[deliverable/linux.git] / Documentation / media / uapi / v4l / vidioc-cropcap.rst

.. -*- coding: utf-8; mode: rst -*-

.. _VIDIOC_CROPCAP:

********************
ioctl VIDIOC_CROPCAP
********************

Name
====

VIDIOC_CROPCAP - Information about the video cropping and scaling abilities


Synopsis
========

.. c:function:: int ioctl( int fd, VIDIOC_CROPCAP, struct v4l2_cropcap *argp )
    :name: VIDIOC_CROPCAP


Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <func-open>`.

``argp``


Description
===========

Applications use this function to query the cropping limits, the pixel
aspect of images and to calculate scale factors. They set the ``type``
field of a v4l2_cropcap structure to the respective buffer (stream)
type and call the :ref:`VIDIOC_CROPCAP` ioctl with a pointer to this
structure. Drivers fill the rest of the structure. The results are
constant except when switching the video standard. Remember this switch
can occur implicit when switching the video input or output.

Do not use the multiplanar buffer types. Use
``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use
``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``.

This ioctl must be implemented for video capture or output devices that
support cropping and/or scaling and/or have non-square pixels, and for
overlay devices.


.. c:type:: v4l2_cropcap

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|

.. flat-table:: struct v4l2_cropcap
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2


    -  .. row 1

       -  __u32

       -  ``type``

       -  Type of the data stream, set by the application. Only these types
	  are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
	  ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and
	  ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`.

    -  .. row 2

       -  struct :ref:`v4l2_rect <v4l2-rect-crop>`

       -  ``bounds``

       -  Defines the window within capturing or output is possible, this
	  may exclude for example the horizontal and vertical blanking
	  areas. The cropping rectangle cannot exceed these limits. Width
	  and height are defined in pixels, the driver writer is free to
	  choose origin and units of the coordinate system in the analog
	  domain.

    -  .. row 3

       -  struct :ref:`v4l2_rect <v4l2-rect-crop>`

       -  ``defrect``

       -  Default cropping rectangle, it shall cover the "whole picture".
	  Assuming pixel aspect 1/1 this could be for example a 640 × 480
	  rectangle for NTSC, a 768 × 576 rectangle for PAL and SECAM
	  centered over the active picture area. The same co-ordinate system
	  as for ``bounds`` is used.

    -  .. row 4

       -  struct :c:type:`v4l2_fract`

       -  ``pixelaspect``

       -  This is the pixel aspect (y / x) when no scaling is applied, the
	  ratio of the actual sampling frequency and the frequency required
	  to get square pixels.

	  When cropping coordinates refer to square pixels, the driver sets
	  ``pixelaspect`` to 1/1. Other common values are 54/59 for PAL and
	  SECAM, 11/10 for NTSC sampled according to [:ref:`itu601`].


.. _v4l2-rect-crop:

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|

.. flat-table:: struct v4l2_rect
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2


    -  .. row 1

       -  __s32

       -  ``left``

       -  Horizontal offset of the top, left corner of the rectangle, in
	  pixels.

    -  .. row 2

       -  __s32

       -  ``top``

       -  Vertical offset of the top, left corner of the rectangle, in
	  pixels.

    -  .. row 3

       -  __u32

       -  ``width``

       -  Width of the rectangle, in pixels.

    -  .. row 4

       -  __u32

       -  ``height``

       -  Height of the rectangle, in pixels.


Return Value
============

On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.

EINVAL
    The struct :c:type:`v4l2_cropcap` ``type`` is
    invalid.

ENODATA
    Cropping is not supported for this input or output.
Commit	Line	Data
5377d91f MH	1	.. -- coding: utf-8; mode: rst --
5377d91f MH	2
af4a4d0d	3	.. _VIDIOC_CROPCAP:
5377d91f MH	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
15e7d615 MCC	14
15e7d615 MCC	15	Synopsis
5377d91f MH	16	========
5377d91f MH	17
41d80465 MCC	18	.. c:function:: int ioctl( int fd, VIDIOC_CROPCAP, struct v4l2_cropcap *argp )
41d80465 MCC	19	:name: VIDIOC_CROPCAP
5377d91f	20
586027ce	21
15e7d615	22	Arguments
5377d91f MH	23	=========
	24
	25	``fd``
	26	File descriptor returned by :ref:`open() <func-open>`.
	27
5377d91f MH	28	``argp``
	29
	30
15e7d615	31	Description
5377d91f MH	32	===========
	33
	34	Applications use this function to query the cropping limits, the pixel
	35	aspect of images and to calculate scale factors. They set the ``type``
	36	field of a v4l2_cropcap structure to the respective buffer (stream)
2212ff25	37	type and call the :ref:`VIDIOC_CROPCAP` ioctl with a pointer to this
5377d91f MH	38	structure. Drivers fill the rest of the structure. The results are
	39	constant except when switching the video standard. Remember this switch
	40	can occur implicit when switching the video input or output.
	41
	42	Do not use the multiplanar buffer types. Use
	43	``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
	44	``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use
	45	``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
	46	``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``.
	47
	48	This ioctl must be implemented for video capture or output devices that
	49	support cropping and/or scaling and/or have non-square pixels, and for
	50	overlay devices.
	51
	52
e8be7e97	53	.. c:type:: v4l2_cropcap
5377d91f	54
5bd4bb78 MCC	55	.. tabularcolumns:: \|p{4.4cm}\|p{4.4cm}\|p{8.7cm}\|
5bd4bb78 MCC	56
5377d91f MH	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
0579e6e3 MCC	70	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
0579e6e3 MCC	71	``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and
56683d7d	72	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`.
5377d91f MH	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
0579e6e3 MCC	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.
5377d91f MH	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".
0579e6e3 MCC	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.
5377d91f MH	98
	99	- .. row 4
	100
e8be7e97	101	- struct :c:type:`v4l2_fract`
5377d91f MH	102
	103	- ``pixelaspect``
	104
	105	- This is the pixel aspect (y / x) when no scaling is applied, the
0579e6e3 MCC	106	ratio of the actual sampling frequency and the frequency required
0579e6e3 MCC	107	to get square pixels.
5377d91f	108
0579e6e3 MCC	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`].
5377d91f MH	112
	113
	114
	115	.. _v4l2-rect-crop:
	116
5bd4bb78 MCC	117	.. tabularcolumns:: \|p{4.4cm}\|p{4.4cm}\|p{8.7cm}\|
5bd4bb78 MCC	118
5377d91f MH	119	.. flat-table:: struct v4l2_rect
	120	:header-rows: 0
	121	:stub-columns: 0
	122	:widths: 1 1 2
	123
	124
	125	- .. row 1
	126
	127	- __s32
	128
	129	- ``left``
	130
	131	- Horizontal offset of the top, left corner of the rectangle, in
0579e6e3	132	pixels.
5377d91f MH	133
	134	- .. row 2
	135
	136	- __s32
	137
	138	- ``top``
	139
	140	- Vertical offset of the top, left corner of the rectangle, in
0579e6e3	141	pixels.
5377d91f MH	142
	143	- .. row 3
	144
	145	- __u32
	146
	147	- ``width``
	148
	149	- Width of the rectangle, in pixels.
	150
	151	- .. row 4
	152
	153	- __u32
	154
	155	- ``height``
	156
	157	- Height of the rectangle, in pixels.
	158
	159
15e7d615	160	Return Value
5377d91f MH	161	============
	162
	163	On success 0 is returned, on error -1 and the ``errno`` variable is set
	164	appropriately. The generic error codes are described at the
	165	:ref:`Generic Error Codes <gen-errors>` chapter.
	166
	167	EINVAL
e8be7e97	168	The struct :c:type:`v4l2_cropcap` ``type`` is
5377d91f	169	invalid.
3f8d56b0 HV	170
	171	ENODATA
	172	Cropping is not supported for this input or output.