Detect when outgoing call is been answered on a rooted device

I don't mind rooting a device as the application will only be used privately, i'm working on a project that requires to monitor the call state of a device, have read the documentation on it

https://developer.android.com/reference/android/telecom/Call.html

and i have been using it but i'm having issue knowing when a call is picked, have checked the documentation and stackoverflow, have realized is a known issue from google itself.

Detecting outgoing call answered on Android

In rooted device detect if an outgoing call has been answered

and many others that i have tried. i understand there is no documented method to achieve this, i'm sure this will be possible because android itself calculate the time spent on a call and also some applications too like TRUE CALLER and some other private app monitor the time spent which is based on when a call is picked and when they hang-up from the call. Have tried a lot myself before deciding to post this, any suggestion on how to achieve this on a ROOTED device.