cannam@154: /***********************************************************************
cannam@154: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
cannam@154: Redistribution and use in source and binary forms, with or without
cannam@154: modification, are permitted provided that the following conditions
cannam@154: are met:
cannam@154: - Redistributions of source code must retain the above copyright notice,
cannam@154: this list of conditions and the following disclaimer.
cannam@154: - Redistributions in binary form must reproduce the above copyright
cannam@154: notice, this list of conditions and the following disclaimer in the
cannam@154: documentation and/or other materials provided with the distribution.
cannam@154: - Neither the name of Internet Society, IETF or IETF Trust, nor the
cannam@154: names of specific contributors, may be used to endorse or promote
cannam@154: products derived from this software without specific prior written
cannam@154: permission.
cannam@154: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
cannam@154: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
cannam@154: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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cannam@154: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
cannam@154: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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cannam@154: ***********************************************************************/
cannam@154: 
cannam@154: #ifdef HAVE_CONFIG_H
cannam@154: #include "config.h"
cannam@154: #endif
cannam@154: 
cannam@154: #include "main.h"
cannam@154: 
cannam@154: /* Find least-squares prediction gain for one signal based on another and quantize it */
cannam@154: opus_int32 silk_stereo_find_predictor(                          /* O    Returns predictor in Q13                    */
cannam@154:     opus_int32                  *ratio_Q14,                     /* O    Ratio of residual and mid energies          */
cannam@154:     const opus_int16            x[],                            /* I    Basis signal                                */
cannam@154:     const opus_int16            y[],                            /* I    Target signal                               */
cannam@154:     opus_int32                  mid_res_amp_Q0[],               /* I/O  Smoothed mid, residual norms                */
cannam@154:     opus_int                    length,                         /* I    Number of samples                           */
cannam@154:     opus_int                    smooth_coef_Q16                 /* I    Smoothing coefficient                       */
cannam@154: )
cannam@154: {
cannam@154:     opus_int   scale, scale1, scale2;
cannam@154:     opus_int32 nrgx, nrgy, corr, pred_Q13, pred2_Q10;
cannam@154: 
cannam@154:     /* Find  predictor */
cannam@154:     silk_sum_sqr_shift( &nrgx, &scale1, x, length );
cannam@154:     silk_sum_sqr_shift( &nrgy, &scale2, y, length );
cannam@154:     scale = silk_max_int( scale1, scale2 );
cannam@154:     scale = scale + ( scale & 1 );          /* make even */
cannam@154:     nrgy = silk_RSHIFT32( nrgy, scale - scale2 );
cannam@154:     nrgx = silk_RSHIFT32( nrgx, scale - scale1 );
cannam@154:     nrgx = silk_max_int( nrgx, 1 );
cannam@154:     corr = silk_inner_prod_aligned_scale( x, y, scale, length );
cannam@154:     pred_Q13 = silk_DIV32_varQ( corr, nrgx, 13 );
cannam@154:     pred_Q13 = silk_LIMIT( pred_Q13, -(1 << 14), 1 << 14 );
cannam@154:     pred2_Q10 = silk_SMULWB( pred_Q13, pred_Q13 );
cannam@154: 
cannam@154:     /* Faster update for signals with large prediction parameters */
cannam@154:     smooth_coef_Q16 = (opus_int)silk_max_int( smooth_coef_Q16, silk_abs( pred2_Q10 ) );
cannam@154: 
cannam@154:     /* Smoothed mid and residual norms */
cannam@154:     silk_assert( smooth_coef_Q16 < 32768 );
cannam@154:     scale = silk_RSHIFT( scale, 1 );
cannam@154:     mid_res_amp_Q0[ 0 ] = silk_SMLAWB( mid_res_amp_Q0[ 0 ], silk_LSHIFT( silk_SQRT_APPROX( nrgx ), scale ) - mid_res_amp_Q0[ 0 ],
cannam@154:         smooth_coef_Q16 );
cannam@154:     /* Residual energy = nrgy - 2 * pred * corr + pred^2 * nrgx */
cannam@154:     nrgy = silk_SUB_LSHIFT32( nrgy, silk_SMULWB( corr, pred_Q13 ), 3 + 1 );
cannam@154:     nrgy = silk_ADD_LSHIFT32( nrgy, silk_SMULWB( nrgx, pred2_Q10 ), 6 );
cannam@154:     mid_res_amp_Q0[ 1 ] = silk_SMLAWB( mid_res_amp_Q0[ 1 ], silk_LSHIFT( silk_SQRT_APPROX( nrgy ), scale ) - mid_res_amp_Q0[ 1 ],
cannam@154:         smooth_coef_Q16 );
cannam@154: 
cannam@154:     /* Ratio of smoothed residual and mid norms */
cannam@154:     *ratio_Q14 = silk_DIV32_varQ( mid_res_amp_Q0[ 1 ], silk_max( mid_res_amp_Q0[ 0 ], 1 ), 14 );
cannam@154:     *ratio_Q14 = silk_LIMIT( *ratio_Q14, 0, 32767 );
cannam@154: 
cannam@154:     return pred_Q13;
cannam@154: }