lsp.c

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#endif

    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 = FREQ_SCALE;               	/* start at point xl = 1 		*/


    for(j=0;j<lpcrdr;j++){
	if(j&1)            	/* 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 >= -FREQ_SCALE)){
           spx_word16_t dd;
           /* Modified by JMV to provide smaller steps around x=+-1 */
#ifdef FIXED_POINT
           dd = MULT16_16_Q15(delta,SUB16(FREQ_SCALE, MULT16_16_Q14(MULT16_16_Q14(xl,xl),14000)));
           if (psuml<512 && psuml>-512)
              dd = PSHR16(dd,1);
#else
           dd=delta*(1-.9*xl*xl);
           if (fabs(psuml)<.2)
              dd *= .5;
#endif
           xr = SUB16(xl, dd);                        	/* 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(SIGN_CHANGE(psumr,psuml))
            {
		roots++;

		psumm=psuml;
		for(k=0;k<=nb;k++){
#ifdef FIXED_POINT
		    xm = ADD16(PSHR16(xl,1),PSHR16(xr,1));        	/* bisect the interval 	*/
#else
                    xm = .5*(xl+xr);        	/* bisect the interval 	*/
#endif
		    psumm=cheb_poly_eva(pt,xm,lpcrdr,stack);
		    /*if(psumm*psuml>0.)*/
		    if(!SIGN_CHANGE(psumm,psuml))
                    {
			psuml=psumm;
			xl=xm;
		    } else {
			psumr=psumm;
			xr=xm;
		    }
		}

	       /* once zero is found, reset initial interval to xr 	*/
	       freq[j] = X2ANGLE(xm);
	       xl = xm;
	       flag = 0;       		/* reset flag for next search 	*/
	    }
	    else{
		psuml=temp_psumr;
		xl=temp_xr;
	    }
	}
    }
    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.

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

#ifdef FIXED_POINT

void lsp_to_lpc(spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *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;
    spx_word32_t xout1,xout2,xin1,xin2;
    VARDECL(spx_word32_t *Wp);
    spx_word32_t *pw,*n1,*n2,*n3,*n4=NULL;
    VARDECL(spx_word16_t *freqn);
    int m = lpcrdr>>1;
    
    ALLOC(freqn, lpcrdr, spx_word16_t);
    for (i=0;i<lpcrdr;i++)
       freqn[i] = ANGLE2X(freq[i]);

    ALLOC(Wp, 4*m+2, spx_word32_t);
    pw = Wp;


    /* initialise contents of array */

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

    /* Set pointers up */

    pw = Wp;
    xin1 = 1048576;
    xin2 = 1048576;

    /* 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++){
       spx_word16_t *fr=freqn;
	for(i=0;i<m;i++){
	    n1 = pw+(i<<2);
	    n2 = n1 + 1;
	    n3 = n2 + 1;
	    n4 = n3 + 1;
	    xout1 = ADD32(SUB32(xin1, MULT16_32_Q14(*fr,*n1)), *n2);
            fr++;
            xout2 = ADD32(SUB32(xin2, MULT16_32_Q14(*fr,*n3)), *n4);
            fr++;
	    *n2 = *n1;
	    *n4 = *n3;
	    *n1 = xin1;
	    *n3 = xin2;
	    xin1 = xout1;
	    xin2 = xout2;
	}
	xout1 = xin1 + *(n4+1);
	xout2 = xin2 - *(n4+2);
        /* FIXME: perhaps apply bandwidth expansion in case of overflow? */
	if (j>0)
	{
        if (xout1 + xout2>SHL32(EXTEND32(32766),8))
           ak[j-1] = 32767;
        else if (xout1 + xout2 < -SHL32(EXTEND32(32766),8))
           ak[j-1] = -32767;
        else
           ak[j-1] = EXTRACT16(PSHR32(ADD32(xout1,xout2),8));
	} else {/*speex_warning_int("ak[0] = ", EXTRACT16(PSHR32(ADD32(xout1,xout2),8)));*/}
	*(n4+1) = xin1;
	*(n4+2) = xin2;

	xin1 = 0;
	xin2 = 0;
    }
}
#else

void lsp_to_lpc(spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *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;
    VARDECL(float *Wp);
    float *pw,*n1,*n2,*n3,*n4=NULL;
    VARDECL(float *x_freq);
    int m = lpcrdr>>1;

    ALLOC(Wp, 4*m+2, float);
    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;

    ALLOC(x_freq, lpcrdr, float);
    for (i=0;i<lpcrdr;i++)
       x_freq[i] = ANGLE2X(freq[i]);

    /* 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++){
       int i2=0;
	for(i=0;i<m;i++,i2+=2){
	    n1 = pw+(i*4);
	    n2 = n1 + 1;
	    n3 = n2 + 1;
	    n4 = n3 + 1;
	    xout1 = xin1 - 2.f*x_freq[i2] * *n1 + *n2;
	    xout2 = xin2 - 2.f*x_freq[i2+1] * *n3 + *n4;
	    *n2 = *n1;
	    *n4 = *n3;
	    *n1 = xin1;
	    *n3 = xin2;
	    xin1 = xout1;
	    xin2 = xout2;
	}
	xout1 = xin1 + *(n4+1);
	xout2 = xin2 - *(n4+2);
	if (j>0)
	   ak[j-1] = (xout1 + xout2)*0.5f;
	*(n4+1) = xin1;
	*(n4+2) = xin2;

	xin1 = 0.0;
	xin2 = 0.0;
    }

}
#endif


#ifdef FIXED_POINT

/*Makes sure the LSPs are stable*/
void lsp_enforce_margin(spx_lsp_t *lsp, int len, spx_word16_t margin)
{
   int i;
   spx_word16_t m = margin;
   spx_word16_t m2 = 25736-margin;
  
   if (lsp[0]<m)
      lsp[0]=m;
   if (lsp[len-1]>m2)
      lsp[len-1]=m2;
   for (i=1;i<len-1;i++)
   {
      if (lsp[i]<lsp[i-1]+m)
         lsp[i]=lsp[i-1]+m;

      if (lsp[i]>lsp[i+1]-m)
         lsp[i]= SHR16(lsp[i],1) + SHR16(lsp[i+1]-m,1);
   }
}


void lsp_interpolate(spx_lsp_t *old_lsp, spx_lsp_t *new_lsp, spx_lsp_t *interp_lsp, int len, int subframe, int nb_subframes)
{
   int i;
   spx_word16_t tmp = DIV32_16(SHL32(EXTEND32(1 + subframe),14),nb_subframes);
   spx_word16_t tmp2 = 16384-tmp;
   for (i=0;i<len;i++)
   {
      interp_lsp[i] = MULT16_16_P14(tmp2,old_lsp[i]) + MULT16_16_P14(tmp,new_lsp[i]);
   }
}

#else

/*Makes sure the LSPs are stable*/
void lsp_enforce_margin(spx_lsp_t *lsp, int len, spx_word16_t margin)
{
   int i;
   if (lsp[0]<LSP_SCALING*margin)
      lsp[0]=LSP_SCALING*margin;
   if (lsp[len-1]>LSP_SCALING*(M_PI-margin))
      lsp[len-1]=LSP_SCALING*(M_PI-margin);
   for (i=1;i<len-1;i++)
   {
      if (lsp[i]<lsp[i-1]+LSP_SCALING*margin)
         lsp[i]=lsp[i-1]+LSP_SCALING*margin;

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


void lsp_interpolate(spx_lsp_t *old_lsp, spx_lsp_t *new_lsp, spx_lsp_t *interp_lsp, int len, int subframe, int nb_subframes)
{
   int i;
   float tmp = (1.0f + subframe)/nb_subframes;
   for (i=0;i<len;i++)
   {
      interp_lsp[i] = (1-tmp)*old_lsp[i] + tmp*new_lsp[i];
   }
}

#endif