FFmpeg
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  */
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
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 typedef unsigned LPC_TYPE_U;
121 #else
122 #ifdef LPC_USE_DOUBLE
123 typedef double LPC_TYPE;
124 typedef double LPC_TYPE_U;
125 #else
126 typedef float LPC_TYPE;
127 typedef float LPC_TYPE_U;
128 #endif
129 #endif // USE_FIXED
130 
131 /**
132  * Schur recursion.
133  * Produces reflection coefficients from autocorrelation data.
134  */
135 static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
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] / ((USE_FIXED || err) ? err : 1);
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] / ((USE_FIXED || err) ? err : 1);
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  */
166 static 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 
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  if (err)
190  r /= err;
191  err *= FIXR(1.0) - (r * r);
192  }
193 
194  lpc[i] = r;
195 
196  for(j=0; j < (i+1)>>1; j++) {
197  LPC_TYPE f = lpc_last[ j];
198  LPC_TYPE b = lpc_last[i-1-j];
199  lpc[ j] = f + (LPC_TYPE_U)AAC_MUL26(r, b);
200  lpc[i-1-j] = b + (LPC_TYPE_U)AAC_MUL26(r, f);
201  }
202 
203  if (fail && err < 0)
204  return -1;
205 
206  lpc_last = lpc;
207  lpc += lpc_stride;
208  }
209 
210  return 0;
211 }
212 
213 #endif /* AVCODEC_LPC_H */
error
static void error(const char *err)
Definition: target_bsf_fuzzer.c:30
LLSModel
Linear least squares model.
Definition: lls.h:38
FFLPCType
FFLPCType
LPC analysis type.
Definition: lpc.h:43
r
const char * r
Definition: vf_curves.c:116
ff_lpc_end
void ff_lpc_end(LPCContext *s)
Uninitialize LPCContext.
Definition: lpc.c:323
FF_LPC_TYPE_CHOLESKY
@ FF_LPC_TYPE_CHOLESKY
Cholesky factorization.
Definition: lpc.h:48
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:166
b
#define b
Definition: input.c:41
data
const char data[16]
Definition: mxf.c:142
LPCContext::windowed_buffer
double * windowed_buffer
Definition: lpc.h:56
LPCContext
Definition: lpc.h:52
fail
#define fail()
Definition: checkasm.h:133
ff_lpc_init
int ff_lpc_init(LPCContext *s, int blocksize, int max_order, enum FFLPCType lpc_type)
Initialize LPCContext.
Definition: lpc.c:301
LPCContext::lpc_apply_welch_window
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
FF_LPC_TYPE_DEFAULT
@ FF_LPC_TYPE_DEFAULT
use the codec default LPC type
Definition: lpc.h:44
avassert.h
USE_FIXED
#define USE_FIXED
Definition: aac_defines.h:25
s
#define s(width, name)
Definition: cbs_vp9.c:257
LPCContext::lpc_type
enum FFLPCType lpc_type
Definition: lpc.h:55
LPC_TYPE
float LPC_TYPE
Definition: lpc.h:126
lls.h
f
#define f(width, name)
Definition: cbs_vp9.c:255
int32_t
int32_t
Definition: audio_convert.c:194
LPCContext::lls_models
LLSModel lls_models[2]
Definition: lpc.h:86
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:172
LPCContext::max_order
int max_order
Definition: lpc.h:54
ff_lpc_calc_ref_coefs
int ff_lpc_calc_ref_coefs(LPCContext *s, const int32_t *samples, int order, double *ref)
Definition: lpc.c:160
LPCContext::lpc_compute_autocorr
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
LPCContext::blocksize
int blocksize
Definition: lpc.h:53
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:201
FF_LPC_TYPE_NB
@ FF_LPC_TYPE_NB
Not part of ABI.
Definition: lpc.h:49
MAX_LPC_ORDER
#define MAX_LPC_ORDER
Definition: lpc.h:38
ff_lpc_init_x86
void ff_lpc_init_x86(LPCContext *s)
Definition: lpc.c:152
LPCContext::windowed_samples
double * windowed_samples
Definition: lpc.h:57
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
int i
Definition: input.c:407
AAC_MUL26
#define AAC_MUL26(x, y)
Definition: aac_defines.h:102
AAC_RENAME
#define AAC_RENAME(x)
Definition: aac_defines.h:85
len
int len
Definition: vorbis_enc_data.h:452
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:135
AAC_SRA_R
#define AAC_SRA_R(x, y)
Definition: aac_defines.h:114
normalize
static void normalize(NormalizeContext *s, AVFrame *in, AVFrame *out)
Definition: vf_normalize.c:291
ref
static int ref[MAX_W *MAX_W]
Definition: jpeg2000dwt.c:107
samples
Filter the word “frame” indicates either a video frame or a group of audio samples
Definition: filter_design.txt:8
shift
static int shift(int a, int b)
Definition: sonic.c:82
aac_defines.h
FF_LPC_TYPE_NONE
@ FF_LPC_TYPE_NONE
do not use LPC prediction or use all zero coefficients
Definition: lpc.h:45
FF_LPC_TYPE_LEVINSON
@ FF_LPC_TYPE_LEVINSON
Levinson-Durbin recursion.
Definition: lpc.h:47
FF_LPC_TYPE_FIXED
@ FF_LPC_TYPE_FIXED
fixed LPC coefficients
Definition: lpc.h:46
FIXR
#define FIXR(x)
Definition: aac_defines.h:94
LPC_TYPE_U
float LPC_TYPE_U
Definition: lpc.h:127