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
       5             : are met:
       6             : - Redistributions of source code must retain the above copyright notice,
       7             : this list of conditions and the following disclaimer.
       8             : - Redistributions in binary form must reproduce the above copyright
       9             : notice, this list of conditions and the following disclaimer in the
      10             : documentation and/or other materials provided with the distribution.
      11             : - Neither the name of Internet Society, IETF or IETF Trust, nor the
      12             : names of specific contributors, may be used to endorse or promote
      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
      17             : IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
      18             : ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
      19             : LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
      20             : CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
      21             : SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
      22             : INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
      23             : CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
      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             : /* Approximate sigmoid function */
      33             : 
      34             : #include "SigProc_FIX.h"
      35             : 
      36             : /* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
      37             : static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
      38             :     237, 153, 73, 30, 12, 7
      39             : };
      40             : /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
      41             : static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
      42             :     16384, 23955, 28861, 31213, 32178, 32548
      43             : };
      44             : /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
      45             : static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
      46             :     16384, 8812, 3906, 1554, 589, 219
      47             : };
      48             : 
      49           0 : opus_int silk_sigm_Q15(
      50             :     opus_int                    in_Q5               /* I                                                                */
      51             : )
      52             : {
      53             :     opus_int ind;
      54             : 
      55           0 :     if( in_Q5 < 0 ) {
      56             :         /* Negative input */
      57           0 :         in_Q5 = -in_Q5;
      58           0 :         if( in_Q5 >= 6 * 32 ) {
      59           0 :             return 0;        /* Clip */
      60             :         } else {
      61             :             /* Linear interpolation of look up table */
      62           0 :             ind = silk_RSHIFT( in_Q5, 5 );
      63           0 :             return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
      64             :         }
      65             :     } else {
      66             :         /* Positive input */
      67           0 :         if( in_Q5 >= 6 * 32 ) {
      68           0 :             return 32767;        /* clip */
      69             :         } else {
      70             :             /* Linear interpolation of look up table */
      71           0 :             ind = silk_RSHIFT( in_Q5, 5 );
      72           0 :             return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
      73             :         }
      74             :     }
      75             : }
      76             :