static inline spx_word32_t cheb_poly_eva(
spx_word16_t *coef, /* P or Q coefs in Q13 format */
spx_word16_t x, /* cos of freq (-1.0 to 1.0) in Q14 format */
int m, /* LPC order/2 */
char *stack
)
{
int i;
spx_word16_t b0, b1;
spx_word32_t sum;
/*Prevents overflows*/
if (x>16383)
x = 16383;
if (x<-16383)
x = -16383;
/* Initialise values */
b1=16384;
b0=x;
/* Evaluate Chebyshev series formulation usin g iterative approach */
sum = ADD32(EXTEND32(coef[m]), EXTEND32(MULT16_16_P14(coef[m-1],x)));
for(i=2;i<=m;i++)
{
spx_word16_t tmp=b0;
b0 = SUB16(MULT16_16_Q13(x,b0), b1);
b1 = tmp;
sum = ADD32(sum, EXTEND32(MULT16_16_P14(coef[m-i],b0)));
}
return sum;
}
/* returns minimum mean square error */
spx_word32_t _spx_lpc(
spx_coef_t *lpc, /* out: [0...p-1] LPC coefficients */
const spx_word16_t *ac, /* in: [0...p] autocorrelation values */
int p
)
{
int i, j;
spx_word16_t r;
spx_word16_t error = ac[0];
if (ac[0] == 0)
{
for (i = 0; i < p; i++)
lpc[i] = 0;
return 0;
}
for (i = 0; i < p; i++) {
/* Sum up this iteration's reflection coefficient */
spx_word32_t rr = NEG32(SHL32(EXTEND32(ac[i + 1]),13));
for (j = 0; j < i; j++)
rr = SUB32(rr,MULT16_16(lpc[j],ac[i - j]));
#ifdef FIXED_POINT
r = DIV32_16(rr+PSHR32(error,1),ADD16(error,8));
#else
r = rr/(error+.003*ac[0]);
#endif
/* Update LPC coefficients and total error */
lpc[i] = r;
for (j = 0; j < i>>1; j++)
{
spx_word16_t tmp = lpc[j];
lpc[j] = MAC16_16_P13(lpc[j],r,lpc[i-1-j]);
lpc[i-1-j] = MAC16_16_P13(lpc[i-1-j],r,tmp);
}
if (i & 1)
lpc[j] = MAC16_16_P13(lpc[j],lpc[j],r);
error = SUB16(error,MULT16_16_Q13(r,MULT16_16_Q13(error,r)));
}
return error;
}
static inline spx_word32_t cheb_poly_eva(spx_word32_t *coef,spx_word16_t x,int m,char *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;
spx_word16_t *T;
spx_word32_t sum;
int m2=m>>1;
spx_word16_t *coefn;
/*Prevents overflows*/
if (x>16383)
x = 16383;
if (x<-16383)
x = -16383;
/* Allocate memory for Chebyshev series formulation */
T=PUSH(stack, m2+1, spx_word16_t);
coefn=PUSH(stack, m2+1, spx_word16_t);
for (i=0;i<m2+1;i++)
{
coefn[i] = coef[i];
/*printf ("%f ", coef[i]);*/
}
/*printf ("\n");*/
/* Initialise values */
T[0]=16384;
T[1]=x;
/* Evaluate Chebyshev series formulation using iterative approach */
/* Evaluate polynomial and return value also free memory space */
sum = ADD32(coefn[m2], MULT16_16_P14(coefn[m2-1],x));
/*x *= 2;*/
for(i=2;i<=m2;i++)
{
T[i] = MULT16_16_Q13(x,T[i-1]) - T[i-2];
sum = ADD32(sum, MULT16_16_P14(coefn[m2-i],T[i]));
/*printf ("%f ", sum);*/
}
/*printf ("\n");*/
return sum;
}
