1 files changed, 79 insertions, 0 deletions
diff --git a/doc/opus_compare.m b/doc/opus_compare.m
new file mode 100644
index 00000000..72739aaf
--- /dev/null
+++ b/doc/opus_compare.m
@@ -0,0 +1,79 @@
+%% Tests bit-stream compliance for the Opus codec
+%% x: Signal from the Opus reference implementation (float or fixed)
+%% y: Signal from the decoder under test
+%% stereo: 0 for mono, 1 for stereo
+function [err, NMR] = opus_compare(x, y, stereo)
+
+% Bands on which we compute the pseudo-NMR (Bark-derived CELT bands)
+b = 2*[0,1,2,3,4,5,6,7,8,10,12,14,16,20,24,28,34,40,48,60,78,100];
+d = diff(b);
+
+% Per-band SNR threshold
+T = 50-.7*[1:21];
+
+% Noise floor
+N = 10 .^ ((10-0.6*[1:21])/10);
+
+% Error signal
+e=x-y;
+
+%Add a +/- 1 dead zone on the error
+e = e - min(1, max(-1, e));
+
+% Compute spectrum of original and error
+if (stereo)
+  X=(abs(specgram(x(1:2:end),480))+abs(specgram(x(2:2:end),480)))/2;
+  E=(abs(specgram(e(1:2:end),480))+abs(specgram(e(2:2:end),480)))/2;
+else
+  X=abs(specgram(x,480));
+  E=abs(specgram(e,480));
+endif
+
+% Group energy per band
+for k=1:21
+   Xb(k,:) = sum(X(b(k)+1:b(k+1),:).^2)/d(k)+1;
+   Eb(k,:) = sum(E(b(k)+1:b(k+1),:).^2)/d(k)+1;
+end
+
+% Frequency masking (low to high) with 10 dB/Bark slope
+Xb = filter(1, [1, -.1], Xb);
+% Frequency masking (high to low) with 15 dB/Bark slope
+Xb(end:-1:1,:) = filter(1, [1, -.03], Xb(end:-1:1,:));
+
+% Temporal masking with 5 dB/5 ms slope
+Xb = filter(1, [1, -.3], Xb')';
+
+% NMR threshold
+T0 = ones(length(Eb), 1)*(10.^((T)/10));
+
+% Time-frequency SNR
+NMR = (Xb./Eb)';
+
+%Picking only errors in the 90th percentile
+tmp = Eb(:);
+thresh = sort(tmp)(round(.90*length(tmp)));
+weight = Eb'>thresh;
+
+printf("Average pseudo-NMR: %3.2f dB\n", mean(mean(10*log10(NMR))));
+
+if (sum(sum(weight))<1)
+   printf("Mismatch level: below noise floor\n");
+   err = -100;
+else
+   M = (T0./NMR) .* weight;
+
+   err = 10*log10(sum(sum(M)) / sum(sum(weight)));
+
+   printf("Weighted mismatch: %3.2f dB\n", err);
+endif
+
+printf("\n");
+
+if (err < 0)
+   printf("**Decoder PASSES test (mismatch < 0 dB)\n");
+else
+   printf("**Decoder FAILS test (mismatch >= 0 dB)\n");
+endif
+
+
+