FFmpeg
lpc.h
Go to the documentation of this 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 <stddef.h>
27 #include "libavutil/avassert.h"
28 #include "libavutil/lls.h"
29 #include "aac_defines.h"
30 
31 #define ORDER_METHOD_EST 0
32 #define ORDER_METHOD_2LEVEL 1
33 #define ORDER_METHOD_4LEVEL 2
34 #define ORDER_METHOD_8LEVEL 3
35 #define ORDER_METHOD_SEARCH 4
36 #define ORDER_METHOD_LOG 5
37 
38 #define MIN_LPC_ORDER 1
39 #define MAX_LPC_ORDER 32
40 
41 /**
42  * LPC analysis type
43  */
44 enum FFLPCType {
45  FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type
46  FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients
47  FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients
48  FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion
49  FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization
50  FF_LPC_TYPE_NB , ///< Not part of ABI
51 };
52 
53 typedef struct LPCContext {
54  int blocksize;
55  int max_order;
57  double *windowed_buffer;
59 
60  /**
61  * Apply a Welch window to an array of input samples.
62  * The output samples have the same scale as the input, but are in double
63  * sample format.
64  * @param data input samples
65  * @param len number of input samples
66  * @param w_data output samples
67  */
68  void (*lpc_apply_welch_window)(const int32_t *data, ptrdiff_t len,
69  double *w_data);
70  /**
71  * Perform autocorrelation on input samples with delay of 0 to lag.
72  * @param data input samples.
73  * constraints: no alignment needed, but must have at
74  * least lag*sizeof(double) valid bytes preceding it, and
75  * size must be at least (len+1)*sizeof(double) if data is
76  * 16-byte aligned or (len+2)*sizeof(double) if data is
77  * unaligned.
78  * @param len number of input samples to process
79  * @param lag maximum delay to calculate
80  * @param autoc output autocorrelation coefficients.
81  * constraints: array size must be at least lag+1.
82  */
83  void (*lpc_compute_autocorr)(const double *data, ptrdiff_t len, int lag,
84  double *autoc);
85 
86  // TODO: these should be allocated to reduce ABI compatibility issues
88 } LPCContext;
89 
90 
91 /**
92  * Calculate LPC coefficients for multiple orders
93  */
95  const int32_t *samples, int blocksize, int min_order,
96  int max_order, int precision,
97  int32_t coefs[][MAX_LPC_ORDER], int *shift,
98  enum FFLPCType lpc_type, int lpc_passes,
99  int omethod, int min_shift, int max_shift, int zero_shift);
100 
102  const int32_t *samples, int order, double *ref);
103 
104 double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
105  int order, double *ref);
106 
107 /**
108  * Initialize LPCContext.
109  */
110 int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
111  enum FFLPCType lpc_type);
113 
114 /**
115  * Uninitialize LPCContext.
116  */
117 void ff_lpc_end(LPCContext *s);
118 
119 #if USE_FIXED
120 typedef int LPC_TYPE;
121 typedef unsigned LPC_TYPE_U;
122 #else
123 #ifdef LPC_USE_DOUBLE
124 typedef double LPC_TYPE;
125 typedef double LPC_TYPE_U;
126 #else
127 typedef float LPC_TYPE;
128 typedef float LPC_TYPE_U;
129 #endif
130 #endif // USE_FIXED
131 
132 /**
133  * Schur recursion.
134  * Produces reflection coefficients from autocorrelation data.
135  */
136 static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
138 {
139  int i, j;
140  LPC_TYPE err;
141  LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
142 
143  for (i = 0; i < max_order; i++)
144  gen0[i] = gen1[i] = autoc[i + 1];
145 
146  err = autoc[0];
147  ref[0] = -gen1[0] / ((USE_FIXED || err) ? err : 1);
148  err += gen1[0] * ref[0];
149  if (error)
150  error[0] = err;
151  for (i = 1; i < max_order; i++) {
152  for (j = 0; j < max_order - i; j++) {
153  gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
154  gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
155  }
156  ref[i] = -gen1[0] / ((USE_FIXED || err) ? err : 1);
157  err += gen1[0] * ref[i];
158  if (error)
159  error[i] = err;
160  }
161 }
162 
163 /**
164  * Levinson-Durbin recursion.
165  * Produce LPC coefficients from autocorrelation data.
166  */
167 static inline int AAC_RENAME(compute_lpc_coefs)(const LPC_TYPE *autoc, int max_order,
168  LPC_TYPE *lpc, int lpc_stride, int fail,
169  int normalize)
170 {
171  int i, j;
172  LPC_TYPE err = 0;
173  LPC_TYPE *lpc_last = lpc;
174 
176 
177  if (normalize)
178  err = *autoc++;
179 
180  if (fail && (autoc[max_order - 1] == 0 || err <= 0))
181  return -1;
182 
183  for(i=0; i<max_order; i++) {
184  LPC_TYPE r = AAC_SRA_R(-autoc[i], 5);
185 
186  if (normalize) {
187  for(j=0; j<i; j++)
188  r -= lpc_last[j] * autoc[i-j-1];
189 
190  if (err)
191  r /= err;
192  err *= FIXR(1.0) - (r * r);
193  }
194 
195  lpc[i] = r;
196 
197  for(j=0; j < (i+1)>>1; j++) {
198  LPC_TYPE f = lpc_last[ j];
199  LPC_TYPE b = lpc_last[i-1-j];
200  lpc[ j] = f + (LPC_TYPE_U)AAC_MUL26(r, b);
201  lpc[i-1-j] = b + (LPC_TYPE_U)AAC_MUL26(r, f);
202  }
203 
204  if (fail && err < 0)
205  return -1;
206 
207  lpc_last = lpc;
208  lpc += lpc_stride;
209  }
210 
211  return 0;
212 }
213 
214 #endif /* AVCODEC_LPC_H */
error
static void error(const char *err)
Definition: target_bsf_fuzzer.c:31
LLSModel
Linear least squares model.
Definition: lls.h:37
FFLPCType
FFLPCType
LPC analysis type.
Definition: lpc.h:44
LPCContext::lpc_apply_welch_window
void(* lpc_apply_welch_window)(const int32_t *data, ptrdiff_t len, double *w_data)
Apply a Welch window to an array of input samples.
Definition: lpc.h:68
r
const char * r
Definition: vf_curves.c:126
ff_lpc_end
void ff_lpc_end(LPCContext *s)
Uninitialize LPCContext.
Definition: lpc.c:330
FF_LPC_TYPE_CHOLESKY
@ FF_LPC_TYPE_CHOLESKY
Cholesky factorization.
Definition: lpc.h:49
compute_lpc_coefs
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:167
b
#define b
Definition: input.c:41
data
const char data[16]
Definition: mxf.c:146
LPCContext::windowed_buffer
double * windowed_buffer
Definition: lpc.h:57
LPCContext
Definition: lpc.h:53
fail
#define fail()
Definition: checkasm.h:134
normalize
static float normalize(float r, float g, float b, float max)
Definition: preserve_color.h:37
ff_lpc_init
int ff_lpc_init(LPCContext *s, int blocksize, int max_order, enum FFLPCType lpc_type)
Initialize LPCContext.
Definition: lpc.c:307
FF_LPC_TYPE_DEFAULT
@ FF_LPC_TYPE_DEFAULT
use the codec default LPC type
Definition: lpc.h:45
avassert.h
USE_FIXED
#define USE_FIXED
Definition: aac_defines.h:25
s
#define s(width, name)
Definition: cbs_vp9.c:256
LPCContext::lpc_type
enum FFLPCType lpc_type
Definition: lpc.h:56
LPC_TYPE
float LPC_TYPE
Definition: lpc.h:127
lls.h
LPCContext::lls_models
LLSModel lls_models[2]
Definition: lpc.h:87
ff_lpc_calc_ref_coefs_f
double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len, int order, double *ref)
Definition: lpc.c:178
LPCContext::max_order
int max_order
Definition: lpc.h:55
ff_lpc_calc_ref_coefs
int ff_lpc_calc_ref_coefs(LPCContext *s, const int32_t *samples, int order, double *ref)
Definition: lpc.c:166
LPCContext::blocksize
int blocksize
Definition: lpc.h:54
LPCContext::lpc_compute_autocorr
void(* lpc_compute_autocorr)(const double *data, ptrdiff_t len, int lag, double *autoc)
Perform autocorrelation on input samples with delay of 0 to lag.
Definition: lpc.h:83
ff_lpc_calc_coefs
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:207
f
f
Definition: af_crystalizer.c:122
shift
static int shift(int a, int b)
Definition: bonk.c:253
FF_LPC_TYPE_NB
@ FF_LPC_TYPE_NB
Not part of ABI.
Definition: lpc.h:50
MAX_LPC_ORDER
#define MAX_LPC_ORDER
Definition: lpc.h:39
ff_lpc_init_x86
void ff_lpc_init_x86(LPCContext *s)
Definition: lpc_init.c:106
LPCContext::windowed_samples
double * windowed_samples
Definition: lpc.h:58
normalize
Definition: normalize.py:1
av_assert2
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:64
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:269
AAC_MUL26
#define AAC_MUL26(x, y)
Definition: aac_defines.h:96
AAC_RENAME
#define AAC_RENAME(x)
Definition: aac_defines.h:79
len
int len
Definition: vorbis_enc_data.h:426
compute_ref_coefs
static void compute_ref_coefs(const LPC_TYPE *autoc, int max_order, LPC_TYPE *ref, LPC_TYPE *error)
Schur recursion.
Definition: lpc.h:136
AAC_SRA_R
#define AAC_SRA_R(x, y)
Definition: aac_defines.h:108
ref
static int ref[MAX_W *MAX_W]
Definition: jpeg2000dwt.c:112
samples
Filter the word “frame” indicates either a video frame or a group of audio samples
Definition: filter_design.txt:8
int32_t
int32_t
Definition: audioconvert.c:56
aac_defines.h
FF_LPC_TYPE_NONE
@ FF_LPC_TYPE_NONE
do not use LPC prediction or use all zero coefficients
Definition: lpc.h:46
FF_LPC_TYPE_LEVINSON
@ FF_LPC_TYPE_LEVINSON
Levinson-Durbin recursion.
Definition: lpc.h:48
FF_LPC_TYPE_FIXED
@ FF_LPC_TYPE_FIXED
fixed LPC coefficients
Definition: lpc.h:47
FIXR
#define FIXR(x)
Definition: aac_defines.h:88
LPC_TYPE_U
float LPC_TYPE_U
Definition: lpc.h:128