AMBE (3600x2400, D-STAR), AMBE+2 (3600x2450: DMR, P25 Phase 2, YSF DN,
NXDN, dPMR) and IMBE (7200x4400: P25 Phase 1, YSF VW, NXDN full rate)
the full encoder API with its options and front end,
the transcoder and tone frames need <mbevocoder/mbevocoder.h>.

Encoder features:
 - automatic tone detection
 - VAD/DTX with silence frames and comfort noise for the gaps
 - noise suppressor
 - echo canceller.

Speed (on one desktop core):
 - encoder about 65x real time
 - decoder about 1600x