ref: 1aa851445b984a78941a4bad786a7af6b3fdfe73
dir: /silk/sigm_Q15.c/
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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
/* Approximate sigmoid function */
#include "SigProc_FIX.h"
/* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
237, 153, 73, 30, 12, 7
};
/* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
16384, 23955, 28861, 31213, 32178, 32548
};
/* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
16384, 8812, 3906, 1554, 589, 219
};
opus_int silk_sigm_Q15(
opus_int in_Q5 /* I */
)
{
opus_int ind;
if( in_Q5 < 0 ) {
/* Negative input */
in_Q5 = -in_Q5;
if( in_Q5 >= 6 * 32 ) {
return 0; /* Clip */
} else {
/* Linear interpolation of look up table */
ind = silk_RSHIFT( in_Q5, 5 );
return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
}
} else {
/* Positive input */
if( in_Q5 >= 6 * 32 ) {
return 32767; /* clip */
} else {
/* Linear interpolation of look up table */
ind = silk_RSHIFT( in_Q5, 5 );
return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
}
}
}