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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
af4a4d0d | 3 | .. _VIDIOC_CROPCAP: |
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4 | |
5 | ******************** | |
6 | ioctl VIDIOC_CROPCAP | |
7 | ******************** | |
8 | ||
15e7d615 | 9 | Name |
586027ce | 10 | ==== |
5377d91f | 11 | |
586027ce | 12 | VIDIOC_CROPCAP - Information about the video cropping and scaling abilities |
5377d91f | 13 | |
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14 | |
15 | Synopsis | |
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16 | ======== |
17 | ||
b7e67f6c | 18 | .. cpp:function:: int ioctl( int fd, int request, struct v4l2_cropcap *argp ) |
5377d91f | 19 | |
586027ce | 20 | |
15e7d615 | 21 | Arguments |
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22 | ========= |
23 | ||
24 | ``fd`` | |
25 | File descriptor returned by :ref:`open() <func-open>`. | |
26 | ||
27 | ``request`` | |
28 | VIDIOC_CROPCAP | |
29 | ||
30 | ``argp`` | |
31 | ||
32 | ||
15e7d615 | 33 | Description |
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34 | =========== |
35 | ||
36 | Applications use this function to query the cropping limits, the pixel | |
37 | aspect of images and to calculate scale factors. They set the ``type`` | |
38 | field of a v4l2_cropcap structure to the respective buffer (stream) | |
2212ff25 | 39 | type and call the :ref:`VIDIOC_CROPCAP` ioctl with a pointer to this |
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40 | structure. Drivers fill the rest of the structure. The results are |
41 | constant except when switching the video standard. Remember this switch | |
42 | can occur implicit when switching the video input or output. | |
43 | ||
44 | Do not use the multiplanar buffer types. Use | |
45 | ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of | |
46 | ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use | |
47 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of | |
48 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``. | |
49 | ||
50 | This ioctl must be implemented for video capture or output devices that | |
51 | support cropping and/or scaling and/or have non-square pixels, and for | |
52 | overlay devices. | |
53 | ||
54 | ||
55 | .. _v4l2-cropcap: | |
56 | ||
57 | .. flat-table:: struct v4l2_cropcap | |
58 | :header-rows: 0 | |
59 | :stub-columns: 0 | |
60 | :widths: 1 1 2 | |
61 | ||
62 | ||
63 | - .. row 1 | |
64 | ||
65 | - __u32 | |
66 | ||
67 | - ``type`` | |
68 | ||
69 | - Type of the data stream, set by the application. Only these types | |
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70 | are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, |
71 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and | |
72 | ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`. | |
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73 | |
74 | - .. row 2 | |
75 | ||
76 | - struct :ref:`v4l2_rect <v4l2-rect-crop>` | |
77 | ||
78 | - ``bounds`` | |
79 | ||
80 | - Defines the window within capturing or output is possible, this | |
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81 | may exclude for example the horizontal and vertical blanking |
82 | areas. The cropping rectangle cannot exceed these limits. Width | |
83 | and height are defined in pixels, the driver writer is free to | |
84 | choose origin and units of the coordinate system in the analog | |
85 | domain. | |
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86 | |
87 | - .. row 3 | |
88 | ||
89 | - struct :ref:`v4l2_rect <v4l2-rect-crop>` | |
90 | ||
91 | - ``defrect`` | |
92 | ||
93 | - Default cropping rectangle, it shall cover the "whole picture". | |
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94 | Assuming pixel aspect 1/1 this could be for example a 640 × 480 |
95 | rectangle for NTSC, a 768 × 576 rectangle for PAL and SECAM | |
96 | centered over the active picture area. The same co-ordinate system | |
97 | as for ``bounds`` is used. | |
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98 | |
99 | - .. row 4 | |
100 | ||
101 | - struct :ref:`v4l2_fract <v4l2-fract>` | |
102 | ||
103 | - ``pixelaspect`` | |
104 | ||
105 | - This is the pixel aspect (y / x) when no scaling is applied, the | |
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106 | ratio of the actual sampling frequency and the frequency required |
107 | to get square pixels. | |
5377d91f | 108 | |
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109 | When cropping coordinates refer to square pixels, the driver sets |
110 | ``pixelaspect`` to 1/1. Other common values are 54/59 for PAL and | |
111 | SECAM, 11/10 for NTSC sampled according to [:ref:`itu601`]. | |
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112 | |
113 | ||
114 | ||
115 | .. _v4l2-rect-crop: | |
116 | ||
117 | .. flat-table:: struct v4l2_rect | |
118 | :header-rows: 0 | |
119 | :stub-columns: 0 | |
120 | :widths: 1 1 2 | |
121 | ||
122 | ||
123 | - .. row 1 | |
124 | ||
125 | - __s32 | |
126 | ||
127 | - ``left`` | |
128 | ||
129 | - Horizontal offset of the top, left corner of the rectangle, in | |
0579e6e3 | 130 | pixels. |
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131 | |
132 | - .. row 2 | |
133 | ||
134 | - __s32 | |
135 | ||
136 | - ``top`` | |
137 | ||
138 | - Vertical offset of the top, left corner of the rectangle, in | |
0579e6e3 | 139 | pixels. |
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140 | |
141 | - .. row 3 | |
142 | ||
143 | - __u32 | |
144 | ||
145 | - ``width`` | |
146 | ||
147 | - Width of the rectangle, in pixels. | |
148 | ||
149 | - .. row 4 | |
150 | ||
151 | - __u32 | |
152 | ||
153 | - ``height`` | |
154 | ||
155 | - Height of the rectangle, in pixels. | |
156 | ||
157 | ||
15e7d615 | 158 | Return Value |
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159 | ============ |
160 | ||
161 | On success 0 is returned, on error -1 and the ``errno`` variable is set | |
162 | appropriately. The generic error codes are described at the | |
163 | :ref:`Generic Error Codes <gen-errors>` chapter. | |
164 | ||
165 | EINVAL | |
166 | The struct :ref:`v4l2_cropcap <v4l2-cropcap>` ``type`` is | |
167 | invalid. |