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Diffstat (limited to 'vocoder~/lpc.c')
| -rw-r--r-- | vocoder~/lpc.c | 252 |
1 files changed, 0 insertions, 252 deletions
diff --git a/vocoder~/lpc.c b/vocoder~/lpc.c deleted file mode 100644 index 33159d4..0000000 --- a/vocoder~/lpc.c +++ /dev/null @@ -1,252 +0,0 @@ -/* -vox - a musical real-time vocoder. version 1.0 -Copyright (C) 2000 Simon MORLAT (simon.morlat@free.fr) - -This program is free software; you can redistribute it and/or -modify it under the terms of the GNU General Public License -as published by the Free Software Foundation; either version 2 -of the License, or (at your option) any later version. - -This program is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with this program; if not, write to the Free Software -Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. -*/ - -#include "tables.h" -#include "lpc.h" -#define THRES 0.06 -#define Dmin 10.81e-3 - -/* Levinson Durbin algorithm for computing LPC coefficients using -autocorrelation fonction */ -void lev_durb(double *corr,double *lpc_coef) -{ - double k[11],tab[11]; - double err,acc; - int i,j; - double *a=tab; - double *prev_a=lpc_coef; - double *exch; - - - /*init vectors*/ - for (i=0;i<11;i++) - { - prev_a[i]=0; - a[i]=0; - }; - err=corr[0]; - for(i=1;i<11;i++) - { - prev_a[0]=1; - acc=0; - for(j=0;j<i;j++) - { - acc=acc+prev_a[j]*corr[i-j]; - }; - a[i]=k[i]=-acc/err; - for(j=1;j<i;j++) - { - a[j]=prev_a[j]+k[i]*prev_a[i-j]; - }; - err=(1-k[i]*k[i])*err; - exch=prev_a; - prev_a=a; - a=exch; - }; -} - -void comp_lpc(double *buf_x,double *corr,double *lpc_coef,int n) -{ - double buffer[n*3]; - double acc,max=0; - int i,j; - /* computes LPC analysis for one subframe */ - /* hamming windowing*/ - acc=0; - for(i=0;i<2*n;i++) - { - acc+=buf_x[i]*buf_x[i]; - }; - if (acc>THRES) - { - for(i=0;i<3*n;i++) - { - buffer[i]=buf_x[i-n]*HammingWindowTable[i]; - }; - /* autocorrelation computation*/ - for(i=0;i<11;i++) - { - acc=0; - for(j=i;j<n*3;j++) - { - acc=acc+buffer[j]*buffer[j-i]; - }; - /* correction with binomial coeffs */ - corr[i]=acc;//*BinomialWindowTable[i]; - }; - corr[0]=corr[0]*(1.0+1.0/1024.0); - lev_durb(corr,lpc_coef); - } - else - { - for(i=0;i<11;i++) - { - lpc_coef[i]=0; - }; - } -} - - - -/* LPC to LSP coefficients conversion */ - -/* evaluate function C(x) (whose roots are LSP coeffs)*/ - -double evalc(double cw,double *fonc) -{ - double b[7]; - double x,res; - int k; - - x=cw; - b[5]=1; - b[6]=0; - for(k=4;k>0;k--) - { - b[k]=2*x*b[k+1]-b[k+2]+fonc[5-k]; - }; - res=x*b[1]-b[2]+fonc[5]/2; - return(res); -} - - - -/* converts LPC vector into LSP frequency vector */ -/* all LSP frenquencies are in [0;PI] but are normalized to be in [0;1] */ -void lpc2lsp(double lpc_coef[],double *f1,double *f2,double lsp_coef[]) -{ - - int i,k=1; - double *fonc,*prev_f,*f_exch; - double prev_sign1,sign,prev_sign2; - double *s, *prev_s,*s_exch; - double lpc_exp[11]; - - /* first computes an additional bandwidth expansion on LPC coeffs*/ - for(i=1;i<11;i++) - { - lpc_exp[i]=lpc_coef[i]*BandExpTable[i]; - }; - /* computes the F1 and F2 coeffs*/ - f1[0]=f2[0]=1; - for(i=0;i<5;i++) - { - f1[i+1]=lpc_exp[i+1]+lpc_exp[10-i]-f1[i]; - f2[i+1]=lpc_exp[i+1]-lpc_exp[10-i]+f2[i]; - }; - - /*find the roots of C(x) alternatively for F1 and F2*/ - fonc=f1; - prev_f=f2; - prev_sign1=evalc(1.0,f1); - prev_sign2=evalc(1.0,f2); - s=&prev_sign1; - prev_s=&prev_sign2; - for(i=1;i<256;i++) - { - sign=evalc(CosineTable[i],fonc); - if ((sign)*(*s)<0) - { - /* interpolate to find root*/ - lsp_coef[k]=((double)i-(*s)/(sign-(*s)))/256.0; - k++; - /* chek if all roots are found */ - if (k==11) i=257; - (*s)=sign; - /* pointers exchange */ - s_exch=s; - s=prev_s; - prev_s=s_exch; - f_exch=fonc; - fonc=prev_f; - prev_f=f_exch; - } - else (*s)=sign; - } - /* if here all roots are not found , use lspDC vector */ - if (k!=11) - { - for(i=1;i<11;i++) - { - lsp_coef[i]=LspDcTable[i]; - }; - }; -} - - -/* converts lsp frequencies to lpc coeffs */ - -void lsp2lpc(double *lsp_coef,double *lpc_coef) -{ - int i,j=0,index,ok=1; - double lspcos[11],delta,tmp,p_avg; - double F1[12],F2[12]; /* begin at indice two*/ - - F1[0]=0;F1[1]=1; - F2[0]=0;F2[1]=1; - /* stability check */ - while(ok && (j<11)) - { - ok=0; - for(i=1;i<10;i++) - { - if( (lsp_coef[i+1]-lsp_coef[i]) < Dmin) - { - ok=1; - p_avg=(lsp_coef[i]+lsp_coef[i+1])/2.0; - lsp_coef[i]=p_avg-Dmin/2.0; - lsp_coef[i+1]=p_avg+Dmin/2.0; - }; - }; - j++; - } - - /* first converts lsp frequencies to lsp coefficients */ - for (i=1;i<11;i++) - { - /* interpolation */ - tmp=lsp_coef[i]*255.0; - index=(int)tmp; - delta=CosineTable[index+1]-CosineTable[index]; - lspcos[i]=CosineTable[index]+delta*(tmp-index); - }; - - for(i=2;i<7;i++) - { - F1[i]=-2*lspcos[2*i-3]*F1[i-1]+2*F1[i-2]; - F2[i]=-2*lspcos[2*i-2]*F2[i-1]+2*F2[i-2]; - for(j=i-1;j>1;j--) - { - F1[j]=F1[j]-2*lspcos[2*i-3]*F1[j-1]+F1[j-2]; - F2[j]=F2[j]-2*lspcos[2*i-2]*F2[j-1]+F2[j-2]; - }; - }; - for(i=6;i>1;i--) - { - F1[i]=F1[i]+F1[i-1]; - F2[i]=F2[i]-F2[i-1]; - }; - for(i=2;i<7;i++) - { - lpc_coef[i-1]=(F1[i]+F2[i])*0.5; - lpc_coef[i+4]=(F1[8-i]-F2[8-i])*0.5; - }; - lpc_coef[0]=1; -} - |