#6 Detection of DTMF tones

[Serguei A. Mokhov]

[ I am opening this featire request as resulted from
the the following forum post: ]

https://sourceforge.net/forum/forum.php?thread_id=1638171&forum_id=213051

By: Nobody/Anonymous (nobody) - 2006-12-26 01:51
I'd like to create a simple application that "listens" to an audio file (.wav or .mp3) for DTMF tones and give me a list of specific locations (timecode style, e.g. 00:01:11.21 - 00:01:12.21 + "6Key") to indicate that a 1 second press of the "6" key occured at a specific timecode location.

Is this a reasonable and easy task to accomplish?

It should be easy enough given that you know the sampling rate (which you do)
and an index at which you detect a DTMF tone (which you also do, e.g. in MARF it is 8000hz).
It is better to use the Goertzel aglorithm instead of FFT as it is better suited for
detection FFT (and that's what the industry is using anyways for the touch
tones). Also, in order to give a better location, the silence from the sample
should not be removed in the preprocessing.

MARF itself does not have the Goertzel algorithm or DTMF detection app
immediately implemented, which I am considering as a feature request, but
for your immediate start you may consider this:

http://en.wikipedia.org/wiki/Goertzel_algorithm

It has the C code sample of the algorithm. I am considering of porting it
to MARF.