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#ifndef AVCODEC_LPC_H 23#define AVCODEC_LPC_H 24 25#include <stdint.h> 26#include "dsputil.h" 27 28#define ORDER_METHOD_EST 0 29#define ORDER_METHOD_2LEVEL 1 30#define ORDER_METHOD_4LEVEL 2 31#define ORDER_METHOD_8LEVEL 3 32#define ORDER_METHOD_SEARCH 4 33#define ORDER_METHOD_LOG 5 34 35#define MIN_LPC_ORDER 1 36#define MAX_LPC_ORDER 32 37 38/** 39 * LPC analysis type 40 */ 41enum FFLPCType { 42 FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type 43 FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients 44 FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients 45 FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion 46 FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization 47 FF_LPC_TYPE_NB , ///< Not part of ABI 48}; 49 50typedef struct LPCContext { 51 int blocksize; 52 int max_order; 53 enum FFLPCType lpc_type; 54 double *windowed_samples; 55 56 /** 57 * Apply a Welch window to an array of input samples. 58 * The output samples have the same scale as the input, but are in double 59 * sample format. 60 * @param data input samples 61 * @param len number of input samples 62 * @param w_data output samples 63 */ 64 void (*lpc_apply_welch_window)(const int32_t *data, int len, 65 double *w_data); 66 /** 67 * Perform autocorrelation on input samples with delay of 0 to lag. 68 * @param data input samples. 69 * constraints: no alignment needed, but must have have at 70 * least lag*sizeof(double) valid bytes preceding it, and 71 * size must be at least (len+1)*sizeof(double) if data is 72 * 16-byte aligned or (len+2)*sizeof(double) if data is 73 * unaligned. 74 * @param len number of input samples to process 75 * @param lag maximum delay to calculate 76 * @param autoc output autocorrelation coefficients. 77 * constraints: array size must be at least lag+1. 78 */ 79 void (*lpc_compute_autocorr)(const double *data, int len, int lag, 80 double *autoc); 81} LPCContext; 82 83 84/** 85 * Calculate LPC coefficients for multiple orders 86 */ 87int ff_lpc_calc_coefs(LPCContext *s, 88 const int32_t *samples, int blocksize, int min_order, 89 int max_order, int precision, 90 int32_t coefs[][MAX_LPC_ORDER], int *shift, 91 enum FFLPCType lpc_type, int lpc_passes, 92 int omethod, int max_shift, int zero_shift); 93 94/** 95 * Initialize LPCContext. 96 */ 97int ff_lpc_init(LPCContext *s, int blocksize, int max_order, 98 enum FFLPCType lpc_type); 99void ff_lpc_init_x86(LPCContext *s); 100 101/** 102 * Uninitialize LPCContext. 103 */ 104void ff_lpc_end(LPCContext *s); 105 106#ifdef LPC_USE_DOUBLE 107#define LPC_TYPE double 108#else 109#define LPC_TYPE float 110#endif 111 112/** 113 * Levinson-Durbin recursion. 114 * Produce LPC coefficients from autocorrelation data. 115 */ 116static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, 117 LPC_TYPE *lpc, int lpc_stride, int fail, 118 int normalize) 119{ 120 int i, j; 121 LPC_TYPE err; 122 LPC_TYPE *lpc_last = lpc; 123 124 if (normalize) 125 err = *autoc++; 126 127 if (fail && (autoc[max_order - 1] == 0 || err <= 0)) 128 return -1; 129 130 for(i=0; i<max_order; i++) { 131 LPC_TYPE r = -autoc[i]; 132 133 if (normalize) { 134 for(j=0; j<i; j++) 135 r -= lpc_last[j] * autoc[i-j-1]; 136 137 r /= err; 138 err *= 1.0 - (r * r); 139 } 140 141 lpc[i] = r; 142 143 for(j=0; j < (i+1)>>1; j++) { 144 LPC_TYPE f = lpc_last[ j]; 145 LPC_TYPE b = lpc_last[i-1-j]; 146 lpc[ j] = f + r * b; 147 lpc[i-1-j] = b + r * f; 148 } 149 150 if (fail && err < 0) 151 return -1; 152 153 lpc_last = lpc; 154 lpc += lpc_stride; 155 } 156 157 return 0; 158} 159 160#endif /* AVCODEC_LPC_H */ 161