Currently, CallManager has only 2 call states (InCall / NotInCall) and a separate list of pending calls. This limitation brings up several issues:

• the app starts sending audio frames as soon as the caller initiates the call, rather than when the callee accepts it, resulting in literally hundreds of error messages in the logcat.
• the only indication of establishing the call is audible voice "hello" from the called user
• the "link down" situation without received hangup signal can only be guessed from silence
• the call timing for the caller starts from initiating the call, for the callee -- from accepting the call

Probably, any solution will require redesign of CallManager (that by its essence should be a state machine), CallFragment and their dependencies.