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Author: gaoyongyu

README.md

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+
+Computation of two signal convolution and correlation
+==============================
+This repo is self-coded for two signal convolution and correlation.
+
+My objective to do that is to review the basic implementation of how signal works..
+
+How to use
+==========
+Check __main.m__ 

cross_correlation.m

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+clear all;clc;close all;
+farend_speech_path = '/home/yongyug/data/aec_challenge/datasets/synthetic/farend_speech/farend_speech_fileid_8109.wav';
+nearend_mic_path = '/home/yongyug/data/aec_challenge/datasets/synthetic/nearend_mic_signal/nearend_mic_fileid_8109.wav';
+
+[farend_speech_data, fs] = audioread(farend_speech_path);
+[nearend_mic_data, fs] = audioread(nearend_mic_path);
+
+e_idx = min(size(farend_speech_data, 1), size(nearend_mic_data, 1));
+[cofs, lags] = xcorr(farend_speech_data, nearend_mic_data, 'coeff');
+[val, idx] = max(cofs);
+offset = lags(idx);
+minlength = length(farend_speech_data) - abs(offset);
+disp(offset);
+plot(lags,cofs);
+xlabel('shift');ylabel('relative cof');
+
+if offset>0
+    farend_speech_data = [farend_speech_data(offset:160000); zeros(offset, 1)];
+    nearend_mic_data = nearend_mic_data(1:160000);
+else
+    nearend_mic_data = [nearend_mic_data(-offset:160000) ;zeros(-offset, 1)];
+    farend_speech_data = farend_speech_data(1:160000);
+end
+
+audiowrite('/home/yongyug/data/8109_far.wav', farend_speech_data, 16000);
+audiowrite('/home/yongyug/data/8109_mic.wav', nearend_mic_data, 16000);

learn_cross_cor.m

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+clear all;clc;close all;
+dt = .1;
+t = [0:dt:100];
+x = cos(t);
+plot(x);

main.m

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+clear all;clc;close all;
+
+%%%% you can set arry a and arry b in different value, try some trails
+a = [1 2 1 2 1 ];  
+b = [2 2 3 3 3];
+
+%compute convolution
+res = my_conv(a,b);
+c = conv(a, b);
+d = xcorr(a, b);
+e = my_conv_usingfft(a, b);
+
+
+b = flip(b);
+%compute corss correlation
+f = my_conv_usingfft(a,b);
+g = my_conv(a, b);
+
+%%%
+%%% Check the results of my function with official function
+%%% Check if c = e = res for convolution computation
+%%% Check if d = f = g
+%%%
+
+
+
+

my_conv.m

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+function [ convRes ] = my_conv(aSignal, bSignal)
+aLen= length(aSignal);
+bLen = length(bSignal);
+N = aLen + bLen - 1;           %lenth of convolution results must be aLen + bLen -1
+
+bSignal = [bSignal  zeros(1, aLen - 1)]; 
+bSignal = flip(bSignal);%flip the signal
+
+aBuffer = [aSignal zeros(1, aLen - 1)];
+bBuffer = zeros(1, length(aBuffer));
+convRes = zeros(1, N);
+
+for i = 1: N
+    
+    bBuffer(:, 2:length(bBuffer)) = bBuffer(:, 1:length(bBuffer)-1);  %shift to the right
+    bBuffer(:, 1) = bSignal(:, N-i+1);             %move bsignal from left to right
+    convRes(:, i) = aBuffer(:,:) * bBuffer(:, :)'; %compute convolution
+
+end
+
+end
+

my_conv_usingfft.m

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+function [ c ] = my_conv_usingfft( a ,b )
+alen = length(a);
+blen = length(b);
+
+a = [a zeros(1, blen-1)];
+b = [b zeros(1, alen-1)];
+
+A = fft(a);
+B = fft(b);
+c = real(ifft(A.*B));
+
+
+end
+