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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
silk_sigm_Q15(opus_int in_Q5)49 opus_int silk_sigm_Q15(
50 opus_int in_Q5 /* I */
51 )
52 {
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 */
62 ind = silk_RSHIFT( in_Q5, 5 );
63 return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
64 }
65 } else {
66 /* Positive input */
67 if( in_Q5 >= 6 * 32 ) {
68 return 32767; /* clip */
69 } else {
70 /* Linear interpolation of look up table */
71 ind = silk_RSHIFT( in_Q5, 5 );
72 return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
73 }
74 }
75 }
76
77