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-rw-r--r--lpc.c392
1 files changed, 197 insertions, 195 deletions
diff --git a/lpc.c b/lpc.c
index 33159d4..e680588 100644
--- a/lpc.c
+++ b/lpc.c
@@ -22,86 +22,86 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#define THRES 0.06
#define Dmin 10.81e-3
-/* Levinson Durbin algorithm for computing LPC coefficients using
+/* 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;
- };
+ 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;
- };
- }
+ 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 */
@@ -110,19 +110,19 @@ void comp_lpc(double *buf_x,double *corr,double *lpc_coef,int n)
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);
+ 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);
}
@@ -131,62 +131,62 @@ double evalc(double cw,double *fonc)
/* 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];
- };
- };
+
+ 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];
+ };
+ };
}
@@ -194,59 +194,61 @@ void lpc2lsp(double lpc_coef[],double *f1,double *f2,double lsp_coef[])
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;
+ 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;
}
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