[OLPC Security] Audio applications

[Greg Thompson]

Hi -

I'm new to the mailing list, so I apologize if I'm asking a question  
that may have been raised in the past.

I'm attempting to wrap my head around the "appropriate" model for  
working with audio on the XO.  More specifically, I am trying to make  
use of Csound in the most effective way.  The main problem involves  
the need for multiple activities to 'share' the audio device.

Perhaps a scenario will help illuminate the problem. Let's say we  
have the following situation:

- IM application is running in the background
- playing a game with music and sound effects in the foreground

Let's assume the IM application uses Csound to generate sounds to  
notify users of certain actions (as most IM apps do).  So, someone  
sends a message to the IM app and it wishes to play a sound to notify  
the user.

The problem here is that more than one process wishes to make use of  
the DAC (and possibly the ADC) at the same time.  I believe Csound  
currently uses a direct ALSA implementation and/or Port Audio which  
wraps ALSA to communicate with the DAC.  I know some have discussed  
the pulseaudio option http://wiki.laptop.org/go/Pulseaudio, but I'm  
not sure if its truly being adopted.  If it is, then this may not be  
a huge problem.

The alternative was to provide a service of sorts that multiple  
activities could communicate with to work with Csound and share  
Csound and the device via the service.

I'm curious what the current security recommendation would be...

thanks
greg