Atanh | Autocorrelation | Bandpass Filter | C++ | Conv | Database | Deconv | Excel | FFT | Filter | Filtering | FIR | Fourier Transfrom | FSK | Gaussian Noise | Haykin | IFFT | Image | Java | LFSR | LMS | LPC | MEX | OFDM | QPSK | Radix | Random | Sampling | Segmentation | Simulink | Visual Basic | Waveform | Wavelet

hi.
frist of all,i'm sorry for my poor english.
i need your help.i;m working on 'formant detection via LPC method'.i've found a
site that done this project via matlab.but i want to write it in c.i cant
understand it's algorithm.can you help me.please,nobody answer me

Formants Detection via LPC Method 
LPC 
% NAME
%   spLpc - The linear predictive coding (one-step finite observation 
%           wiener filter prediction)
% SYNOPSIS
%   [a P e] = spLpc(x, fs, ncoef, show)
% DESCRIPTION
%   Obtain LPC coefficients (AR model)
% INPUTS
%   x        (vector) of size Nx1 which contains signal
%   fs       (scalar) the sampling frequency
%   [ncoef]  (scalar) the number of coefficients. The default uses
%              ncoef = 2 + fs / 1000;
%             as a rule of thumb. 
% OUTPUTS
%   a        (vector) of size ncoefx1 which contains LPC coefficients
%   P        (scalar) variance (power) of the prediction error
%   e        (vector) of size Nx1 which contains residual error signals
% AUTHOR
%   Naotoshi Seo, April 2008
% USES
%   lpc.m (Signal Processing toolbox)
function [a P e] = spLpc(x, fs, ncoef)
 if ~exist('ncoef', 'var') || isempty(ncoef)
     ncoef = 2 + round(fs / 1000); % rule of thumb for human speech
 end
 [a P] = lpc(x, ncoef);
 if nargout > 2,
    est_x = filter([0 -a(2:end)],1,x);    % Estimated signal
    e = x - est_x;                        % Residual signal
 end 
end[x, fs] = wavread('bee.wav');
a = spLpc(x, fs, [], 'plot');Formants Detection 
% NAME
%   spFormantsLpc - Formants Estimation via LPC Method
% SYNOPSIS
%   [F] = spFormantsLpc(a, fs)
% DESCRIPTION
%   Estimate formants frequencies
% INPUTS
%   a        (vector) of size ncoefx1 which contains the LPC coefficients
%             of the original signal. Use spLpc.m
%   fs       (scalar) the sampling frequency of the original signal
% OUTPUTS
%   F        (vector) of size ncoefx1 which contains formants
% AUTHOR
%   Naotoshi Seo, April 2008
% SEE ALSO
%   spLpc.m
function [F] = spFormantsLpc(a, fs)
 r = roots(a);
 r = r(imag(r)>0.01);
 F = sort(atan2(imag(r),real(r))*fs/(2*pi));
endFormants Tracking in Short-Time Frames 
% NAME
%   spFormantsTrackLpc: Formants Tracking via the LPC Method 
% SYNOPSIS
%   [F, T] = spFormantsTrackLpc(x, fs, ncoef, 
%               frame_length, frame_overlap, window, show)
% DESCRIPTION
%   Formants Tracking via the LPC method
% INPUTS
%   x      (vector) of size Nx1.
%   fs     (scalar) the sampling rate in Hz. 
%   [ncoef](scalar) the number of LPC coefficients used for
%           estimation. ncoef = 2 + fs / 1000 is the default.
%   [frame_length]
%          (scalar) the length of each frame in micro second. 
%           The default is 30ms.  
%   [frame_overlap] 
%          (scalar) the length of each frame overlaps in micro second. 
%           The default is frame_length / 2. 
%   [window]
%          (string) the window function such as rectwin, hamming.  
%           if not specified, equivalent to hamming
%   [show] (boolean) plot or not. The default is 0.
% OUTPUTS
%   F      (vector) formants (fm = F(find(T == 0.01))
%   T      (vector) formant times
% AUTHOR
%   Naotoshi Seo, April 2006
function [F, T] = spFormantsTrackLpc(x, fs, ncoef, frame_length, frame_overlap,
window, show)
 %% Initialization
 N = length(x);
 if ~exist('frame_length', 'var') || isempty(frame_length)
     frame_length = 30;
 end
 if ~exist('frame_overlap', 'var') || isempty(frame_overlap)
     frame_overlap = 20;
 end
 if ~exist('window', 'var') || isempty(window)
     window = 'hamming';
 end
 if ~exist('show', 'var') || isempty(show)
     show = 0;
 end
 if ~exist('ncoef', 'var')
     ncoef = [];
 end
 nsample = round(frame_length  * fs / 1000); % convert ms to points
 noverlap = round(frame_overlap * fs / 1000); % convert ms to points
 window   = eval(sprintf('%s(nsample)', window)); % e.g., hamming(nfft)

 pos = 1; t = 1;
 F = []; % formants
 T = []; % time (s) at the frame
 mid = round(nsample/2);
 while (pos+nsample <= N)
     frame = x(pos:pos+nsample-1);
     frame = frame - mean(frame);
     a = spLpc(frame, fs, ncoef);
     fm = spFormantsLpc(a, fs);
     for i=1:length(fm)
        F = [F fm(i)]; % number of formants are not same for each frame
        T = [T (pos+mid)/fs];
     end
     pos = pos + (nsample - noverlap);
     t = t + 1;
 end

 if show
     % plot waveform
     t=(0:N-1)/fs;
     subplot(2,1,1);
     plot(t,x);
     legend('Waveform');
     xlabel('Time (s)');
     ylabel('Amplitude');
     xlim([t(1) t(end)]);

     % plot formants trace
     subplot(2,1,2);
     plot(T, F, '.');
     hold off;
     legend('Formants');
     xlabel('Time (s)');
     ylabel('Frequency (Hz)');
     xlim([t(1) t(end)]);
 end[x, fs] = wavread('bee.wav');
[F, T] = spFormantsTrackLpc(x, fs, [], 30, 20, 'hamming', 'plot');

______________________________
New Code Sharing Section now Live on DSPRelated.com. Learn about the Reward Program for Contributors here.



(You need to be a member of matlab -- send a blank email to matlab-subscribe@yahoogroups.com )