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DTMF detection within PCM audio

Started by Mark January 2, 2004
Hi,

I am trying to implement an IVR functionality as a part of Windows
application. I don't want to use TAPI.

So, I am looking for a source code detecting DTMF signals within a PCM
audio stream.

Can anybody help me on this? Any references?

Thanks in advance,
Mark
mark10@mail.com (Mark) wrote in message news:<a30790de.0401021312.76464072@posting.google.com>...
> Hi, > > I am trying to implement an IVR functionality as a part of Windows > application. I don't want to use TAPI. > > So, I am looking for a source code detecting DTMF signals within a PCM > audio stream. > > Can anybody help me on this? Any references? > > Thanks in advance, > Mark
To demodulate multiple tones, you need to use a simple FFT. This can be done by analyzing only the real part of the signal for instance. You will find plenty of info at www.analog.com or www.ti.com. The first step however, is to linearize the data and undo any Mu or A law encoding. Cheers, Herman http://www.AerospaceSoftware.com
mark10@mail.com (Mark) wrote in message news:<a30790de.0401021312.76464072@posting.google.com>...
> Hi, > > I am trying to implement an IVR functionality as a part of Windows > application. I don't want to use TAPI. > > So, I am looking for a source code detecting DTMF signals within a PCM > audio stream. > > Can anybody help me on this? Any references? > > Thanks in advance, > Mark
Here are some references on the Goertzel real mode FFT: http://www.isip.msstate.edu/conferences/dsp95/paper_dtmf.pdf http://www.embedded.com/story/OEG20020819S0057 You can also find PCM Mu/A law and DTMF schtuff on my site here: http://www.aerospacesoftware.com/contents.htm Cheers, Herman
Thanks, Herman.
Your answer was very helpful.

Mark