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/lls2.h" 24 25#define LPC_USE_DOUBLE 26#include "lpc.h" 27#include "libavutil/avassert.h" 28 29 30/** 31 * Apply Welch window function to audio block 32 */ 33static void lpc_apply_welch_window_c(const int32_t *data, int len, 34 double *w_data) 35{ 36 int i, n2; 37 double w; 38 double c; 39 40 /* The optimization in commit fa4ed8c does not support odd len. 41 * If someone wants odd len extend that change. */ 42 av_assert2(!(len & 1)); 43 44 n2 = (len >> 1); 45 c = 2.0 / (len - 1.0); 46 47 w_data+=n2; 48 data+=n2; 49 for(i=0; i<n2; i++) { 50 w = c - n2 + i; 51 w = 1.0 - (w * w); 52 w_data[-i-1] = data[-i-1] * w; 53 w_data[+i ] = data[+i ] * w; 54 } 55} 56 57/** 58 * Calculate autocorrelation data from audio samples 59 * A Welch window function is applied before calculation. 60 */ 61static void lpc_compute_autocorr_c(const double *data, int len, int lag, 62 double *autoc) 63{ 64 int i, j; 65 66 for(j=0; j<lag; j+=2){ 67 double sum0 = 1.0, sum1 = 1.0; 68 for(i=j; i<len; i++){ 69 sum0 += data[i] * data[i-j]; 70 sum1 += data[i] * data[i-j-1]; 71 } 72 autoc[j ] = sum0; 73 autoc[j+1] = sum1; 74 } 75 76 if(j==lag){ 77 double sum = 1.0; 78 for(i=j-1; i<len; i+=2){ 79 sum += data[i ] * data[i-j ] 80 + data[i+1] * data[i-j+1]; 81 } 82 autoc[j] = sum; 83 } 84} 85 86/** 87 * Quantize LPC coefficients 88 */ 89static void quantize_lpc_coefs(double *lpc_in, int order, int precision, 90 int32_t *lpc_out, int *shift, int max_shift, int zero_shift) 91{ 92 int i; 93 double cmax, error; 94 int32_t qmax; 95 int sh; 96 97 /* define maximum levels */ 98 qmax = (1 << (precision - 1)) - 1; 99 100 /* find maximum coefficient value */ 101 cmax = 0.0; 102 for(i=0; i<order; i++) { 103 cmax= FFMAX(cmax, fabs(lpc_in[i])); 104 } 105 106 /* if maximum value quantizes to zero, return all zeros */ 107 if(cmax * (1 << max_shift) < 1.0) { 108 *shift = zero_shift; 109 memset(lpc_out, 0, sizeof(int32_t) * order); 110 return; 111 } 112 113 /* calculate level shift which scales max coeff to available bits */ 114 sh = max_shift; 115 while((cmax * (1 << sh) > qmax) && (sh > 0)) { 116 sh--; 117 } 118 119 /* since negative shift values are unsupported in decoder, scale down 120 coefficients instead */ 121 if(sh == 0 && cmax > qmax) { 122 double scale = ((double)qmax) / cmax; 123 for(i=0; i<order; i++) { 124 lpc_in[i] *= scale; 125 } 126 } 127 128 /* output quantized coefficients and level shift */ 129 error=0; 130 for(i=0; i<order; i++) { 131 error -= lpc_in[i] * (1 << sh); 132 lpc_out[i] = av_clip(lrintf(error), -qmax, qmax); 133 error -= lpc_out[i]; 134 } 135 *shift = sh; 136} 137 138static int estimate_best_order(double *ref, int min_order, int max_order) 139{ 140 int i, est; 141 142 est = min_order; 143 for(i=max_order-1; i>=min_order-1; i--) { 144 if(ref[i] > 0.10) { 145 est = i+1; 146 break; 147 } 148 } 149 return est; 150} 151 152int ff_lpc_calc_ref_coefs(LPCContext *s, 153 const int32_t *samples, int order, double *ref) 154{ 155 double autoc[MAX_LPC_ORDER + 1]; 156 157 s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples); 158 s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc); 159 compute_ref_coefs(autoc, order, ref, NULL); 160 161 return order; 162} 163 164/** 165 * Calculate LPC coefficients for multiple orders 166 * 167 * @param lpc_type LPC method for determining coefficients, 168 * see #FFLPCType for details 169 */ 170int ff_lpc_calc_coefs(LPCContext *s, 171 const int32_t *samples, int blocksize, int min_order, 172 int max_order, int precision, 173 int32_t coefs[][MAX_LPC_ORDER], int *shift, 174 enum FFLPCType lpc_type, int lpc_passes, 175 int omethod, int max_shift, int zero_shift) 176{ 177 double autoc[MAX_LPC_ORDER+1]; 178 double ref[MAX_LPC_ORDER]; 179 double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER]; 180 int i, j, pass = 0; 181 int opt_order; 182 183 av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && 184 lpc_type > FF_LPC_TYPE_FIXED); 185 av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY || lpc_type == FF_LPC_TYPE_LEVINSON); 186 187 /* reinit LPC context if parameters have changed */ 188 if (blocksize != s->blocksize || max_order != s->max_order || 189 lpc_type != s->lpc_type) { 190 ff_lpc_end(s); 191 ff_lpc_init(s, blocksize, max_order, lpc_type); 192 } 193 194 if(lpc_passes <= 0) 195 lpc_passes = 2; 196 197 if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) { 198 s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples); 199 200 s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc); 201 202 compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1); 203 204 for(i=0; i<max_order; i++) 205 ref[i] = fabs(lpc[i][i]); 206 207 pass++; 208 } 209 210 if (lpc_type == FF_LPC_TYPE_CHOLESKY) { 211 LLSModel2 m[2]; 212 LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]); 213 double av_uninit(weight); 214 memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var)); 215 216 for(j=0; j<max_order; j++) 217 m[0].coeff[max_order-1][j] = -lpc[max_order-1][j]; 218 219 for(; pass<lpc_passes; pass++){ 220 avpriv_init_lls2(&m[pass&1], max_order); 221 222 weight=0; 223 for(i=max_order; i<blocksize; i++){ 224 for(j=0; j<=max_order; j++) 225 var[j]= samples[i-j]; 226 227 if(pass){ 228 double eval, inv, rinv; 229 eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1); 230 eval= (512>>pass) + fabs(eval - var[0]); 231 inv = 1/eval; 232 rinv = sqrt(inv); 233 for(j=0; j<=max_order; j++) 234 var[j] *= rinv; 235 weight += inv; 236 }else 237 weight++; 238 239 m[pass&1].update_lls(&m[pass&1], var); 240 } 241 avpriv_solve_lls2(&m[pass&1], 0.001, 0); 242 } 243 244 for(i=0; i<max_order; i++){ 245 for(j=0; j<max_order; j++) 246 lpc[i][j]=-m[(pass-1)&1].coeff[i][j]; 247 ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000; 248 } 249 for(i=max_order-1; i>0; i--) 250 ref[i] = ref[i-1] - ref[i]; 251 } 252 253 opt_order = max_order; 254 255 if(omethod == ORDER_METHOD_EST) { 256 opt_order = estimate_best_order(ref, min_order, max_order); 257 i = opt_order-1; 258 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift); 259 } else { 260 for(i=min_order-1; i<max_order; i++) { 261 quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift); 262 } 263 } 264 265 return opt_order; 266} 267 268av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order, 269 enum FFLPCType lpc_type) 270{ 271 s->blocksize = blocksize; 272 s->max_order = max_order; 273 s->lpc_type = lpc_type; 274 275 s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) * 276 sizeof(*s->windowed_samples)); 277 if (!s->windowed_buffer) 278 return AVERROR(ENOMEM); 279 s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4); 280 281 s->lpc_apply_welch_window = lpc_apply_welch_window_c; 282 s->lpc_compute_autocorr = lpc_compute_autocorr_c; 283 284 if (ARCH_X86) 285 ff_lpc_init_x86(s); 286 287 return 0; 288} 289 290av_cold void ff_lpc_end(LPCContext *s) 291{ 292 av_freep(&s->windowed_buffer); 293} 294