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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