Hi, can anyone recommend a C or C++ package for PC decoding DTMF digits
from a wave file or soundcard?
Posted by Howard Long●February 17, 2005
> Hi, can anyone recommend a C or C++ package for PC decoding DTMF digits
> from a wave file or soundcard?
I'd not call it a package, but I wrote a program, with source code, to do
exactly this at
It should not be too tough to rip out the bits of interest. You will not
require any of the telemetry decoding parts of course.
This is not necessarily the best DTMF decode implementation, but it's the
most accurate I've seen for a PC (even though I say so myself). My program
uses FFTs and therefore uses the frequency domain characteristics to decode.
An alternative, the time domain Goertzel filter based system, is often
regarded as a better method.
As it stands there are possibilities to improve the FFT algorithm, such as
using overlap methods and using the energy of an adjacent bin where DTMF
frequencies spread nextdoor, improving sensitivity.
Posted by Steve Underwood●February 17, 2005
>Hi, can anyone recommend a C or C++ package for PC decoding DTMF digits
>from a wave file or soundcard?
If you grab my spandsp library from ftp.spandsp.org, it pretty much
gives you what you need. Its in C. Rip everything out of the DTMF test
suite, except the last bit where it reads through the Bellcore test tape
files. Change that bit a little, so it reads through the file names you
want, and you basically have what you are looking for. It will expect
the wave files to be 16bit 8000 sample/second mono files. If your files
are not, you will need to run them through a converter, like sox, to get
them into that form. The DTMF detector passes all the standard tests, as
you will find if you run the test suite.