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 <stddef.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, ptrdiff_t 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, ptrdiff_t 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 min_shift, 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 double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
 103                                int order, double *ref);
 104
 105 /**
 106  * Initialize LPCContext.
 107  */
 108 int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
 109                 enum FFLPCType lpc_type);
 110 void ff_lpc_init_riscv(LPCContext *s);
 111 void ff_lpc_init_x86(LPCContext *s);
 112
 113 /**
 114  * Uninitialize LPCContext.
 115  */
 116 void ff_lpc_end(LPCContext *s);
 117
 118 #endif /* AVCODEC_LPC_H */