aboutsummaryrefslogtreecommitdiffstats
path: root/libavfilter/vf_thumbnail.c
blob: fb67d4fdbdf1138328a7d1b2e78dcde41d600eb8 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
/*
 * Copyright (c) 2011 Smartjog S.A.S, Clément Bœsch <clement.boesch@smartjog.com>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * Potential thumbnail lookup filter to reduce the risk of an inappropriate
 * selection (such as a black frame) we could get with an absolute seek.
 *
 * Simplified version of algorithm by Vadim Zaliva <lord@crocodile.org>.
 * @see http://notbrainsurgery.livejournal.com/29773.html
 */

#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
#include "avfilter.h"
#include "internal.h"

#define HIST_SIZE (3*256)

struct thumb_frame {
    AVFrame *buf;               ///< cached frame
    int histogram[HIST_SIZE];   ///< RGB color distribution histogram of the frame
};

typedef struct ThumbContext {
    const AVClass *class;
    int n;                      ///< current frame
    int n_frames;               ///< number of frames for analysis
    struct thumb_frame *frames; ///< the n_frames frames
    AVRational tb;              ///< copy of the input timebase to ease access

    int planewidth[4];
    int planeheight[4];
} ThumbContext;

#define OFFSET(x) offsetof(ThumbContext, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM

static const AVOption thumbnail_options[] = {
    { "n", "set the frames batch size", OFFSET(n_frames), AV_OPT_TYPE_INT, {.i64=100}, 2, INT_MAX, FLAGS },
    { NULL }
};

AVFILTER_DEFINE_CLASS(thumbnail);

static av_cold int init(AVFilterContext *ctx)
{
    ThumbContext *s = ctx->priv;

    s->frames = av_calloc(s->n_frames, sizeof(*s->frames));
    if (!s->frames) {
        av_log(ctx, AV_LOG_ERROR,
               "Allocation failure, try to lower the number of frames\n");
        return AVERROR(ENOMEM);
    }
    av_log(ctx, AV_LOG_VERBOSE, "batch size: %d frames\n", s->n_frames);
    return 0;
}

/**
 * @brief        Compute Sum-square deviation to estimate "closeness".
 * @param hist   color distribution histogram
 * @param median average color distribution histogram
 * @return       sum of squared errors
 */
static double frame_sum_square_err(const int *hist, const double *median)
{
    int i;
    double err, sum_sq_err = 0;

    for (i = 0; i < HIST_SIZE; i++) {
        err = median[i] - (double)hist[i];
        sum_sq_err += err*err;
    }
    return sum_sq_err;
}

static AVFrame *get_best_frame(AVFilterContext *ctx)
{
    AVFrame *picref;
    ThumbContext *s = ctx->priv;
    int i, j, best_frame_idx = 0;
    int nb_frames = s->n;
    double avg_hist[HIST_SIZE] = {0}, sq_err, min_sq_err = -1;

    // average histogram of the N frames
    for (j = 0; j < FF_ARRAY_ELEMS(avg_hist); j++) {
        for (i = 0; i < nb_frames; i++)
            avg_hist[j] += (double)s->frames[i].histogram[j];
        avg_hist[j] /= nb_frames;
    }

    // find the frame closer to the average using the sum of squared errors
    for (i = 0; i < nb_frames; i++) {
        sq_err = frame_sum_square_err(s->frames[i].histogram, avg_hist);
        if (i == 0 || sq_err < min_sq_err)
            best_frame_idx = i, min_sq_err = sq_err;
    }

    // free and reset everything (except the best frame buffer)
    for (i = 0; i < nb_frames; i++) {
        memset(s->frames[i].histogram, 0, sizeof(s->frames[i].histogram));
        if (i != best_frame_idx)
            av_frame_free(&s->frames[i].buf);
    }
    s->n = 0;

    // raise the chosen one
    picref = s->frames[best_frame_idx].buf;
    av_log(ctx, AV_LOG_INFO, "frame id #%d (pts_time=%f) selected "
           "from a set of %d images\n", best_frame_idx,
           picref->pts * av_q2d(s->tb), nb_frames);
    s->frames[best_frame_idx].buf = NULL;

    return picref;
}

static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
{
    int i, j;
    AVFilterContext *ctx  = inlink->dst;
    ThumbContext *s   = ctx->priv;
    AVFilterLink *outlink = ctx->outputs[0];
    int *hist = s->frames[s->n].histogram;
    const uint8_t *p = frame->data[0];

    // keep a reference of each frame
    s->frames[s->n].buf = frame;

    // update current frame histogram
    switch (inlink->format) {
    case AV_PIX_FMT_RGB24:
    case AV_PIX_FMT_BGR24:
        for (j = 0; j < inlink->h; j++) {
            for (i = 0; i < inlink->w; i++) {
                hist[0*256 + p[i*3    ]]++;
                hist[1*256 + p[i*3 + 1]]++;
                hist[2*256 + p[i*3 + 2]]++;
            }
            p += frame->linesize[0];
        }
        break;
    case AV_PIX_FMT_RGB0:
    case AV_PIX_FMT_BGR0:
    case AV_PIX_FMT_RGBA:
    case AV_PIX_FMT_BGRA:
        for (j = 0; j < inlink->h; j++) {
            for (i = 0; i < inlink->w; i++) {
                hist[0*256 + p[i*4    ]]++;
                hist[1*256 + p[i*4 + 1]]++;
                hist[2*256 + p[i*4 + 2]]++;
            }
            p += frame->linesize[0];
        }
        break;
    case AV_PIX_FMT_0RGB:
    case AV_PIX_FMT_0BGR:
    case AV_PIX_FMT_ARGB:
    case AV_PIX_FMT_ABGR:
        for (j = 0; j < inlink->h; j++) {
            for (i = 0; i < inlink->w; i++) {
                hist[0*256 + p[i*4 + 1]]++;
                hist[1*256 + p[i*4 + 2]]++;
                hist[2*256 + p[i*4 + 3]]++;
            }
            p += frame->linesize[0];
        }
        break;
    default:
        for (int plane = 0; plane < 3; plane++) {
            const uint8_t *p = frame->data[plane];
            for (j = 0; j < s->planeheight[plane]; j++) {
                for (i = 0; i < s->planewidth[plane]; i++)
                    hist[256*plane + p[i]]++;
                p += frame->linesize[plane];
            }
        }
        break;
    }

    // no selection until the buffer of N frames is filled up
    s->n++;
    if (s->n < s->n_frames)
        return 0;

    return ff_filter_frame(outlink, get_best_frame(ctx));
}

static av_cold void uninit(AVFilterContext *ctx)
{
    int i;
    ThumbContext *s = ctx->priv;
    for (i = 0; i < s->n_frames && s->frames && s->frames[i].buf; i++)
        av_frame_free(&s->frames[i].buf);
    av_freep(&s->frames);
}

static int request_frame(AVFilterLink *link)
{
    AVFilterContext *ctx = link->src;
    ThumbContext *s = ctx->priv;
    int ret = ff_request_frame(ctx->inputs[0]);

    if (ret == AVERROR_EOF && s->n) {
        ret = ff_filter_frame(link, get_best_frame(ctx));
        if (ret < 0)
            return ret;
        ret = AVERROR_EOF;
    }
    if (ret < 0)
        return ret;
    return 0;
}

static int config_props(AVFilterLink *inlink)
{
    AVFilterContext *ctx = inlink->dst;
    ThumbContext *s = ctx->priv;
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);

    s->tb = inlink->time_base;
    s->planewidth[1]  = s->planewidth[2]  = AV_CEIL_RSHIFT(inlink->w, desc->log2_chroma_w);
    s->planewidth[0]  = s->planewidth[3]  = inlink->w;
    s->planeheight[1] = s->planeheight[2] = AV_CEIL_RSHIFT(inlink->h, desc->log2_chroma_h);
    s->planeheight[0] = s->planeheight[3] = inlink->h;

    return 0;
}

static const enum AVPixelFormat pix_fmts[] = {
    AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
    AV_PIX_FMT_RGBA,  AV_PIX_FMT_BGRA,
    AV_PIX_FMT_RGB0,  AV_PIX_FMT_BGR0,
    AV_PIX_FMT_ABGR,  AV_PIX_FMT_ARGB,
    AV_PIX_FMT_0BGR,  AV_PIX_FMT_0RGB,
    AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV411P,
    AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P,
    AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUV444P,
    AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ422P,
    AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ444P,
    AV_PIX_FMT_YUVJ411P,
    AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA444P,
    AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRAP,
    AV_PIX_FMT_NONE
};

static const AVFilterPad thumbnail_inputs[] = {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_VIDEO,
        .config_props = config_props,
        .filter_frame = filter_frame,
    },
};

static const AVFilterPad thumbnail_outputs[] = {
    {
        .name          = "default",
        .type          = AVMEDIA_TYPE_VIDEO,
        .request_frame = request_frame,
    },
};

const AVFilter ff_vf_thumbnail = {
    .name          = "thumbnail",
    .description   = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."),
    .priv_size     = sizeof(ThumbContext),
    .init          = init,
    .uninit        = uninit,
    FILTER_INPUTS(thumbnail_inputs),
    FILTER_OUTPUTS(thumbnail_outputs),
    FILTER_PIXFMTS_ARRAY(pix_fmts),
    .priv_class    = &thumbnail_class,
    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
};