media/libvorbis/lib/vorbis_lpc.c@b8a032363ba2 (annotated)
media/libvorbis/lib/vorbis_lpc.c
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
| michael@0 | 1 | /******************************************************************** |
| michael@0 | 2 | * * |
| michael@0 | 3 | * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE. * |
| michael@0 | 4 | * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS * |
| michael@0 | 5 | * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE * |
| michael@0 | 6 | * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. * |
| michael@0 | 7 | * * |
| michael@0 | 8 | * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009 * |
| michael@0 | 9 | * by the Xiph.Org Foundation http://www.xiph.org/ * |
| michael@0 | 10 | * * |
| michael@0 | 11 | ******************************************************************** |
| michael@0 | 12 | |
| michael@0 | 13 | function: LPC low level routines |
| michael@0 | 14 | last mod: $Id: lpc.c 16227 2009-07-08 06:58:46Z xiphmont $ |
| michael@0 | 15 | |
| michael@0 | 16 | ********************************************************************/ |
| michael@0 | 17 | |
| michael@0 | 18 | /* Some of these routines (autocorrelator, LPC coefficient estimator) |
| michael@0 | 19 | are derived from code written by Jutta Degener and Carsten Bormann; |
| michael@0 | 20 | thus we include their copyright below. The entirety of this file |
| michael@0 | 21 | is freely redistributable on the condition that both of these |
| michael@0 | 22 | copyright notices are preserved without modification. */ |
| michael@0 | 23 | |
| michael@0 | 24 | /* Preserved Copyright: *********************************************/ |
| michael@0 | 25 | |
| michael@0 | 26 | /* Copyright 1992, 1993, 1994 by Jutta Degener and Carsten Bormann, |
| michael@0 | 27 | Technische Universita"t Berlin |
| michael@0 | 28 | |
| michael@0 | 29 | Any use of this software is permitted provided that this notice is not |
| michael@0 | 30 | removed and that neither the authors nor the Technische Universita"t |
| michael@0 | 31 | Berlin are deemed to have made any representations as to the |
| michael@0 | 32 | suitability of this software for any purpose nor are held responsible |
| michael@0 | 33 | for any defects of this software. THERE IS ABSOLUTELY NO WARRANTY FOR |
| michael@0 | 34 | THIS SOFTWARE. |
| michael@0 | 35 | |
| michael@0 | 36 | As a matter of courtesy, the authors request to be informed about uses |
| michael@0 | 37 | this software has found, about bugs in this software, and about any |
| michael@0 | 38 | improvements that may be of general interest. |
| michael@0 | 39 | |
| michael@0 | 40 | Berlin, 28.11.1994 |
| michael@0 | 41 | Jutta Degener |
| michael@0 | 42 | Carsten Bormann |
| michael@0 | 43 | |
| michael@0 | 44 | *********************************************************************/ |
| michael@0 | 45 | |
| michael@0 | 46 | #include <stdlib.h> |
| michael@0 | 47 | #include <string.h> |
| michael@0 | 48 | #include <math.h> |
| michael@0 | 49 | #include "os.h" |
| michael@0 | 50 | #include "smallft.h" |
| michael@0 | 51 | #include "lpc.h" |
| michael@0 | 52 | #include "scales.h" |
| michael@0 | 53 | #include "misc.h" |
| michael@0 | 54 | |
| michael@0 | 55 | /* Autocorrelation LPC coeff generation algorithm invented by |
| michael@0 | 56 | N. Levinson in 1947, modified by J. Durbin in 1959. */ |
| michael@0 | 57 | |
| michael@0 | 58 | /* Input : n elements of time doamin data |
| michael@0 | 59 | Output: m lpc coefficients, excitation energy */ |
| michael@0 | 60 | |
| michael@0 | 61 | float vorbis_lpc_from_data(float *data,float *lpci,int n,int m){ |
| michael@0 | 62 | double *aut=alloca(sizeof(*aut)*(m+1)); |
| michael@0 | 63 | double *lpc=alloca(sizeof(*lpc)*(m)); |
| michael@0 | 64 | double error; |
| michael@0 | 65 | double epsilon; |
| michael@0 | 66 | int i,j; |
| michael@0 | 67 | |
| michael@0 | 68 | /* autocorrelation, p+1 lag coefficients */ |
| michael@0 | 69 | j=m+1; |
| michael@0 | 70 | while(j--){ |
| michael@0 | 71 | double d=0; /* double needed for accumulator depth */ |
| michael@0 | 72 | for(i=j;i<n;i++)d+=(double)data[i]*data[i-j]; |
| michael@0 | 73 | aut[j]=d; |
| michael@0 | 74 | } |
| michael@0 | 75 | |
| michael@0 | 76 | /* Generate lpc coefficients from autocorr values */ |
| michael@0 | 77 | |
| michael@0 | 78 | /* set our noise floor to about -100dB */ |
| michael@0 | 79 | error=aut[0] * (1. + 1e-10); |
| michael@0 | 80 | epsilon=1e-9*aut[0]+1e-10; |
| michael@0 | 81 | |
| michael@0 | 82 | for(i=0;i<m;i++){ |
| michael@0 | 83 | double r= -aut[i+1]; |
| michael@0 | 84 | |
| michael@0 | 85 | if(error<epsilon){ |
| michael@0 | 86 | memset(lpc+i,0,(m-i)*sizeof(*lpc)); |
| michael@0 | 87 | goto done; |
| michael@0 | 88 | } |
| michael@0 | 89 | |
| michael@0 | 90 | /* Sum up this iteration's reflection coefficient; note that in |
| michael@0 | 91 | Vorbis we don't save it. If anyone wants to recycle this code |
| michael@0 | 92 | and needs reflection coefficients, save the results of 'r' from |
| michael@0 | 93 | each iteration. */ |
| michael@0 | 94 | |
| michael@0 | 95 | for(j=0;j<i;j++)r-=lpc[j]*aut[i-j]; |
| michael@0 | 96 | r/=error; |
| michael@0 | 97 | |
| michael@0 | 98 | /* Update LPC coefficients and total error */ |
| michael@0 | 99 | |
| michael@0 | 100 | lpc[i]=r; |
| michael@0 | 101 | for(j=0;j<i/2;j++){ |
| michael@0 | 102 | double tmp=lpc[j]; |
| michael@0 | 103 | |
| michael@0 | 104 | lpc[j]+=r*lpc[i-1-j]; |
| michael@0 | 105 | lpc[i-1-j]+=r*tmp; |
| michael@0 | 106 | } |
| michael@0 | 107 | if(i&1)lpc[j]+=lpc[j]*r; |
| michael@0 | 108 | |
| michael@0 | 109 | error*=1.-r*r; |
| michael@0 | 110 | |
| michael@0 | 111 | } |
| michael@0 | 112 | |
| michael@0 | 113 | done: |
| michael@0 | 114 | |
| michael@0 | 115 | /* slightly damp the filter */ |
| michael@0 | 116 | { |
| michael@0 | 117 | double g = .99; |
| michael@0 | 118 | double damp = g; |
| michael@0 | 119 | for(j=0;j<m;j++){ |
| michael@0 | 120 | lpc[j]*=damp; |
| michael@0 | 121 | damp*=g; |
| michael@0 | 122 | } |
| michael@0 | 123 | } |
| michael@0 | 124 | |
| michael@0 | 125 | for(j=0;j<m;j++)lpci[j]=(float)lpc[j]; |
| michael@0 | 126 | |
| michael@0 | 127 | /* we need the error value to know how big an impulse to hit the |
| michael@0 | 128 | filter with later */ |
| michael@0 | 129 | |
| michael@0 | 130 | return error; |
| michael@0 | 131 | } |
| michael@0 | 132 | |
| michael@0 | 133 | void vorbis_lpc_predict(float *coeff,float *prime,int m, |
| michael@0 | 134 | float *data,long n){ |
| michael@0 | 135 | |
| michael@0 | 136 | /* in: coeff[0...m-1] LPC coefficients |
| michael@0 | 137 | prime[0...m-1] initial values (allocated size of n+m-1) |
| michael@0 | 138 | out: data[0...n-1] data samples */ |
| michael@0 | 139 | |
| michael@0 | 140 | long i,j,o,p; |
| michael@0 | 141 | float y; |
| michael@0 | 142 | float *work=alloca(sizeof(*work)*(m+n)); |
| michael@0 | 143 | |
| michael@0 | 144 | if(!prime) |
| michael@0 | 145 | for(i=0;i<m;i++) |
| michael@0 | 146 | work[i]=0.f; |
| michael@0 | 147 | else |
| michael@0 | 148 | for(i=0;i<m;i++) |
| michael@0 | 149 | work[i]=prime[i]; |
| michael@0 | 150 | |
| michael@0 | 151 | for(i=0;i<n;i++){ |
| michael@0 | 152 | y=0; |
| michael@0 | 153 | o=i; |
| michael@0 | 154 | p=m; |
| michael@0 | 155 | for(j=0;j<m;j++) |
| michael@0 | 156 | y-=work[o++]*coeff[--p]; |
| michael@0 | 157 | |
| michael@0 | 158 | data[i]=work[o]=y; |
| michael@0 | 159 | } |
| michael@0 | 160 | } |
