Need help for DTMF Scoring fucntion

I have written a code for DTMF tone generation. Now for decodiing purpose, i have written code for dtmfscore

function  ss = dtmfscor(xx, freq, L, fs) 
if (nargin < 4), fs = 8000; end; 
hh = (2/L)*cos(2*pi*freq*(0:L-1)/fs); 
ss = (mean(conv(xx,hh).^2) > mean(xx.^2)/5);

the book says that input signal xx to dtmfscor function is actually a short segment from DTMF signal.The task of breaking up the signal so that each segment correspond to one key will be done by another function prior to calling dtmfscore.I m confused about xx. how to address this issue

Plz help me and give me rough skecth of algorithm I am stuck for last 2 days

Answer 1

[Wayne King]

I wouldn't write it like this because the dtmfscor function needs to know which column of tones it needs. But if you call the following:

>>[tones,ss] = dtmfking;

function [tones,ss] = dtmfking
lfg = [697 770 852 941]; % Low frequency group
hfg = [1209 1336 1477];  % High frequency group
% construct table of frequencies
f  = [];
for c=1:4,
    for r=1:3,
        f = [ f [lfg(c);hfg(r)] ];
    end
end
Fs  = 8000;       % Sampling frequency 8 kHz
N = 800;          % Tones of 100 ms
t   = (0:N-1)/Fs; % 800 samples at Fs
pit = 2*pi*t;
tones = zeros(N,size(f,12));
for toneChoice=1:12,
    % Generate tone
    tones(:,toneChoice) = sum(sin(f(:,toneChoice)*pit))';
end

ss = dtmfscor(tones,697,20,8000);
%Here i am giving the first freq and first column to cross check
function ss = dtmfscor(tones, freq, L, fs) 
if (nargin < 4), fs = 8000; end; 
hh = (2/L)*cos(2*pi*freq*(0:L-1)/fs); 
ss = (mean(conv(tones(:,1),hh).^2) > mean(tones(:,1).^2)/5);
end
end

Answer 2

[Wayne King]

I'm assuming xx is the output of your other function as you have stated.

It of course doesn't have to be called xx, xx is just a place holder in your function definition. Then you just feed that output to dtmfscor().

What exactly do you mean you're confused about xx?

Answer 3

[moonman]

Thanks a lot Wayne King. i am stuck with this part for last two days

This is exact statement of book. I have written code for DTMF generation which is working fine.

The next objective is decoding - a process that requires a binary decision on the presence or absence of the individual frequencies. In order to make the signal detection an automated process, we need a score function that rates the different possibilities. (a) Complete the dtmfscor function based on the skeleton given in Table 2. Assume that the input signal xx to the dtmfscor function is actually a short segment from the DTMF signal. The task of breaking up the signal so that each segment corresponds to one key will be done by another function prior to calling dtmfscor.

Now i have written code for dtmfscor, What does he mean by small segment.How to go about this all

thanks i lot

[Wayne King]

It sounds like he is saying to segment your signal, parse your signal so that each segment corresponds to key only. Then you pass that part to your dtmfscor() function which detects which key was passed. You want to make sure the signal you pass contains only one key so that you can make the correct decision.

Have you looked at:

>>dtmfdemo

and the doc example for goertzel

[Wayne King]

"corresponds to ONE key only."

Answer 4

[moonman]

Thanks a lot Wayne King for giving hint of Goertzel

Kindly explain me overall picture of scanrion

1. I have written a function A which generates DTMF tones. The output of this function is dtmf. function [dtmf]=dtmfdial(x);

2. Now I want to write a function which will make segments of each key. this is my effort.Now kindly help me how can i use this in dtmfscor

Here is my effort

function [dtmfseg]=dtmfseg(x);
%This function produces DTMF Tone  corresponding to given 
%key number
low_fg = [697 770 852 941]; % Low frequency group
high_fg = [1209 1336 1477];  % High frequency group
f  = [];   
seg=[];
for a=1:4,
    for b=1:3,
        f = [ f [low_fg(a);high_fg(b)] ];  
    end
end
disp('Table of Frequencies is shown')
table=f'   
dur=.5;   %Duration for each tone is .5 sec
fs=8000;  % Sampling Freq is 8000 Hz for tones 
tt=0:(1/fs):dur;
n=length(x);
D=cell(1,n);  
xx=cell(1,n);
for k=1:n    % This loop will continue for number of keys
    if x(k)==1
        freqa=table(1,1);   %Freq is picked from table(row1,col1)
        freqb=table(1,2);   %Freq is picked from table(row1,col2)
    else if x(k)==2
        freqa=table(2,1);
        freqb=table(2,2);
    else if x(k)==3
        freqa=table(3,1);
        freqb=table(3,2);
    else if x(k)==4
        freqa=table(4,1);
        freqb=table(4,2);
    else if x(k)==5
        freqa=table(5,1);
        freqb=table(5,2);
    else if x(k)==6
        freqa=table(6,1);
        freqb=table(6,2);
    else if x(k)==7
        freqa=table(7,1);
        freqb=table(7,2);
    else if x(k)==8
        freqa=table(8,1);
        freqb=table(8,2);
    else if x(k)==9
        freqa=table(9,1);
        freqb=table(9,2);
    else if x(k)=='*'
        freqa=table(10,1);
        freqb=table(10,2);
    else if x(k)==0
        freqa=table(11,1);
        freqb=table(11,2);
        else x(k)='#';
        freqa=table(12,1);
        freqb=table(12,2);
        end
    end
    end
    end
    end
    end
    end
    end
    end
    end
    end
% Both the tones are generated    
tone1=sin(2*pi*freqa*tt);  % Tone of First Frequency
tone2=sin(2*pi*freqb*tt);  % Tone of Second Frequency
tone=tone1+tone2;   % Now both tones are added
%***** We are making this loop to pick the segment of tone of each %key*****
for w=1:500
    seg(w)=tone(w);  % making segment
sil_dur=.1;  % Defining silence duration between tones
sil_freq=0;  % Since we want to keep silence, so frequency is zero
sil_tt=0:(1/fs):sil_dur;   
sil_tone=sin(2*pi*sil_freq*sil_tt);  % Generating silence tone
D{k} = [tone,sil_tone];   % Concatinatiing tones and then silence
xx{k}=[seg];              
end              %end of for loop
dtmfseg = cat(2, xx{:})

Answer 5

[moonman]

Plz guide me for this

Answer 6

[Wayne King]

Can't you do something like this

function tones = dtmfseg

lfg = [697 770 852 941]; % Low frequency group
hfg = [1209 1336 1477];  % High frequency group
% construct table of frequencies
f  = [];
for c=1:4,
    for r=1:3,
        f = [ f [lfg(c);hfg(r)] ];
    end
end

Fs  = 8000;       % Sampling frequency 8 kHz
N = 800;          % Tones of 100 ms
t   = (0:N-1)/Fs; % 800 samples at Fs
pit = 2*pi*t;

tones = zeros(N,size(f,12));
for toneChoice=1:12,
    % Generate tone
    tones(:,toneChoice) = sum(sin(f(:,toneChoice)*pit))';
end
end

>>tones = dtmfseg;

gives you the output array tones, which is a matrix where each column is a tone (including * and #).

Then each column of the matrix is one of your xx to use with your detection algorithm.

Obviously you can adjust the length as you wish.

Answer 7

[moonman]

Ok thanks King, i was thinking to make short segment of every input. For example if there are 2 keys, then i will make segment of 2 keys but u have given a good idea to make segment of all keys and then use them as required. I will work on it now

Thanks again

Answer 8

[moonman]

Sir King, sorry i am bothering u again, actually i am weak in functions so i m getting stuck. But i hope if this problem is solved then i can move ahead

AS per ur code, the segments have been made. Now as per book i am using dtmfscor function and i want to test it for first freq and column is first So ideally the answer should be returned as 1(True) as freq is present in tone[1] but i am getting error in the code

function tones = dtmfking
lfg = [697 770 852 941]; % Low frequency group
hfg = [1209 1336 1477];  % High frequency group
% construct table of frequencies
f  = [];
for c=1:4,
    for r=1:3,
        f = [ f [lfg(c);hfg(r)] ];
    end
end
Fs  = 8000;       % Sampling frequency 8 kHz
N = 800;          % Tones of 100 ms
t   = (0:N-1)/Fs; % 800 samples at Fs
pit = 2*pi*t;
tones = zeros(N,size(f,12));
for toneChoice=1:12,
    % Generate tone
    tones(:,toneChoice) = sum(sin(f(:,toneChoice)*pit))';
end
end

%Here i am giving the first freq and first column to cross check
%function  
ss = dtmfscor(tones, freq, L, fs) 
freq=697;
if (nargin < 4), fs = 8000; end; 
hh = (2/L)*cos(2*pi*freq*(0:L-1)/fs); 
ss = (mean(conv(tones[1],hh).^2) > mean(xx.^2)/5);

These both functions are in one file. I am getting error

>> tones=dtmfking ??? Error: File: dtmfking.m Line: 29 Column: 22 Unbalanced or unexpected parenthesis or bracket.

Answer 9

[Wayne King]

Hi Moonman, here is a modification that outputs only one tone:

function tone = dtmfseg(symb)

symbol = {'1','2','3','4','5','6','7','8','9','*','0','#'};
[truefalse,toneChoice] = ismember(symb,symbol);

if truefalse
lfg = [697 770 852 941]; % Low frequency group
hfg = [1209 1336 1477];  % High frequency group
% construct table of frequencies
f  = [];
for c=1:4,
    for r=1:3,
        f = [ f [lfg(c);hfg(r)] ];
    end
end

Fs  = 8000;       % Sampling frequency 8 kHz
N = 800;          % Tones of 100 ms
t   = (0:N-1)/Fs; % 800 samples at Fs
pit = 2*pi*t;

tone = sum(sin(f(:,toneChoice)*pit))';

else 
    error('Your input is invalid');
end
end

You would call it like this (for example):

>>tone = dtmfseg('2');

Answer 10

[moonman]

Sir king thanks for ur effort but book requirement is this one

the book says that input signal xx to dtmfscor function is actually a short segment from DTMF signal.The task of breaking up the signal so that each segment correspond to one key will be done by another function prior to calling dtmfscore.I m confused about xx. how to address this issue

I think what u did earilier was in connection withmy requirement

my dtmfscor function is ready Now i want to give input to it a short segment and then verify it with the frequency

I hope i have understood the book problem properly If u can spare some seconds, u can have look at this site I have posted the book page here

http://www.4shared.com/photo/u-a22m9a/1_online.html

I have already generted the DTMF tone by a function which works by this command soundsc(dtmfdial([1 7 '*' '#' 1 3 4 0 7 9 0 3 5]),8000);

Thanks a lot for helping me out in this issue. I am really grateful to u for ur patience and helping attitude

Answer 11

[moonman]

Thanks King I am following ur guidance and things are working smooth uptill now