Ok, the patch file is attached to this post.

The patch file has been created against the v2.00-beta3 version of the kernel. The patching should go as follows:

% cd kernel/arch/arm/special
% patch < audio_overlay.patch

It modifies the empeg_audio3 and empeg_mixer files. The changes won't affect existing applications, therefore the player and other applications should run as before.

Using the audio overlay system is very simple. When you open the /dev/audio device in your code, you need to specify the O_SYNC flag to determine that you want to overlay audio with the player application.

For example:
int handle = open( "/dev/audio", O_WRONLY | O_SYNC );

That's all. Now, every time you write something to the handle, it will automatically fade the volumes and mix the audio.

Kim