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1 /*********************************************************************** | 1 /*********************************************************************** |
2 Copyright (c) 2006-2011, Skype Limited. All rights reserved. | 2 Copyright (c) 2006-2011, Skype Limited. All rights reserved. |
3 Redistribution and use in source and binary forms, with or without | 3 Redistribution and use in source and binary forms, with or without |
4 modification, are permitted provided that the following conditions | 4 modification, are permitted provided that the following conditions |
5 are met: | 5 are met: |
6 - Redistributions of source code must retain the above copyright notice, | 6 - Redistributions of source code must retain the above copyright notice, |
7 this list of conditions and the following disclaimer. | 7 this list of conditions and the following disclaimer. |
8 - Redistributions in binary form must reproduce the above copyright | 8 - Redistributions in binary form must reproduce the above copyright |
9 notice, this list of conditions and the following disclaimer in the | 9 notice, this list of conditions and the following disclaimer in the |
10 documentation and/or other materials provided with the distribution. | 10 documentation and/or other materials provided with the distribution. |
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34 /* Approximation of 2^() (very close inverse of silk_lin2log()) */ | 34 /* Approximation of 2^() (very close inverse of silk_lin2log()) */ |
35 /* Convert input to a linear scale */ | 35 /* Convert input to a linear scale */ |
36 opus_int32 silk_log2lin( | 36 opus_int32 silk_log2lin( |
37 const opus_int32 inLog_Q7 /* I input on log scale
*/ | 37 const opus_int32 inLog_Q7 /* I input on log scale
*/ |
38 ) | 38 ) |
39 { | 39 { |
40 opus_int32 out, frac_Q7; | 40 opus_int32 out, frac_Q7; |
41 | 41 |
42 if( inLog_Q7 < 0 ) { | 42 if( inLog_Q7 < 0 ) { |
43 return 0; | 43 return 0; |
44 } | 44 } else if ( inLog_Q7 >= 3967 ) { |
| 45 » » return silk_int32_MAX; |
| 46 » } |
45 | 47 |
46 out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) ); | 48 out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) ); |
47 frac_Q7 = inLog_Q7 & 0x7F; | 49 frac_Q7 = inLog_Q7 & 0x7F; |
48 if( inLog_Q7 < 2048 ) { | 50 if( inLog_Q7 < 2048 ) { |
49 /* Piece-wise parabolic approximation */ | 51 /* Piece-wise parabolic approximation */ |
50 out = silk_ADD_RSHIFT32( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_
SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ), 7 ); | 52 out = silk_ADD_RSHIFT32( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_
SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ), 7 ); |
51 } else { | 53 } else { |
52 /* Piece-wise parabolic approximation */ | 54 /* Piece-wise parabolic approximation */ |
53 out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_S
MULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ); | 55 out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_S
MULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ); |
54 } | 56 } |
55 return out; | 57 return out; |
56 } | 58 } |
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