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/libavcodec/lpc.h

http://github.com/FFmpeg/FFmpeg
C Header | 212 lines | 119 code | 31 blank | 62 comment | 17 complexity | 8e2f82d33310f79e200ee5983ef9aaf6 MD5 | raw file
  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] / err;
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] / err;
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            r /= err;
190            err *= FIXR(1.0) - (r * r);
191        }
192
193        lpc[i] = r;
194
195        for(j=0; j < (i+1)>>1; j++) {
196            LPC_TYPE f = lpc_last[    j];
197            LPC_TYPE b = lpc_last[i-1-j];
198            lpc[    j] = f + (LPC_TYPE_U)AAC_MUL26(r, b);
199            lpc[i-1-j] = b + (LPC_TYPE_U)AAC_MUL26(r, f);
200        }
201
202        if (fail && err < 0)
203            return -1;
204
205        lpc_last = lpc;
206        lpc += lpc_stride;
207    }
208
209    return 0;
210}
211
212#endif /* AVCODEC_LPC_H */