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{8.5cm}| 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 coordinate 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{8.5cm}| 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