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