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path: root/libavfilter/vf_thumbnail.c (plain)
blob: 417ccd56d0947e8c4351cd4db98a675c3da4a315
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
36struct thumb_frame {
37 AVFrame *buf; ///< cached frame
38 int histogram[HIST_SIZE]; ///< RGB color distribution histogram of the frame
39};
40
41typedef 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
52static 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
57AVFILTER_DEFINE_CLASS(thumbnail);
58
59static av_cold int init(AVFilterContext *ctx)
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 */
79static 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
91static AVFrame *get_best_frame(AVFilterContext *ctx)
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
131static 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
161static av_cold void uninit(AVFilterContext *ctx)
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
170static 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
187static 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
196static int query_formats(AVFilterContext *ctx)
197{
198 static const enum AVPixelFormat pix_fmts[] = {
199 AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
200 AV_PIX_FMT_NONE
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
208static 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
218static const AVFilterPad thumbnail_outputs[] = {
219 {
220 .name = "default",
221 .type = AVMEDIA_TYPE_VIDEO,
222 .request_frame = request_frame,
223 },
224 { NULL }
225};
226
227AVFilter ff_vf_thumbnail = {
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,
233 .query_formats = query_formats,
234 .inputs = thumbnail_inputs,
235 .outputs = thumbnail_outputs,
236 .priv_class = &thumbnail_class,
237};
238
generated by cgit at 2024-05-17 02:02:44 (GMT)