I haven’t found a link to the sources of Unity3d (just quick browsing), but what I saw in the documentation it seems like it uses (also) OpenAL?
If so I would create a subclass of AudioIODevice which calls the callback of the AudioIODeviceCallback to fill an OpenAL buffer. I suggested that already here (but had no time to make a proof of concept):
Or did you actuall want to go the other way round and feed the game sound into JUCE buffers?
