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Diffstat (limited to 'src/libvorbis-1.3.4/lib/lpc.c')
| -rw-r--r-- | src/libvorbis-1.3.4/lib/lpc.c | 160 |
1 files changed, 0 insertions, 160 deletions
diff --git a/src/libvorbis-1.3.4/lib/lpc.c b/src/libvorbis-1.3.4/lib/lpc.c deleted file mode 100644 index f5199ec2..00000000 --- a/src/libvorbis-1.3.4/lib/lpc.c +++ /dev/null @@ -1,160 +0,0 @@ -/******************************************************************** - * * - * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE. * - * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS * - * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE * - * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. * - * * - * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009 * - * by the Xiph.Org Foundation http://www.xiph.org/ * - * * - ******************************************************************** - - function: LPC low level routines - last mod: $Id: lpc.c 16227 2009-07-08 06:58:46Z xiphmont $ - - ********************************************************************/ - -/* Some of these routines (autocorrelator, LPC coefficient estimator) - are derived from code written by Jutta Degener and Carsten Bormann; - thus we include their copyright below. The entirety of this file - is freely redistributable on the condition that both of these - copyright notices are preserved without modification. */ - -/* Preserved Copyright: *********************************************/ - -/* Copyright 1992, 1993, 1994 by Jutta Degener and Carsten Bormann, -Technische Universita"t Berlin - -Any use of this software is permitted provided that this notice is not -removed and that neither the authors nor the Technische Universita"t -Berlin are deemed to have made any representations as to the -suitability of this software for any purpose nor are held responsible -for any defects of this software. THERE IS ABSOLUTELY NO WARRANTY FOR -THIS SOFTWARE. - -As a matter of courtesy, the authors request to be informed about uses -this software has found, about bugs in this software, and about any -improvements that may be of general interest. - -Berlin, 28.11.1994 -Jutta Degener -Carsten Bormann - -*********************************************************************/ - -#include <stdlib.h> -#include <string.h> -#include <math.h> -#include "os.h" -#include "smallft.h" -#include "lpc.h" -#include "scales.h" -#include "misc.h" - -/* Autocorrelation LPC coeff generation algorithm invented by - N. Levinson in 1947, modified by J. Durbin in 1959. */ - -/* Input : n elements of time doamin data - Output: m lpc coefficients, excitation energy */ - -float vorbis_lpc_from_data(float *data,float *lpci,int n,int m){ - double *aut=alloca(sizeof(*aut)*(m+1)); - double *lpc=alloca(sizeof(*lpc)*(m)); - double error; - double epsilon; - int i,j; - - /* autocorrelation, p+1 lag coefficients */ - j=m+1; - while(j--){ - double d=0; /* double needed for accumulator depth */ - for(i=j;i<n;i++)d+=(double)data[i]*data[i-j]; - aut[j]=d; - } - - /* Generate lpc coefficients from autocorr values */ - - /* set our noise floor to about -100dB */ - error=aut[0] * (1. + 1e-10); - epsilon=1e-9*aut[0]+1e-10; - - for(i=0;i<m;i++){ - double r= -aut[i+1]; - - if(error<epsilon){ - memset(lpc+i,0,(m-i)*sizeof(*lpc)); - goto done; - } - - /* Sum up this iteration's reflection coefficient; note that in - Vorbis we don't save it. If anyone wants to recycle this code - and needs reflection coefficients, save the results of 'r' from - each iteration. */ - - for(j=0;j<i;j++)r-=lpc[j]*aut[i-j]; - r/=error; - - /* Update LPC coefficients and total error */ - - lpc[i]=r; - for(j=0;j<i/2;j++){ - double tmp=lpc[j]; - - lpc[j]+=r*lpc[i-1-j]; - lpc[i-1-j]+=r*tmp; - } - if(i&1)lpc[j]+=lpc[j]*r; - - error*=1.-r*r; - - } - - done: - - /* slightly damp the filter */ - { - double g = .99; - double damp = g; - for(j=0;j<m;j++){ - lpc[j]*=damp; - damp*=g; - } - } - - for(j=0;j<m;j++)lpci[j]=(float)lpc[j]; - - /* we need the error value to know how big an impulse to hit the - filter with later */ - - return error; -} - -void vorbis_lpc_predict(float *coeff,float *prime,int m, - float *data,long n){ - - /* in: coeff[0...m-1] LPC coefficients - prime[0...m-1] initial values (allocated size of n+m-1) - out: data[0...n-1] data samples */ - - long i,j,o,p; - float y; - float *work=alloca(sizeof(*work)*(m+n)); - - if(!prime) - for(i=0;i<m;i++) - work[i]=0.f; - else - for(i=0;i<m;i++) - work[i]=prime[i]; - - for(i=0;i<n;i++){ - y=0; - o=i; - p=m; - for(j=0;j<m;j++) - y-=work[o++]*coeff[--p]; - - data[i]=work[o]=y; - } -} |