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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 | ||
59 | static av_cold int init(AVFilterContext *ctx) | |
60 | { | |
61 | ThumbContext *thumb = ctx->priv; | |
62 | ||
63 | thumb->frames = av_calloc(thumb->n_frames, sizeof(*thumb->frames)); | |
64 | if (!thumb->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", thumb->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 | ||
91 | static AVFrame *get_best_frame(AVFilterContext *ctx) | |
92 | { | |
93 | AVFrame *picref; | |
94 | ThumbContext *thumb = ctx->priv; | |
95 | int i, j, best_frame_idx = 0; | |
96 | int nb_frames = thumb->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)thumb->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(thumb->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(thumb->frames[i].histogram, 0, sizeof(thumb->frames[i].histogram)); | |
116 | if (i != best_frame_idx) | |
117 | av_frame_free(&thumb->frames[i].buf); | |
118 | } | |
119 | thumb->n = 0; | |
120 | ||
121 | // raise the chosen one | |
122 | picref = thumb->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(thumb->tb), nb_frames); | |
126 | thumb->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 *thumb = ctx->priv; | |
136 | AVFilterLink *outlink = ctx->outputs[0]; | |
137 | int *hist = thumb->frames[thumb->n].histogram; | |
138 | const uint8_t *p = frame->data[0]; | |
139 | ||
140 | // keep a reference of each frame | |
141 | thumb->frames[thumb->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 | thumb->n++; | |
155 | if (thumb->n < thumb->n_frames) | |
156 | return 0; | |
157 | ||
158 | return ff_filter_frame(outlink, get_best_frame(ctx)); | |
159 | } | |
160 | ||
161 | static av_cold void uninit(AVFilterContext *ctx) | |
162 | { | |
163 | int i; | |
164 | ThumbContext *thumb = ctx->priv; | |
165 | for (i = 0; i < thumb->n_frames && thumb->frames[i].buf; i++) | |
166 | av_frame_free(&thumb->frames[i].buf); | |
167 | av_freep(&thumb->frames); | |
168 | } | |
169 | ||
170 | static int request_frame(AVFilterLink *link) | |
171 | { | |
172 | AVFilterContext *ctx = link->src; | |
173 | ThumbContext *thumb = ctx->priv; | |
174 | ||
175 | /* loop until a frame thumbnail is available (when a frame is queued, | |
176 | * thumb->n is reset to zero) */ | |
177 | do { | |
178 | int ret = ff_request_frame(ctx->inputs[0]); | |
179 | if (ret == AVERROR_EOF && thumb->n) { | |
180 | ret = ff_filter_frame(link, get_best_frame(ctx)); | |
181 | if (ret < 0) | |
182 | return ret; | |
183 | ret = AVERROR_EOF; | |
184 | } | |
185 | if (ret < 0) | |
186 | return ret; | |
187 | } while (thumb->n); | |
188 | return 0; | |
189 | } | |
190 | ||
191 | static int config_props(AVFilterLink *inlink) | |
192 | { | |
193 | AVFilterContext *ctx = inlink->dst; | |
194 | ThumbContext *thumb = ctx->priv; | |
195 | ||
196 | thumb->tb = inlink->time_base; | |
197 | return 0; | |
198 | } | |
199 | ||
200 | static int query_formats(AVFilterContext *ctx) | |
201 | { | |
202 | static const enum AVPixelFormat pix_fmts[] = { | |
203 | AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24, | |
204 | AV_PIX_FMT_NONE | |
205 | }; | |
206 | ff_set_common_formats(ctx, ff_make_format_list(pix_fmts)); | |
207 | return 0; | |
208 | } | |
209 | ||
210 | static const AVFilterPad thumbnail_inputs[] = { | |
211 | { | |
212 | .name = "default", | |
213 | .type = AVMEDIA_TYPE_VIDEO, | |
214 | .config_props = config_props, | |
215 | .filter_frame = filter_frame, | |
216 | }, | |
217 | { NULL } | |
218 | }; | |
219 | ||
220 | static const AVFilterPad thumbnail_outputs[] = { | |
221 | { | |
222 | .name = "default", | |
223 | .type = AVMEDIA_TYPE_VIDEO, | |
224 | .request_frame = request_frame, | |
225 | }, | |
226 | { NULL } | |
227 | }; | |
228 | ||
229 | AVFilter ff_vf_thumbnail = { | |
230 | .name = "thumbnail", | |
231 | .description = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."), | |
232 | .priv_size = sizeof(ThumbContext), | |
233 | .init = init, | |
234 | .uninit = uninit, | |
235 | .query_formats = query_formats, | |
236 | .inputs = thumbnail_inputs, | |
237 | .outputs = thumbnail_outputs, | |
238 | .priv_class = &thumbnail_class, | |
239 | }; |