Express DSP compliant C55x DTMF detector software is proposed in two versions: one with a 5 ms frame
size and one with a 10 ms frame size. The versions are quite similar in behavior. The version with a 10 ms
frame size is faster, but the overall quality is higher in the 5 ms version, due to lower time granularity. DTMF算法for TI DSP 54X/55X
