cannam@154: /***********************************************************************
cannam@154: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
cannam@154: Redistribution and use in source and binary forms, with or without
cannam@154: modification, are permitted provided that the following conditions
cannam@154: are met:
cannam@154: - Redistributions of source code must retain the above copyright notice,
cannam@154: this list of conditions and the following disclaimer.
cannam@154: - Redistributions in binary form must reproduce the above copyright
cannam@154: notice, this list of conditions and the following disclaimer in the
cannam@154: documentation and/or other materials provided with the distribution.
cannam@154: - Neither the name of Internet Society, IETF or IETF Trust, nor the
cannam@154: names of specific contributors, may be used to endorse or promote
cannam@154: products derived from this software without specific prior written
cannam@154: permission.
cannam@154: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
cannam@154: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
cannam@154: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
cannam@154: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
cannam@154: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
cannam@154: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
cannam@154: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
cannam@154: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
cannam@154: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
cannam@154: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
cannam@154: POSSIBILITY OF SUCH DAMAGE.
cannam@154: ***********************************************************************/
cannam@154: 
cannam@154: #ifdef HAVE_CONFIG_H
cannam@154: #include "config.h"
cannam@154: #endif
cannam@154: 
cannam@154: /* Approximate sigmoid function */
cannam@154: 
cannam@154: #include "SigProc_FIX.h"
cannam@154: 
cannam@154: /* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
cannam@154: static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
cannam@154:     237, 153, 73, 30, 12, 7
cannam@154: };
cannam@154: /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
cannam@154: static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
cannam@154:     16384, 23955, 28861, 31213, 32178, 32548
cannam@154: };
cannam@154: /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
cannam@154: static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
cannam@154:     16384, 8812, 3906, 1554, 589, 219
cannam@154: };
cannam@154: 
cannam@154: opus_int silk_sigm_Q15(
cannam@154:     opus_int                    in_Q5               /* I                                                                */
cannam@154: )
cannam@154: {
cannam@154:     opus_int ind;
cannam@154: 
cannam@154:     if( in_Q5 < 0 ) {
cannam@154:         /* Negative input */
cannam@154:         in_Q5 = -in_Q5;
cannam@154:         if( in_Q5 >= 6 * 32 ) {
cannam@154:             return 0;        /* Clip */
cannam@154:         } else {
cannam@154:             /* Linear interpolation of look up table */
cannam@154:             ind = silk_RSHIFT( in_Q5, 5 );
cannam@154:             return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
cannam@154:         }
cannam@154:     } else {
cannam@154:         /* Positive input */
cannam@154:         if( in_Q5 >= 6 * 32 ) {
cannam@154:             return 32767;        /* clip */
cannam@154:         } else {
cannam@154:             /* Linear interpolation of look up table */
cannam@154:             ind = silk_RSHIFT( in_Q5, 5 );
cannam@154:             return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
cannam@154:         }
cannam@154:     }
cannam@154: }
cannam@154: