问题
I'm currently searching for options on how to manipulate audio on android. The goal is to process audio from the microphone in real time during a phone call. The best solution would be to do this on a native call. But rebuilding a telephone app (no VOIP) would be fine too. Are there any ways to achieve this with Android APIs (also undocumented)? If not, which steps would be necessary to get things running?
On iOS there are some apps which manipulate voice but create a VOIP connection. I heard that on Android you can "clone" the telephone app and eventually feed it with your own audio stream? Aren't there apps which add noises during a call? What kind of APIs are involved?
回答1:
The best solution would be to do this on a native call.
This is not possible. You have no access to the in-call audio stream, except perhaps in speakerphone mode.
But rebuilding a telephone app (no VOIP) would be fine too.
The last official word from Google (2010), the entire OS has no access to the in-call audio stream, as it is all handled at a lower level. Even if newer versions of Android do have access to the in-call audio stream, "rebuilding a telephone app" is only possible if you are creating custom firmware.
回答2:
As a drawback i could imagine to record the Downlink Stream using the MediaRecorder API and write it back to hardware using AudioTracks write() method. By this i could manipulate incoming voice. But still I think this wont work during phone calls. And I do not see a way to choose different hardware destinations.
来源：https://stackoverflow.com/questions/9671914/android-manipulating-voice-in-phone-calls