1 files changed, 27 insertions, 0 deletions
diff --git a/octave/diff_fft_mag.m b/octave/diff_fft_mag.m
new file mode 100644
index 0000000..005be70
--- /dev/null
+++ b/octave/diff_fft_mag.m
@@ -0,0 +1,27 @@
+% Compare the magnitude spectrum of two int16 raw files
+function diff_fft_mag(filename1, filename2, threshdB = -40, ignore=1000)
+  % load samples and ignore any start up transients
+  s1 = load_raw(filename1)'; 
+  s1 = s1(ignore:end);
+  s2 = load_raw(filename2)'; 
+  s2 = s2(ignore:end);
+
+  len = min([length(s1) length(s2)]);
+  s1 = s1(1:len); s2 = s2(1:len);
+  
+  S1 = abs(fft(s1.*hanning(length(s1))'));
+  S2 = abs(fft(s2.*hanning(length(s2))'));
+  
+  figure(1): clf;
+  plot(20*log10(S1)); hold on; plot(20*log10(S2)); plot(20*log10(abs(S1-S2)),'r'); hold off;
+  error = S1 - S2;
+  error_energy = error*error';
+  ratio = error_energy/(S1*S1');
+  ratio_dB = 10*log10(ratio);
+  printf("ratio_dB: %4.2f\n", ratio_dB);
+  if ratio_dB < threshdB
+    printf('PASS\n');
+  else
+    printf('FAIL\n');
+  end
+endfunction