76 lines
3.1 KiB
C
76 lines
3.1 KiB
C
/***********************************************************************
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Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of Internet Society, IETF or IETF Trust, nor the
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names of specific contributors, may be used to endorse or promote
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products derived from this software without specific prior written
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permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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/* Approximate sigmoid function */
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#include "SigProc_FIX.h"
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/* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
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static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
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237, 153, 73, 30, 12, 7
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};
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/* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
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static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
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16384, 23955, 28861, 31213, 32178, 32548
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};
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/* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
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static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
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16384, 8812, 3906, 1554, 589, 219
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};
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opus_int silk_sigm_Q15(
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opus_int in_Q5 /* I */
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)
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{
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opus_int ind;
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if( in_Q5 < 0 ) {
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/* Negative input */
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in_Q5 = -in_Q5;
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if( in_Q5 >= 6 * 32 ) {
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return 0; /* Clip */
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} else {
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/* Linear interpolation of look up table */
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ind = silk_RSHIFT( in_Q5, 5 );
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return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
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}
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} else {
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/* Positive input */
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if( in_Q5 >= 6 * 32 ) {
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return 32767; /* clip */
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} else {
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/* Linear interpolation of look up table */
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ind = silk_RSHIFT( in_Q5, 5 );
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return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
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}
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}
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}
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