Extend the slice filter to make it issue slice height values randomly
[libav.git] / libavfilter / vf_slicify.c
1 /*
2 * copyright (c) 2007 Bobby Bingham
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 libavfilter/vf_slicify.c
23 * video slicing filter
24 */
25
26 #include "avfilter.h"
27 #include "libavutil/pixdesc.h"
28
29 typedef struct {
30 int h; ///< output slice height
31 int vshift; ///< vertical chroma subsampling shift
32 uint32_t lcg_state; ///< LCG state used to compute random slice height
33 int use_random_h; ///< enable the use of random slice height values
34 } SliceContext;
35
36 static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
37 {
38 SliceContext *slice = ctx->priv;
39
40 slice->h = 16;
41 if (args) {
42 if (!strcmp(args, "random")) {
43 slice->use_random_h = 1;
44 } else {
45 sscanf(args, "%d", &slice->h);
46 }
47 }
48 return 0;
49 }
50
51 static int config_props(AVFilterLink *link)
52 {
53 SliceContext *slice = link->dst->priv;
54
55 slice->vshift = av_pix_fmt_descriptors[link->format].log2_chroma_h;
56
57 return 0;
58 }
59
60 static AVFilterPicRef *get_video_buffer(AVFilterLink *link, int perms,
61 int w, int h)
62 {
63 return avfilter_get_video_buffer(link->dst->outputs[0], perms, w, h);
64 }
65
66 static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
67 {
68 SliceContext *slice = link->dst->priv;
69
70 if (slice->use_random_h) {
71 slice->lcg_state = slice->lcg_state * 1664525 + 1013904223;
72 slice->h = 8 + (uint64_t)slice->lcg_state * 25 / UINT32_MAX;
73 }
74
75 /* ensure that slices play nice with chroma subsampling, and enforce
76 * a reasonable minimum size for the slices */
77 slice->h = FFMAX(8, slice->h & (-1 << slice->vshift));
78
79 av_log(link->dst, AV_LOG_DEBUG, "h:%d\n", slice->h);
80
81 avfilter_start_frame(link->dst->outputs[0], picref);
82 }
83
84 static void end_frame(AVFilterLink *link)
85 {
86 avfilter_end_frame(link->dst->outputs[0]);
87 }
88
89 static void draw_slice(AVFilterLink *link, int y, int h, int slice_dir)
90 {
91 SliceContext *slice = link->dst->priv;
92 int y2;
93
94 if (slice_dir == 1) {
95 for (y2 = y; y2 + slice->h <= y + h; y2 += slice->h)
96 avfilter_draw_slice(link->dst->outputs[0], y2, slice->h, slice_dir);
97
98 if (y2 < y + h)
99 avfilter_draw_slice(link->dst->outputs[0], y2, y + h - y2, slice_dir);
100 } else if (slice_dir == -1) {
101 for (y2 = y + h; y2 - slice->h >= y; y2 -= slice->h)
102 avfilter_draw_slice(link->dst->outputs[0], y2 - slice->h, slice->h, slice_dir);
103
104 if (y2 > y)
105 avfilter_draw_slice(link->dst->outputs[0], y, y2 - y, slice_dir);
106 }
107 }
108
109 AVFilter avfilter_vf_slicify = {
110 .name = "slicify",
111 .description = "Pass the images of input video on to next video filter as multiple slices.",
112
113 .init = init,
114
115 .priv_size = sizeof(SliceContext),
116
117 .inputs = (AVFilterPad[]) {{ .name = "default",
118 .type = CODEC_TYPE_VIDEO,
119 .get_video_buffer = get_video_buffer,
120 .start_frame = start_frame,
121 .draw_slice = draw_slice,
122 .config_props = config_props,
123 .end_frame = end_frame, },
124 { .name = NULL}},
125 .outputs = (AVFilterPad[]) {{ .name = "default",
126 .type = CODEC_TYPE_VIDEO, },
127 { .name = NULL}},
128 };