michael@0: /***********************************************************************
michael@0: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
michael@0: Redistribution and use in source and binary forms, with or without
michael@0: modification, are permitted provided that the following conditions
michael@0: are met:
michael@0: - Redistributions of source code must retain the above copyright notice,
michael@0: this list of conditions and the following disclaimer.
michael@0: - Redistributions in binary form must reproduce the above copyright
michael@0: notice, this list of conditions and the following disclaimer in the
michael@0: documentation and/or other materials provided with the distribution.
michael@0: - Neither the name of Internet Society, IETF or IETF Trust, nor the
michael@0: names of specific contributors, may be used to endorse or promote
michael@0: products derived from this software without specific prior written
michael@0: permission.
michael@0: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
michael@0: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
michael@0: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
michael@0: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
michael@0: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
michael@0: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
michael@0: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
michael@0: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
michael@0: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
michael@0: POSSIBILITY OF SUCH DAMAGE.
michael@0: ***********************************************************************/
michael@0: 
michael@0: #ifdef HAVE_CONFIG_H
michael@0: #include "config.h"
michael@0: #endif
michael@0: 
michael@0: /* Approximate sigmoid function */
michael@0: 
michael@0: #include "SigProc_FIX.h"
michael@0: 
michael@0: /* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
michael@0: static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
michael@0:     237, 153, 73, 30, 12, 7
michael@0: };
michael@0: /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
michael@0: static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
michael@0:     16384, 23955, 28861, 31213, 32178, 32548
michael@0: };
michael@0: /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
michael@0: static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
michael@0:     16384, 8812, 3906, 1554, 589, 219
michael@0: };
michael@0: 
michael@0: opus_int silk_sigm_Q15(
michael@0:     opus_int                    in_Q5               /* I                                                                */
michael@0: )
michael@0: {
michael@0:     opus_int ind;
michael@0: 
michael@0:     if( in_Q5 < 0 ) {
michael@0:         /* Negative input */
michael@0:         in_Q5 = -in_Q5;
michael@0:         if( in_Q5 >= 6 * 32 ) {
michael@0:             return 0;        /* Clip */
michael@0:         } else {
michael@0:             /* Linear interpolation of look up table */
michael@0:             ind = silk_RSHIFT( in_Q5, 5 );
michael@0:             return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
michael@0:         }
michael@0:     } else {
michael@0:         /* Positive input */
michael@0:         if( in_Q5 >= 6 * 32 ) {
michael@0:             return 32767;        /* clip */
michael@0:         } else {
michael@0:             /* Linear interpolation of look up table */
michael@0:             ind = silk_RSHIFT( in_Q5, 5 );
michael@0:             return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
michael@0:         }
michael@0:     }
michael@0: }
michael@0: