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#ifndef AVCODEC_LPC_H 23#define AVCODEC_LPC_H 24 25#include <stdint.h> 26#include "libavutil/avassert.h" 27#include "libavutil/lls.h" 28#include "aac_defines.h" 29 30#define ORDER_METHOD_EST 0 31#define ORDER_METHOD_2LEVEL 1 32#define ORDER_METHOD_4LEVEL 2 33#define ORDER_METHOD_8LEVEL 3 34#define ORDER_METHOD_SEARCH 4 35#define ORDER_METHOD_LOG 5 36 37#define MIN_LPC_ORDER 1 38#define MAX_LPC_ORDER 32 39 40/** 41 * LPC analysis type 42 */ 43enum FFLPCType { 44 FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type 45 FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients 46 FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients 47 FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion 48 FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization 49 FF_LPC_TYPE_NB , ///< Not part of ABI 50}; 51 52typedef struct LPCContext { 53 int blocksize; 54 int max_order; 55 enum FFLPCType lpc_type; 56 double *windowed_buffer; 57 double *windowed_samples; 58 59 /** 60 * Apply a Welch window to an array of input samples. 61 * The output samples have the same scale as the input, but are in double 62 * sample format. 63 * @param data input samples 64 * @param len number of input samples 65 * @param w_data output samples 66 */ 67 void (*lpc_apply_welch_window)(const int32_t *data, int len, 68 double *w_data); 69 /** 70 * Perform autocorrelation on input samples with delay of 0 to lag. 71 * @param data input samples. 72 * constraints: no alignment needed, but must have at 73 * least lag*sizeof(double) valid bytes preceding it, and 74 * size must be at least (len+1)*sizeof(double) if data is 75 * 16-byte aligned or (len+2)*sizeof(double) if data is 76 * unaligned. 77 * @param len number of input samples to process 78 * @param lag maximum delay to calculate 79 * @param autoc output autocorrelation coefficients. 80 * constraints: array size must be at least lag+1. 81 */ 82 void (*lpc_compute_autocorr)(const double *data, int len, int lag, 83 double *autoc); 84 85 // TODO: these should be allocated to reduce ABI compatibility issues 86 LLSModel lls_models[2]; 87} LPCContext; 88 89 90/** 91 * Calculate LPC coefficients for multiple orders 92 */ 93int ff_lpc_calc_coefs(LPCContext *s, 94 const int32_t *samples, int blocksize, int min_order, 95 int max_order, int precision, 96 int32_t coefs[][MAX_LPC_ORDER], int *shift, 97 enum FFLPCType lpc_type, int lpc_passes, 98 int omethod, int min_shift, int max_shift, int zero_shift); 99 100int ff_lpc_calc_ref_coefs(LPCContext *s, 101 const int32_t *samples, int order, double *ref); 102 103double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len, 104 int order, double *ref); 105 106/** 107 * Initialize LPCContext. 108 */ 109int ff_lpc_init(LPCContext *s, int blocksize, int max_order, 110 enum FFLPCType lpc_type); 111void ff_lpc_init_x86(LPCContext *s); 112 113/** 114 * Uninitialize LPCContext. 115 */ 116void ff_lpc_end(LPCContext *s); 117 118#if USE_FIXED 119typedef int LPC_TYPE; 120typedef unsigned LPC_TYPE_U; 121#else 122#ifdef LPC_USE_DOUBLE 123typedef double LPC_TYPE; 124typedef double LPC_TYPE_U; 125#else 126typedef float LPC_TYPE; 127typedef float LPC_TYPE_U; 128#endif 129#endif // USE_FIXED 130 131/** 132 * Schur recursion. 133 * Produces reflection coefficients from autocorrelation data. 134 */ 135static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order, 136 LPC_TYPE *ref, LPC_TYPE *error) 137{ 138 int i, j; 139 LPC_TYPE err; 140 LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER]; 141 142 for (i = 0; i < max_order; i++) 143 gen0[i] = gen1[i] = autoc[i + 1]; 144 145 err = autoc[0]; 146 ref[0] = -gen1[0] / ((USE_FIXED || err) ? err : 1); 147 err += gen1[0] * ref[0]; 148 if (error) 149 error[0] = err; 150 for (i = 1; i < max_order; i++) { 151 for (j = 0; j < max_order - i; j++) { 152 gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j]; 153 gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j]; 154 } 155 ref[i] = -gen1[0] / ((USE_FIXED || err) ? err : 1); 156 err += gen1[0] * ref[i]; 157 if (error) 158 error[i] = err; 159 } 160} 161 162/** 163 * Levinson-Durbin recursion. 164 * Produce LPC coefficients from autocorrelation data. 165 */ 166static inline int AAC_RENAME(compute_lpc_coefs)(const LPC_TYPE *autoc, int max_order, 167 LPC_TYPE *lpc, int lpc_stride, int fail, 168 int normalize) 169{ 170 int i, j; 171 LPC_TYPE err = 0; 172 LPC_TYPE *lpc_last = lpc; 173 174 av_assert2(normalize || !fail); 175 176 if (normalize) 177 err = *autoc++; 178 179 if (fail && (autoc[max_order - 1] == 0 || err <= 0)) 180 return -1; 181 182 for(i=0; i<max_order; i++) { 183 LPC_TYPE r = AAC_SRA_R(-autoc[i], 5); 184 185 if (normalize) { 186 for(j=0; j<i; j++) 187 r -= lpc_last[j] * autoc[i-j-1]; 188 189 if (err) 190 r /= err; 191 err *= FIXR(1.0) - (r * r); 192 } 193 194 lpc[i] = r; 195 196 for(j=0; j < (i+1)>>1; j++) { 197 LPC_TYPE f = lpc_last[ j]; 198 LPC_TYPE b = lpc_last[i-1-j]; 199 lpc[ j] = f + (LPC_TYPE_U)AAC_MUL26(r, b); 200 lpc[i-1-j] = b + (LPC_TYPE_U)AAC_MUL26(r, f); 201 } 202 203 if (fail && err < 0) 204 return -1; 205 206 lpc_last = lpc; 207 lpc += lpc_stride; 208 } 209 210 return 0; 211} 212 213#endif /* AVCODEC_LPC_H */ 214