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Weighting theta rdo based on channel energy

--- a/celt/bands.c

+++ b/celt/bands.c

@@ -360,6 +360,30 @@

    }

 }

+/* Compute the weights to use for optimizing normalized distortion across

+   channels. We use the amplitude to weight square distortion, which means

+   that we use the square root of the value we would have been using if we

+   wanted to minimize the MSE in the non-normalized domain. This roughly

+   corresponds to some quick-and-dirty perceptual experiments I ran to

+   measure inter-aural masking (there doesn't seem to be any published data

+   on the topic). */

+static void compute_channel_weights(celt_ener Ex, celt_ener Ey, opus_val16 w[2])

+{

+   celt_ener minE;

+   minE = MIN32(Ex, Ey);

+#if FIXED_POINT

+   int shift;

+#endif

+   /* Adjustment to make the weights a bit more conservative. */

+   Ex = ADD32(Ex, minE/3);

+   Ey = ADD32(Ey, minE/3);

+#if FIXED_POINT

+   shift = celt_ilog2(EPSILON+MAX32(Ex, Ey))-14;

+#endif

+   w[0] = VSHR32(Ex, shift);

+   w[1] = VSHR32(Ey, shift);

+}

+

 static void intensity_stereo(const CELTMode *m, celt_norm * OPUS_RESTRICT X, const celt_norm * OPUS_RESTRICT Y, const celt_ener *bandE, int bandID, int N)

 {

    int i = bandID;

@@ -1510,6 +1534,8 @@

                int nstart_bytes, nend_bytes, save_bytes;

                unsigned char *bytes_buf;

                unsigned char bytes_save[1275];

+               opus_val16 w[2];

+               compute_channel_weights(bandE[i], bandE[i+m->nbEBands], w);

                /* Make a copy. */

                cm = x_cm|y_cm;

                ec_save = *ec;

@@ -1521,7 +1547,7 @@

                x_cm = quant_band_stereo(&ctx, X, Y, N, b, B,

                      effective_lowband != -1 ? norm+effective_lowband : NULL, LM,

                      last?NULL:norm+M*eBands[i]-norm_offset, lowband_scratch, cm);

-               dist0 = celt_inner_prod(X_save, X, N, arch) + celt_inner_prod(Y_save, Y, N, arch);

+               dist0 = MULT16_32_Q15(w[0], celt_inner_prod(X_save, X, N, arch)) + MULT16_32_Q15(w[1], celt_inner_prod(Y_save, Y, N, arch));

                /* Save first result. */

                cm2 = x_cm;

@@ -1547,7 +1573,7 @@

                x_cm = quant_band_stereo(&ctx, X, Y, N, b, B,

                      effective_lowband != -1 ? norm+effective_lowband : NULL, LM,

                      last?NULL:norm+M*eBands[i]-norm_offset, lowband_scratch, cm);

-               dist1 = celt_inner_prod(X_save, X, N, arch) + celt_inner_prod(Y_save, Y, N, arch);

+               dist1 = MULT16_32_Q15(w[0], celt_inner_prod(X_save, X, N, arch)) + MULT16_32_Q15(w[1], celt_inner_prod(Y_save, Y, N, arch));

                if (dist0 >= dist1) {

                   x_cm = cm2;

                   *ec = ec_save2;