1*a58d3d2aSXin Li /***********************************************************************
2*a58d3d2aSXin Li Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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7*a58d3d2aSXin Li this list of conditions and the following disclaimer.
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26*a58d3d2aSXin Li ***********************************************************************/
27*a58d3d2aSXin Li
28*a58d3d2aSXin Li #ifdef HAVE_CONFIG_H
29*a58d3d2aSXin Li #include "config.h"
30*a58d3d2aSXin Li #endif
31*a58d3d2aSXin Li
32*a58d3d2aSXin Li #include "main.h"
33*a58d3d2aSXin Li
34*a58d3d2aSXin Li /* Find least-squares prediction gain for one signal based on another and quantize it */
silk_stereo_find_predictor(opus_int32 * ratio_Q14,const opus_int16 x[],const opus_int16 y[],opus_int32 mid_res_amp_Q0[],opus_int length,opus_int smooth_coef_Q16)35*a58d3d2aSXin Li opus_int32 silk_stereo_find_predictor( /* O Returns predictor in Q13 */
36*a58d3d2aSXin Li opus_int32 *ratio_Q14, /* O Ratio of residual and mid energies */
37*a58d3d2aSXin Li const opus_int16 x[], /* I Basis signal */
38*a58d3d2aSXin Li const opus_int16 y[], /* I Target signal */
39*a58d3d2aSXin Li opus_int32 mid_res_amp_Q0[], /* I/O Smoothed mid, residual norms */
40*a58d3d2aSXin Li opus_int length, /* I Number of samples */
41*a58d3d2aSXin Li opus_int smooth_coef_Q16 /* I Smoothing coefficient */
42*a58d3d2aSXin Li )
43*a58d3d2aSXin Li {
44*a58d3d2aSXin Li opus_int scale, scale1, scale2;
45*a58d3d2aSXin Li opus_int32 nrgx, nrgy, corr, pred_Q13, pred2_Q10;
46*a58d3d2aSXin Li
47*a58d3d2aSXin Li /* Find predictor */
48*a58d3d2aSXin Li silk_sum_sqr_shift( &nrgx, &scale1, x, length );
49*a58d3d2aSXin Li silk_sum_sqr_shift( &nrgy, &scale2, y, length );
50*a58d3d2aSXin Li scale = silk_max_int( scale1, scale2 );
51*a58d3d2aSXin Li scale = scale + ( scale & 1 ); /* make even */
52*a58d3d2aSXin Li nrgy = silk_RSHIFT32( nrgy, scale - scale2 );
53*a58d3d2aSXin Li nrgx = silk_RSHIFT32( nrgx, scale - scale1 );
54*a58d3d2aSXin Li nrgx = silk_max_int( nrgx, 1 );
55*a58d3d2aSXin Li corr = silk_inner_prod_aligned_scale( x, y, scale, length );
56*a58d3d2aSXin Li pred_Q13 = silk_DIV32_varQ( corr, nrgx, 13 );
57*a58d3d2aSXin Li pred_Q13 = silk_LIMIT( pred_Q13, -(1 << 14), 1 << 14 );
58*a58d3d2aSXin Li pred2_Q10 = silk_SMULWB( pred_Q13, pred_Q13 );
59*a58d3d2aSXin Li
60*a58d3d2aSXin Li /* Faster update for signals with large prediction parameters */
61*a58d3d2aSXin Li smooth_coef_Q16 = (opus_int)silk_max_int( smooth_coef_Q16, silk_abs( pred2_Q10 ) );
62*a58d3d2aSXin Li
63*a58d3d2aSXin Li /* Smoothed mid and residual norms */
64*a58d3d2aSXin Li silk_assert( smooth_coef_Q16 < 32768 );
65*a58d3d2aSXin Li scale = silk_RSHIFT( scale, 1 );
66*a58d3d2aSXin Li mid_res_amp_Q0[ 0 ] = silk_SMLAWB( mid_res_amp_Q0[ 0 ], silk_LSHIFT( silk_SQRT_APPROX( nrgx ), scale ) - mid_res_amp_Q0[ 0 ],
67*a58d3d2aSXin Li smooth_coef_Q16 );
68*a58d3d2aSXin Li /* Residual energy = nrgy - 2 * pred * corr + pred^2 * nrgx */
69*a58d3d2aSXin Li nrgy = silk_SUB_LSHIFT32( nrgy, silk_SMULWB( corr, pred_Q13 ), 3 + 1 );
70*a58d3d2aSXin Li nrgy = silk_ADD_LSHIFT32( nrgy, silk_SMULWB( nrgx, pred2_Q10 ), 6 );
71*a58d3d2aSXin Li mid_res_amp_Q0[ 1 ] = silk_SMLAWB( mid_res_amp_Q0[ 1 ], silk_LSHIFT( silk_SQRT_APPROX( nrgy ), scale ) - mid_res_amp_Q0[ 1 ],
72*a58d3d2aSXin Li smooth_coef_Q16 );
73*a58d3d2aSXin Li
74*a58d3d2aSXin Li /* Ratio of smoothed residual and mid norms */
75*a58d3d2aSXin Li *ratio_Q14 = silk_DIV32_varQ( mid_res_amp_Q0[ 1 ], silk_max( mid_res_amp_Q0[ 0 ], 1 ), 14 );
76*a58d3d2aSXin Li *ratio_Q14 = silk_LIMIT( *ratio_Q14, 0, 32767 );
77*a58d3d2aSXin Li
78*a58d3d2aSXin Li return pred_Q13;
79*a58d3d2aSXin Li }
80