Thanks for your clarifications. But…
a) Normal DISCs are not part of CDR.
b) Lets say at a distance from the BTS, SACCH will fail at regardless of whether AMR/NonAMR codec. (Though I know the user will have better voice quaility with AMR codec).
c) So the user drops it due to radio problems on SACCH anyhow and so the CDR (regardless of whatever speech codec he was on).
Theoretically CDR should be same.
I appreciate everyone’s patience so far.