Route phone audio call to a custom sound service in android?

Question

I have implemented my custom audio interface which is derived from AudioHardwareBase, and I have initialized it in AudioFlinger constructor class. This class will stream the audio through network. This work fine when I play sound from a file, but not when make phone call. The problem is due probably because the audio of phone call come from hardware unlike audio file (which come from software). I'm willing to modify basic android library/driver in order to get this work. Any idea how can I overcome this issue?

Thanks