lpc.c
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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 Libav.
6  *
7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "libavutil/common.h"
23 #include "libavutil/lls.h"
24 
25 #define LPC_USE_DOUBLE
26 #include "lpc.h"
27 
28 
32 static void lpc_apply_welch_window_c(const int32_t *data, int len,
33  double *w_data)
34 {
35  int i, n2;
36  double w;
37  double c;
38 
39  /* The optimization in commit fa4ed8c does not support odd len.
40  * If someone wants odd len extend that change. */
41  assert(!(len & 1));
42 
43  n2 = (len >> 1);
44  c = 2.0 / (len - 1.0);
45 
46  w_data+=n2;
47  data+=n2;
48  for(i=0; i<n2; i++) {
49  w = c - n2 + i;
50  w = 1.0 - (w * w);
51  w_data[-i-1] = data[-i-1] * w;
52  w_data[+i ] = data[+i ] * w;
53  }
54 }
55 
60 static void lpc_compute_autocorr_c(const double *data, int len, int lag,
61  double *autoc)
62 {
63  int i, j;
64 
65  for(j=0; j<lag; j+=2){
66  double sum0 = 1.0, sum1 = 1.0;
67  for(i=j; i<len; i++){
68  sum0 += data[i] * data[i-j];
69  sum1 += data[i] * data[i-j-1];
70  }
71  autoc[j ] = sum0;
72  autoc[j+1] = sum1;
73  }
74 
75  if(j==lag){
76  double sum = 1.0;
77  for(i=j-1; i<len; i+=2){
78  sum += data[i ] * data[i-j ]
79  + data[i+1] * data[i-j+1];
80  }
81  autoc[j] = sum;
82  }
83 }
84 
88 static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
89  int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
90 {
91  int i;
92  double cmax, error;
93  int32_t qmax;
94  int sh;
95 
96  /* define maximum levels */
97  qmax = (1 << (precision - 1)) - 1;
98 
99  /* find maximum coefficient value */
100  cmax = 0.0;
101  for(i=0; i<order; i++) {
102  cmax= FFMAX(cmax, fabs(lpc_in[i]));
103  }
104 
105  /* if maximum value quantizes to zero, return all zeros */
106  if(cmax * (1 << max_shift) < 1.0) {
107  *shift = zero_shift;
108  memset(lpc_out, 0, sizeof(int32_t) * order);
109  return;
110  }
111 
112  /* calculate level shift which scales max coeff to available bits */
113  sh = max_shift;
114  while((cmax * (1 << sh) > qmax) && (sh > 0)) {
115  sh--;
116  }
117 
118  /* since negative shift values are unsupported in decoder, scale down
119  coefficients instead */
120  if(sh == 0 && cmax > qmax) {
121  double scale = ((double)qmax) / cmax;
122  for(i=0; i<order; i++) {
123  lpc_in[i] *= scale;
124  }
125  }
126 
127  /* output quantized coefficients and level shift */
128  error=0;
129  for(i=0; i<order; i++) {
130  error -= lpc_in[i] * (1 << sh);
131  lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
132  error -= lpc_out[i];
133  }
134  *shift = sh;
135 }
136 
137 static int estimate_best_order(double *ref, int min_order, int max_order)
138 {
139  int i, est;
140 
141  est = min_order;
142  for(i=max_order-1; i>=min_order-1; i--) {
143  if(ref[i] > 0.10) {
144  est = i+1;
145  break;
146  }
147  }
148  return est;
149 }
150 
152  const int32_t *samples, int order, double *ref)
153 {
154  double autoc[MAX_LPC_ORDER + 1];
155 
157  s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc);
158  compute_ref_coefs(autoc, order, ref, NULL);
159 
160  return order;
161 }
162 
170  const int32_t *samples, int blocksize, int min_order,
171  int max_order, int precision,
172  int32_t coefs[][MAX_LPC_ORDER], int *shift,
173  enum FFLPCType lpc_type, int lpc_passes,
174  int omethod, int max_shift, int zero_shift)
175 {
176  double autoc[MAX_LPC_ORDER+1];
177  double ref[MAX_LPC_ORDER];
178  double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
179  int i, j, pass;
180  int opt_order;
181 
182  assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
183  lpc_type > FF_LPC_TYPE_FIXED);
184 
185  /* reinit LPC context if parameters have changed */
186  if (blocksize != s->blocksize || max_order != s->max_order ||
187  lpc_type != s->lpc_type) {
188  ff_lpc_end(s);
189  ff_lpc_init(s, blocksize, max_order, lpc_type);
190  }
191 
192  if (lpc_type == FF_LPC_TYPE_LEVINSON) {
193  s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);
194 
195  s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);
196 
197  compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
198 
199  for(i=0; i<max_order; i++)
200  ref[i] = fabs(lpc[i][i]);
201  } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
202  LLSModel m[2];
203  double var[MAX_LPC_ORDER+1], av_uninit(weight);
204 
205  for(pass=0; pass<lpc_passes; pass++){
206  av_init_lls(&m[pass&1], max_order);
207 
208  weight=0;
209  for(i=max_order; i<blocksize; i++){
210  for(j=0; j<=max_order; j++)
211  var[j]= samples[i-j];
212 
213  if(pass){
214  double eval, inv, rinv;
215  eval= av_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
216  eval= (512>>pass) + fabs(eval - var[0]);
217  inv = 1/eval;
218  rinv = sqrt(inv);
219  for(j=0; j<=max_order; j++)
220  var[j] *= rinv;
221  weight += inv;
222  }else
223  weight++;
224 
225  av_update_lls(&m[pass&1], var, 1.0);
226  }
227  av_solve_lls(&m[pass&1], 0.001, 0);
228  }
229 
230  for(i=0; i<max_order; i++){
231  for(j=0; j<max_order; j++)
232  lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
233  ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
234  }
235  for(i=max_order-1; i>0; i--)
236  ref[i] = ref[i-1] - ref[i];
237  }
238  opt_order = max_order;
239 
240  if(omethod == ORDER_METHOD_EST) {
241  opt_order = estimate_best_order(ref, min_order, max_order);
242  i = opt_order-1;
243  quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
244  } else {
245  for(i=min_order-1; i<max_order; i++) {
246  quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
247  }
248  }
249 
250  return opt_order;
251 }
252 
253 av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
254  enum FFLPCType lpc_type)
255 {
256  s->blocksize = blocksize;
257  s->max_order = max_order;
258  s->lpc_type = lpc_type;
259 
260  if (lpc_type == FF_LPC_TYPE_LEVINSON) {
261  s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) *
262  sizeof(*s->windowed_samples));
263  if (!s->windowed_buffer)
264  return AVERROR(ENOMEM);
265  s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4);
266  } else {
267  s->windowed_samples = NULL;
268  }
269 
272 
273  if (ARCH_X86)
274  ff_lpc_init_x86(s);
275 
276  return 0;
277 }
278 
280 {
282 }
static int16_t * samples
Linear least squares model.
Definition: lls.h:33
Definition: lpc.h:50
#define MAX_LPC_ORDER
Definition: lpc.h:36
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 max_shift, int zero_shift)
Calculate LPC coefficients for multiple orders.
Definition: lpc.c:169
static void lpc_compute_autocorr_c(const double *data, int len, int lag, double *autoc)
Calculate autocorrelation data from audio samples A Welch window function is applied before calculati...
Definition: lpc.c:60
#define ARCH_X86
Definition: config.h:33
#define pass
Definition: fft.c:334
void av_freep(void *arg)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc() and set the pointer ...
Definition: mem.c:151
static void compute_ref_coefs(const LPC_TYPE *autoc, int max_order, LPC_TYPE *ref, LPC_TYPE *error)
Schur recursion.
Definition: lpc.h:120
enum FFLPCType lpc_type
Definition: lpc.h:53
av_cold void ff_lpc_init_x86(LPCContext *c)
Definition: lpc.c:144
double coeff[MAX_VARS][MAX_VARS]
Definition: lls.h:35
void av_solve_lls(LLSModel *m, double threshold, int min_order)
Definition: lls.c:51
const char data[16]
Definition: mxf.c:66
double * windowed_buffer
Definition: lpc.h:54
int ff_lpc_calc_ref_coefs(LPCContext *s, const int32_t *samples, int order, double *ref)
Definition: lpc.c:151
int max_order
Definition: lpc.h:52
int blocksize
Definition: lpc.h:51
static int estimate_best_order(double *ref, int min_order, int max_order)
Definition: lpc.c:137
av_cold void ff_lpc_end(LPCContext *s)
Uninitialize LPCContext.
Definition: lpc.c:279
static void lpc_apply_welch_window_c(const int32_t *data, int len, double *w_data)
Apply Welch window function to audio block.
Definition: lpc.c:32
int32_t
static av_always_inline av_const long int lrintf(float x)
Definition: libm.h:144
static void quantize_lpc_coefs(double *lpc_in, int order, int precision, int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
Quantize LPC coefficients.
Definition: lpc.c:88
NULL
Definition: eval.c:52
static int 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:151
#define MIN_LPC_ORDER
Definition: lpc.h:35
Levinson-Durbin recursion.
Definition: lpc.h:45
#define ORDER_METHOD_EST
Definition: lpc.h:28
void av_init_lls(LLSModel *m, int indep_count)
Definition: lls.c:33
double * windowed_samples
Definition: lpc.h:55
av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order, enum FFLPCType lpc_type)
Initialize LPCContext.
Definition: lpc.c:253
static const uint16_t scale[4]
double av_evaluate_lls(LLSModel *m, double *param, int order)
Definition: lls.c:108
FFLPCType
LPC analysis type.
Definition: lpc.h:41
Cholesky factorization.
Definition: lpc.h:46
void av_update_lls(LLSModel *m, double *var, double decay)
Definition: lls.c:39
common internal and external API header
fixed LPC coefficients
Definition: lpc.h:44
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:80
int len
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:65
void * av_mallocz(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:158