The dtmfdecode utility is part of the isdn4bsd package and is used to detect DTMF tones in the audio stream.
It reads audio G.711 A-Law coded data from stdin and outputs the detected numbers values as ASCII characters to stdout.
The detector is implemented as 8 narrow band-pass filters realized with an integer double-cross recursive algorithm. Various ad-hoc methods are employed to provide hysteresis and anti-bounce for the detected signals.
dtmfdecode < beep.al
will print a "1" to stdout.
ITU Recommendations G.711
.An -nosplit The dtmfdecode utility was written by
.An Poul-Henning Kamp Aq phk@FreeBSD.org . This man page was written by
.An Hellmuth Michaelis Aq hm@FreeBSD.org .