www.pudn.com > 200411301125332697.rar > lpc.c
/*
ITU-T G.729 Speech Coder with Annex B ANSI-C Source Code
Version 1.3 Last modified: August 1997
Copyright (c) 1996,
AT&T, France Telecom, NTT, Universite de Sherbrooke, Lucent Technologies,
Rockwell International
All rights reserved.
*/
/*-----------------------------------------------------*
* Function Autocorr() *
* *
* Compute autocorrelations of signal with windowing *
* *
*-----------------------------------------------------*/
#include "typedef.h"
#include "basic_op.h"
#include "oper_32b.h"
#include "ld8k.h"
#include "tab_ld8k.h"
void Autocorr(
Word16 x[], /* (i) : Input signal */
Word16 m, /* (i) : LPC order */
Word16 r_h[], /* (o) : Autocorrelations (msb) */
Word16 r_l[], /* (o) : Autocorrelations (lsb) */
Word16 *exp_R0
)
{
Word16 i, j, norm;
Word16 y[L_WINDOW];
Word32 sum;
extern Flag Overflow;
/* Windowing of signal */
for(i=0; i mantissa in Q31 plus exponent |
| A[i] Q27 +- 15.999.. |
| |
| The additions are performed in 32 bit. For the summation used |
| to calculate the K[i], we multiply numbers in Q31 by numbers |
| in Q27, with the result of the multiplications in Q27, |
| resulting in a dynamic of +- 16. This is sufficient to avoid |
| overflow, since the final result of the summation is |
| necessarily < 1.0 as both the K[i] and Alpha are |
| theoretically < 1.0. |
|___________________________________________________________________________|
*/
/* Last A(z) for case of unstable filter */
static Word16 old_A[M+1]={4096,0,0,0,0,0,0,0,0,0,0};
static Word16 old_rc[2]={0,0};
void Levinson(
Word16 Rh[], /* (i) : Rh[M+1] Vector of autocorrelations (msb) */
Word16 Rl[], /* (i) : Rl[M+1] Vector of autocorrelations (lsb) */
Word16 A[], /* (o) Q12 : A[M] LPC coefficients (m = 10) */
Word16 rc[], /* (o) Q15 : rc[M] Reflection coefficients. */
Word16 *Err /* (o) : Residual energy */
)
{
Word16 i, j;
Word16 hi, lo;
Word16 Kh, Kl; /* reflection coefficient; hi and lo */
Word16 alp_h, alp_l, alp_exp; /* Prediction gain; hi lo and exponent */
Word16 Ah[M+1], Al[M+1]; /* LPC coef. in double prec. */
Word16 Anh[M+1], Anl[M+1]; /* LPC coef.for next iteration in double prec. */
Word32 t0, t1, t2; /* temporary variable */
/* K = A[1] = -R[1] / R[0] */
t1 = L_Comp(Rh[1], Rl[1]); /* R[1] in Q31 */
t2 = L_abs(t1); /* abs R[1] */
t0 = Div_32(t2, Rh[0], Rl[0]); /* R[1]/R[0] in Q31 */
if(t1 > 0) t0= L_negate(t0); /* -R[1]/R[0] */
L_Extract(t0, &Kh, &Kl); /* K in DPF */
rc[0] = Kh;
t0 = L_shr(t0,4); /* A[1] in Q27 */
L_Extract(t0, &Ah[1], &Al[1]); /* A[1] in DPF */
/* Alpha = R[0] * (1-K**2) */
t0 = Mpy_32(Kh ,Kl, Kh, Kl); /* K*K in Q31 */
t0 = L_abs(t0); /* Some case <0 !! */
t0 = L_sub( (Word32)0x7fffffffL, t0 ); /* 1 - K*K in Q31 */
L_Extract(t0, &hi, &lo); /* DPF format */
t0 = Mpy_32(Rh[0] ,Rl[0], hi, lo); /* Alpha in Q31 */
/* Normalize Alpha */
alp_exp = norm_l(t0);
t0 = L_shl(t0, alp_exp);
L_Extract(t0, &alp_h, &alp_l); /* DPF format */
/*--------------------------------------*
* ITERATIONS I=2 to M *
*--------------------------------------*/
for(i= 2; i<=M; i++)
{
/* t0 = SUM ( R[j]*A[i-j] ,j=1,i-1 ) + R[i] */
t0 = 0;
for(j=1; j convert to Q31 */
/* No overflow possible */
t1 = L_Comp(Rh[i],Rl[i]);
t0 = L_add(t0, t1); /* add R[i] in Q31 */
/* K = -t0 / Alpha */
t1 = L_abs(t0);
t2 = Div_32(t1, alp_h, alp_l); /* abs(t0)/Alpha */
if(t0 > 0) t2= L_negate(t2); /* K =-t0/Alpha */
t2 = L_shl(t2, alp_exp); /* denormalize; compare to Alpha */
L_Extract(t2, &Kh, &Kl); /* K in DPF */
rc[i-1] = Kh;
/* Test for unstable filter. If unstable keep old A(z) */
if (sub(abs_s(Kh), 32750) > 0)
{
for(j=0; j<=M; j++)
{
A[j] = old_A[j];
}
rc[0] = old_rc[0]; /* only two rc coefficients are needed */
rc[1] = old_rc[1];
return;
}
/*------------------------------------------*
* Compute new LPC coeff. -> An[i] *
* An[j]= A[j] + K*A[i-j] , j=1 to i-1 *
* An[i]= K *
*------------------------------------------*/
for(j=1; jconvert to Q27 */
L_Extract(t2, &Anh[i], &Anl[i]); /* An[i] in Q27 */
/* Alpha = Alpha * (1-K**2) */
t0 = Mpy_32(Kh ,Kl, Kh, Kl); /* K*K in Q31 */
t0 = L_abs(t0); /* Some case <0 !! */
t0 = L_sub( (Word32)0x7fffffffL, t0 ); /* 1 - K*K in Q31 */
L_Extract(t0, &hi, &lo); /* DPF format */
t0 = Mpy_32(alp_h , alp_l, hi, lo); /* Alpha in Q31 */
/* Normalize Alpha */
j = norm_l(t0);
t0 = L_shl(t0, j);
L_Extract(t0, &alp_h, &alp_l); /* DPF format */
alp_exp = add(alp_exp, j); /* Add normalization to alp_exp */
/* A[j] = An[j] */
for(j=1; j<=i; j++)
{
Ah[j] =Anh[j];
Al[j] =Anl[j];
}
}
*Err = shr(alp_h, alp_exp);
/* Truncate A[i] in Q27 to Q12 with rounding */
A[0] = 4096;
for(i=1; i<=M; i++)
{
t0 = L_Comp(Ah[i], Al[i]);
old_A[i] = A[i] = round(L_shl(t0, 1));
}
old_rc[0] = rc[0];
old_rc[1] = rc[1];
return;
}
/*-------------------------------------------------------------*
* procedure Az_lsp: *
* ~~~~~~ *
* Compute the LSPs from the LPC coefficients (order=10) *
*-------------------------------------------------------------*/
/* local function */
static Word16 Chebps_11(Word16 x, Word16 f[], Word16 n);
static Word16 Chebps_10(Word16 x, Word16 f[], Word16 n);
void Az_lsp(
Word16 a[], /* (i) Q12 : predictor coefficients */
Word16 lsp[], /* (o) Q15 : line spectral pairs */
Word16 old_lsp[] /* (i) : old lsp[] (in case not found 10 roots) */
)
{
Word16 i, j, nf, ip;
Word16 xlow, ylow, xhigh, yhigh, xmid, ymid, xint;
Word16 x, y, sign, exp;
Word16 *coef;
Word16 f1[M/2+1], f2[M/2+1];
Word32 t0, L_temp;
Flag ovf_coef;
Word16 (*pChebps)(Word16 x, Word16 f[], Word16 n);
/*-------------------------------------------------------------*
* find the sum and diff. pol. F1(z) and F2(z) *
* F1(z) <--- F1(z)/(1+z**-1) & F2(z) <--- F2(z)/(1-z**-1) *
* *
* f1[0] = 1.0; *
* f2[0] = 1.0; *
* *
* for (i = 0; i< NC; i++) *
* { *
* f1[i+1] = a[i+1] + a[M-i] - f1[i] ; *
* f2[i+1] = a[i+1] - a[M-i] + f2[i] ; *
* } *
*-------------------------------------------------------------*/
ovf_coef = 0;
pChebps = Chebps_11;
f1[0] = 2048; /* f1[0] = 1.0 is in Q11 */
f2[0] = 2048; /* f2[0] = 1.0 is in Q11 */
for (i = 0; i< NC; i++)
{
Overflow = 0;
t0 = L_mult(a[i+1], 16384); /* x = (a[i+1] + a[M-i]) >> 1 */
t0 = L_mac(t0, a[M-i], 16384); /* -> From Q12 to Q11 */
x = extract_h(t0);
if ( Overflow ) {
ovf_coef = 1; }
Overflow = 0;
f1[i+1] = sub(x, f1[i]); /* f1[i+1] = a[i+1] + a[M-i] - f1[i] */
if ( Overflow ) {
ovf_coef = 1; }
Overflow = 0;
t0 = L_mult(a[i+1], 16384); /* x = (a[i+1] - a[M-i]) >> 1 */
t0 = L_msu(t0, a[M-i], 16384); /* -> From Q12 to Q11 */
x = extract_h(t0);
if ( Overflow ) {
ovf_coef = 1; }
Overflow = 0;
f2[i+1] = add(x, f2[i]); /* f2[i+1] = a[i+1] - a[M-i] + f2[i] */
if ( Overflow ) {
ovf_coef = 1; }
}
if ( ovf_coef ) {
/*printf("===== OVF ovf_coef =====\n");*/
pChebps = Chebps_10;
f1[0] = 1024; /* f1[0] = 1.0 is in Q10 */
f2[0] = 1024; /* f2[0] = 1.0 is in Q10 */
for (i = 0; i< NC; i++)
{
t0 = L_mult(a[i+1], 8192); /* x = (a[i+1] + a[M-i]) >> 1 */
t0 = L_mac(t0, a[M-i], 8192); /* -> From Q11 to Q10 */
x = extract_h(t0);
f1[i+1] = sub(x, f1[i]); /* f1[i+1] = a[i+1] + a[M-i] - f1[i] */
t0 = L_mult(a[i+1], 8192); /* x = (a[i+1] - a[M-i]) >> 1 */
t0 = L_msu(t0, a[M-i], 8192); /* -> From Q11 to Q10 */
x = extract_h(t0);
f2[i+1] = add(x, f2[i]); /* f2[i+1] = a[i+1] - a[M-i] + f2[i] */
}
}
/*-------------------------------------------------------------*
* find the LSPs using the Chebichev pol. evaluation *
*-------------------------------------------------------------*/
nf=0; /* number of found frequencies */
ip=0; /* indicator for f1 or f2 */
coef = f1;
xlow = grid[0];
ylow = (*pChebps)(xlow, coef, NC);
j = 0;
while ( (nf < M) && (j < GRID_POINTS) )
{
j =add(j,1);
xhigh = xlow;
yhigh = ylow;
xlow = grid[j];
ylow = (*pChebps)(xlow,coef,NC);
L_temp = L_mult(ylow ,yhigh);
if ( L_temp <= (Word32)0)
{
/* divide 4 times the interval */
for (i = 0; i < 4; i++)
{
xmid = add( shr(xlow, 1) , shr(xhigh, 1)); /* xmid = (xlow + xhigh)/2 */
ymid = (*pChebps)(xmid,coef,NC);
L_temp = L_mult(ylow,ymid);
if ( L_temp <= (Word32)0)
{
yhigh = ymid;
xhigh = xmid;
}
else
{
ylow = ymid;
xlow = xmid;
}
}
/*-------------------------------------------------------------*
* Linear interpolation *
* xint = xlow - ylow*(xhigh-xlow)/(yhigh-ylow); *
*-------------------------------------------------------------*/
x = sub(xhigh, xlow);
y = sub(yhigh, ylow);
if(y == 0)
{
xint = xlow;
}
else
{
sign= y;
y = abs_s(y);
exp = norm_s(y);
y = shl(y, exp);
y = div_s( (Word16)16383, y);
t0 = L_mult(x, y);
t0 = L_shr(t0, sub(20, exp) );
y = extract_l(t0); /* y= (xhigh-xlow)/(yhigh-ylow) in Q11 */
if(sign < 0) y = negate(y);
t0 = L_mult(ylow, y); /* result in Q26 */
t0 = L_shr(t0, 11); /* result in Q15 */
xint = sub(xlow, extract_l(t0)); /* xint = xlow - ylow*y */
}
lsp[nf] = xint;
xlow = xint;
nf =add(nf,1);
if(ip == 0)
{
ip = 1;
coef = f2;
}
else
{
ip = 0;
coef = f1;
}
ylow = (*pChebps)(xlow,coef,NC);
}
}
/* Check if M roots found */
if( sub(nf, M) < 0)
{
for(i=0; i