--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/intercom/ilbc/helpfun.c	Fri Jun 25 09:57:52 2010 +0200
@@ -0,0 +1,326 @@
+
+   /******************************************************************
+
+       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 "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;
+}