I did a lot of research regarding transferring a custom sound clip(wav,mp3 etc) to an ongoing GSM voice call in Android so that the other party can hear it but it seems it cannot be done.
But when in a call if I press a key(1,2,3,4 etc) that key's DTMF tone is heard by the other party as well, so is there any way to change the default DTMF tones (let's say to replace the DTMF of key 2 to a wav clip) and when on a call if a user presses key 2 the other party is able to hear the replaced DTMF tone which is the wav clip?
Additional info: Granting Root permission is ok.
No this is not possible. Since even though you hear a sound when keypad is pressed, it is not the same audio that is passed onto the call. A message is passed to the modem saying which DTMF tone is to be generated. The Modem will generate the DTMF tone. This Message passing is proprietory to each OEM