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
Chris@69: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
Chris@69: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
Chris@69: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
Chris@69: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
Chris@69: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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: /* Approximate sigmoid function */
Chris@69: 
Chris@69: #include "SigProc_FIX.h"
Chris@69: 
Chris@69: /* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
Chris@69: static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
Chris@69:     237, 153, 73, 30, 12, 7
Chris@69: };
Chris@69: /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
Chris@69: static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
Chris@69:     16384, 23955, 28861, 31213, 32178, 32548
Chris@69: };
Chris@69: /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
Chris@69: static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
Chris@69:     16384, 8812, 3906, 1554, 589, 219
Chris@69: };
Chris@69: 
Chris@69: opus_int silk_sigm_Q15(
Chris@69:     opus_int                    in_Q5               /* I                                                                */
Chris@69: )
Chris@69: {
Chris@69:     opus_int ind;
Chris@69: 
Chris@69:     if( in_Q5 < 0 ) {
Chris@69:         /* Negative input */
Chris@69:         in_Q5 = -in_Q5;
Chris@69:         if( in_Q5 >= 6 * 32 ) {
Chris@69:             return 0;        /* Clip */
Chris@69:         } else {
Chris@69:             /* Linear interpolation of look up table */
Chris@69:             ind = silk_RSHIFT( in_Q5, 5 );
Chris@69:             return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
Chris@69:         }
Chris@69:     } else {
Chris@69:         /* Positive input */
Chris@69:         if( in_Q5 >= 6 * 32 ) {
Chris@69:             return 32767;        /* clip */
Chris@69:         } else {
Chris@69:             /* Linear interpolation of look up table */
Chris@69:             ind = silk_RSHIFT( in_Q5, 5 );
Chris@69:             return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
Chris@69:         }
Chris@69:     }
Chris@69: }
Chris@69: