Alexandre Lision | 744f742 | 2013-09-25 11:39:37 -0400 | [diff] [blame] | 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 |
| 22 | INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 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 | ***********************************************************************/ |
| 27 | |
| 28 | #ifdef HAVE_CONFIG_H |
| 29 | #include "config.h" |
| 30 | #endif |
| 31 | |
| 32 | /* Approximate sigmoid function */ |
| 33 | |
| 34 | #include "SigProc_FIX.h" |
| 35 | |
| 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 | }; |
| 48 | |
| 49 | opus_int silk_sigm_Q15( |
| 50 | opus_int in_Q5 /* I */ |
| 51 | ) |
| 52 | { |
| 53 | opus_int ind; |
| 54 | |
| 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 | } |
| 76 | |