Alexandre Lision | 7c6f4a6 | 2013-09-05 13:27:01 -0400 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische |
| 3 | * Universitaet Berlin. See the accompanying file "COPYRIGHT" for |
| 4 | * details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE. |
| 5 | */ |
| 6 | |
| 7 | #include <stdio.h> |
| 8 | #include <assert.h> |
| 9 | |
| 10 | #include "gsm610_priv.h" |
| 11 | |
| 12 | /* |
| 13 | * 4.2.4 .. 4.2.7 LPC ANALYSIS SECTION |
| 14 | */ |
| 15 | |
| 16 | /* 4.2.4 */ |
| 17 | |
| 18 | |
| 19 | static void Autocorrelation ( |
| 20 | word * s, /* [0..159] IN/OUT */ |
| 21 | longword * L_ACF) /* [0..8] OUT */ |
| 22 | /* |
| 23 | * The goal is to compute the array L_ACF[k]. The signal s[i] must |
| 24 | * be scaled in order to avoid an overflow situation. |
| 25 | */ |
| 26 | { |
| 27 | register int k, i; |
| 28 | |
| 29 | word temp, smax, scalauto; |
| 30 | |
| 31 | #ifdef USE_FLOAT_MUL |
| 32 | float float_s[160]; |
| 33 | #endif |
| 34 | |
| 35 | /* Dynamic scaling of the array s[0..159] |
| 36 | */ |
| 37 | |
| 38 | /* Search for the maximum. |
| 39 | */ |
| 40 | smax = 0; |
| 41 | for (k = 0; k <= 159; k++) { |
| 42 | temp = GSM_ABS( s[k] ); |
| 43 | if (temp > smax) smax = temp; |
| 44 | } |
| 45 | |
| 46 | /* Computation of the scaling factor. |
| 47 | */ |
| 48 | if (smax == 0) scalauto = 0; |
| 49 | else { |
| 50 | assert(smax > 0); |
| 51 | scalauto = 4 - gsm_norm( (longword)smax << 16 );/* sub(4,..) */ |
| 52 | } |
| 53 | |
| 54 | /* Scaling of the array s[0...159] |
| 55 | */ |
| 56 | |
| 57 | if (scalauto > 0) { |
| 58 | |
| 59 | # ifdef USE_FLOAT_MUL |
| 60 | # define SCALE(n) \ |
| 61 | case n: for (k = 0; k <= 159; k++) \ |
| 62 | float_s[k] = (float) \ |
| 63 | (s[k] = GSM_MULT_R(s[k], 16384 >> (n-1)));\ |
| 64 | break; |
| 65 | # else |
| 66 | # define SCALE(n) \ |
| 67 | case n: for (k = 0; k <= 159; k++) \ |
| 68 | s[k] = GSM_MULT_R( s[k], 16384 >> (n-1) );\ |
| 69 | break; |
| 70 | # endif /* USE_FLOAT_MUL */ |
| 71 | |
| 72 | switch (scalauto) { |
| 73 | SCALE(1) |
| 74 | SCALE(2) |
| 75 | SCALE(3) |
| 76 | SCALE(4) |
| 77 | } |
| 78 | # undef SCALE |
| 79 | } |
| 80 | # ifdef USE_FLOAT_MUL |
| 81 | else for (k = 0; k <= 159; k++) float_s[k] = (float) s[k]; |
| 82 | # endif |
| 83 | |
| 84 | /* Compute the L_ACF[..]. |
| 85 | */ |
| 86 | { |
| 87 | # ifdef USE_FLOAT_MUL |
| 88 | register float * sp = float_s; |
| 89 | register float sl = *sp; |
| 90 | |
| 91 | # define STEP(k) L_ACF[k] += (longword)(sl * sp[ -(k) ]); |
| 92 | # else |
| 93 | word * sp = s; |
| 94 | word sl = *sp; |
| 95 | |
| 96 | # define STEP(k) L_ACF[k] += ((longword)sl * sp[ -(k) ]); |
| 97 | # endif |
| 98 | |
| 99 | # define NEXTI sl = *++sp |
| 100 | |
| 101 | |
| 102 | for (k = 9; k--; L_ACF[k] = 0) ; |
| 103 | |
| 104 | STEP (0); |
| 105 | NEXTI; |
| 106 | STEP(0); STEP(1); |
| 107 | NEXTI; |
| 108 | STEP(0); STEP(1); STEP(2); |
| 109 | NEXTI; |
| 110 | STEP(0); STEP(1); STEP(2); STEP(3); |
| 111 | NEXTI; |
| 112 | STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); |
| 113 | NEXTI; |
| 114 | STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); |
| 115 | NEXTI; |
| 116 | STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); STEP(6); |
| 117 | NEXTI; |
| 118 | STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); STEP(6); STEP(7); |
| 119 | |
| 120 | for (i = 8; i <= 159; i++) { |
| 121 | |
| 122 | NEXTI; |
| 123 | |
| 124 | STEP(0); |
| 125 | STEP(1); STEP(2); STEP(3); STEP(4); |
| 126 | STEP(5); STEP(6); STEP(7); STEP(8); |
| 127 | } |
| 128 | |
| 129 | for (k = 9; k--; L_ACF[k] <<= 1) ; |
| 130 | |
| 131 | } |
| 132 | /* Rescaling of the array s[0..159] |
| 133 | */ |
| 134 | if (scalauto > 0) { |
| 135 | assert(scalauto <= 4); |
| 136 | for (k = 160; k--; *s++ <<= scalauto) ; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | #if defined(USE_FLOAT_MUL) && defined(FAST) |
| 141 | |
| 142 | static void Fast_Autocorrelation ( |
| 143 | word * s, /* [0..159] IN/OUT */ |
| 144 | longword * L_ACF) /* [0..8] OUT */ |
| 145 | { |
| 146 | register int k, i; |
| 147 | float f_L_ACF[9]; |
| 148 | float scale; |
| 149 | |
| 150 | float s_f[160]; |
| 151 | register float *sf = s_f; |
| 152 | |
| 153 | for (i = 0; i < 160; ++i) sf[i] = s[i]; |
| 154 | for (k = 0; k <= 8; k++) { |
| 155 | register float L_temp2 = 0; |
| 156 | register float *sfl = sf - k; |
| 157 | for (i = k; i < 160; ++i) L_temp2 += sf[i] * sfl[i]; |
| 158 | f_L_ACF[k] = L_temp2; |
| 159 | } |
| 160 | scale = MAX_LONGWORD / f_L_ACF[0]; |
| 161 | |
| 162 | for (k = 0; k <= 8; k++) { |
| 163 | L_ACF[k] = f_L_ACF[k] * scale; |
| 164 | } |
| 165 | } |
| 166 | #endif /* defined (USE_FLOAT_MUL) && defined (FAST) */ |
| 167 | |
| 168 | /* 4.2.5 */ |
| 169 | |
| 170 | static void Reflection_coefficients ( |
| 171 | longword * L_ACF, /* 0...8 IN */ |
| 172 | register word * r /* 0...7 OUT */ |
| 173 | ) |
| 174 | { |
| 175 | register int i, m, n; |
| 176 | register word temp; |
| 177 | word ACF[9]; /* 0..8 */ |
| 178 | word P[ 9]; /* 0..8 */ |
| 179 | word K[ 9]; /* 2..8 */ |
| 180 | |
| 181 | /* Schur recursion with 16 bits arithmetic. |
| 182 | */ |
| 183 | |
| 184 | if (L_ACF[0] == 0) { |
| 185 | for (i = 8; i--; *r++ = 0) ; |
| 186 | return; |
| 187 | } |
| 188 | |
| 189 | assert( L_ACF[0] != 0 ); |
| 190 | temp = gsm_norm( L_ACF[0] ); |
| 191 | |
| 192 | assert(temp >= 0 && temp < 32); |
| 193 | |
| 194 | /* ? overflow ? */ |
| 195 | for (i = 0; i <= 8; i++) ACF[i] = SASR_L( L_ACF[i] << temp, 16 ); |
| 196 | |
| 197 | /* Initialize array P[..] and K[..] for the recursion. |
| 198 | */ |
| 199 | |
| 200 | for (i = 1; i <= 7; i++) K[ i ] = ACF[ i ]; |
| 201 | for (i = 0; i <= 8; i++) P[ i ] = ACF[ i ]; |
| 202 | |
| 203 | /* Compute reflection coefficients |
| 204 | */ |
| 205 | for (n = 1; n <= 8; n++, r++) { |
| 206 | |
| 207 | temp = P[1]; |
| 208 | temp = GSM_ABS(temp); |
| 209 | if (P[0] < temp) { |
| 210 | for (i = n; i <= 8; i++) *r++ = 0; |
| 211 | return; |
| 212 | } |
| 213 | |
| 214 | *r = gsm_div( temp, P[0] ); |
| 215 | |
| 216 | assert(*r >= 0); |
| 217 | if (P[1] > 0) *r = -*r; /* r[n] = sub(0, r[n]) */ |
| 218 | assert (*r != MIN_WORD); |
| 219 | if (n == 8) return; |
| 220 | |
| 221 | /* Schur recursion |
| 222 | */ |
| 223 | temp = GSM_MULT_R( P[1], *r ); |
| 224 | P[0] = GSM_ADD( P[0], temp ); |
| 225 | |
| 226 | for (m = 1; m <= 8 - n; m++) { |
| 227 | temp = GSM_MULT_R( K[ m ], *r ); |
| 228 | P[m] = GSM_ADD( P[ m+1 ], temp ); |
| 229 | |
| 230 | temp = GSM_MULT_R( P[ m+1 ], *r ); |
| 231 | K[m] = GSM_ADD( K[ m ], temp ); |
| 232 | } |
| 233 | } |
| 234 | } |
| 235 | |
| 236 | /* 4.2.6 */ |
| 237 | |
| 238 | static void Transformation_to_Log_Area_Ratios ( |
| 239 | register word * r /* 0..7 IN/OUT */ |
| 240 | ) |
| 241 | /* |
| 242 | * The following scaling for r[..] and LAR[..] has been used: |
| 243 | * |
| 244 | * r[..] = integer( real_r[..]*32768. ); -1 <= real_r < 1. |
| 245 | * LAR[..] = integer( real_LAR[..] * 16384 ); |
| 246 | * with -1.625 <= real_LAR <= 1.625 |
| 247 | */ |
| 248 | { |
| 249 | register word temp; |
| 250 | register int i; |
| 251 | |
| 252 | |
| 253 | /* Computation of the LAR[0..7] from the r[0..7] |
| 254 | */ |
| 255 | for (i = 1; i <= 8; i++, r++) { |
| 256 | |
| 257 | temp = *r; |
| 258 | temp = GSM_ABS(temp); |
| 259 | assert(temp >= 0); |
| 260 | |
| 261 | if (temp < 22118) { |
| 262 | temp >>= 1; |
| 263 | } else if (temp < 31130) { |
| 264 | assert( temp >= 11059 ); |
| 265 | temp -= 11059; |
| 266 | } else { |
| 267 | assert( temp >= 26112 ); |
| 268 | temp -= 26112; |
| 269 | temp <<= 2; |
| 270 | } |
| 271 | |
| 272 | *r = *r < 0 ? -temp : temp; |
| 273 | assert( *r != MIN_WORD ); |
| 274 | } |
| 275 | } |
| 276 | |
| 277 | /* 4.2.7 */ |
| 278 | |
| 279 | static void Quantization_and_coding ( |
| 280 | register word * LAR /* [0..7] IN/OUT */ |
| 281 | ) |
| 282 | { |
| 283 | register word temp; |
| 284 | |
| 285 | /* This procedure needs four tables; the following equations |
| 286 | * give the optimum scaling for the constants: |
| 287 | * |
| 288 | * A[0..7] = integer( real_A[0..7] * 1024 ) |
| 289 | * B[0..7] = integer( real_B[0..7] * 512 ) |
| 290 | * MAC[0..7] = maximum of the LARc[0..7] |
| 291 | * MIC[0..7] = minimum of the LARc[0..7] |
| 292 | */ |
| 293 | |
| 294 | # undef STEP |
| 295 | # define STEP( A, B, MAC, MIC ) \ |
| 296 | temp = GSM_MULT( A, *LAR ); \ |
| 297 | temp = GSM_ADD( temp, B ); \ |
| 298 | temp = GSM_ADD( temp, 256 ); \ |
| 299 | temp = SASR_W( temp, 9 ); \ |
| 300 | *LAR = temp>MAC ? MAC - MIC : (temp<MIC ? 0 : temp - MIC); \ |
| 301 | LAR++; |
| 302 | |
| 303 | STEP( 20480, 0, 31, -32 ); |
| 304 | STEP( 20480, 0, 31, -32 ); |
| 305 | STEP( 20480, 2048, 15, -16 ); |
| 306 | STEP( 20480, -2560, 15, -16 ); |
| 307 | |
| 308 | STEP( 13964, 94, 7, -8 ); |
| 309 | STEP( 15360, -1792, 7, -8 ); |
| 310 | STEP( 8534, -341, 3, -4 ); |
| 311 | STEP( 9036, -1144, 3, -4 ); |
| 312 | |
| 313 | # undef STEP |
| 314 | } |
| 315 | |
| 316 | void Gsm_LPC_Analysis ( |
| 317 | struct gsm_state *S, |
| 318 | word * s, /* 0..159 signals IN/OUT */ |
| 319 | word * LARc) /* 0..7 LARc's OUT */ |
| 320 | { |
| 321 | longword L_ACF[9]; |
| 322 | |
| 323 | #if defined(USE_FLOAT_MUL) && defined(FAST) |
| 324 | if (S->fast) Fast_Autocorrelation (s, L_ACF ); |
| 325 | else |
| 326 | #endif |
| 327 | Autocorrelation (s, L_ACF ); |
| 328 | Reflection_coefficients (L_ACF, LARc ); |
| 329 | Transformation_to_Log_Area_Ratios (LARc); |
| 330 | Quantization_and_coding (LARc); |
| 331 | } |