Modify AOSP-11 to play audio file during phone calls

[krunal indrodiya]

Hi,

I would like to play audio file during ongoing phone calls on uplink call audio stream.

I love to modify AOSP-11 source code and work on customise android OS for this feature. I don't want to publish this AOSP build this is for testing purpose only.

I had implemented system level application and successfully install on the devices.

I will appreciate if anyone share knowledge or example regarding how it can be possible. I also went throw some the links but there is no any example available.