Modifying in-call voice playback in Android custom ROM

[Omer Gilad]

I would like to know if it's possible to modify Android OS (official
image from AOSP) to add preprocessing to normal phone call playback
sound - and how.


I already know it's possible to do so for app audio playback (by
modifying HAL), but I'm not sure if that will also work for phone
calls. I need to know whether it's possible before getting into a
longer project - right now I don't have a quick way to test it.


I'm OK with targeting only a specific device (Nexus 5X), and modifying
Qualcomm code. Also, I only need to filter playback - I don't care
about recording (uplink).