Adding matlab files for arbitrary resampler

matlab/resampler/arb_resample_linear.m

@@ -0,0 +1,46 @@
+function out = arb_resample_linear(sig, rate)
+
+N = 32;
+M = 8;
+step = (1/rate)*N;
+
+load('arb_filter.mat');
+
+figure;plot(Num);title('Filter impulse response');
+[h,w] = freqz(Num, 1);
+figure;plot(20*log10(abs(h)));title('Filter freq response');
+
+% Create polyphase partition
+poly = reshape(Num, N, M);
+
+% Filter
+sig = [zeros(1,(M/2)-1) sig];
+k=0;
+acc=0;
+index=0;
+frac=0;
+out = [];
+while k < length(sig)-M
+    sig_reg = fliplr(sig(k+1:k+M));
+    filt_reg1 = poly(index+1, :);
+    filt_reg2 = poly(mod(index+1,N)+1, :);
+    res1 = sig_reg*filt_reg1';
+    res2 = sig_reg*filt_reg2';
+    
+    if index+1 == 32
+        res = res1;
+    else
+        res = res1 + (res2-res1)*frac;
+    end
+    
+    out = [out res];
+    
+    acc = acc+step;
+    index = fix(acc);
+    while index >= N
+        acc = acc - N;
+        index = index - N;
+        k = k+1;
+    end
+    frac = abs(acc-index);
+end

matlab/resampler/arb_resample_nearest.m

@@ -0,0 +1,37 @@
+function out = arb_resample_nearest(sig, rate)
+
+N = 32;
+M = 8;
+step = (1/rate)*N;
+
+load('arb_filter.mat');
+
+figure;plot(Num);title('Filter impulse response');
+[h,w] = freqz(Num, 1);
+figure;plot(20*log10(abs(h)));title('Filter frequency response');
+
+% Create polyphase partition
+poly = reshape(Num, N, M);
+
+% Filter
+sig = [zeros(1,(M/2)-1) sig];
+k=0;
+acc=0;
+index=0;
+frac=0;
+out = [];
+while k < length(sig)-M
+    sig_reg = fliplr(sig(k+1:k+M));
+    filt_reg1 = poly(index+1, :);
+    res = sig_reg*filt_reg1';
+    
+    out = [out res];
+    
+    acc = acc+step;
+    index = round(acc);
+    while index >= N
+        acc = acc - N;
+        index = index - N;
+        k = k+1;
+    end
+end

matlab/resampler/arb_resample_test.m

@@ -0,0 +1,33 @@
+close all 
+clear all
+
+up = 24;
+down = 25;
+d_rate = up/down;
+Fs = 100;          % Arbitrary sample rate (used for displays)
+Fsin = 1;
+
+% Create a sine wave
+t = 0:1/Fs:1-1/Fs;
+sig = sin(2*pi*t);
+
+out = arb_resample_nearest(sig,d_rate);
+
+% matlab resample for comparison
+out2 = resample(sig, up, down);
+figure;hold on;title('Ours and matlabs');
+l = min(length(out), length(out2));
+stem(out(1:l));
+stem(out2(1:l), 'r', 'filled');
+diff = out2(1:l)-out(1:l);
+figure;plot(diff);title('Difference between ours and matlabs');
+
+figure; hold on;title('Original and resampled - no time scaling');
+stem(sig);
+stem(out, 'r', 'filled');
+
+% Time align and plot
+figure;hold on;title('Original and resampled - with time scaling');
+stem((1:75)/Fs,real(sig(1:75)));  
+stem((1:72)/(Fs*d_rate),real(out(1:72)),'r','filled');
+xlabel('Time (sec)');ylabel('Signal value');