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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 | | #include "SigProc_FIX.h" |
33 | | |
34 | | /* Approximation of 2^() (very close inverse of silk_lin2log()) */ |
35 | | /* Convert input to a linear scale */ |
36 | | opus_int32 silk_log2lin( |
37 | | const opus_int32 inLog_Q7 /* I input on log scale */ |
38 | | ) |
39 | 0 | { |
40 | 0 | opus_int32 out, frac_Q7; |
41 | |
|
42 | 0 | if( inLog_Q7 < 0 ) { |
43 | 0 | return 0; |
44 | 0 | } else if ( inLog_Q7 >= 3967 ) { |
45 | 0 | return silk_int32_MAX; |
46 | 0 | } |
47 | | |
48 | 0 | out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) ); |
49 | 0 | frac_Q7 = inLog_Q7 & 0x7F; |
50 | 0 | if( inLog_Q7 < 2048 ) { |
51 | | /* Piece-wise parabolic approximation */ |
52 | 0 | out = silk_ADD_RSHIFT32( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ), 7 ); |
53 | 0 | } else { |
54 | | /* Piece-wise parabolic approximation */ |
55 | 0 | out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ); |
56 | 0 | } |
57 | 0 | return out; |
58 | 0 | } |