FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
vf_dejudder.c
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2014 Nicholas Robbins
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * remove judder in video stream
24  *
25  * Algorithm:
26  * - If the old packets had PTS of old_pts[i]. Replace these with new
27  * value based on the running average of the last n=cycle frames. So
28  *
29  * new_pts[i] = Sum(k=i-n+1, i, old_pts[k])/n
30  * + (old_pts[i]-old_pts[i-n])*(n-1)/2n
31  *
32  * For any repeating pattern of length n of judder this will produce
33  * an even progression of PTS's.
34  *
35  * - In order to avoid calculating this sum ever frame, a running tally
36  * is maintained in ctx->new_pts. Each frame the new term at the start
37  * of the sum is added, the one and the end is removed, and the offset
38  * terms (second line in formula above) are recalculated.
39  *
40  * - To aid in this a ringbuffer of the last n-2 PTS's is maintained in
41  * ctx->ringbuff. With the indices of the first two and last two entries
42  * stored in i1, i2, i3, & i4.
43  *
44  * - To ensure that the new PTS's are integers, time_base is divided
45  * by 2n. This removes the division in the new_pts calculation.
46  *
47  * - frame_rate is also multiplied by 2n to allow the frames to fall
48  * where they may in what may now be a VFR output. This produces more
49  * even output then setting frame_rate=1/0 in practice.
50  */
51 
52 #include "libavutil/opt.h"
53 #include "libavutil/mathematics.h"
54 #include "avfilter.h"
55 #include "internal.h"
56 #include "video.h"
57 
58 typedef struct {
59  const AVClass *class;
60  int64_t *ringbuff;
61  int i1, i2, i3, i4;
62  int64_t new_pts;
64 
65  /* options */
66  int cycle;
68 
69 #define OFFSET(x) offsetof(DejudderContext, x)
70 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM
71 
72 static const AVOption dejudder_options[] = {
73  {"cycle", "set the length of the cycle to use for dejuddering",
74  OFFSET(cycle), AV_OPT_TYPE_INT, {.i64 = 4}, 2, 240, .flags = FLAGS},
75  {NULL}
76 };
77 
78 AVFILTER_DEFINE_CLASS(dejudder);
79 
80 static int config_out_props(AVFilterLink *outlink)
81 {
82  AVFilterContext *ctx = outlink->src;
83  DejudderContext *dj = ctx->priv;
84  AVFilterLink *inlink = outlink->src->inputs[0];
85 
86  outlink->time_base = av_mul_q(inlink->time_base, av_make_q(1, 2 * dj->cycle));
87  outlink->frame_rate = av_mul_q(inlink->frame_rate, av_make_q(2 * dj->cycle, 1));
88 
89  av_log(ctx, AV_LOG_VERBOSE, "cycle:%d\n", dj->cycle);
90 
91  return 0;
92 }
93 
95 {
96  DejudderContext *dj = ctx->priv;
97 
98  dj->ringbuff = av_mallocz_array(dj->cycle+2, sizeof(*dj->ringbuff));
99  if (!dj->ringbuff)
100  return AVERROR(ENOMEM);
101 
102  dj->new_pts = 0;
103  dj->i1 = 0;
104  dj->i2 = 1;
105  dj->i3 = 2;
106  dj->i4 = 3;
107  dj->start_count = dj->cycle + 2;
108 
109  return 0;
110 }
111 
113 {
114  DejudderContext *dj = ctx->priv;
115 
116  av_freep(&(dj->ringbuff));
117 }
118 
119 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
120 {
121  int k;
122  AVFilterContext *ctx = inlink->dst;
123  AVFilterLink *outlink = ctx->outputs[0];
124  DejudderContext *dj = ctx->priv;
125  int64_t *judbuff = dj->ringbuff;
126  int64_t next_pts = frame->pts;
127  int64_t offset;
128 
129  if (next_pts == AV_NOPTS_VALUE)
130  return ff_filter_frame(outlink, frame);
131 
132  if (dj->start_count) {
133  dj->start_count--;
134  dj->new_pts = next_pts * 2 * dj->cycle;
135  } else {
136  if (next_pts < judbuff[dj->i2]) {
137  offset = next_pts + judbuff[dj->i3] - judbuff[dj->i4] - judbuff[dj->i1];
138  for (k = 0; k < dj->cycle + 2; k++)
139  judbuff[k] += offset;
140  }
141  dj->new_pts += (dj->cycle - 1) * (judbuff[dj->i3] - judbuff[dj->i1])
142  + (dj->cycle + 1) * (next_pts - judbuff[dj->i4]);
143  }
144 
145  judbuff[dj->i2] = next_pts;
146  dj->i1 = dj->i2;
147  dj->i2 = dj->i3;
148  dj->i3 = dj->i4;
149  dj->i4 = (dj->i4 + 1) % (dj->cycle + 2);
150 
151  frame->pts = dj->new_pts;
152 
153  for (k = 0; k < dj->cycle + 2; k++)
154  av_log(ctx, AV_LOG_DEBUG, "%"PRId64"\t", judbuff[k]);
155  av_log(ctx, AV_LOG_DEBUG, "next=%"PRId64", new=%"PRId64"\n", next_pts, frame->pts);
156 
157  return ff_filter_frame(outlink, frame);
158 }
159 
160 static const AVFilterPad dejudder_inputs[] = {
161  {
162  .name = "default",
163  .type = AVMEDIA_TYPE_VIDEO,
164  .filter_frame = filter_frame,
165  },
166  { NULL }
167 };
168 
169 static const AVFilterPad dejudder_outputs[] = {
170  {
171  .name = "default",
172  .type = AVMEDIA_TYPE_VIDEO,
173  .config_props = config_out_props,
174  },
175  { NULL }
176 };
177 
179  .name = "dejudder",
180  .description = NULL_IF_CONFIG_SMALL("Remove judder produced by pullup."),
181  .priv_size = sizeof(DejudderContext),
182  .priv_class = &dejudder_class,
183  .inputs = dejudder_inputs,
184  .outputs = dejudder_outputs,
185  .init = dejudder_init,
187 };