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Gregory Maxwellae231142011-07-30 08:18:48 -04001/***********************************************************************
2Copyright (c) 2006-2011, Skype Limited. All rights reserved.
3Redistribution and use in source and binary forms, with or without
Jean-Marc Valinae00e602012-04-20 16:31:04 -04004modification, are permitted provided that the following conditions
5are met:
Gregory Maxwellae231142011-07-30 08:18:48 -04006- Redistributions of source code must retain the above copyright notice,
7this list of conditions and the following disclaimer.
8- Redistributions in binary form must reproduce the above copyright
9notice, this list of conditions and the following disclaimer in the
10documentation and/or other materials provided with the distribution.
Ralph Gilesf2446c22013-09-16 14:40:04 -070011- Neither the name of Internet Society, IETF or IETF Trust, nor the
Jean-Marc Valinae00e602012-04-20 16:31:04 -040012names of specific contributors, may be used to endorse or promote
13products derived from this software without specific prior written
14permission.
Timothy B. Terriberry80ad3832013-05-19 18:00:39 -070015THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
Jean-Marc Valinae00e602012-04-20 16:31:04 -040016AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
19LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
21SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
24ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25POSSIBILITY OF SUCH DAMAGE.
Gregory Maxwellae231142011-07-30 08:18:48 -040026***********************************************************************/
27
Jean-Marc Valin5a484122011-08-15 10:49:53 -040028#ifdef HAVE_CONFIG_H
29#include "config.h"
30#endif
31
Gregory Maxwellae231142011-07-30 08:18:48 -040032/* Approximate sigmoid function */
33
Jean-Marc Valin1c2f5632011-09-16 01:16:53 -070034#include "SigProc_FIX.h"
Gregory Maxwellae231142011-07-30 08:18:48 -040035
36/* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
37static 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))))); */
41static 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))))); */
45static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
46 16384, 8812, 3906, 1554, 589, 219
47};
48
Ralph Giles5f6e4722012-03-19 17:10:13 -070049opus_int silk_sigm_Q15(
Koen Vosacc7a6c2011-10-28 19:44:26 -040050 opus_int in_Q5 /* I */
51)
Gregory Maxwellae231142011-07-30 08:18:48 -040052{
53 opus_int ind;
54
55 if( in_Q5 < 0 ) {
56 /* Negative input */
57 in_Q5 = -in_Q5;
58 if( in_Q5 >= 6 * 32 ) {
59 return 0; /* Clip */
60 } else {
61 /* Linear interpolation of look up table */
Jean-Marc Valinfb3a4372011-09-16 00:58:26 -070062 ind = silk_RSHIFT( in_Q5, 5 );
63 return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
Gregory Maxwellae231142011-07-30 08:18:48 -040064 }
65 } else {
66 /* Positive input */
67 if( in_Q5 >= 6 * 32 ) {
68 return 32767; /* clip */
69 } else {
70 /* Linear interpolation of look up table */
Jean-Marc Valinfb3a4372011-09-16 00:58:26 -070071 ind = silk_RSHIFT( in_Q5, 5 );
72 return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
Gregory Maxwellae231142011-07-30 08:18:48 -040073 }
74 }
75}
76