The Tor Browser: media/libopus/silk/sigm

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 /***********************************************************************

     2 Copyright (c) 2006-2011, Skype Limited. All rights reserved.

     3 Redistribution and use in source and binary forms, with or without

     4 modification, are permitted provided that the following conditions

     5 are met:

     6 - Redistributions of source code must retain the above copyright notice,

     7 this list of conditions and the following disclaimer.

     8 - Redistributions in binary form must reproduce the above copyright

     9 notice, this list of conditions and the following disclaimer in the

    10 documentation and/or other materials provided with the distribution.

    11 - Neither the name of Internet Society, IETF or IETF Trust, nor the

    12 names of specific contributors, may be used to endorse or promote

    13 products derived from this software without specific prior written

    14 permission.

    15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

    16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

    18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

    19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

    20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

    21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

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    23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

    24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

    25 POSSIBILITY OF SUCH DAMAGE.

    26 ***********************************************************************/

    28 #ifdef HAVE_CONFIG_H

    29 #include "config.h"

    30 #endif

    32 /* Approximate sigmoid function */

    34 #include "SigProc_FIX.h"

    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 };

    49 opus_int silk_sigm_Q15(

    50     opus_int                    in_Q5               /* I                                                                */

    51 )

    52 {

    53     opus_int ind;

    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 }

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