Line data    Source code

       1             : /***********************************************************************
       2             : Copyright (c) 2006-2011, Skype Limited. All rights reserved.
       3             : Redistribution and use in source and binary forms, with or without
       4             : modification, are permitted provided that the following conditions
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       9             : notice, this list of conditions and the following disclaimer in the
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      13             : products derived from this software without specific prior written
      14             : permission.
      15             : THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
      16             : AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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      22             : INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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      24             : ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
      25             : POSSIBILITY OF SUCH DAMAGE.
      26             : ***********************************************************************/
      27             : 
      28             : #ifdef HAVE_CONFIG_H
      29             : #include "config.h"
      30             : #endif
      31             : 
      32             : #include "main.h"
      33             : 
      34             : /* Find least-squares prediction gain for one signal based on another and quantize it */
      35           0 : opus_int32 silk_stereo_find_predictor(                          /* O    Returns predictor in Q13                    */
      36             :     opus_int32                  *ratio_Q14,                     /* O    Ratio of residual and mid energies          */
      37             :     const opus_int16            x[],                            /* I    Basis signal                                */
      38             :     const opus_int16            y[],                            /* I    Target signal                               */
      39             :     opus_int32                  mid_res_amp_Q0[],               /* I/O  Smoothed mid, residual norms                */
      40             :     opus_int                    length,                         /* I    Number of samples                           */
      41             :     opus_int                    smooth_coef_Q16                 /* I    Smoothing coefficient                       */
      42             : )
      43             : {
      44             :     opus_int   scale, scale1, scale2;
      45             :     opus_int32 nrgx, nrgy, corr, pred_Q13, pred2_Q10;
      46             : 
      47             :     /* Find  predictor */
      48           0 :     silk_sum_sqr_shift( &nrgx, &scale1, x, length );
      49           0 :     silk_sum_sqr_shift( &nrgy, &scale2, y, length );
      50           0 :     scale = silk_max_int( scale1, scale2 );
      51           0 :     scale = scale + ( scale & 1 );          /* make even */
      52           0 :     nrgy = silk_RSHIFT32( nrgy, scale - scale2 );
      53           0 :     nrgx = silk_RSHIFT32( nrgx, scale - scale1 );
      54           0 :     nrgx = silk_max_int( nrgx, 1 );
      55           0 :     corr = silk_inner_prod_aligned_scale( x, y, scale, length );
      56           0 :     pred_Q13 = silk_DIV32_varQ( corr, nrgx, 13 );
      57           0 :     pred_Q13 = silk_LIMIT( pred_Q13, -(1 << 14), 1 << 14 );
      58           0 :     pred2_Q10 = silk_SMULWB( pred_Q13, pred_Q13 );
      59             : 
      60             :     /* Faster update for signals with large prediction parameters */
      61           0 :     smooth_coef_Q16 = (opus_int)silk_max_int( smooth_coef_Q16, silk_abs( pred2_Q10 ) );
      62             : 
      63             :     /* Smoothed mid and residual norms */
      64           0 :     silk_assert( smooth_coef_Q16 < 32768 );
      65           0 :     scale = silk_RSHIFT( scale, 1 );
      66           0 :     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             :         smooth_coef_Q16 );
      68             :     /* Residual energy = nrgy - 2 * pred * corr + pred^2 * nrgx */
      69           0 :     nrgy = silk_SUB_LSHIFT32( nrgy, silk_SMULWB( corr, pred_Q13 ), 3 + 1 );
      70           0 :     nrgy = silk_ADD_LSHIFT32( nrgy, silk_SMULWB( nrgx, pred2_Q10 ), 6 );
      71           0 :     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             :         smooth_coef_Q16 );
      73             : 
      74             :     /* Ratio of smoothed residual and mid norms */
      75           0 :     *ratio_Q14 = silk_DIV32_varQ( mid_res_amp_Q0[ 1 ], silk_max( mid_res_amp_Q0[ 0 ], 1 ), 14 );
      76           0 :     *ratio_Q14 = silk_LIMIT( *ratio_Q14, 0, 32767 );
      77             : 
      78           0 :     return pred_Q13;
      79             : }