libspeex/lsp.c - platform/external/speex - Git at Google

 /*---------------------------------------------------------------------------*\

 	FILE........: AKSLSPD.C
 	TYPE........: Turbo C
 	COMPANY.....: Voicetronix
 	AUTHOR......: David Rowe
 	DATE CREATED: 24/2/93


     This file contains functions for LPC to LSP conversion and
     LSP to LPC conversion. Note that the LSP coefficients are not in
     radians format but in the x domain of the unit circle.

 \*---------------------------------------------------------------------------*/

 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include "lsp.h"
 #include "stack_alloc.h"


 #ifndef M_PI
 #define M_PI           3.14159265358979323846  /* pi */
 #endif


 /*---------------------------------------------------------------------------*\

 	FUNCTION....: cheb_poly_eva()

 	AUTHOR......: David Rowe
 	DATE CREATED: 24/2/93

     This function evalutes a series of chebyshev polynomials

 \*---------------------------------------------------------------------------*/


 float cheb_poly_eva(float *coef,float x,int m,float *stack)
 /*  float coef[]  	coefficients of the polynomial to be evaluated 	*/
 /*  float x   		the point where polynomial is to be evaluated 	*/
 /*  int m 		order of the polynomial 			*/


 {
     int i;
     float *T,*t,*u,*v,sum;

     /* Allocate memory for chebyshev series formulation */

     T=PUSH(stack, m/2+1);

     /* Initialise pointers */

     t = T;                          	/* T[i-2] 			*/
     *t++ = 1.0;
     u = t--;                        	/* T[i-1] 			*/
     *u++ = x;
     v = u--;                        	/* T[i] 			*/

     /* Evaluate chebyshev series formulation using iterative approach 	*/

     for(i=2;i<=m/2;i++)
 	*v++ = (2*x)*(*u++) - *t++;  	/* T[i] = 2*x*T[i-1] - T[i-2]	*/

     sum=0.0;                        	/* initialise sum to zero 	*/
     t = T;                          	/* reset pointer 		*/

     /* Evaluate polynomial and return value also free memory space */

     for(i=0;i<=m/2;i++)
 	sum+=coef[(m/2)-i]**t++;

     POP(stack);
     return sum;
 }


 /*---------------------------------------------------------------------------*\

 	FUNCTION....: lpc_to_lsp()

 	AUTHOR......: David Rowe
 	DATE CREATED: 24/2/93

     This function converts LPC coefficients to LSP
     coefficients.

 \*---------------------------------------------------------------------------*/


 int lpc_to_lsp (float *a,int lpcrdr,float *freq,int nb,float delta, float *stack)
 /*  float *a 		     	lpc coefficients			*/
 /*  int lpcrdr			order of LPC coefficients (10) 		*/
 /*  float *freq 	      	LSP frequencies in the x domain       	*/
 /*  int nb			number of sub-intervals (4) 		*/
 /*  float delta			grid spacing interval (0.02) 		*/


 {

     float psuml,psumr,psumm,temp_xr,xl,xr,xm=0;
     float temp_psumr/*,temp_qsumr*/;
     int i,j,m,flag,k;
     float *Q;                 	/* ptrs for memory allocation 		*/
     float *P;
     float *px;                	/* ptrs of respective P'(z) & Q'(z)	*/
     float *qx;
     float *p;
     float *q;
     float *pt;                	/* ptr used for cheb_poly_eval()
 				whether P' or Q' 			*/
     int roots=0;              	/* DR 8/2/94: number of roots found 	*/
     flag = 1;                	/*  program is searching for a root when,
 				1 else has found one 			*/
     m = lpcrdr/2;            	/* order of P'(z) & Q'(z) polynimials 	*/


     /* Allocate memory space for polynomials */
     Q = PUSH(stack, (m+1));
     P = PUSH(stack, (m+1));

     /* determine P'(z)'s and Q'(z)'s coefficients where
       P'(z) = P(z)/(1 + z^(-1)) and Q'(z) = Q(z)/(1-z^(-1)) */

     px = P;                      /* initilaise ptrs 			*/
     qx = Q;
     p = px;
     q = qx;
     *px++ = 1.0;
     *qx++ = 1.0;
     for(i=1;i<=m;i++){
 	*px++ = a[i]+a[lpcrdr+1-i]-*p++;
 	*qx++ = a[i]-a[lpcrdr+1-i]+*q++;
     }
     px = P;
     qx = Q;
     for(i=0;i<m;i++){
 	*px = 2**px;
 	*qx = 2**qx;
 	 px++;
 	 qx++;
     }
     px = P;             	/* re-initialise ptrs 			*/
     qx = Q;

     /* Search for a zero in P'(z) polynomial first and then alternate to Q'(z).
     Keep alternating between the two polynomials as each zero is found 	*/

     xr = 0;             	/* initialise xr to zero 		*/
     xl = 1.0;               	/* start at point xl = 1 		*/


     for(j=0;j<lpcrdr;j++){
 	if(j%2)            	/* determines whether P' or Q' is eval. */
 	    pt = qx;
 	else
 	    pt = px;

 	psuml = cheb_poly_eva(pt,xl,lpcrdr,stack);	/* evals poly. at xl 	*/
 	flag = 1;
 	while(flag && (xr >= -1.0)){
 	    xr = xl - delta ;                  	/* interval spacing 	*/
 	    psumr = cheb_poly_eva(pt,xr,lpcrdr,stack);/* poly(xl-delta_x) 	*/
 	    temp_psumr = psumr;
 	    temp_xr = xr;

     /* if no sign change increment xr and re-evaluate poly(xr). Repeat til
     sign change.
     if a sign change has occurred the interval is bisected and then
     checked again for a sign change which determines in which
     interval the zero lies in.
     If there is no sign change between poly(xm) and poly(xl) set interval
     between xm and xr else set interval between xl and xr and repeat till
     root is located within the specified limits 			*/

 	    if((psumr*psuml)<0.0){
 		roots++;

 		psumm=psuml;
 		for(k=0;k<=nb;k++){
 		    xm = (xl+xr)/2;        	/* bisect the interval 	*/
 		    psumm=cheb_poly_eva(pt,xm,lpcrdr,stack);
 		    if(psumm*psuml>0.){
 			psuml=psumm;
 			xl=xm;
 		    }
 		    else{
 			psumr=psumm;
 			xr=xm;
 		    }
 		}

 	       /* once zero is found, reset initial interval to xr 	*/
 	       freq[j] = (xm);
 	       xl = xm;
 	       flag = 0;       		/* reset flag for next search 	*/
 	    }
 	    else{
 		psuml=temp_psumr;
 		xl=temp_xr;
 	    }
 	}
     }
     POP(stack);
     POP(stack);
     return(roots);
 }


 /*---------------------------------------------------------------------------*\

 	FUNCTION....: lsp_to_lpc()

 	AUTHOR......: David Rowe
 	DATE CREATED: 24/2/93

     lsp_to_lpc: This function converts LSP coefficients to LPC
     coefficients.

 \*---------------------------------------------------------------------------*/


 void lsp_to_lpc(float *freq,float *ak,int lpcrdr, float *stack)
 /*  float *freq 	array of LSP frequencies in the x domain	*/
 /*  float *ak 		array of LPC coefficients 			*/
 /*  int lpcrdr  	order of LPC coefficients 			*/


 {
     int i,j;
     float xout1,xout2,xin1,xin2;
     float *Wp;
     float *pw,*n1,*n2,*n3,*n4=NULL;
     int m = lpcrdr/2;

     Wp = PUSH(stack, 4*m+2);
     pw = Wp;

     /* initialise contents of array */

     for(i=0;i<=4*m+1;i++){       	/* set contents of buffer to 0 */
 	*pw++ = 0.0;
     }

     /* Set pointers up */

     pw = Wp;
     xin1 = 1.0;
     xin2 = 1.0;

     /* reconstruct P(z) and Q(z) by  cascading second order
       polynomials in form 1 - 2xz(-1) +z(-2), where x is the
       LSP coefficient */

     for(j=0;j<=lpcrdr;j++){
 	for(i=0;i<m;i++){
 	    n1 = pw+(i*4);
 	    n2 = n1 + 1;
 	    n3 = n2 + 1;
 	    n4 = n3 + 1;
 	    xout1 = xin1 - 2*(freq[2*i]) * *n1 + *n2;
 	    xout2 = xin2 - 2*(freq[2*i+1]) * *n3 + *n4;
 	    *n2 = *n1;
 	    *n4 = *n3;
 	    *n1 = xin1;
 	    *n3 = xin2;
 	    xin1 = xout1;
 	    xin2 = xout2;
 	}
 	xout1 = xin1 + *(n4+1);
 	xout2 = xin2 - *(n4+2);
 	ak[j] = (xout1 + xout2)*0.5;
 	*(n4+1) = xin1;
 	*(n4+2) = xin2;

 	xin1 = 0.0;
 	xin2 = 0.0;
     }
     POP(stack);
 }


 void lsp_enforce_margin(float *lsp, int len, float margin)
 {
    int i;
    if (lsp[0]<margin)
       lsp[0]=margin;
    if (lsp[len-1]>M_PI-margin)
       lsp[len]=margin;
    for (i=1;i<len-1;i++)
    {
       if (lsp[i]<lsp[i-1]+margin)
          lsp[i]=lsp[i-1]+margin;

       if (lsp[i]>lsp[i+1]-margin)
          lsp[i]= .5* (lsp[i] + lsp[i+1]-margin);
    }
 }
	/---------------------------------------------------------------------------\

	FILE........: AKSLSPD.C
	TYPE........: Turbo C
	COMPANY.....: Voicetronix
	AUTHOR......: David Rowe
	DATE CREATED: 24/2/93


	This file contains functions for LPC to LSP conversion and
	LSP to LPC conversion. Note that the LSP coefficients are not in
	radians format but in the x domain of the unit circle.

	\---------------------------------------------------------------------------/

	#include <math.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include "lsp.h"
	#include "stack_alloc.h"


	#ifndef M_PI
	#define M_PI 3.14159265358979323846 /* pi */
	#endif


	/---------------------------------------------------------------------------\

	FUNCTION....: cheb_poly_eva()

	AUTHOR......: David Rowe
	DATE CREATED: 24/2/93

	This function evalutes a series of chebyshev polynomials

	\---------------------------------------------------------------------------/



	float cheb_poly_eva(float coef,float x,int m,float stack)
	/* float coef[] coefficients of the polynomial to be evaluated */
	/* float x the point where polynomial is to be evaluated */
	/* int m order of the polynomial */


	{
	int i;
	float T,t,u,v,sum;

	/* Allocate memory for chebyshev series formulation */

	T=PUSH(stack, m/2+1);

	/* Initialise pointers */

	t = T; /* T[i-2] */
	*t++ = 1.0;
	u = t--; /* T[i-1] */
	*u++ = x;
	v = u--; /* T[i] */

	/* Evaluate chebyshev series formulation using iterative approach */

	for(i=2;i<=m/2;i++)
	v++ = (2x)(u++) - t++; / T[i] = 2xT[i-1] - T[i-2] */

	sum=0.0; /* initialise sum to zero */
	t = T; /* reset pointer */

	/* Evaluate polynomial and return value also free memory space */

	for(i=0;i<=m/2;i++)
	sum+=coef[(m/2)-i]**t++;

	POP(stack);
	return sum;
	}


	/---------------------------------------------------------------------------\

	FUNCTION....: lpc_to_lsp()

	AUTHOR......: David Rowe
	DATE CREATED: 24/2/93

	This function converts LPC coefficients to LSP
	coefficients.

	\---------------------------------------------------------------------------/


	int lpc_to_lsp (float a,int lpcrdr,float freq,int nb,float delta, float *stack)
	/* float a lpc coefficients /
	/* int lpcrdr order of LPC coefficients (10) */
	/* float freq LSP frequencies in the x domain /
	/* int nb number of sub-intervals (4) */
	/* float delta grid spacing interval (0.02) */


	{

	float psuml,psumr,psumm,temp_xr,xl,xr,xm=0;
	float temp_psumr/,temp_qsumr/;
	int i,j,m,flag,k;
	float Q; / ptrs for memory allocation */
	float *P;
	float px; / ptrs of respective P'(z) & Q'(z) */
	float *qx;
	float *p;
	float *q;
	float pt; / ptr used for cheb_poly_eval()
	whether P' or Q' */
	int roots=0; /* DR 8/2/94: number of roots found */
	flag = 1; /* program is searching for a root when,
	1 else has found one */
	m = lpcrdr/2; /* order of P'(z) & Q'(z) polynimials */


	/* Allocate memory space for polynomials */
	Q = PUSH(stack, (m+1));
	P = PUSH(stack, (m+1));

	/* determine P'(z)'s and Q'(z)'s coefficients where
	P'(z) = P(z)/(1 + z^(-1)) and Q'(z) = Q(z)/(1-z^(-1)) */

	px = P; /* initilaise ptrs */
	qx = Q;
	p = px;
	q = qx;
	*px++ = 1.0;
	*qx++ = 1.0;
	for(i=1;i<=m;i++){
	px++ = a[i]+a[lpcrdr+1-i]-p++;
	qx++ = a[i]-a[lpcrdr+1-i]+q++;
	}
	px = P;
	qx = Q;
	for(i=0;i<m;i++){
	px = 2*px;
	qx = 2*qx;
	px++;
	qx++;
	}
	px = P; /* re-initialise ptrs */
	qx = Q;

	/* Search for a zero in P'(z) polynomial first and then alternate to Q'(z).
	Keep alternating between the two polynomials as each zero is found */

	xr = 0; /* initialise xr to zero */
	xl = 1.0; /* start at point xl = 1 */


	for(j=0;j<lpcrdr;j++){
	if(j%2) /* determines whether P' or Q' is eval. */
	pt = qx;
	else
	pt = px;

	psuml = cheb_poly_eva(pt,xl,lpcrdr,stack); /* evals poly. at xl */
	flag = 1;
	while(flag && (xr >= -1.0)){
	xr = xl - delta ; /* interval spacing */
	psumr = cheb_poly_eva(pt,xr,lpcrdr,stack);/* poly(xl-delta_x) */
	temp_psumr = psumr;
	temp_xr = xr;

	/* if no sign change increment xr and re-evaluate poly(xr). Repeat til
	sign change.
	if a sign change has occurred the interval is bisected and then
	checked again for a sign change which determines in which
	interval the zero lies in.
	If there is no sign change between poly(xm) and poly(xl) set interval
	between xm and xr else set interval between xl and xr and repeat till
	root is located within the specified limits */

	if((psumr*psuml)<0.0){
	roots++;

	psumm=psuml;
	for(k=0;k<=nb;k++){
	xm = (xl+xr)/2; /* bisect the interval */
	psumm=cheb_poly_eva(pt,xm,lpcrdr,stack);
	if(psumm*psuml>0.){
	psuml=psumm;
	xl=xm;
	}
	else{
	psumr=psumm;
	xr=xm;
	}
	}

	/* once zero is found, reset initial interval to xr */
	freq[j] = (xm);
	xl = xm;
	flag = 0; /* reset flag for next search */
	}
	else{
	psuml=temp_psumr;
	xl=temp_xr;
	}
	}
	}
	POP(stack);
	POP(stack);
	return(roots);
	}


	/---------------------------------------------------------------------------\

	FUNCTION....: lsp_to_lpc()

	AUTHOR......: David Rowe
	DATE CREATED: 24/2/93

	lsp_to_lpc: This function converts LSP coefficients to LPC
	coefficients.

	\---------------------------------------------------------------------------/


	void lsp_to_lpc(float freq,float ak,int lpcrdr, float *stack)
	/* float freq array of LSP frequencies in the x domain /
	/* float ak array of LPC coefficients /
	/* int lpcrdr order of LPC coefficients */


	{
	int i,j;
	float xout1,xout2,xin1,xin2;
	float *Wp;
	float pw,n1,n2,n3,*n4=NULL;
	int m = lpcrdr/2;

	Wp = PUSH(stack, 4*m+2);
	pw = Wp;

	/* initialise contents of array */

	for(i=0;i<=4m+1;i++){ / set contents of buffer to 0 */
	*pw++ = 0.0;
	}

	/* Set pointers up */

	pw = Wp;
	xin1 = 1.0;
	xin2 = 1.0;

	/* reconstruct P(z) and Q(z) by cascading second order
	polynomials in form 1 - 2xz(-1) +z(-2), where x is the
	LSP coefficient */

	for(j=0;j<=lpcrdr;j++){
	for(i=0;i<m;i++){
	n1 = pw+(i*4);
	n2 = n1 + 1;
	n3 = n2 + 1;
	n4 = n3 + 1;
	xout1 = xin1 - 2(freq[2i]) * n1 + n2;
	xout2 = xin2 - 2(freq[2i+1]) * n3 + n4;
	n2 = n1;
	n4 = n3;
	*n1 = xin1;
	*n3 = xin2;
	xin1 = xout1;
	xin2 = xout2;
	}
	xout1 = xin1 + *(n4+1);
	xout2 = xin2 - *(n4+2);
	ak[j] = (xout1 + xout2)*0.5;
	*(n4+1) = xin1;
	*(n4+2) = xin2;

	xin1 = 0.0;
	xin2 = 0.0;
	}
	POP(stack);
	}


	void lsp_enforce_margin(float *lsp, int len, float margin)
	{
	int i;
	if (lsp[0]<margin)
	lsp[0]=margin;
	if (lsp[len-1]>M_PI-margin)
	lsp[len]=margin;
	for (i=1;i<len-1;i++)
	{
	if (lsp[i]<lsp[i-1]+margin)
	lsp[i]=lsp[i-1]+margin;

	if (lsp[i]>lsp[i+1]-margin)
	lsp[i]= .5* (lsp[i] + lsp[i+1]-margin);
	}
	}