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vf_field.c
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1 /*
2  * Copyright (c) 2003 Rich Felker
3  * Copyright (c) 2012 Stefano Sabatini
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * field filter, based on libmpcodecs/vf_field.c by Rich Felker
25  */
26 
27 #include "libavutil/opt.h"
28 #include "libavutil/pixdesc.h"
29 #include "avfilter.h"
30 #include "internal.h"
31 
33 
34 typedef struct {
35  const AVClass *class;
37  int nb_planes; ///< number of planes of the current format
38 } FieldContext;
39 
40 #define OFFSET(x) offsetof(FieldContext, x)
41 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
42 
43 static const AVOption field_options[] = {
44  {"type", "set field type (top or bottom)", OFFSET(type), AV_OPT_TYPE_INT, {.i64=FIELD_TYPE_TOP}, 0, 1, FLAGS, "field_type" },
45  {"top", "select top field", 0, AV_OPT_TYPE_CONST, {.i64=FIELD_TYPE_TOP}, INT_MIN, INT_MAX, FLAGS, "field_type"},
46  {"bottom", "select bottom field", 0, AV_OPT_TYPE_CONST, {.i64=FIELD_TYPE_BOTTOM}, INT_MIN, INT_MAX, FLAGS, "field_type"},
47 
48  {NULL}
49 };
50 
52 
53 static av_cold int init(AVFilterContext *ctx, const char *args)
54 {
55  FieldContext *field = ctx->priv;
56  static const char *shorthand[] = { "type", NULL };
57 
58  field->class = &field_class;
59  av_opt_set_defaults(field);
60 
61  return av_opt_set_from_string(field, args, shorthand, "=", ":");
62 }
63 
64 static int config_props_output(AVFilterLink *outlink)
65 {
66  AVFilterContext *ctx = outlink->src;
67  FieldContext *field = ctx->priv;
68  AVFilterLink *inlink = ctx->inputs[0];
69  const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
70  int i;
71 
72  for (i = 0; i < desc->nb_components; i++)
73  field->nb_planes = FFMAX(field->nb_planes, desc->comp[i].plane);
74  field->nb_planes++;
75 
76  outlink->w = inlink->w;
77  outlink->h = (inlink->h + (field->type == FIELD_TYPE_TOP)) / 2;
78 
79  av_log(ctx, AV_LOG_VERBOSE, "w:%d h:%d type:%s -> w:%d h:%d\n",
80  inlink->w, inlink->h, field->type == FIELD_TYPE_BOTTOM ? "bottom" : "top",
81  outlink->w, outlink->h);
82  return 0;
83 }
84 
85 static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
86 {
87  FieldContext *field = inlink->dst->priv;
88  AVFilterLink *outlink = inlink->dst->outputs[0];
89  int i;
90 
91  inpicref->video->h = outlink->h;
92  inpicref->video->interlaced = 0;
93 
94  for (i = 0; i < field->nb_planes; i++) {
95  if (field->type == FIELD_TYPE_BOTTOM)
96  inpicref->data[i] = inpicref->data[i] + inpicref->linesize[i];
97  inpicref->linesize[i] = 2 * inpicref->linesize[i];
98  }
99  return ff_filter_frame(outlink, inpicref);
100 }
101 
102 static const AVFilterPad field_inputs[] = {
103  {
104  .name = "default",
105  .type = AVMEDIA_TYPE_VIDEO,
106  .get_video_buffer = ff_null_get_video_buffer,
107  .filter_frame = filter_frame,
108  },
109  { NULL }
110 };
111 
112 static const AVFilterPad field_outputs[] = {
113  {
114  .name = "default",
115  .type = AVMEDIA_TYPE_VIDEO,
116  .config_props = config_props_output,
117  },
118  { NULL }
119 };
120 
122  .name = "field",
123  .description = NULL_IF_CONFIG_SMALL("Extract a field from the input video."),
124 
125  .priv_size = sizeof(FieldContext),
126  .init = init,
127 
128  .inputs = field_inputs,
129  .outputs = field_outputs,
130  .priv_class = &field_class,
131 };