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vf_thumbnail.c
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1 /*
2  * Copyright (c) 2011 Smartjog S.A.S, Clément Bœsch <clement.boesch@smartjog.com>
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  * Potential thumbnail lookup filter to reduce the risk of an inappropriate
24  * selection (such as a black frame) we could get with an absolute seek.
25  *
26  * Simplified version of algorithm by Vadim Zaliva <lord@crocodile.org>.
27  * @see http://notbrainsurgery.livejournal.com/29773.html
28  */
29 
30 #include "libavutil/opt.h"
31 #include "avfilter.h"
32 #include "internal.h"
33 
34 #define HIST_SIZE (3*256)
35 
36 struct thumb_frame {
37  AVFrame *buf; ///< cached frame
38  int histogram[HIST_SIZE]; ///< RGB color distribution histogram of the frame
39 };
40 
41 typedef struct {
42  const AVClass *class;
43  int n; ///< current frame
44  int n_frames; ///< number of frames for analysis
45  struct thumb_frame *frames; ///< the n_frames frames
46  AVRational tb; ///< copy of the input timebase to ease access
47 } ThumbContext;
48 
49 #define OFFSET(x) offsetof(ThumbContext, x)
50 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
51 
52 static const AVOption thumbnail_options[] = {
53  { "n", "set the frames batch size", OFFSET(n_frames), AV_OPT_TYPE_INT, {.i64=100}, 2, INT_MAX, FLAGS },
54  { NULL }
55 };
56 
57 AVFILTER_DEFINE_CLASS(thumbnail);
58 
60 {
61  ThumbContext *s = ctx->priv;
62 
63  s->frames = av_calloc(s->n_frames, sizeof(*s->frames));
64  if (!s->frames) {
65  av_log(ctx, AV_LOG_ERROR,
66  "Allocation failure, try to lower the number of frames\n");
67  return AVERROR(ENOMEM);
68  }
69  av_log(ctx, AV_LOG_VERBOSE, "batch size: %d frames\n", s->n_frames);
70  return 0;
71 }
72 
73 /**
74  * @brief Compute Sum-square deviation to estimate "closeness".
75  * @param hist color distribution histogram
76  * @param median average color distribution histogram
77  * @return sum of squared errors
78  */
79 static double frame_sum_square_err(const int *hist, const double *median)
80 {
81  int i;
82  double err, sum_sq_err = 0;
83 
84  for (i = 0; i < HIST_SIZE; i++) {
85  err = median[i] - (double)hist[i];
86  sum_sq_err += err*err;
87  }
88  return sum_sq_err;
89 }
90 
92 {
93  AVFrame *picref;
94  ThumbContext *s = ctx->priv;
95  int i, j, best_frame_idx = 0;
96  int nb_frames = s->n;
97  double avg_hist[HIST_SIZE] = {0}, sq_err, min_sq_err = -1;
98 
99  // average histogram of the N frames
100  for (j = 0; j < FF_ARRAY_ELEMS(avg_hist); j++) {
101  for (i = 0; i < nb_frames; i++)
102  avg_hist[j] += (double)s->frames[i].histogram[j];
103  avg_hist[j] /= nb_frames;
104  }
105 
106  // find the frame closer to the average using the sum of squared errors
107  for (i = 0; i < nb_frames; i++) {
108  sq_err = frame_sum_square_err(s->frames[i].histogram, avg_hist);
109  if (i == 0 || sq_err < min_sq_err)
110  best_frame_idx = i, min_sq_err = sq_err;
111  }
112 
113  // free and reset everything (except the best frame buffer)
114  for (i = 0; i < nb_frames; i++) {
115  memset(s->frames[i].histogram, 0, sizeof(s->frames[i].histogram));
116  if (i != best_frame_idx)
117  av_frame_free(&s->frames[i].buf);
118  }
119  s->n = 0;
120 
121  // raise the chosen one
122  picref = s->frames[best_frame_idx].buf;
123  av_log(ctx, AV_LOG_INFO, "frame id #%d (pts_time=%f) selected "
124  "from a set of %d images\n", best_frame_idx,
125  picref->pts * av_q2d(s->tb), nb_frames);
126  s->frames[best_frame_idx].buf = NULL;
127 
128  return picref;
129 }
130 
131 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
132 {
133  int i, j;
134  AVFilterContext *ctx = inlink->dst;
135  ThumbContext *s = ctx->priv;
136  AVFilterLink *outlink = ctx->outputs[0];
137  int *hist = s->frames[s->n].histogram;
138  const uint8_t *p = frame->data[0];
139 
140  // keep a reference of each frame
141  s->frames[s->n].buf = frame;
142 
143  // update current frame RGB histogram
144  for (j = 0; j < inlink->h; j++) {
145  for (i = 0; i < inlink->w; i++) {
146  hist[0*256 + p[i*3 ]]++;
147  hist[1*256 + p[i*3 + 1]]++;
148  hist[2*256 + p[i*3 + 2]]++;
149  }
150  p += frame->linesize[0];
151  }
152 
153  // no selection until the buffer of N frames is filled up
154  s->n++;
155  if (s->n < s->n_frames)
156  return 0;
157 
158  return ff_filter_frame(outlink, get_best_frame(ctx));
159 }
160 
162 {
163  int i;
164  ThumbContext *s = ctx->priv;
165  for (i = 0; i < s->n_frames && s->frames[i].buf; i++)
166  av_frame_free(&s->frames[i].buf);
167  av_freep(&s->frames);
168 }
169 
170 static int request_frame(AVFilterLink *link)
171 {
172  AVFilterContext *ctx = link->src;
173  ThumbContext *s = ctx->priv;
174  int ret = ff_request_frame(ctx->inputs[0]);
175 
176  if (ret == AVERROR_EOF && s->n) {
177  ret = ff_filter_frame(link, get_best_frame(ctx));
178  if (ret < 0)
179  return ret;
180  ret = AVERROR_EOF;
181  }
182  if (ret < 0)
183  return ret;
184  return 0;
185 }
186 
187 static int config_props(AVFilterLink *inlink)
188 {
189  AVFilterContext *ctx = inlink->dst;
190  ThumbContext *s = ctx->priv;
191 
192  s->tb = inlink->time_base;
193  return 0;
194 }
195 
197 {
198  static const enum AVPixelFormat pix_fmts[] = {
201  };
202  AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
203  if (!fmts_list)
204  return AVERROR(ENOMEM);
205  return ff_set_common_formats(ctx, fmts_list);
206 }
207 
208 static const AVFilterPad thumbnail_inputs[] = {
209  {
210  .name = "default",
211  .type = AVMEDIA_TYPE_VIDEO,
212  .config_props = config_props,
213  .filter_frame = filter_frame,
214  },
215  { NULL }
216 };
217 
218 static const AVFilterPad thumbnail_outputs[] = {
219  {
220  .name = "default",
221  .type = AVMEDIA_TYPE_VIDEO,
222  .request_frame = request_frame,
223  },
224  { NULL }
225 };
226 
228  .name = "thumbnail",
229  .description = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."),
230  .priv_size = sizeof(ThumbContext),
231  .init = init,
232  .uninit = uninit,
234  .inputs = thumbnail_inputs,
235  .outputs = thumbnail_outputs,
236  .priv_class = &thumbnail_class,
237 };
#define NULL
Definition: coverity.c:32
const char * s
Definition: avisynth_c.h:768
This structure describes decoded (raw) audio or video data.
Definition: frame.h:184
AVOption.
Definition: opt.h:245
AVFrame * buf
cached frame
Definition: vf_thumbnail.c:37
Main libavfilter public API header.
packed RGB 8:8:8, 24bpp, RGBRGB...
Definition: pixfmt.h:64
static av_cold int init(AVFilterContext *ctx)
Definition: vf_thumbnail.c:59
int n
current frame
Definition: vf_thumbnail.c:43
void * av_calloc(size_t nmemb, size_t size)
Non-inlined equivalent of av_mallocz_array().
Definition: mem.c:260
AVFilterFormats * ff_make_format_list(const int *fmts)
Create a list of supported formats.
Definition: formats.c:283
const char * name
Pad name.
Definition: internal.h:59
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:315
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
Send a frame of data to the next filter.
Definition: avfilter.c:1180
uint8_t
#define av_cold
Definition: attributes.h:82
AVOptions.
#define OFFSET(x)
Definition: vf_thumbnail.c:49
int64_t pts
Presentation timestamp in time_base units (time when frame should be shown to user).
Definition: frame.h:268
static AVFrame * frame
struct thumb_frame * frames
the n_frames frames
Definition: vf_thumbnail.c:45
static double av_q2d(AVRational a)
Convert an AVRational to a double.
Definition: rational.h:104
#define AVERROR_EOF
End of file.
Definition: error.h:55
#define AV_LOG_VERBOSE
Detailed information.
Definition: log.h:192
#define av_log(a,...)
A filter pad used for either input or output.
Definition: internal.h:53
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
int ff_set_common_formats(AVFilterContext *ctx, AVFilterFormats *formats)
A helper for query_formats() which sets all links to the same list of formats.
Definition: formats.c:568
#define AVERROR(e)
Definition: error.h:43
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:153
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:176
void * priv
private data for use by the filter
Definition: avfilter.h:322
static const AVFilterPad thumbnail_outputs[]
Definition: vf_thumbnail.c:218
static int query_formats(AVFilterContext *ctx)
Definition: vf_thumbnail.c:196
#define FLAGS
Definition: vf_thumbnail.c:50
int histogram[HIST_SIZE]
RGB color distribution histogram of the frame.
Definition: vf_thumbnail.c:38
AVFormatContext * ctx
Definition: movenc.c:48
packed RGB 8:8:8, 24bpp, BGRBGR...
Definition: pixfmt.h:65
static AVFrame * get_best_frame(AVFilterContext *ctx)
Definition: vf_thumbnail.c:91
static const AVFilterPad outputs[]
Definition: af_afftfilt.c:386
#define FF_ARRAY_ELEMS(a)
static int request_frame(AVFilterLink *link)
Definition: vf_thumbnail.c:170
#define AV_LOG_INFO
Standard information.
Definition: log.h:187
static const AVFilterPad inputs[]
Definition: af_afftfilt.c:376
AVFilter ff_vf_thumbnail
Definition: vf_thumbnail.c:227
int linesize[AV_NUM_DATA_POINTERS]
For video, size in bytes of each picture line.
Definition: frame.h:215
static int config_props(AVFilterLink *inlink)
Definition: vf_thumbnail.c:187
AVRational tb
copy of the input timebase to ease access
Definition: vf_thumbnail.c:46
Describe the class of an AVClass context structure.
Definition: log.h:67
Filter definition.
Definition: avfilter.h:144
int n_frames
number of frames for analysis
Definition: vf_thumbnail.c:44
Rational number (pair of numerator and denominator).
Definition: rational.h:58
const char * name
Filter name.
Definition: avfilter.h:148
static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
Definition: vf_thumbnail.c:131
AVFilterLink ** outputs
array of pointers to output links
Definition: avfilter.h:319
static av_cold void uninit(AVFilterContext *ctx)
Definition: vf_thumbnail.c:161
static enum AVPixelFormat pix_fmts[]
Definition: libkvazaar.c:262
static double frame_sum_square_err(const int *hist, const double *median)
Compute Sum-square deviation to estimate "closeness".
Definition: vf_thumbnail.c:79
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:198
#define HIST_SIZE
Definition: vf_thumbnail.c:34
AVFILTER_DEFINE_CLASS(thumbnail)
static const AVOption thumbnail_options[]
Definition: vf_thumbnail.c:52
A list of supported formats for one end of a filter link.
Definition: formats.h:64
An instance of a filter.
Definition: avfilter.h:307
#define av_freep(p)
int ff_request_frame(AVFilterLink *link)
Request an input frame from the filter at the other end of the link.
Definition: avfilter.c:369
internal API functions
AVPixelFormat
Pixel format.
Definition: pixfmt.h:60
static const AVFilterPad thumbnail_inputs[]
Definition: vf_thumbnail.c:208