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lpc.h
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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  */
43 enum 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 
52 typedef struct LPCContext {
53  int blocksize;
54  int max_order;
56  double *windowed_buffer;
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  */
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
87 } LPCContext;
88 
89 
90 /**
91  * Calculate LPC coefficients for multiple orders
92  */
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 
101  const int32_t *samples, int order, double *ref);
102 
103 double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
104  int order, double *ref);
105 
106 /**
107  * Initialize LPCContext.
108  */
109 int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
110  enum FFLPCType lpc_type);
112 
113 /**
114  * Uninitialize LPCContext.
115  */
116 void ff_lpc_end(LPCContext *s);
117 
118 #if USE_FIXED
119 typedef int LPC_TYPE;
120 #else
121 #ifdef LPC_USE_DOUBLE
122 typedef double LPC_TYPE;
123 #else
124 typedef float LPC_TYPE;
125 #endif
126 #endif // USE_FIXED
127 
128 /**
129  * Schur recursion.
130  * Produces reflection coefficients from autocorrelation data.
131  */
132 static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
133  LPC_TYPE *ref, LPC_TYPE *error)
134 {
135  int i, j;
136  LPC_TYPE err;
137  LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
138 
139  for (i = 0; i < max_order; i++)
140  gen0[i] = gen1[i] = autoc[i + 1];
141 
142  err = autoc[0];
143  ref[0] = -gen1[0] / err;
144  err += gen1[0] * ref[0];
145  if (error)
146  error[0] = err;
147  for (i = 1; i < max_order; i++) {
148  for (j = 0; j < max_order - i; j++) {
149  gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
150  gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
151  }
152  ref[i] = -gen1[0] / err;
153  err += gen1[0] * ref[i];
154  if (error)
155  error[i] = err;
156  }
157 }
158 
159 /**
160  * Levinson-Durbin recursion.
161  * Produce LPC coefficients from autocorrelation data.
162  */
163 static inline int AAC_RENAME(compute_lpc_coefs)(const LPC_TYPE *autoc, int max_order,
164  LPC_TYPE *lpc, int lpc_stride, int fail,
165  int normalize)
166 {
167  int i, j;
168  LPC_TYPE err = 0;
169  LPC_TYPE *lpc_last = lpc;
170 
171  av_assert2(normalize || !fail);
172 
173  if (normalize)
174  err = *autoc++;
175 
176  if (fail && (autoc[max_order - 1] == 0 || err <= 0))
177  return -1;
178 
179  for(i=0; i<max_order; i++) {
180  LPC_TYPE r = AAC_SRA_R(-autoc[i], 5);
181 
182  if (normalize) {
183  for(j=0; j<i; j++)
184  r -= lpc_last[j] * autoc[i-j-1];
185 
186  r /= err;
187  err *= FIXR(1.0) - (r * r);
188  }
189 
190  lpc[i] = r;
191 
192  for(j=0; j < (i+1)>>1; j++) {
193  LPC_TYPE f = lpc_last[ j];
194  LPC_TYPE b = lpc_last[i-1-j];
195  lpc[ j] = f + AAC_MUL26(r, b);
196  lpc[i-1-j] = b + AAC_MUL26(r, f);
197  }
198 
199  if (fail && err < 0)
200  return -1;
201 
202  lpc_last = lpc;
203  lpc += lpc_stride;
204  }
205 
206  return 0;
207 }
208 
209 #endif /* AVCODEC_LPC_H */
const char * s
Definition: avisynth_c.h:768
static int shift(int a, int b)
Definition: sonic.c:82
Linear least squares model.
Definition: lls.h:38
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:101
Definition: lpc.h:52
#define AAC_MUL26(x, y)
Definition: aac_defines.h:98
#define MAX_LPC_ORDER
Definition: lpc.h:38
const char * b
Definition: vf_curves.c:113
static void compute_ref_coefs(const LPC_TYPE *autoc, int max_order, LPC_TYPE *ref, LPC_TYPE *error)
Schur recursion.
Definition: lpc.h:132
enum FFLPCType lpc_type
Definition: lpc.h:55
#define FIXR(x)
Definition: aac_defines.h:90
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:63
do not use LPC prediction or use all zero coefficients
Definition: lpc.h:45
double * windowed_buffer
Definition: lpc.h:56
int max_order
Definition: lpc.h:54
int blocksize
Definition: lpc.h:53
const char * r
Definition: vf_curves.c:111
simple assert() macros that are a bit more flexible than ISO C assert().
int ff_lpc_calc_ref_coefs(LPCContext *s, const int32_t *samples, int order, double *ref)
Definition: lpc.c:159
#define fail()
Definition: checkasm.h:82
#define AAC_RENAME(x)
Definition: aac_defines.h:83
LLSModel lls_models[2]
Definition: lpc.h:86
int ff_lpc_calc_coefs(LPCContext *s, const int32_t *samples, int blocksize, int min_order, int max_order, int precision, int32_t coefs[][MAX_LPC_ORDER], int *shift, enum FFLPCType lpc_type, int lpc_passes, int omethod, int min_shift, int max_shift, int zero_shift)
Calculate LPC coefficients for multiple orders.
Definition: lpc.c:200
typedef void(APIENTRY *FF_PFNGLACTIVETEXTUREPROC)(GLenum texture)
int32_t
int ff_lpc_init(LPCContext *s, int blocksize, int max_order, enum FFLPCType lpc_type)
Initialize LPCContext.
Definition: lpc.c:300
static int AAC_RENAME() compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, LPC_TYPE *lpc, int lpc_stride, int fail, int normalize)
Levinson-Durbin recursion.
Definition: lpc.h:163
Not part of ABI.
Definition: lpc.h:49
void ff_lpc_end(LPCContext *s)
Uninitialize LPCContext.
Definition: lpc.c:322
Levinson-Durbin recursion.
Definition: lpc.h:47
use the codec default LPC type
Definition: lpc.h:44
double * windowed_samples
Definition: lpc.h:57
#define AAC_SRA_R(x, y)
Definition: aac_defines.h:110
FFLPCType
LPC analysis type.
Definition: lpc.h:43
Cholesky factorization.
Definition: lpc.h:48
static int ref[MAX_W *MAX_W]
Definition: jpeg2000dwt.c:107
fixed LPC coefficients
Definition: lpc.h:46
void(* lpc_compute_autocorr)(const double *data, int len, int lag, double *autoc)
Perform autocorrelation on input samples with delay of 0 to lag.
Definition: lpc.h:82
int len
double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len, int order, double *ref)
Definition: lpc.c:171
void(* lpc_apply_welch_window)(const int32_t *data, int len, double *w_data)
Apply a Welch window to an array of input samples.
Definition: lpc.h:67
float LPC_TYPE
Definition: lpc.h:124
void ff_lpc_init_x86(LPCContext *s)
Definition: lpc.c:152