FFmpeg
timefilter.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include <stdio.h>
20 
21 #include "libavutil/common.h"
22 #include "libavutil/lfg.h"
23 
24 #include "libavdevice/timefilter.h"
25 
26 #define LFG_MAX ((1LL << 32) - 1)
27 
28 int main(void)
29 {
30  AVLFG prng;
31  double n0, n1;
32 #define SAMPLES 1000
33  double ideal[SAMPLES];
34  double samples[SAMPLES];
35  double samplet[SAMPLES];
36  for (n0 = 0; n0 < 40; n0 = 2 * n0 + 1) {
37  for (n1 = 0; n1 < 10; n1 = 2 * n1 + 1) {
38  double best_error = 1000000000;
39  double bestpar0 = n0 ? 1 : 100000;
40  double bestpar1 = 1;
41  int better, i;
42 
43  av_lfg_init(&prng, 123);
44  for (i = 0; i < SAMPLES; i++) {
45  samplet[i] = 10 + i + (av_lfg_get(&prng) < LFG_MAX/2 ? 0 : 0.999);
46  ideal[i] = samplet[i] + n1 * i / (1000);
47  samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2) / (LFG_MAX * 10LL);
48  if(i && samples[i]<samples[i-1])
49  samples[i]=samples[i-1]+0.001;
50  }
51 
52  do {
53  double par0, par1;
54  better = 0;
55  for (par0 = bestpar0 * 0.8; par0 <= bestpar0 * 1.21; par0 += bestpar0 * 0.05) {
56  for (par1 = bestpar1 * 0.8; par1 <= bestpar1 * 1.21; par1 += bestpar1 * 0.05) {
57  double error = 0;
58  TimeFilter *tf = ff_timefilter_new(1, par0, par1);
59  if (!tf) {
60  printf("Could not allocate memory for timefilter.\n");
61  exit(1);
62  }
63  for (i = 0; i < SAMPLES; i++) {
64  double filtered;
65  filtered = ff_timefilter_update(tf, samples[i], i ? (samplet[i] - samplet[i-1]) : 1);
66  if(filtered < 0 || filtered > 1000000000)
67  printf("filter is unstable\n");
68  error += (filtered - ideal[i]) * (filtered - ideal[i]);
69  }
71  if (error < best_error) {
72  best_error = error;
73  bestpar0 = par0;
74  bestpar1 = par1;
75  better = 1;
76  }
77  }
78  }
79  } while (better);
80  printf(" [%12f %11f %9f]", bestpar0, bestpar1, best_error);
81  }
82  printf("\n");
83  }
84  return 0;
85 }
Context structure for the Lagged Fibonacci PRNG.
Definition: lfg.h:33
void ff_timefilter_destroy(TimeFilter *self)
Free all resources associated with the filter.
Definition: timefilter.c:62
#define LFG_MAX
Definition: timefilter.c:26
static void error(const char *err)
#define tf
Definition: regdef.h:73
Opaque type representing a time filter state.
Definition: timefilter.c:30
TimeFilter * ff_timefilter_new(double time_base, double period, double bandwidth)
Create a new Delay Locked Loop time filter.
Definition: timefilter.c:46
static unsigned int av_lfg_get(AVLFG *c)
Get the next random unsigned 32-bit number using an ALFG.
Definition: lfg.h:53
int main(void)
Definition: timefilter.c:28
#define SAMPLES
av_cold void av_lfg_init(AVLFG *c, unsigned int seed)
Definition: lfg.c:32
double ff_timefilter_update(TimeFilter *self, double system_time, double period)
Update the filter.
Definition: timefilter.c:72
common internal and external API header
printf("static const uint8_t my_array[100] = {\n")
Filter the word “frame” indicates either a video frame or a group of audio samples
int i
Definition: input.c:406