yes, the same codec is used from one MS to the other MS, therefore there is no “transcoding” performed in the TC. For instance, 2 MS in EFR (12.2kb/s) –> the 12.2kb/s are not coded into 64kb/s and then back to 12.2kb/s.
The TFO can be used only during MS-MS call.
Benefit: comparing one codec with or without TFO, you’ll notice a better voice quality with TFO.
Constraint: specific parameters shall be tuned, in order to manage the strategy of TFO vs. AMR and TFO vs. HR codecs.