Chris@69: /***********************************************************************
Chris@69: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
Chris@69: Redistribution and use in source and binary forms, with or without
Chris@69: modification, are permitted provided that the following conditions
Chris@69: are met:
Chris@69: - Redistributions of source code must retain the above copyright notice,
Chris@69: this list of conditions and the following disclaimer.
Chris@69: - Redistributions in binary form must reproduce the above copyright
Chris@69: notice, this list of conditions and the following disclaimer in the
Chris@69: documentation and/or other materials provided with the distribution.
Chris@69: - Neither the name of Internet Society, IETF or IETF Trust, nor the
Chris@69: names of specific contributors, may be used to endorse or promote
Chris@69: products derived from this software without specific prior written
Chris@69: permission.
Chris@69: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
Chris@69: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
Chris@69: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
Chris@69: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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Chris@69: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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Chris@69: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
Chris@69: POSSIBILITY OF SUCH DAMAGE.
Chris@69: ***********************************************************************/
Chris@69: 
Chris@69: #ifdef HAVE_CONFIG_H
Chris@69: #include "config.h"
Chris@69: #endif
Chris@69: 
Chris@69: #include "main.h"
Chris@69: 
Chris@69: /* Find least-squares prediction gain for one signal based on another and quantize it */
Chris@69: opus_int32 silk_stereo_find_predictor(                          /* O    Returns predictor in Q13                    */
Chris@69:     opus_int32                  *ratio_Q14,                     /* O    Ratio of residual and mid energies          */
Chris@69:     const opus_int16            x[],                            /* I    Basis signal                                */
Chris@69:     const opus_int16            y[],                            /* I    Target signal                               */
Chris@69:     opus_int32                  mid_res_amp_Q0[],               /* I/O  Smoothed mid, residual norms                */
Chris@69:     opus_int                    length,                         /* I    Number of samples                           */
Chris@69:     opus_int                    smooth_coef_Q16                 /* I    Smoothing coefficient                       */
Chris@69: )
Chris@69: {
Chris@69:     opus_int   scale, scale1, scale2;
Chris@69:     opus_int32 nrgx, nrgy, corr, pred_Q13, pred2_Q10;
Chris@69: 
Chris@69:     /* Find  predictor */
Chris@69:     silk_sum_sqr_shift( &nrgx, &scale1, x, length );
Chris@69:     silk_sum_sqr_shift( &nrgy, &scale2, y, length );
Chris@69:     scale = silk_max_int( scale1, scale2 );
Chris@69:     scale = scale + ( scale & 1 );          /* make even */
Chris@69:     nrgy = silk_RSHIFT32( nrgy, scale - scale2 );
Chris@69:     nrgx = silk_RSHIFT32( nrgx, scale - scale1 );
Chris@69:     nrgx = silk_max_int( nrgx, 1 );
Chris@69:     corr = silk_inner_prod_aligned_scale( x, y, scale, length );
Chris@69:     pred_Q13 = silk_DIV32_varQ( corr, nrgx, 13 );
Chris@69:     pred_Q13 = silk_LIMIT( pred_Q13, -(1 << 14), 1 << 14 );
Chris@69:     pred2_Q10 = silk_SMULWB( pred_Q13, pred_Q13 );
Chris@69: 
Chris@69:     /* Faster update for signals with large prediction parameters */
Chris@69:     smooth_coef_Q16 = (opus_int)silk_max_int( smooth_coef_Q16, silk_abs( pred2_Q10 ) );
Chris@69: 
Chris@69:     /* Smoothed mid and residual norms */
Chris@69:     silk_assert( smooth_coef_Q16 < 32768 );
Chris@69:     scale = silk_RSHIFT( scale, 1 );
Chris@69:     mid_res_amp_Q0[ 0 ] = silk_SMLAWB( mid_res_amp_Q0[ 0 ], silk_LSHIFT( silk_SQRT_APPROX( nrgx ), scale ) - mid_res_amp_Q0[ 0 ],
Chris@69:         smooth_coef_Q16 );
Chris@69:     /* Residual energy = nrgy - 2 * pred * corr + pred^2 * nrgx */
Chris@69:     nrgy = silk_SUB_LSHIFT32( nrgy, silk_SMULWB( corr, pred_Q13 ), 3 + 1 );
Chris@69:     nrgy = silk_ADD_LSHIFT32( nrgy, silk_SMULWB( nrgx, pred2_Q10 ), 6 );
Chris@69:     mid_res_amp_Q0[ 1 ] = silk_SMLAWB( mid_res_amp_Q0[ 1 ], silk_LSHIFT( silk_SQRT_APPROX( nrgy ), scale ) - mid_res_amp_Q0[ 1 ],
Chris@69:         smooth_coef_Q16 );
Chris@69: 
Chris@69:     /* Ratio of smoothed residual and mid norms */
Chris@69:     *ratio_Q14 = silk_DIV32_varQ( mid_res_amp_Q0[ 1 ], silk_max( mid_res_amp_Q0[ 0 ], 1 ), 14 );
Chris@69:     *ratio_Q14 = silk_LIMIT( *ratio_Q14, 0, 32767 );
Chris@69: 
Chris@69:     return pred_Q13;
Chris@69: }