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comparison: media/libopus/silk/float/levinsondurbin_FLP.c
media/libopus/silk/float/levinsondurbin_FLP.c
- branch
- TOR_BUG_9701
- changeset 10
- ac0c01689b40
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| -1:000000000000 | 0:cb8fe4e3ce8d |
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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_FLP.h" | |
| 33 | |
| 34 /* Solve the normal equations using the Levinson-Durbin recursion */ | |
| 35 silk_float silk_levinsondurbin_FLP( /* O prediction error energy */ | |
| 36 silk_float A[], /* O prediction coefficients [order] */ | |
| 37 const silk_float corr[], /* I input auto-correlations [order + 1] */ | |
| 38 const opus_int order /* I prediction order */ | |
| 39 ) | |
| 40 { | |
| 41 opus_int i, mHalf, m; | |
| 42 silk_float min_nrg, nrg, t, km, Atmp1, Atmp2; | |
| 43 | |
| 44 min_nrg = 1e-12f * corr[ 0 ] + 1e-9f; | |
| 45 nrg = corr[ 0 ]; | |
| 46 nrg = silk_max_float(min_nrg, nrg); | |
| 47 A[ 0 ] = corr[ 1 ] / nrg; | |
| 48 nrg -= A[ 0 ] * corr[ 1 ]; | |
| 49 nrg = silk_max_float(min_nrg, nrg); | |
| 50 | |
| 51 for( m = 1; m < order; m++ ) | |
| 52 { | |
| 53 t = corr[ m + 1 ]; | |
| 54 for( i = 0; i < m; i++ ) { | |
| 55 t -= A[ i ] * corr[ m - i ]; | |
| 56 } | |
| 57 | |
| 58 /* reflection coefficient */ | |
| 59 km = t / nrg; | |
| 60 | |
| 61 /* residual energy */ | |
| 62 nrg -= km * t; | |
| 63 nrg = silk_max_float(min_nrg, nrg); | |
| 64 | |
| 65 mHalf = m >> 1; | |
| 66 for( i = 0; i < mHalf; i++ ) { | |
| 67 Atmp1 = A[ i ]; | |
| 68 Atmp2 = A[ m - i - 1 ]; | |
| 69 A[ m - i - 1 ] -= km * Atmp1; | |
| 70 A[ i ] -= km * Atmp2; | |
| 71 } | |
| 72 if( m & 1 ) { | |
| 73 A[ mHalf ] -= km * A[ mHalf ]; | |
| 74 } | |
| 75 A[ m ] = km; | |
| 76 } | |
| 77 | |
| 78 /* return the residual energy */ | |
| 79 return nrg; | |
| 80 } | |
| 81 |
