doVAD.asv

%Tavas, Romelio Jr. 2011-11218
%Gomez, Emilio Vicente 2009-22091

%HONOR CODE
%I do hereby affirm, on my honor as a student at the end of this exam, that
%I had no unlawful knowledge of the questions or answers prior to this 
%exercise and that I have neither given nor received assistance in answering 
%any of the questions during this exam.
%
%calcSTZCR
% Computes the short time zero crossing rate
%
% USAGE:	[sig,fs,vad] = doVAD(wave); 
% INPUT:	
%           wave = file name ('AudioFiles/vowel_i.wav')       
% OUTPUT:	sig = signal vector of wav file
%           fs = sampling frequency of wav file
%           regions = transition regions 

function [sig,fs,regions] = doVAD(wave)


[sig,fs] = wavread(wave);
% Noise reduction code
% n = 7;
% beginFreq = 2100 / (fs/2);
% endFreq = 12000 / (fs/2);
% [b,a] = butter(n, [beginFreq, endFreq], 'bandpass');

% sig = filter(b,a,sig);

frame_len = 320; %20ms

z = calcSTZCR(sig,frame_len,frame_len/4,'rectwin');
energy = calcSTE(sig,frame_len,frame_len/4,'hamming');


% %assume first 50 frames are noise

Sc = 1000;
w = (energy .* (1-z)) * Sc; 
w_10 = w(1:10);
%define trigger
alpha = 5*var(w_10)^-0.92;
t = mean(w_10) + alpha * var(w_10);

vad = zeros(length(z),1);



for i = 1:length(z)
    if w(i)>t
        vad(i) = 1;
    else
        vad(i) = 0;
    end
end
%getting initial regions
r = [];
for i = 1 : length(vad)-1
    if vad(i+1) ~= vad(i)
        r = [r i+1];
    end
end
%smoothing out regions: removes the transitions if they are less than 10
%frams away from each other. 10 frames was chosen empirically 
r2 = [r(1)];
for i = 1:length(r)
    if i == length(r)
        if r(i) - r(i-1) < 10
        else
            r2(length(r2)) = r(i);
        end
    else 
        if r(i+1) - r2(length(r2)) < 10
            r2(length(r2)) = r(i);
        else
            r2 = [r2 r(i+1)];
        end
    end 
end
vad2 = [zeros(1,r2(1)-1)];
for i = 2:2:length(r2)
   vad2 = [vad2 ones(1,r2(i)-r2(i-1))];
end 
if length(vad2) < length(vad)
    vad2 = [vad2 zeros(1,length(vad)-length(vad2))];
end

regions = zeros(2,length(r2)/2);

% startpt = find(vad,1,'first') * frame_len;
% endpt = find(vad,1,'last') * frame_len;
% figure;
% plot(abs(sig));
figure;
hold on;
plot(z);
plot(vad,'r');
plot(vad2,'g');
hold off;
legend('ZCR','Voiced Region');
%legend('ZCR','Voiced Region');
xlabel('frame number');
ylabel('ZCR');
title('zero crossing contour');



end