mirror of
https://github.com/asterisk/asterisk.git
synced 2025-10-26 06:26:41 +00:00
2c65582b66
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7221 65c4cc65-6c06-0410-ace0-fbb531ad65f3
265 lines
7.2 KiB
C
265 lines
7.2 KiB
C
|
|
/******************************************************************
|
|
|
|
iLBC Speech Coder ANSI-C Source Code
|
|
|
|
lsf.c
|
|
|
|
Copyright (C) The Internet Society (2004).
|
|
All Rights Reserved.
|
|
|
|
******************************************************************/
|
|
|
|
#include <string.h>
|
|
#include <math.h>
|
|
|
|
#include "iLBC_define.h"
|
|
#include "lsf.h"
|
|
|
|
/*----------------------------------------------------------------*
|
|
* conversion from lpc coefficients to lsf coefficients
|
|
*---------------------------------------------------------------*/
|
|
|
|
void a2lsf(
|
|
float *freq,/* (o) lsf coefficients */
|
|
float *a /* (i) lpc coefficients */
|
|
){
|
|
float steps[LSF_NUMBER_OF_STEPS] =
|
|
{(float)0.00635, (float)0.003175, (float)0.0015875,
|
|
(float)0.00079375};
|
|
float step;
|
|
int step_idx;
|
|
int lsp_index;
|
|
float p[LPC_HALFORDER];
|
|
float q[LPC_HALFORDER];
|
|
float p_pre[LPC_HALFORDER];
|
|
|
|
|
|
float q_pre[LPC_HALFORDER];
|
|
float old_p, old_q, *old;
|
|
float *pq_coef;
|
|
float omega, old_omega;
|
|
int i;
|
|
float hlp, hlp1, hlp2, hlp3, hlp4, hlp5;
|
|
|
|
for (i=0; i<LPC_HALFORDER; i++) {
|
|
p[i] = (float)-1.0 * (a[i + 1] + a[LPC_FILTERORDER - i]);
|
|
q[i] = a[LPC_FILTERORDER - i] - a[i + 1];
|
|
}
|
|
|
|
p_pre[0] = (float)-1.0 - p[0];
|
|
p_pre[1] = - p_pre[0] - p[1];
|
|
p_pre[2] = - p_pre[1] - p[2];
|
|
p_pre[3] = - p_pre[2] - p[3];
|
|
p_pre[4] = - p_pre[3] - p[4];
|
|
p_pre[4] = p_pre[4] / 2;
|
|
|
|
q_pre[0] = (float)1.0 - q[0];
|
|
q_pre[1] = q_pre[0] - q[1];
|
|
q_pre[2] = q_pre[1] - q[2];
|
|
q_pre[3] = q_pre[2] - q[3];
|
|
q_pre[4] = q_pre[3] - q[4];
|
|
q_pre[4] = q_pre[4] / 2;
|
|
|
|
omega = 0.0;
|
|
old_omega = 0.0;
|
|
|
|
old_p = FLOAT_MAX;
|
|
old_q = FLOAT_MAX;
|
|
|
|
/* Here we loop through lsp_index to find all the
|
|
LPC_FILTERORDER roots for omega. */
|
|
|
|
for (lsp_index = 0; lsp_index<LPC_FILTERORDER; lsp_index++) {
|
|
|
|
/* Depending on lsp_index being even or odd, we
|
|
alternatively solve the roots for the two LSP equations. */
|
|
|
|
|
|
if ((lsp_index & 0x1) == 0) {
|
|
pq_coef = p_pre;
|
|
old = &old_p;
|
|
} else {
|
|
pq_coef = q_pre;
|
|
old = &old_q;
|
|
}
|
|
|
|
/* Start with low resolution grid */
|
|
|
|
for (step_idx = 0, step = steps[step_idx];
|
|
step_idx < LSF_NUMBER_OF_STEPS;){
|
|
|
|
|
|
|
|
/* cos(10piw) + pq(0)cos(8piw) + pq(1)cos(6piw) +
|
|
pq(2)cos(4piw) + pq(3)cod(2piw) + pq(4) */
|
|
|
|
hlp = (float)cos(omega * TWO_PI);
|
|
hlp1 = (float)2.0 * hlp + pq_coef[0];
|
|
hlp2 = (float)2.0 * hlp * hlp1 - (float)1.0 +
|
|
pq_coef[1];
|
|
hlp3 = (float)2.0 * hlp * hlp2 - hlp1 + pq_coef[2];
|
|
hlp4 = (float)2.0 * hlp * hlp3 - hlp2 + pq_coef[3];
|
|
hlp5 = hlp * hlp4 - hlp3 + pq_coef[4];
|
|
|
|
|
|
if (((hlp5 * (*old)) <= 0.0) || (omega >= 0.5)){
|
|
|
|
if (step_idx == (LSF_NUMBER_OF_STEPS - 1)){
|
|
|
|
if (fabs(hlp5) >= fabs(*old)) {
|
|
freq[lsp_index] = omega - step;
|
|
} else {
|
|
freq[lsp_index] = omega;
|
|
}
|
|
|
|
|
|
if ((*old) >= 0.0){
|
|
*old = (float)-1.0 * FLOAT_MAX;
|
|
} else {
|
|
*old = FLOAT_MAX;
|
|
}
|
|
|
|
omega = old_omega;
|
|
step_idx = 0;
|
|
|
|
step_idx = LSF_NUMBER_OF_STEPS;
|
|
} else {
|
|
|
|
if (step_idx == 0) {
|
|
old_omega = omega;
|
|
}
|
|
|
|
step_idx++;
|
|
omega -= steps[step_idx];
|
|
|
|
/* Go back one grid step */
|
|
|
|
step = steps[step_idx];
|
|
}
|
|
} else {
|
|
|
|
/* increment omega until they are of different sign,
|
|
and we know there is at least one root between omega
|
|
and old_omega */
|
|
*old = hlp5;
|
|
omega += step;
|
|
}
|
|
|
|
|
|
}
|
|
}
|
|
|
|
for (i = 0; i<LPC_FILTERORDER; i++) {
|
|
freq[i] = freq[i] * TWO_PI;
|
|
}
|
|
}
|
|
|
|
/*----------------------------------------------------------------*
|
|
* conversion from lsf coefficients to lpc coefficients
|
|
*---------------------------------------------------------------*/
|
|
|
|
void lsf2a(
|
|
float *a_coef, /* (o) lpc coefficients */
|
|
float *freq /* (i) lsf coefficients */
|
|
){
|
|
int i, j;
|
|
float hlp;
|
|
float p[LPC_HALFORDER], q[LPC_HALFORDER];
|
|
float a[LPC_HALFORDER + 1], a1[LPC_HALFORDER],
|
|
a2[LPC_HALFORDER];
|
|
float b[LPC_HALFORDER + 1], b1[LPC_HALFORDER],
|
|
b2[LPC_HALFORDER];
|
|
|
|
for (i=0; i<LPC_FILTERORDER; i++) {
|
|
freq[i] = freq[i] * PI2;
|
|
}
|
|
|
|
/* Check input for ill-conditioned cases. This part is not
|
|
found in the TIA standard. It involves the following 2 IF
|
|
blocks. If "freq" is judged ill-conditioned, then we first
|
|
modify freq[0] and freq[LPC_HALFORDER-1] (normally
|
|
LPC_HALFORDER = 10 for LPC applications), then we adjust
|
|
the other "freq" values slightly */
|
|
|
|
|
|
if ((freq[0] <= 0.0) || (freq[LPC_FILTERORDER - 1] >= 0.5)){
|
|
|
|
|
|
if (freq[0] <= 0.0) {
|
|
freq[0] = (float)0.022;
|
|
}
|
|
|
|
|
|
if (freq[LPC_FILTERORDER - 1] >= 0.5) {
|
|
freq[LPC_FILTERORDER - 1] = (float)0.499;
|
|
}
|
|
|
|
hlp = (freq[LPC_FILTERORDER - 1] - freq[0]) /
|
|
(float) (LPC_FILTERORDER - 1);
|
|
|
|
for (i=1; i<LPC_FILTERORDER; i++) {
|
|
freq[i] = freq[i - 1] + hlp;
|
|
}
|
|
|
|
|
|
}
|
|
|
|
memset(a1, 0, LPC_HALFORDER*sizeof(float));
|
|
memset(a2, 0, LPC_HALFORDER*sizeof(float));
|
|
memset(b1, 0, LPC_HALFORDER*sizeof(float));
|
|
memset(b2, 0, LPC_HALFORDER*sizeof(float));
|
|
memset(a, 0, (LPC_HALFORDER+1)*sizeof(float));
|
|
memset(b, 0, (LPC_HALFORDER+1)*sizeof(float));
|
|
|
|
/* p[i] and q[i] compute cos(2*pi*omega_{2j}) and
|
|
cos(2*pi*omega_{2j-1} in eqs. 4.2.2.2-1 and 4.2.2.2-2.
|
|
Note that for this code p[i] specifies the coefficients
|
|
used in .Q_A(z) while q[i] specifies the coefficients used
|
|
in .P_A(z) */
|
|
|
|
for (i=0; i<LPC_HALFORDER; i++) {
|
|
p[i] = (float)cos(TWO_PI * freq[2 * i]);
|
|
q[i] = (float)cos(TWO_PI * freq[2 * i + 1]);
|
|
}
|
|
|
|
a[0] = 0.25;
|
|
b[0] = 0.25;
|
|
|
|
for (i= 0; i<LPC_HALFORDER; i++) {
|
|
a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i];
|
|
b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i];
|
|
a2[i] = a1[i];
|
|
a1[i] = a[i];
|
|
b2[i] = b1[i];
|
|
b1[i] = b[i];
|
|
}
|
|
|
|
for (j=0; j<LPC_FILTERORDER; j++) {
|
|
|
|
if (j == 0) {
|
|
a[0] = 0.25;
|
|
b[0] = -0.25;
|
|
} else {
|
|
a[0] = b[0] = 0.0;
|
|
}
|
|
|
|
for (i=0; i<LPC_HALFORDER; i++) {
|
|
a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i];
|
|
b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i];
|
|
a2[i] = a1[i];
|
|
a1[i] = a[i];
|
|
b2[i] = b1[i];
|
|
b1[i] = b[i];
|
|
}
|
|
|
|
a_coef[j + 1] = 2 * (a[LPC_HALFORDER] + b[LPC_HALFORDER]);
|
|
}
|
|
|
|
a_coef[0] = 1.0;
|
|
|
|
|
|
}
|
|
|
|
|