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2 /******************************************************************
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3
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4 iLBC Speech Coder ANSI-C Source Code
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5
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6 helpfun.c
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7
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8 Copyright (C) The Internet Society (2004).
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9 All Rights Reserved.
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10
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11 ******************************************************************/
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12
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13 #include <math.h>
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14
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15 #include "iLBC_define.h"
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16 #include "constants.h"
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17
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18 /*----------------------------------------------------------------*
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19 * calculation of auto correlation
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20 *---------------------------------------------------------------*/
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21
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22 void autocorr(float *r, /* (o) autocorrelation vector */
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23 const float *x, /* (i) data vector */
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24 int N, /* (i) length of data vector */
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25 int order /* largest lag for calculated
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26 autocorrelations */
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27 )
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28 {
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29 int lag, n;
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30 float sum;
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31
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32 for (lag = 0; lag <= order; lag++) {
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33 sum = 0;
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34 for (n = 0; n < N - lag; n++) {
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35 sum += x[n] * x[n + lag];
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36 }
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37 r[lag] = sum;
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38 }
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39
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40
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41
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42
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43
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44 }
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45
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46 /*----------------------------------------------------------------*
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47 * window multiplication
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48 *---------------------------------------------------------------*/
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49
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50 void window(float *z, /* (o) the windowed data */
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51 const float *x, /* (i) the original data vector */
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52 const float *y, /* (i) the window */
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53 int N /* (i) length of all vectors */
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54 )
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55 {
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56 int i;
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57
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58 for (i = 0; i < N; i++) {
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59 z[i] = x[i] * y[i];
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60 }
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61 }
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62
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63 /*----------------------------------------------------------------*
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64 * levinson-durbin solution for lpc coefficients
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65 *---------------------------------------------------------------*/
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66
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67 void levdurb(float *a, /* (o) lpc coefficient vector starting
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68 with 1.0 */
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69 float *k, /* (o) reflection coefficients */
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70 float *r, /* (i) autocorrelation vector */
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71 int order /* (i) order of lpc filter */
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72 )
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73 {
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74 float sum, alpha;
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75 int m, m_h, i;
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76
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77 a[0] = 1.0;
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78
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79 if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */
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80 for (i = 0; i < order; i++) {
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81 k[i] = 0;
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82 a[i + 1] = 0;
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83 }
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84 } else {
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85 a[1] = k[0] = -r[1] / r[0];
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86 alpha = r[0] + r[1] * k[0];
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87 for (m = 1; m < order; m++) {
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88 sum = r[m + 1];
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89 for (i = 0; i < m; i++) {
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90 sum += a[i + 1] * r[m - i];
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91 }
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92
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93
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94
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95
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96
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97 k[m] = -sum / alpha;
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98 alpha += k[m] * sum;
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99 m_h = (m + 1) >> 1;
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100 for (i = 0; i < m_h; i++) {
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101 sum = a[i + 1] + k[m] * a[m - i];
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102 a[m - i] += k[m] * a[i + 1];
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103 a[i + 1] = sum;
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104 }
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105 a[m + 1] = k[m];
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106 }
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107 }
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108 }
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109
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110 /*----------------------------------------------------------------*
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111 * interpolation between vectors
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112 *---------------------------------------------------------------*/
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113
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114 void interpolate(float *out, /* (o) the interpolated vector */
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115 float *in1, /* (i) the first vector for the
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116 interpolation */
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117 float *in2, /* (i) the second vector for the
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118 interpolation */
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119 float coef, /* (i) interpolation weights */
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120 int length /* (i) length of all vectors */
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121 )
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122 {
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123 int i;
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124 float invcoef;
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125
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126 invcoef = (float) 1.0 - coef;
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127 for (i = 0; i < length; i++) {
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128 out[i] = coef * in1[i] + invcoef * in2[i];
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129 }
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130 }
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131
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132 /*----------------------------------------------------------------*
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133 * lpc bandwidth expansion
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134 *---------------------------------------------------------------*/
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135
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136 void bwexpand(float *out, /* (o) the bandwidth expanded lpc
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137 coefficients */
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138 float *in, /* (i) the lpc coefficients before bandwidth
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139 expansion */
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140 float coef, /* (i) the bandwidth expansion factor */
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141 int length /* (i) the length of lpc coefficient vectors */
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142 )
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143 {
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144 int i;
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145
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146
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147
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148
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149
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150 float chirp;
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151
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152 chirp = coef;
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153
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154 out[0] = in[0];
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155 for (i = 1; i < length; i++) {
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156 out[i] = chirp * in[i];
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157 chirp *= coef;
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158 }
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159 }
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160
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161 /*----------------------------------------------------------------*
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162 * vector quantization
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163 *---------------------------------------------------------------*/
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164
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165 void vq(float *Xq, /* (o) the quantized vector */
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166 int *index, /* (o) the quantization index */
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167 const float *CB, /* (i) the vector quantization codebook */
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168 float *X, /* (i) the vector to quantize */
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169 int n_cb, /* (i) the number of vectors in the codebook */
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170 int dim /* (i) the dimension of all vectors */
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171 )
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172 {
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173 int i, j;
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174 int pos, minindex;
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175 float dist, tmp, mindist;
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176
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177 pos = 0;
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178 mindist = FLOAT_MAX;
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179 minindex = 0;
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180 for (j = 0; j < n_cb; j++) {
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181 dist = X[0] - CB[pos];
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182 dist *= dist;
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183 for (i = 1; i < dim; i++) {
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184 tmp = X[i] - CB[pos + i];
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185 dist += tmp * tmp;
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186 }
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187
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188 if (dist < mindist) {
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189 mindist = dist;
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190 minindex = j;
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191 }
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192 pos += dim;
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193 }
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194 for (i = 0; i < dim; i++) {
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195 Xq[i] = CB[minindex * dim + i];
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196 }
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197 *index = minindex;
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198
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199
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200
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201
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202
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203 }
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204
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205 /*----------------------------------------------------------------*
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206 * split vector quantization
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207 *---------------------------------------------------------------*/
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208
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209 void SplitVQ(float *qX, /* (o) the quantized vector */
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210 int *index, /* (o) a vector of indexes for all vector
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211 codebooks in the split */
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212 float *X, /* (i) the vector to quantize */
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213 const float *CB, /* (i) the quantizer codebook */
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214 int nsplit, /* the number of vector splits */
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215 const int *dim, /* the dimension of X and qX */
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216 const int *cbsize /* the number of vectors in the codebook */
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217 )
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218 {
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219 int cb_pos, X_pos, i;
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220
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221 cb_pos = 0;
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222 X_pos = 0;
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223 for (i = 0; i < nsplit; i++) {
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224 vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos,
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225 cbsize[i], dim[i]);
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226 X_pos += dim[i];
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227 cb_pos += dim[i] * cbsize[i];
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228 }
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229 }
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230
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231 /*----------------------------------------------------------------*
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232 * scalar quantization
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233 *---------------------------------------------------------------*/
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234
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235 void sort_sq(float *xq, /* (o) the quantized value */
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236 int *index, /* (o) the quantization index */
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237 float x, /* (i) the value to quantize */
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238 const float *cb, /* (i) the quantization codebook */
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239 int cb_size /* (i) the size of the quantization codebook */
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240 )
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241 {
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242 int i;
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243
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244 if (x <= cb[0]) {
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245 *index = 0;
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246 *xq = cb[0];
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247 } else {
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248 i = 0;
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249 while ((x > cb[i]) && i < cb_size - 1) {
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250 i++;
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251
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252
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253
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254
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255
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256 }
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257
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258 if (x > ((cb[i] + cb[i - 1]) / 2)) {
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259 *index = i;
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260 *xq = cb[i];
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261 } else {
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262 *index = i - 1;
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263 *xq = cb[i - 1];
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264 }
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265 }
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266 }
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267
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268 /*----------------------------------------------------------------*
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269 * check for stability of lsf coefficients
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270 *---------------------------------------------------------------*/
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271
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272 int LSF_check( /* (o) 1 for stable lsf vectors and 0 for
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273 nonstable ones */
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274 float *lsf, /* (i) a table of lsf vectors */
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275 int dim, /* (i) the dimension of each lsf vector */
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276 int NoAn /* (i) the number of lsf vectors in the
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277 table */
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278 )
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279 {
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280 int k, n, m, Nit = 2, change = 0, pos;
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281 float tmp;
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282 static float eps = (float) 0.039; /* 50 Hz */
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283 static float eps2 = (float) 0.0195;
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284 static float maxlsf = (float) 3.14; /* 4000 Hz */
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285 static float minlsf = (float) 0.01; /* 0 Hz */
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286
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287 /* LSF separation check */
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288
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289 for (n = 0; n < Nit; n++) { /* Run through a couple of times */
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290 for (m = 0; m < NoAn; m++) { /* Number of analyses per frame */
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291 for (k = 0; k < (dim - 1); k++) {
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292 pos = m * dim + k;
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293
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294 if ((lsf[pos + 1] - lsf[pos]) < eps) {
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295
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296 if (lsf[pos + 1] < lsf[pos]) {
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297 tmp = lsf[pos + 1];
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298 lsf[pos + 1] = lsf[pos] + eps2;
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299 lsf[pos] = lsf[pos + 1] - eps2;
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300 } else {
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301 lsf[pos] -= eps2;
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302 lsf[pos + 1] += eps2;
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303 }
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304 change = 1;
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305
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306
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307
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308
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309
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310 }
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311
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312 if (lsf[pos] < minlsf) {
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313 lsf[pos] = minlsf;
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314 change = 1;
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315 }
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316
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317 if (lsf[pos] > maxlsf) {
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318 lsf[pos] = maxlsf;
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319 change = 1;
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320 }
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321 }
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322 }
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323 }
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324
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325 return change;
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326 }
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