2 * Copyright (c) 2011 Smartjog S.A.S, Clément Bœsch <clement.boesch@smartjog.com>
4 * This file is part of FFmpeg.
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.
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.
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
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.
26 * Simplified version of algorithm by Vadim Zaliva <lord@crocodile.org>.
27 * @see http://notbrainsurgery.livejournal.com/29773.html
30 #include "libavutil/opt.h"
34 #define HIST_SIZE (3*256)
37 AVFrame *buf; ///< cached frame
38 int histogram[HIST_SIZE]; ///< RGB color distribution histogram of the frame
41 typedef struct ThumbContext {
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
49 #define OFFSET(x) offsetof(ThumbContext, x)
50 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
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 },
57 AVFILTER_DEFINE_CLASS(thumbnail);
59 static av_cold int init(AVFilterContext *ctx)
61 ThumbContext *s = ctx->priv;
63 s->frames = av_calloc(s->n_frames, sizeof(*s->frames));
65 av_log(ctx, AV_LOG_ERROR,
66 "Allocation failure, try to lower the number of frames\n");
67 return AVERROR(ENOMEM);
69 av_log(ctx, AV_LOG_VERBOSE, "batch size: %d frames\n", s->n_frames);
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
79 static double frame_sum_square_err(const int *hist, const double *median)
82 double err, sum_sq_err = 0;
84 for (i = 0; i < HIST_SIZE; i++) {
85 err = median[i] - (double)hist[i];
86 sum_sq_err += err*err;
91 static AVFrame *get_best_frame(AVFilterContext *ctx)
94 ThumbContext *s = ctx->priv;
95 int i, j, best_frame_idx = 0;
97 double avg_hist[HIST_SIZE] = {0}, sq_err, min_sq_err = -1;
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;
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;
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);
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;
131 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
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];
140 // keep a reference of each frame
141 s->frames[s->n].buf = frame;
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]]++;
150 p += frame->linesize[0];
153 // no selection until the buffer of N frames is filled up
155 if (s->n < s->n_frames)
158 return ff_filter_frame(outlink, get_best_frame(ctx));
161 static av_cold void uninit(AVFilterContext *ctx)
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);
170 static int request_frame(AVFilterLink *link)
172 AVFilterContext *ctx = link->src;
173 ThumbContext *s = ctx->priv;
174 int ret = ff_request_frame(ctx->inputs[0]);
176 if (ret == AVERROR_EOF && s->n) {
177 ret = ff_filter_frame(link, get_best_frame(ctx));
187 static int config_props(AVFilterLink *inlink)
189 AVFilterContext *ctx = inlink->dst;
190 ThumbContext *s = ctx->priv;
192 s->tb = inlink->time_base;
196 static int query_formats(AVFilterContext *ctx)
198 static const enum AVPixelFormat pix_fmts[] = {
199 AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
202 AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
204 return AVERROR(ENOMEM);
205 return ff_set_common_formats(ctx, fmts_list);
208 static const AVFilterPad thumbnail_inputs[] = {
211 .type = AVMEDIA_TYPE_VIDEO,
212 .config_props = config_props,
213 .filter_frame = filter_frame,
218 static const AVFilterPad thumbnail_outputs[] = {
221 .type = AVMEDIA_TYPE_VIDEO,
222 .request_frame = request_frame,
227 AVFilter ff_vf_thumbnail = {
229 .description = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."),
230 .priv_size = sizeof(ThumbContext),
233 .query_formats = query_formats,
234 .inputs = thumbnail_inputs,
235 .outputs = thumbnail_outputs,
236 .priv_class = &thumbnail_class,