1/* 2 * LPC utility code 3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22#include "libavutil/common.h" 23#include "libavutil/lls.h" 24#include "libavutil/mem_internal.h" 25 26#define LPC_USE_DOUBLE 27#include "lpc.h" 28#include "libavutil/avassert.h" 29 30 31/** 32 * Apply Welch window function to audio block 33 */ 34static void lpc_apply_welch_window_c(const int32_t *data, int len, 35 double *w_data) 36{ 37 int i, n2; 38 double w; 39 double c; 40 41 n2 = (len >> 1); 42 c = 2.0 / (len - 1.0); 43 44 if (len & 1) { 45 for(i=0; i<n2; i++) { 46 w = c - i - 1.0; 47 w = 1.0 - (w * w); 48 w_data[i] = data[i] * w; 49 w_data[len-1-i] = data[len-1-i] * w; 50 } 51 return; 52 } 53 54 w_data+=n2; 55 data+=n2; 56 for(i=0; i<n2; i++) { 57 w = c - n2 + i; 58 w = 1.0 - (w * w); 59 w_data[-i-1] = data[-i-1] * w; 60 w_data[+i ] = data[+i ] * w; 61 } 62} 63 64/** 65 * Calculate autocorrelation data from audio samples 66 * A Welch window function is applied before calculation. 67 */ 68static void lpc_compute_autocorr_c(const double *data, int len, int lag, 69 double *autoc) 70{ 71 int i, j; 72 73 for(j=0; j<lag; j+=2){ 74 double sum0 = 1.0, sum1 = 1.0; 75 for(i=j; i<len; i++){ 76 sum0 += data[i] * data[i-j]; 77 sum1 += data[i] * data[i-j-1]; 78 } 79 autoc[j ] = sum0; 80 autoc[j+1] = sum1; 81 } 82 83 if(j==lag){ 84 double sum = 1.0; 85 for(i=j-1; i<len; i+=2){ 86 sum += data[i ] * data[i-j ] 87 + data[i+1] * data[i-j+1]; 88 } 89 autoc[j] = sum; 90 } 91} 92 93/** 94 * Quantize LPC coefficients 95 */ 96static void quantize_lpc_coefs(double *lpc_in, int order, int precision, 97 int32_t *lpc_out, int *shift, int min_shift, 98 int max_shift, int zero_shift) 99{ 100 int i; 101 double cmax, error; 102 int32_t qmax; 103 int sh; 104 105 /* define maximum levels */ 106 qmax = (1 << (precision - 1)) - 1; 107 108 /* find maximum coefficient value */ 109 cmax = 0.0; 110 for(i=0; i<order; i++) { 111 cmax= FFMAX(cmax, fabs(lpc_in[i])); 112 } 113 114 /* if maximum value quantizes to zero, return all zeros */ 115 if(cmax * (1 << max_shift) < 1.0) { 116 *shift = zero_shift; 117 memset(lpc_out, 0, sizeof(int32_t) * order); 118 return; 119 } 120 121 /* calculate level shift which scales max coeff to available bits */ 122 sh = max_shift; 123 while((cmax * (1 << sh) > qmax) && (sh > min_shift)) { 124 sh--; 125 } 126 127 /* since negative shift values are unsupported in decoder, scale down 128 coefficients instead */ 129 if(sh == 0 && cmax > qmax) { 130 double scale = ((double)qmax) / cmax; 131 for(i=0; i<order; i++) { 132 lpc_in[i] *= scale; 133 } 134 } 135 136 /* output quantized coefficients and level shift */ 137 error=0; 138 for(i=0; i<order; i++) { 139 error -= lpc_in[i] * (1 << sh); 140 lpc_out[i] = av_clip(lrintf(error), -qmax, qmax); 141 error -= lpc_out[i]; 142 } 143 *shift = sh; 144} 145 146static int estimate_best_order(double *ref, int min_order, int max_order) 147{ 148 int i, est; 149 150 est = min_order; 151 for(i=max_order-1; i>=min_order-1; i--) { 152 if(ref[i] > 0.10) { 153 est = i+1; 154 break; 155 } 156 } 157 return est; 158} 159 160int ff_lpc_calc_ref_coefs(LPCContext *s, 161 const int32_t *samples, int order, double *ref) 162{ 163 double autoc[MAX_LPC_ORDER + 1]; 164 165 s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples); 166 s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc); 167 compute_ref_coefs(autoc, order, ref, NULL); 168 169 return order; 170} 171 172double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len, 173 int order, double *ref) 174{ 175 int i; 176 double signal = 0.0f, avg_err = 0.0f; 177 double autoc[MAX_LPC_ORDER+1] = {0}, error[MAX_LPC_ORDER+1] = {0}; 178 const double a = 0.5f, b = 1.0f - a; 179 180 /* Apply windowing */ 181 for (i = 0; i <= len / 2; i++) { 182 double weight = a - b*cos((2*M_PI*i)/(len - 1)); 183 s->windowed_samples[i] = weight*samples[i]; 184 s->windowed_samples[len-1-i] = weight*samples[len-1-i]; 185 } 186 187 s->lpc_compute_autocorr(s->windowed_samples, len, order, autoc); 188 signal = autoc[0]; 189 compute_ref_coefs(autoc, order, ref, error); 190 for (i = 0; i < order; i++) 191 avg_err = (avg_err + error[i])/2.0f; 192 return avg_err ? signal/avg_err : NAN; 193} 194 195/** 196 * Calculate LPC coefficients for multiple orders 197 * 198 * @param lpc_type LPC method for determining coefficients, 199 * see #FFLPCType for details 200 */ 201int ff_lpc_calc_coefs(LPCContext *s, 202 const int32_t *samples, int blocksize, int min_order, 203 int max_order, int precision, 204 int32_t coefs[][MAX_LPC_ORDER], int *shift, 205 enum FFLPCType lpc_type, int lpc_passes, 206 int omethod, int min_shift, int max_shift, int zero_shift) 207{ 208 double autoc[MAX_LPC_ORDER+1]; 209 double ref[MAX_LPC_ORDER] = { 0 }; 210 double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER]; 211 int i, j, pass = 0; 212 int opt_order; 213 214 av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && 215 lpc_type > FF_LPC_TYPE_FIXED); 216 av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY || lpc_type == FF_LPC_TYPE_LEVINSON); 217 218 /* reinit LPC context if parameters have changed */ 219 if (blocksize != s->blocksize || max_order != s->max_order || 220 lpc_type != s->lpc_type) { 221 ff_lpc_end(s); 222 ff_lpc_init(s, blocksize, max_order, lpc_type); 223 } 224 225 if(lpc_passes <= 0) 226 lpc_passes = 2; 227 228 if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) { 229 s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples); 230 231 s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc); 232 233 compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1); 234 235 for(i=0; i<max_order; i++) 236 ref[i] = fabs(lpc[i][i]); 237 238 pass++; 239 } 240 241 if (lpc_type == FF_LPC_TYPE_CHOLESKY) { 242 LLSModel *m = s->lls_models; 243 LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]); 244 double av_uninit(weight); 245 memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var)); 246 247 for(j=0; j<max_order; j++) 248 m[0].coeff[max_order-1][j] = -lpc[max_order-1][j]; 249 250 for(; pass<lpc_passes; pass++){ 251 avpriv_init_lls(&m[pass&1], max_order); 252 253 weight=0; 254 for(i=max_order; i<blocksize; i++){ 255 for(j=0; j<=max_order; j++) 256 var[j]= samples[i-j]; 257 258 if(pass){ 259 double eval, inv, rinv; 260 eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1); 261 eval= (512>>pass) + fabs(eval - var[0]); 262 inv = 1/eval; 263 rinv = sqrt(inv); 264 for(j=0; j<=max_order; j++) 265 var[j] *= rinv; 266 weight += inv; 267 }else 268 weight++; 269 270 m[pass&1].update_lls(&m[pass&1], var); 271 } 272 avpriv_solve_lls(&m[pass&1], 0.001, 0); 273 } 274 275 for(i=0; i<max_order; i++){ 276 for(j=0; j<max_order; j++) 277 lpc[i][j]=-m[(pass-1)&1].coeff[i][j]; 278 ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000; 279 } 280 for(i=max_order-1; i>0; i--) 281 ref[i] = ref[i-1] - ref[i]; 282 } 283 284 opt_order = max_order; 285 286 if(omethod == ORDER_METHOD_EST) { 287 opt_order = estimate_best_order(ref, min_order, max_order); 288 i = opt_order-1; 289 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], 290 min_shift, max_shift, zero_shift); 291 } else { 292 for(i=min_order-1; i<max_order; i++) { 293 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], 294 min_shift, max_shift, zero_shift); 295 } 296 } 297 298 return opt_order; 299} 300 301av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order, 302 enum FFLPCType lpc_type) 303{ 304 s->blocksize = blocksize; 305 s->max_order = max_order; 306 s->lpc_type = lpc_type; 307 308 s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) * 309 sizeof(*s->windowed_samples)); 310 if (!s->windowed_buffer) 311 return AVERROR(ENOMEM); 312 s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4); 313 314 s->lpc_apply_welch_window = lpc_apply_welch_window_c; 315 s->lpc_compute_autocorr = lpc_compute_autocorr_c; 316 317#if ARCH_X86 318 ff_lpc_init_x86(s); 319#endif 320 321 return 0; 322} 323 324av_cold void ff_lpc_end(LPCContext *s) 325{ 326 av_freep(&s->windowed_buffer); 327} 328