Alter voice while talking

Question

So i would like to try to make an android app which alters the users voice while talking with someone else over the phone (alterations like "darth vader" effect and such, its more a fun app than anything else) and i would like to know if that's possible.

i'm aware of the telephony manager and i'm able to "notice" in my app when the user is talking on the phone, but i need to somehow "edit on the fly"

In short the structure im trying to accomplish:

-Microphone recieves voice data
-Data gets altered in a way the user chose while setting the app up
-Encrypted data is sent like usual to the receiver like usual when talking over phone
-The user hears the voice real-time (well if the app has a lot of work then there will probably be a small delay) with the voice effect

Anything like this made before and is it even possible?

Answer 1

The answer is "No". The voice stream is not available to modify, but you can modify recorded voices.

Answer 2

You cannot access or modify the in call audio stream in any way on Android.