1/** 2 * LPC utility code 3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> 4 * 5 * This file is part of Libav. 6 * 7 * Libav 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 * Libav 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 Libav; 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/lls.h" 23 24#define LPC_USE_DOUBLE 25#include "lpc.h" 26 27 28/** 29 * Apply Welch window function to audio block 30 */ 31static void lpc_apply_welch_window_c(const int32_t *data, int len, 32 double *w_data) 33{ 34 int i, n2; 35 double w; 36 double c; 37 38 /* The optimization in commit fa4ed8c does not support odd len. 39 * If someone wants odd len extend that change. */ 40 assert(!(len & 1)); 41 42 n2 = (len >> 1); 43 c = 2.0 / (len - 1.0); 44 45 w_data+=n2; 46 data+=n2; 47 for(i=0; i<n2; i++) { 48 w = c - n2 + i; 49 w = 1.0 - (w * w); 50 w_data[-i-1] = data[-i-1] * w; 51 w_data[+i ] = data[+i ] * w; 52 } 53} 54 55/** 56 * Calculate autocorrelation data from audio samples 57 * A Welch window function is applied before calculation. 58 */ 59static void lpc_compute_autocorr_c(const double *data, int len, int lag, 60 double *autoc) 61{ 62 int i, j; 63 64 for(j=0; j<lag; j+=2){ 65 double sum0 = 1.0, sum1 = 1.0; 66 for(i=j; i<len; i++){ 67 sum0 += data[i] * data[i-j]; 68 sum1 += data[i] * data[i-j-1]; 69 } 70 autoc[j ] = sum0; 71 autoc[j+1] = sum1; 72 } 73 74 if(j==lag){ 75 double sum = 1.0; 76 for(i=j-1; i<len; i+=2){ 77 sum += data[i ] * data[i-j ] 78 + data[i+1] * data[i-j+1]; 79 } 80 autoc[j] = sum; 81 } 82} 83 84/** 85 * Quantize LPC coefficients 86 */ 87static void quantize_lpc_coefs(double *lpc_in, int order, int precision, 88 int32_t *lpc_out, int *shift, int max_shift, int zero_shift) 89{ 90 int i; 91 double cmax, error; 92 int32_t qmax; 93 int sh; 94 95 /* define maximum levels */ 96 qmax = (1 << (precision - 1)) - 1; 97 98 /* find maximum coefficient value */ 99 cmax = 0.0; 100 for(i=0; i<order; i++) { 101 cmax= FFMAX(cmax, fabs(lpc_in[i])); 102 } 103 104 /* if maximum value quantizes to zero, return all zeros */ 105 if(cmax * (1 << max_shift) < 1.0) { 106 *shift = zero_shift; 107 memset(lpc_out, 0, sizeof(int32_t) * order); 108 return; 109 } 110 111 /* calculate level shift which scales max coeff to available bits */ 112 sh = max_shift; 113 while((cmax * (1 << sh) > qmax) && (sh > 0)) { 114 sh--; 115 } 116 117 /* since negative shift values are unsupported in decoder, scale down 118 coefficients instead */ 119 if(sh == 0 && cmax > qmax) { 120 double scale = ((double)qmax) / cmax; 121 for(i=0; i<order; i++) { 122 lpc_in[i] *= scale; 123 } 124 } 125 126 /* output quantized coefficients and level shift */ 127 error=0; 128 for(i=0; i<order; i++) { 129 error -= lpc_in[i] * (1 << sh); 130 lpc_out[i] = av_clip(lrintf(error), -qmax, qmax); 131 error -= lpc_out[i]; 132 } 133 *shift = sh; 134} 135 136static int estimate_best_order(double *ref, int min_order, int max_order) 137{ 138 int i, est; 139 140 est = min_order; 141 for(i=max_order-1; i>=min_order-1; i--) { 142 if(ref[i] > 0.10) { 143 est = i+1; 144 break; 145 } 146 } 147 return est; 148} 149 150/** 151 * Calculate LPC coefficients for multiple orders 152 * 153 * @param lpc_type LPC method for determining coefficients, 154 * see #FFLPCType for details 155 */ 156int ff_lpc_calc_coefs(LPCContext *s, 157 const int32_t *samples, int blocksize, int min_order, 158 int max_order, int precision, 159 int32_t coefs[][MAX_LPC_ORDER], int *shift, 160 enum FFLPCType lpc_type, int lpc_passes, 161 int omethod, int max_shift, int zero_shift) 162{ 163 double autoc[MAX_LPC_ORDER+1]; 164 double ref[MAX_LPC_ORDER]; 165 double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER]; 166 int i, j, pass; 167 int opt_order; 168 169 assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && 170 lpc_type > FF_LPC_TYPE_FIXED); 171 172 /* reinit LPC context if parameters have changed */ 173 if (blocksize != s->blocksize || max_order != s->max_order || 174 lpc_type != s->lpc_type) { 175 ff_lpc_end(s); 176 ff_lpc_init(s, blocksize, max_order, lpc_type); 177 } 178 179 if (lpc_type == FF_LPC_TYPE_LEVINSON) { 180 double *windowed_samples = s->windowed_samples + max_order; 181 182 s->lpc_apply_welch_window(samples, blocksize, windowed_samples); 183 184 s->lpc_compute_autocorr(windowed_samples, blocksize, max_order, autoc); 185 186 compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1); 187 188 for(i=0; i<max_order; i++) 189 ref[i] = fabs(lpc[i][i]); 190 } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) { 191 LLSModel m[2]; 192 double var[MAX_LPC_ORDER+1], av_uninit(weight); 193 194 for(pass=0; pass<lpc_passes; pass++){ 195 av_init_lls(&m[pass&1], max_order); 196 197 weight=0; 198 for(i=max_order; i<blocksize; i++){ 199 for(j=0; j<=max_order; j++) 200 var[j]= samples[i-j]; 201 202 if(pass){ 203 double eval, inv, rinv; 204 eval= av_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1); 205 eval= (512>>pass) + fabs(eval - var[0]); 206 inv = 1/eval; 207 rinv = sqrt(inv); 208 for(j=0; j<=max_order; j++) 209 var[j] *= rinv; 210 weight += inv; 211 }else 212 weight++; 213 214 av_update_lls(&m[pass&1], var, 1.0); 215 } 216 av_solve_lls(&m[pass&1], 0.001, 0); 217 } 218 219 for(i=0; i<max_order; i++){ 220 for(j=0; j<max_order; j++) 221 lpc[i][j]=-m[(pass-1)&1].coeff[i][j]; 222 ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000; 223 } 224 for(i=max_order-1; i>0; i--) 225 ref[i] = ref[i-1] - ref[i]; 226 } 227 opt_order = max_order; 228 229 if(omethod == ORDER_METHOD_EST) { 230 opt_order = estimate_best_order(ref, min_order, max_order); 231 i = opt_order-1; 232 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift); 233 } else { 234 for(i=min_order-1; i<max_order; i++) { 235 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift); 236 } 237 } 238 239 return opt_order; 240} 241 242av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order, 243 enum FFLPCType lpc_type) 244{ 245 s->blocksize = blocksize; 246 s->max_order = max_order; 247 s->lpc_type = lpc_type; 248 249 if (lpc_type == FF_LPC_TYPE_LEVINSON) { 250 s->windowed_samples = av_mallocz((blocksize + max_order + 2) * 251 sizeof(*s->windowed_samples)); 252 if (!s->windowed_samples) 253 return AVERROR(ENOMEM); 254 } else { 255 s->windowed_samples = NULL; 256 } 257 258 s->lpc_apply_welch_window = lpc_apply_welch_window_c; 259 s->lpc_compute_autocorr = lpc_compute_autocorr_c; 260 261 if (HAVE_MMX) 262 ff_lpc_init_x86(s); 263 264 return 0; 265} 266 267av_cold void ff_lpc_end(LPCContext *s) 268{ 269 av_freep(&s->windowed_samples); 270} 271