dtmf_dec.m

采用matlab编程的DTMF检测程序仿真

function xx=dtmf_dec_duzhou(x);

tone = ['1' '2' '3' 'A' '4' '5' '6' 'B' '7' '8' '9' 'C' '*' '0' '#' 'D'  'e'  ];  
Fs = 8000 ; Ts = 1/Fs ;    % Fs is the sampling rate
T_duration = 30; magnitude=1;             % minmum of signal duration is 40ms, we choose 30ms 
T = T_duration/1000 ;      % the unit is ms
block = floor(T * Fs);     % defining the size of the block
length_all = ceil(length(x)/block);  % determine the numbers of the block
zero_x = zeros( 1, (length_all*block)-length(x) ); % if the length of x less than the all block
x = [x zero_x];                                    % then add zeros to it    
N=205;                           % we choose the number from the paper
k=[18 20 22 24 31 34 38 42];     % we chose the value of k according to the value of N 
d_init=[]; LIMIT=1e6*magnitude;            % limit the threshold to distinguish the DTMF from the speech or noise
for n=0:length_all-1,
    Spectrum = zeros(1,8);        % it only needs 8 spectrum
    period = (1:block) + block*n ;      % 
    for m = 1:8,
        Spectrum(m) = Goertzel( x(period) , k(m) , N ) ;
    end
    Spectrum = reshape(Spectrum,4,2);    % devide the power of low and high frequency into two column 
    [max_mag max_index] = max(Spectrum); % find the hightest two power of low and high frenquency
                                         % get their index respectively 
    tone_index = (max_index(1)-1)*4 + max_index(2); %  according to the index of the
                                                    %  Spectrum we could get the index of
    if ( max_mag(1) * max_mag(2) < LIMIT )          %  the tone
        tone_index=17;  
    end
    d_init=[d_init tone(tone_index)]; 
end
% the part of output %
count = 1;                 % initialize count to '1'
tone_sig_index=[];         % since the array started with '1', not '0'
if (d_init(1)~='e')        % so we should check the signal is right or
    d(1)=d_init(1);        % not then initialize it to '1'
    count = 2;
    tone_sig_index=[1];
end
for i = 2 : length(d_init)
    if ( d_init(i) ~= 'e' ) & ( d_init(i) ~= d_init(i-1) )  % 
        d(count) = d_init(i); 
        count = count+1;
        tone_sig_index = [tone_sig_index i ];
    end
end
len_x=length(tone_sig_index);
sig_show=[];
for n=1:len_x,
    sig_show=[sig_show d_init(tone_sig_index(n))];
end
xx=sig_show;