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1 /***********************************************************************
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2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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3 Redistribution and use in source and binary forms, with or without
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4 modification, are permitted provided that the following conditions
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5 are met:
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6 - Redistributions of source code must retain the above copyright notice,
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7 this list of conditions and the following disclaimer.
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8 - Redistributions in binary form must reproduce the above copyright
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9 notice, this list of conditions and the following disclaimer in the
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10 documentation and/or other materials provided with the distribution.
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11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
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12 names of specific contributors, may be used to endorse or promote
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13 products derived from this software without specific prior written
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14 permission.
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15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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25 POSSIBILITY OF SUCH DAMAGE.
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26 ***********************************************************************/
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27
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28 #ifdef HAVE_CONFIG_H
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29 #include "config.h"
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30 #endif
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31
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32 /* Approximate sigmoid function */
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33
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34 #include "SigProc_FIX.h"
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35
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36 /* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
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37 static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
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38 237, 153, 73, 30, 12, 7
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39 };
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40 /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
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41 static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
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42 16384, 23955, 28861, 31213, 32178, 32548
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43 };
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44 /* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
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45 static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
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46 16384, 8812, 3906, 1554, 589, 219
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47 };
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48
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49 opus_int silk_sigm_Q15(
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50 opus_int in_Q5 /* I */
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51 )
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52 {
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53 opus_int ind;
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54
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55 if( in_Q5 < 0 ) {
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56 /* Negative input */
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57 in_Q5 = -in_Q5;
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58 if( in_Q5 >= 6 * 32 ) {
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59 return 0; /* Clip */
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60 } else {
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61 /* Linear interpolation of look up table */
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62 ind = silk_RSHIFT( in_Q5, 5 );
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63 return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
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64 }
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65 } else {
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66 /* Positive input */
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67 if( in_Q5 >= 6 * 32 ) {
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68 return 32767; /* clip */
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69 } else {
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70 /* Linear interpolation of look up table */
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71 ind = silk_RSHIFT( in_Q5, 5 );
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72 return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
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73 }
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74 }
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75 }
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76
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