On Thu, Sep 17, 2009 at 11:51:33AM +0200, Fabien COMTE wrote:

I have an application that does VoIP and use OSS emulated interface.

I suspect part of your problem here is the in-kernel OSS emulation - that bypasses all the ALSA user space mixing support. If you can't change the OSS using application to use ALSA then I believe there are some other options based on preloading a library to intercept the attempts to open the OSS device and emulate it but I'm not really familiar with them.