Trying to determine DTMF from .wav file

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Amritpal Kaur
Amritpal Kaur 2016-12-2
评论： Star Strider 2016-12-2
So I am trying to determine the numbers dialed in a DTMF wave file by reading the [x, y] co-ordinates of the Fourier analysis plot. The numbers are: 251216. Here is my Matlab code for the same:
% Tone Dialling %
[y,Fs] = audioread('tones.wav');
n = length(y);
p = abs(fft(y));
f = (Fs/n)*(0:n-1);
plot(f,p);
axis([500 1400 0 1000])
xlabel('f(Hz)')
title('Power')
This corresponds to the following plot:
Now this should have 6 peaks, but doesn't! Where am I wrong? The clip is a 6second clip, pulse being played after every 1 second.
Any help is appreciated.

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回答（1 个）

Star Strider
Star Strider 2016-12-2
  2 个评论
Amritpal Kaur
Amritpal Kaur 2016-12-2
I found this out, but I would love to learn it from my code. I am not trying to get a solution but rather learn where I am mistaken.
Star Strider
Star Strider 2016-12-2
You have to use some sort of time-frequency detection method, since the frequencies vary with time. You could create bandpass filters for the various DTMF combinations and code the output so that when a particular combination was ‘high’ that number would be saved, but the times vary enough to make this very difficult. (This is from my personal experience, and the reason I ended up using the spectrogram.)
You can also experiment with wavelets, if you have the Wavelet Toolbox. You will encounter the same problem with timing.

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