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+
+/******************************************************************
+
+ iLBC Speech Coder ANSI-C Source Code
+
+ helpfun.c
+
+ Copyright (C) The Internet Society (2004).
+ All Rights Reserved.
+
+******************************************************************/
+
+#include <math.h>
+
+#include "iLBC_define.h"
+#include "helpfun.h"
+#include "constants.h"
+
+/*----------------------------------------------------------------*
+ * calculation of auto correlation
+ *---------------------------------------------------------------*/
+
+void autocorr(
+ float *r, /* (o) autocorrelation vector */
+ const float *x, /* (i) data vector */
+ int N, /* (i) length of data vector */
+ int order /* largest lag for calculated
+ autocorrelations */
+){
+ int lag, n;
+ float sum;
+
+ for (lag = 0; lag <= order; lag++) {
+ sum = 0;
+ for (n = 0; n < N - lag; n++) {
+ sum += x[n] * x[n+lag];
+ }
+ r[lag] = sum;
+ }
+}
+
+
+
+/*----------------------------------------------------------------*
+ * window multiplication
+ *---------------------------------------------------------------*/
+
+void window(
+ float *z, /* (o) the windowed data */
+ const float *x, /* (i) the original data vector */
+ const float *y, /* (i) the window */
+ int N /* (i) length of all vectors */
+){
+ int i;
+
+ for (i = 0; i < N; i++) {
+ z[i] = x[i] * y[i];
+ }
+}
+
+/*----------------------------------------------------------------*
+ * levinson-durbin solution for lpc coefficients
+ *---------------------------------------------------------------*/
+
+void levdurb(
+ float *a, /* (o) lpc coefficient vector starting
+ with 1.0 */
+ float *k, /* (o) reflection coefficients */
+ float *r, /* (i) autocorrelation vector */
+ int order /* (i) order of lpc filter */
+){
+ float sum, alpha;
+ int m, m_h, i;
+
+ a[0] = 1.0;
+
+ if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */
+ for (i = 0; i < order; i++) {
+ k[i] = 0;
+ a[i+1] = 0;
+ }
+ } else {
+ a[1] = k[0] = -r[1]/r[0];
+ alpha = r[0] + r[1] * k[0];
+ for (m = 1; m < order; m++){
+ sum = r[m + 1];
+ for (i = 0; i < m; i++){
+ sum += a[i+1] * r[m - i];
+ }
+ k[m] = -sum / alpha;
+ alpha += k[m] * sum;
+ m_h = (m + 1) >> 1;
+ for (i = 0; i < m_h; i++){
+ sum = a[i+1] + k[m] * a[m - i];
+ a[m - i] += k[m] * a[i+1];
+ a[i+1] = sum;
+
+
+ }
+ a[m+1] = k[m];
+ }
+ }
+}
+
+/*----------------------------------------------------------------*
+ * interpolation between vectors
+ *---------------------------------------------------------------*/
+
+void interpolate(
+ float *out, /* (o) the interpolated vector */
+ float *in1, /* (i) the first vector for the
+ interpolation */
+ float *in2, /* (i) the second vector for the
+ interpolation */
+ float coef, /* (i) interpolation weights */
+ int length /* (i) length of all vectors */
+){
+ int i;
+ float invcoef;
+
+ invcoef = (float)1.0 - coef;
+ for (i = 0; i < length; i++) {
+ out[i] = coef * in1[i] + invcoef * in2[i];
+ }
+}
+
+/*----------------------------------------------------------------*
+ * lpc bandwidth expansion
+ *---------------------------------------------------------------*/
+
+void bwexpand(
+ float *out, /* (o) the bandwidth expanded lpc
+ coefficients */
+ float *in, /* (i) the lpc coefficients before bandwidth
+ expansion */
+ float coef, /* (i) the bandwidth expansion factor */
+ int length /* (i) the length of lpc coefficient vectors */
+){
+ int i;
+ float chirp;
+
+ chirp = coef;
+
+ out[0] = in[0];
+ for (i = 1; i < length; i++) {
+ out[i] = chirp * in[i];
+ chirp *= coef;
+ }
+}
+
+/*----------------------------------------------------------------*
+ * vector quantization
+
+
+ *---------------------------------------------------------------*/
+
+void vq(
+ float *Xq, /* (o) the quantized vector */
+ int *index, /* (o) the quantization index */
+ const float *CB,/* (i) the vector quantization codebook */
+ float *X, /* (i) the vector to quantize */
+ int n_cb, /* (i) the number of vectors in the codebook */
+ int dim /* (i) the dimension of all vectors */
+){
+ int i, j;
+ int pos, minindex;
+ float dist, tmp, mindist;
+
+ pos = 0;
+ mindist = FLOAT_MAX;
+ minindex = 0;
+ for (j = 0; j < n_cb; j++) {
+ dist = X[0] - CB[pos];
+ dist *= dist;
+ for (i = 1; i < dim; i++) {
+ tmp = X[i] - CB[pos + i];
+ dist += tmp*tmp;
+ }
+
+ if (dist < mindist) {
+ mindist = dist;
+ minindex = j;
+ }
+ pos += dim;
+ }
+ for (i = 0; i < dim; i++) {
+ Xq[i] = CB[minindex*dim + i];
+ }
+ *index = minindex;
+}
+
+/*----------------------------------------------------------------*
+ * split vector quantization
+ *---------------------------------------------------------------*/
+
+void SplitVQ(
+ float *qX, /* (o) the quantized vector */
+ int *index, /* (o) a vector of indexes for all vector
+ codebooks in the split */
+ float *X, /* (i) the vector to quantize */
+ const float *CB,/* (i) the quantizer codebook */
+ int nsplit, /* the number of vector splits */
+ const int *dim, /* the dimension of X and qX */
+ const int *cbsize /* the number of vectors in the codebook */
+){
+ int cb_pos, X_pos, i;
+
+ cb_pos = 0;
+
+
+ X_pos= 0;
+ for (i = 0; i < nsplit; i++) {
+ vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos,
+ cbsize[i], dim[i]);
+ X_pos += dim[i];
+ cb_pos += dim[i] * cbsize[i];
+ }
+}
+
+/*----------------------------------------------------------------*
+ * scalar quantization
+ *---------------------------------------------------------------*/
+
+void sort_sq(
+ float *xq, /* (o) the quantized value */
+ int *index, /* (o) the quantization index */
+ float x, /* (i) the value to quantize */
+ const float *cb,/* (i) the quantization codebook */
+ int cb_size /* (i) the size of the quantization codebook */
+){
+ int i;
+
+ if (x <= cb[0]) {
+ *index = 0;
+ *xq = cb[0];
+ } else {
+ i = 0;
+ while ((x > cb[i]) && i < cb_size - 1) {
+ i++;
+ }
+
+ if (x > ((cb[i] + cb[i - 1])/2)) {
+ *index = i;
+ *xq = cb[i];
+ } else {
+ *index = i - 1;
+ *xq = cb[i - 1];
+ }
+ }
+}
+
+/*----------------------------------------------------------------*
+ * check for stability of lsf coefficients
+ *---------------------------------------------------------------*/
+
+int LSF_check( /* (o) 1 for stable lsf vectors and 0 for
+ nonstable ones */
+ float *lsf, /* (i) a table of lsf vectors */
+ int dim, /* (i) the dimension of each lsf vector */
+ int NoAn /* (i) the number of lsf vectors in the
+ table */
+){
+ int k,n,m, Nit=2, change=0,pos;
+ float tmp;
+
+
+ static float eps=(float)0.039; /* 50 Hz */
+ static float eps2=(float)0.0195;
+ static float maxlsf=(float)3.14; /* 4000 Hz */
+ static float minlsf=(float)0.01; /* 0 Hz */
+
+ /* LSF separation check*/
+
+ for (n=0; n<Nit; n++) { /* Run through a couple of times */
+ for (m=0; m<NoAn; m++) { /* Number of analyses per frame */
+ for (k=0; k<(dim-1); k++) {
+ pos=m*dim+k;
+
+ if ((lsf[pos+1]-lsf[pos])<eps) {
+
+ if (lsf[pos+1]<lsf[pos]) {
+ tmp=lsf[pos+1];
+ lsf[pos+1]= lsf[pos]+eps2;
+ lsf[pos]= lsf[pos+1]-eps2;
+ } else {
+ lsf[pos]-=eps2;
+ lsf[pos+1]+=eps2;
+ }
+ change=1;
+ }
+
+ if (lsf[pos]<minlsf) {
+ lsf[pos]=minlsf;
+ change=1;
+ }
+
+ if (lsf[pos]>maxlsf) {
+ lsf[pos]=maxlsf;
+ change=1;
+ }
+ }
+ }
+ }
+
+ return change;
+}
+
+