www.pudn.com > 200411301125332697.rar > calcexc.c
/*
ITU-T G.729 Annex B ANSI-C Source Code
Version 1.3 Last modified: August 1997
Copyright (c) 1996, France Telecom, Rockwell International,
Universite de Sherbrooke.
All rights reserved.
*/
/* Computation of Comfort Noise excitation */
#include
#include
#include "typedef.h"
#include "ld8k.h"
#include "dtx.h"
#include "basic_op.h"
#include "oper_32b.h"
/* Local functions */
static Word16 Gauss(Word16 *seed);
static Word16 Sqrt( Word32 Num);
/*-----------------------------------------------------------*
* procedure Calc_exc_rand *
* ~~~~~~~~~~~~~ *
* Computes comfort noise excitation *
* for SID and not-transmitted frames *
*-----------------------------------------------------------*/
void Calc_exc_rand(
Word16 cur_gain, /* (i) : target sample gain */
Word16 *exc, /* (i/o) : excitation array */
Word16 *seed, /* (i) : current Vad decision */
Flag flag_cod /* (i) : encoder/decoder flag */
)
{
Word16 i, j, i_subfr;
Word16 temp1, temp2;
Word16 pos[4];
Word16 sign[4];
Word16 t0, frac;
Word16 *cur_exc;
Word16 g, Gp, Gp2;
Word16 excg[L_SUBFR], excs[L_SUBFR];
Word32 L_acc, L_ener, L_k;
Word16 max, hi, lo, inter_exc;
Word16 sh;
Word16 x1, x2;
if(cur_gain == 0) {
for(i=0; i39) excg[i]^2
and alpha = 0.5
alpha x sqrt(L_SUBFR)/2 = 1 + FRAC1
*/
L_acc = Inv_sqrt(L_shr(L_acc,1)); /* Q30 */
L_Extract(L_acc, &hi, &lo);
/* cur_gain = cur_gainR << 3 */
temp1 = mult_r(cur_gain, FRAC1);
temp1 = add(cur_gain, temp1);
/* <=> alpha x cur_gainR x 2^2 x sqrt(L_SUBFR) */
L_acc = Mpy_32_16(hi, lo, temp1); /* fact << 17 */
sh = norm_l(L_acc);
temp1 = extract_h(L_shl(L_acc, sh)); /* fact << (sh+1) */
sh = sub(sh, 14);
for(i=0; i cur_exc */
/**********************************************/
max = 0;
for(i=0; i 0) max = temp1;
}
/* rescale cur_exc -> excs */
if(max == 0) sh = 0;
else {
sh = sub(3, norm_s(max));
if(sh <= 0) sh = 0;
}
for(i=0; i> sh */
inter_exc = 0;
for(i=0; i<4; i++) {
j = pos[i];
if(sign[i] == 0) {
inter_exc = sub(inter_exc, excs[j]);
}
else {
inter_exc = add(inter_exc, excs[j]);
}
}
/* Compute k = cur_gainR x cur_gainR x L_SUBFR */
L_acc = L_mult(cur_gain, L_SUBFR);
L_acc = L_shr(L_acc, 6);
temp1 = extract_l(L_acc); /* cur_gainR x L_SUBFR x 2^(-2) */
L_k = L_mult(cur_gain, temp1); /* k << 2 */
temp1 = add(1, shl(sh,1));
L_acc = L_shr(L_k, temp1); /* k x 2^(-2sh+1) */
/* Compute delta = b^2 - 4 c */
L_acc = L_sub(L_acc, L_ener); /* - 4 c x 2^(-2sh-1) */
inter_exc = shr(inter_exc, 1);
L_acc = L_mac(L_acc, inter_exc, inter_exc); /* 2^(-2sh-1) */
sh = add(sh, 1);
/* inter_exc = b x 2^(-sh) */
/* L_acc = delta x 2^(-2sh+1) */
if(L_acc < 0) {
/* adaptive excitation = 0 */
Copy(excg, cur_exc, L_SUBFR);
temp1 = abs_s(excg[(int)pos[0]]) | abs_s(excg[(int)pos[1]]);
temp2 = abs_s(excg[(int)pos[2]]) | abs_s(excg[(int)pos[3]]);
temp1 = temp1 | temp2;
sh = ((temp1 & (Word16)0x4000) == 0) ? (Word16)1 : (Word16)2;
inter_exc = 0;
for(i=0; i<4; i++) {
temp1 = shr(excg[(int)pos[i]], sh);
if(sign[i] == 0) {
inter_exc = sub(inter_exc, temp1);
}
else {
inter_exc = add(inter_exc, temp1);
}
} /* inter_exc = b >> sh */
L_Extract(L_k, &hi, &lo);
L_acc = Mpy_32_16(hi, lo, K0); /* k x (1- alpha^2) << 2 */
temp1 = sub(shl(sh, 1), 1); /* temp1 > 0 */
L_acc = L_shr(L_acc, temp1); /* 4k x (1 - alpha^2) << (-2sh+1) */
L_acc = L_mac(L_acc, inter_exc, inter_exc); /* delta << (-2sh+1) */
Gp = 0;
}
temp2 = Sqrt(L_acc); /* >> sh */
x1 = sub(temp2, inter_exc);
x2 = negate(add(inter_exc, temp2)); /* x 2^(-sh+2) */
if(sub(abs_s(x2),abs_s(x1)) < 0) x1 = x2;
temp1 = sub(2, sh);
g = shr_r(x1, temp1); /* shl if temp1 < 0 */
if(g >= 0) {
if(sub(g, G_MAX) > 0) g = G_MAX;
}
else {
if(add(g, G_MAX) < 0) g = negate(G_MAX);
}
/* Update cur_exc with ACELP excitation */
for(i=0; i<4; i++) {
j = pos[i];
if(sign[i] != 0) {
cur_exc[j] = add(cur_exc[j], g);
}
else {
cur_exc[j] = sub(cur_exc[j], g);
}
}
if(flag_cod != FLAG_DEC) update_exc_err(Gp, t0);
cur_exc += L_SUBFR;
} /* end of loop on subframes */
return;
}
/*-----------------------------------------------------------*
* Local procedures *
* ~~~~~~~~~~~~~~~~ *
*-----------------------------------------------------------*/
/* Gaussian generation */
/***********************/
static Word16 Gauss(Word16 *seed)
{
/**** Xi = uniform v.a. in [-32768, 32767] ****/
/**** Z = SUM(i=1->12) Xi / 2 x 32768 is N(0,1) ****/
/**** output : Z x 512 < 2^12 ****/
Word16 i;
Word16 temp;
Word32 L_acc;
L_acc = 0L;
for(i=0; i<12; i++) {
L_acc = L_add(L_acc, L_deposit_l(Random(seed)));
}
L_acc = L_shr(L_acc, 7);
temp = extract_l(L_acc);
return(temp);
}
/* Square root function : returns sqrt(Num/2) */
/**********************************************/
static Word16 Sqrt( Word32 Num )
{
Word16 i ;
Word16 Rez = (Word16) 0 ;
Word16 Exp = (Word16) 0x4000 ;
Word32 Acc, L_temp;
for ( i = 0 ; i < 14 ; i ++ ) {
Acc = L_mult(add(Rez, Exp), add(Rez, Exp) );
L_temp = L_sub(Num, Acc);
if(L_temp >= 0L) Rez = add( Rez, Exp);
Exp = shr( Exp, (Word16) 1 ) ;
}
return Rez ;
}