ref: a32fa319d3e300d80df648e7edb2157b599003ab
dir: /silk/sigm_Q15.c/
/***********************************************************************
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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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 ) );
}
}
}