Hi

I want to get some information on how to tap the voice data coming from an incoming call.

what i know is that the Telephony subsystem will notify when an incoming call is in progress and it can also send notification for answering the call.
But what happens just after answering the call ? Where does the voice data comes from and how it flows to the speaker?Which subsystem handles the voice data which comes from line and is played to the speaker.
Are there any API which can tap that real voice  data without being sending it to the speaker?

Thanks