1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_CROPCAP:
5
6********************
7ioctl VIDIOC_CROPCAP
8********************
9
10Name
11====
12
13VIDIOC_CROPCAP - Information about the video cropping and scaling abilities
14
15Synopsis
16========
17
18.. c:macro:: VIDIOC_CROPCAP
19
20``int ioctl(int fd, VIDIOC_CROPCAP, struct v4l2_cropcap *argp)``
21
22Arguments
23=========
24
25``fd``
26    File descriptor returned by :c:func:`open()`.
27
28``argp``
29    Pointer to struct :c:type:`v4l2_cropcap`.
30
31Description
32===========
33
34Applications use this function to query the cropping limits, the pixel
35aspect of images and to calculate scale factors. They set the ``type``
36field of a v4l2_cropcap structure to the respective buffer (stream)
37type and call the :ref:`VIDIOC_CROPCAP` ioctl with a pointer to this
38structure. Drivers fill the rest of the structure. The results are
39constant except when switching the video standard. Remember this switch
40can occur implicit when switching the video input or output.
41
42This ioctl must be implemented for video capture or output devices that
43support cropping and/or scaling and/or have non-square pixels, and for
44overlay devices.
45
46.. c:type:: v4l2_cropcap
47
48.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
49
50.. flat-table:: struct v4l2_cropcap
51    :header-rows:  0
52    :stub-columns: 0
53    :widths:       1 1 2
54
55    * - __u32
56      - ``type``
57      - Type of the data stream, set by the application. Only these types
58	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
59	``V4L2_BUF_TYPE_VIDEO_OUTPUT``, ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
60	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type` and the note below.
61    * - struct :ref:`v4l2_rect <v4l2-rect-crop>`
62      - ``bounds``
63      - Defines the window within capturing or output is possible, this
64	may exclude for example the horizontal and vertical blanking
65	areas. The cropping rectangle cannot exceed these limits. Width
66	and height are defined in pixels, the driver writer is free to
67	choose origin and units of the coordinate system in the analog
68	domain.
69    * - struct :ref:`v4l2_rect <v4l2-rect-crop>`
70      - ``defrect``
71      - Default cropping rectangle, it shall cover the "whole picture".
72	Assuming pixel aspect 1/1 this could be for example a 640 × 480
73	rectangle for NTSC, a 768 × 576 rectangle for PAL and SECAM
74	centered over the active picture area. The same co-ordinate system
75	as for ``bounds`` is used.
76    * - struct :c:type:`v4l2_fract`
77      - ``pixelaspect``
78      - This is the pixel aspect (y / x) when no scaling is applied, the
79	ratio of the actual sampling frequency and the frequency required
80	to get square pixels.
81
82	When cropping coordinates refer to square pixels, the driver sets
83	``pixelaspect`` to 1/1. Other common values are 54/59 for PAL and
84	SECAM, 11/10 for NTSC sampled according to [:ref:`itu601`].
85
86.. note::
87   Unfortunately in the case of multiplanar buffer types
88   (``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``)
89   this API was messed up with regards to how the :c:type:`v4l2_cropcap` ``type`` field
90   should be filled in. Some drivers only accepted the ``_MPLANE`` buffer type while
91   other drivers only accepted a non-multiplanar buffer type (i.e. without the
92   ``_MPLANE`` at the end).
93
94   Starting with kernel 4.13 both variations are allowed.
95
96
97.. _v4l2-rect-crop:
98
99.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
100
101.. flat-table:: struct v4l2_rect
102    :header-rows:  0
103    :stub-columns: 0
104    :widths:       1 1 2
105
106    * - __s32
107      - ``left``
108      - Horizontal offset of the top, left corner of the rectangle, in
109	pixels.
110    * - __s32
111      - ``top``
112      - Vertical offset of the top, left corner of the rectangle, in
113	pixels.
114    * - __u32
115      - ``width``
116      - Width of the rectangle, in pixels.
117    * - __u32
118      - ``height``
119      - Height of the rectangle, in pixels.
120
121Return Value
122============
123
124On success 0 is returned, on error -1 and the ``errno`` variable is set
125appropriately. The generic error codes are described at the
126:ref:`Generic Error Codes <gen-errors>` chapter.
127
128EINVAL
129    The struct :c:type:`v4l2_cropcap` ``type`` is
130    invalid.
131
132ENODATA
133    Cropping is not supported for this input or output.
134