1/*
2 * Copyright (c) 2010 Stefano Sabatini
3 * Copyright (c) 2006 Ivo van Poorten
4 * Copyright (c) 2006 Julian Hall
5 * Copyright (c) 2002-2003 Brian J. Murrell
6 *
7 * This file is part of Libav.
8 *
9 * Libav is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * Libav is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License along
20 * with Libav; if not, write to the Free Software Foundation, Inc.,
21 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22 */
23
24/**
25 * @file
26 * Search for black frames to detect scene transitions.
27 * Ported from MPlayer libmpcodecs/vf_blackframe.c.
28 */
29
30#include "avfilter.h"
31
32typedef struct {
33    unsigned int bamount; ///< black amount
34    unsigned int bthresh; ///< black threshold
35    unsigned int frame;   ///< frame number
36    unsigned int nblack;  ///< number of black pixels counted so far
37} BlackFrameContext;
38
39static int query_formats(AVFilterContext *ctx)
40{
41    static const enum PixelFormat pix_fmts[] = {
42        PIX_FMT_YUV410P, PIX_FMT_YUV420P, PIX_FMT_GRAY8, PIX_FMT_NV12,
43        PIX_FMT_NV21, PIX_FMT_YUV444P, PIX_FMT_YUV422P, PIX_FMT_YUV411P,
44        PIX_FMT_NONE
45    };
46
47    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
48    return 0;
49}
50
51static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
52{
53    BlackFrameContext *blackframe = ctx->priv;
54
55    blackframe->bamount = 98;
56    blackframe->bthresh = 32;
57    blackframe->nblack = 0;
58    blackframe->frame = 0;
59
60    if (args)
61        sscanf(args, "%u:%u", &blackframe->bamount, &blackframe->bthresh);
62
63    av_log(ctx, AV_LOG_INFO, "bamount:%u bthresh:%u\n",
64           blackframe->bamount, blackframe->bthresh);
65
66    if (blackframe->bamount > 100 || blackframe->bthresh > 255) {
67        av_log(ctx, AV_LOG_ERROR, "Too big value for bamount (max is 100) or bthresh (max is 255)\n");
68        return AVERROR(EINVAL);
69    }
70
71    return 0;
72}
73
74static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
75{
76    AVFilterContext *ctx = inlink->dst;
77    BlackFrameContext *blackframe = ctx->priv;
78    AVFilterBufferRef *picref = inlink->cur_buf;
79    int x, i;
80    uint8_t *p = picref->data[0] + y * picref->linesize[0];
81
82    for (i = 0; i < h; i++) {
83        for (x = 0; x < inlink->w; x++)
84            blackframe->nblack += p[x] < blackframe->bthresh;
85        p += picref->linesize[0];
86    }
87
88    avfilter_draw_slice(ctx->outputs[0], y, h, slice_dir);
89}
90
91static void end_frame(AVFilterLink *inlink)
92{
93    AVFilterContext *ctx = inlink->dst;
94    BlackFrameContext *blackframe = ctx->priv;
95    AVFilterBufferRef *picref = inlink->cur_buf;
96    int pblack = 0;
97
98    pblack = blackframe->nblack * 100 / (inlink->w * inlink->h);
99    if (pblack >= blackframe->bamount)
100        av_log(ctx, AV_LOG_INFO, "frame:%u pblack:%u pos:%"PRId64" pts:%"PRId64" t:%f\n",
101               blackframe->frame, pblack, picref->pos, picref->pts,
102               picref->pts == AV_NOPTS_VALUE ? -1 : picref->pts * av_q2d(inlink->time_base));
103
104    blackframe->frame++;
105    blackframe->nblack = 0;
106    avfilter_end_frame(inlink->dst->outputs[0]);
107}
108
109AVFilter avfilter_vf_blackframe = {
110    .name        = "blackframe",
111    .description = NULL_IF_CONFIG_SMALL("Detect frames that are (almost) black."),
112
113    .priv_size = sizeof(BlackFrameContext),
114    .init      = init,
115
116    .query_formats = query_formats,
117
118    .inputs    = (AVFilterPad[]) {{ .name = "default",
119                                    .type             = AVMEDIA_TYPE_VIDEO,
120                                    .draw_slice       = draw_slice,
121                                    .get_video_buffer = avfilter_null_get_video_buffer,
122                                    .start_frame      = avfilter_null_start_frame,
123                                    .end_frame        = end_frame, },
124                                  { .name = NULL}},
125
126    .outputs   = (AVFilterPad[]) {{ .name             = "default",
127                                    .type             = AVMEDIA_TYPE_VIDEO },
128                                  { .name = NULL}},
129};
130