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
|
.. -*- coding: utf-8; mode: rst -*-
********
Examples
********
(A video capture device is assumed; change
``V4L2_BUF_TYPE_VIDEO_CAPTURE`` for other devices; change target to
``V4L2_SEL_TGT_COMPOSE_*`` family to configure composing area)
.. code-block:: c
struct v4l2_selection sel = {
.type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
.target = V4L2_SEL_TGT_CROP_DEFAULT,
};
ret = ioctl(fd, VIDIOC_G_SELECTION, &sel);
if (ret)
exit(-1);
sel.target = V4L2_SEL_TGT_CROP;
ret = ioctl(fd, VIDIOC_S_SELECTION, &sel);
if (ret)
exit(-1);
Setting a composing area on output of size of *at most* half of limit
placed at a center of a display.
.. code-block:: c
struct v4l2_selection sel = {
.type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
.target = V4L2_SEL_TGT_COMPOSE_BOUNDS,
};
struct v4l2_rect r;
ret = ioctl(fd, VIDIOC_G_SELECTION, &sel);
if (ret)
exit(-1);
/* setting smaller compose rectangle */
r.width = sel.r.width / 2;
r.height = sel.r.height / 2;
r.left = sel.r.width / 4;
r.top = sel.r.height / 4;
sel.r = r;
sel.target = V4L2_SEL_TGT_COMPOSE;
sel.flags = V4L2_SEL_FLAG_LE;
ret = ioctl(fd, VIDIOC_S_SELECTION, &sel);
if (ret)
exit(-1);
A video output device is assumed; change ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
for other devices
.. code-block:: c
struct v4l2_selection compose = {
.type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
.target = V4L2_SEL_TGT_COMPOSE,
};
struct v4l2_selection crop = {
.type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
.target = V4L2_SEL_TGT_CROP,
};
double hscale, vscale;
ret = ioctl(fd, VIDIOC_G_SELECTION, &compose);
if (ret)
exit(-1);
ret = ioctl(fd, VIDIOC_G_SELECTION, &crop);
if (ret)
exit(-1);
/* computing scaling factors */
hscale = (double)compose.r.width / crop.r.width;
vscale = (double)compose.r.height / crop.r.height;
.. ------------------------------------------------------------------------------
.. This file was automatically converted from DocBook-XML with the dbxml
.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
.. from the linux kernel, refer to:
..
.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
.. ------------------------------------------------------------------------------
|
