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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
af4a4d0d | 3 | .. _VIDIOC_G_CROP: |
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4 | |
5 | ********************************** | |
6 | ioctl VIDIOC_G_CROP, VIDIOC_S_CROP | |
7 | ********************************** | |
8 | ||
15e7d615 | 9 | Name |
586027ce | 10 | ==== |
5377d91f | 11 | |
586027ce | 12 | VIDIOC_G_CROP - VIDIOC_S_CROP - Get or set the current cropping rectangle |
5377d91f | 13 | |
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14 | |
15 | Synopsis | |
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16 | ======== |
17 | ||
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18 | .. c:function:: int ioctl( int fd, VIDIOC_G_CROP, struct v4l2_crop *argp ) |
19 | :name: VIDIOC_G_CROP | |
5377d91f | 20 | |
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21 | .. c:function:: int ioctl( int fd, VIDIOC_S_CROP, const struct v4l2_crop *argp ) |
22 | :name: VIDIOC_S_CROP | |
5377d91f | 23 | |
586027ce | 24 | |
15e7d615 | 25 | Arguments |
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26 | ========= |
27 | ||
28 | ``fd`` | |
29 | File descriptor returned by :ref:`open() <func-open>`. | |
30 | ||
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31 | ``argp`` |
32 | ||
33 | ||
15e7d615 | 34 | Description |
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35 | =========== |
36 | ||
37 | To query the cropping rectangle size and position applications set the | |
fc78c7c7 | 38 | ``type`` field of a struct :c:type:`v4l2_crop` structure to the |
4e03cb76 | 39 | respective buffer (stream) type and call the :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` ioctl |
5377d91f | 40 | with a pointer to this structure. The driver fills the rest of the |
cdb4af0f | 41 | structure or returns the ``EINVAL`` error code if cropping is not supported. |
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42 | |
43 | To change the cropping rectangle applications initialize the ``type`` | |
e8be7e97 | 44 | and struct :c:type:`v4l2_rect` substructure named ``c`` of a |
2212ff25 | 45 | v4l2_crop structure and call the :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl with a pointer |
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46 | to this structure. |
47 | ||
48 | Do not use the multiplanar buffer types. Use | |
49 | ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of | |
50 | ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use | |
51 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of | |
52 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``. | |
53 | ||
54 | The driver first adjusts the requested dimensions against hardware | |
55 | limits, i. e. the bounds given by the capture/output window, and it | |
56 | rounds to the closest possible values of horizontal and vertical offset, | |
57 | width and height. In particular the driver must round the vertical | |
58 | offset of the cropping rectangle to frame lines modulo two, such that | |
59 | the field order cannot be confused. | |
60 | ||
61 | Second the driver adjusts the image size (the opposite rectangle of the | |
62 | scaling process, source or target depending on the data direction) to | |
63 | the closest size possible while maintaining the current horizontal and | |
64 | vertical scaling factor. | |
65 | ||
66 | Finally the driver programs the hardware with the actual cropping and | |
2212ff25 | 67 | image parameters. :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` is a write-only ioctl, it does not |
5377d91f | 68 | return the actual parameters. To query them applications must call |
4e03cb76 | 69 | :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` and :ref:`VIDIOC_G_FMT`. When the |
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70 | parameters are unsuitable the application may modify the cropping or |
71 | image parameters and repeat the cycle until satisfactory parameters have | |
72 | been negotiated. | |
73 | ||
74 | When cropping is not supported then no parameters are changed and | |
cdb4af0f | 75 | :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` returns the ``EINVAL`` error code. |
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76 | |
77 | ||
e8be7e97 | 78 | .. c:type:: v4l2_crop |
5377d91f | 79 | |
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80 | .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| |
81 | ||
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82 | .. flat-table:: struct v4l2_crop |
83 | :header-rows: 0 | |
84 | :stub-columns: 0 | |
85 | :widths: 1 1 2 | |
86 | ||
87 | ||
88 | - .. row 1 | |
89 | ||
90 | - __u32 | |
91 | ||
92 | - ``type`` | |
93 | ||
94 | - Type of the data stream, set by the application. Only these types | |
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95 | are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, |
96 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and | |
56683d7d | 97 | ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`. |
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98 | |
99 | - .. row 2 | |
100 | ||
e8be7e97 | 101 | - struct :c:type:`v4l2_rect` |
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102 | |
103 | - ``c`` | |
104 | ||
105 | - Cropping rectangle. The same co-ordinate system as for struct | |
e8be7e97 | 106 | :c:type:`v4l2_cropcap` ``bounds`` is used. |
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107 | |
108 | ||
15e7d615 | 109 | Return Value |
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110 | ============ |
111 | ||
112 | On success 0 is returned, on error -1 and the ``errno`` variable is set | |
113 | appropriately. The generic error codes are described at the | |
114 | :ref:`Generic Error Codes <gen-errors>` chapter. | |
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115 | |
116 | ENODATA | |
117 | Cropping is not supported for this input or output. |