path: root/libavfilter/vf_random.c (plain)
blob: 373a7db053af1220b4218828a2e7ddf1003cc569

1	/*
2	* Copyright (c) 2015 Paul B Mahol
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	#include "libavutil/lfg.h"
22	#include "libavutil/opt.h"
23	#include "libavutil/random_seed.h"
24	#include "avfilter.h"
25	#include "formats.h"
26	#include "internal.h"
27	#include "video.h"
28
29	#define MAX_FRAMES 512
30
31	typedef struct RandomContext {
32	const AVClass *class;
33
34	AVLFG lfg;
35	int nb_frames;
36	int64_t random_seed;
37	int nb_frames_filled;
38	AVFrame *frames[MAX_FRAMES];
39	int64_t pts[MAX_FRAMES];
40	int flush_idx;
41	} RandomContext;
42
43	#define OFFSET(x) offsetof(RandomContext, x)
44	#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
45
46	static const AVOption random_options[] = {
47	{ "frames", "set number of frames in cache", OFFSET(nb_frames), AV_OPT_TYPE_INT, {.i64=30}, 2, MAX_FRAMES, FLAGS },
48	{ "seed", "set the seed", OFFSET(random_seed), AV_OPT_TYPE_INT64, {.i64=-1}, -1, UINT32_MAX, FLAGS },
49	{ NULL }
50	};
51
52	AVFILTER_DEFINE_CLASS(random);
53
54	static av_cold int init(AVFilterContext *ctx)
55	{
56	RandomContext *s = ctx->priv;
57	uint32_t seed;
58
59	if (s->random_seed < 0)
60	s->random_seed = av_get_random_seed();
61	seed = s->random_seed;
62	av_lfg_init(&s->lfg, seed);
63
64	return 0;
65	}
66
67	static int filter_frame(AVFilterLink *inlink, AVFrame *in)
68	{
69	AVFilterContext *ctx = inlink->dst;
70	RandomContext *s = ctx->priv;
71	AVFilterLink *outlink = ctx->outputs[0];
72	AVFrame *out;
73	int idx;
74
75	if (s->nb_frames_filled < s->nb_frames) {
76	s->frames[s->nb_frames_filled] = in;
77	s->pts[s->nb_frames_filled++] = in->pts;
78	return 0;
79	}
80
81	idx = av_lfg_get(&s->lfg) % s->nb_frames;
82
83	out = s->frames[idx];
84	out->pts = s->pts[0];
85	memmove(&s->pts[0], &s->pts[1], (s->nb_frames - 1) * sizeof(s->pts[0]));
86	s->frames[idx] = in;
87	s->pts[s->nb_frames - 1] = in->pts;
88
89	return ff_filter_frame(outlink, out);
90	}
91
92	static int request_frame(AVFilterLink *outlink)
93	{
94	AVFilterContext *ctx = outlink->src;
95	RandomContext *s = ctx->priv;
96	int ret;
97
98	ret = ff_request_frame(ctx->inputs[0]);
99
100	if (ret == AVERROR_EOF && !ctx->is_disabled && s->nb_frames > 0) {
101	AVFrame *out = s->frames[s->nb_frames - 1];
102	out->pts = s->pts[s->flush_idx++];
103	ret = ff_filter_frame(outlink, out);
104	s->frames[s->nb_frames - 1] = NULL;
105	s->nb_frames--;
106	}
107
108	return ret;
109	}
110
111	static const AVFilterPad random_inputs[] = {
112	{
113	.name = "default",
114	.type = AVMEDIA_TYPE_VIDEO,
115	.filter_frame = filter_frame,
116	},
117	{ NULL }
118	};
119
120	static const AVFilterPad random_outputs[] = {
121	{
122	.name = "default",
123	.type = AVMEDIA_TYPE_VIDEO,
124	.request_frame = request_frame,
125	},
126	{ NULL }
127	};
128
129	AVFilter ff_vf_random = {
130	.name = "random",
131	.description = NULL_IF_CONFIG_SMALL("Return random frames."),
132	.priv_size = sizeof(RandomContext),
133	.priv_class = &random_class,
134	.init = init,
135	.inputs = random_inputs,
136	.outputs = random_outputs,
137	};
138