ffmpeg/libavcodec/lpc.h

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