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% 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
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