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diff --git a/trunk/codecs/ilbc/lsf.c b/trunk/codecs/ilbc/lsf.c
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+
+/******************************************************************
+
+ 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;
+
+
+}
+
+
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