

Best regards,
Yannick

> 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
> 
> 
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