/src/opus/silk/sigm_Q15.c
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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 | 0 | { |
53 | 0 | opus_int ind; |
54 | |
|
55 | 0 | if( in_Q5 < 0 ) { |
56 | | /* Negative input */ |
57 | 0 | in_Q5 = -in_Q5; |
58 | 0 | if( in_Q5 >= 6 * 32 ) { |
59 | 0 | return 0; /* Clip */ |
60 | 0 | } else { |
61 | | /* Linear interpolation of look up table */ |
62 | 0 | ind = silk_RSHIFT( in_Q5, 5 ); |
63 | 0 | return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) ); |
64 | 0 | } |
65 | 0 | } else { |
66 | | /* Positive input */ |
67 | 0 | if( in_Q5 >= 6 * 32 ) { |
68 | 0 | return 32767; /* clip */ |
69 | 0 | } else { |
70 | | /* Linear interpolation of look up table */ |
71 | 0 | ind = silk_RSHIFT( in_Q5, 5 ); |
72 | 0 | return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) ); |
73 | 0 | } |
74 | 0 | } |
75 | 0 | } |
76 | | |