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

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

.. _VIDIOC_CROPCAP:

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

*man VIDIOC_CROPCAP(2)*

Information about the video cropping and scaling abilities


Synopsis
========

.. cpp:function:: int ioctl( int fd, int request, struct v4l2_cropcap *argp )

Arguments
=========

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

``request``
    VIDIOC_CROPCAP

``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.


.. _v4l2-cropcap:

.. 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 :ref:`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 :ref:`v4l2_fract <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:

.. 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 :ref:`v4l2_cropcap <v4l2-cropcap>` ``type`` is
    invalid.
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
	9	man VIDIOC_CROPCAP(2)
	10
	11	Information about the video cropping and scaling abilities
	12
	13
	14	Synopsis
	15	========
	16
b7e67f6c	17	.. cpp:function:: int ioctl( int fd, int request, struct v4l2_cropcap *argp )
5377d91f MH	18
	19	Arguments
	20	=========
	21
	22	``fd``
	23	File descriptor returned by :ref:`open() <func-open>`.
	24
	25	``request``
	26	VIDIOC_CROPCAP
	27
	28	``argp``
	29
	30
	31	Description
	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
	53	.. _v4l2-cropcap:
	54
	55	.. flat-table:: struct v4l2_cropcap
	56	:header-rows: 0
	57	:stub-columns: 0
	58	:widths: 1 1 2
	59
	60
	61	- .. row 1
	62
	63	- __u32
	64
	65	- ``type``
	66
	67	- Type of the data stream, set by the application. Only these types
0579e6e3 MCC	68	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
	69	``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and
	70	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`.
5377d91f MH	71
	72	- .. row 2
	73
	74	- struct :ref:`v4l2_rect <v4l2-rect-crop>`
	75
	76	- ``bounds``
	77
	78	- Defines the window within capturing or output is possible, this
0579e6e3 MCC	79	may exclude for example the horizontal and vertical blanking
	80	areas. The cropping rectangle cannot exceed these limits. Width
	81	and height are defined in pixels, the driver writer is free to
	82	choose origin and units of the coordinate system in the analog
	83	domain.
5377d91f MH	84
	85	- .. row 3
	86
	87	- struct :ref:`v4l2_rect <v4l2-rect-crop>`
	88
	89	- ``defrect``
	90
	91	- Default cropping rectangle, it shall cover the "whole picture".
0579e6e3 MCC	92	Assuming pixel aspect 1/1 this could be for example a 640 × 480
	93	rectangle for NTSC, a 768 × 576 rectangle for PAL and SECAM
	94	centered over the active picture area. The same co-ordinate system
	95	as for ``bounds`` is used.
5377d91f MH	96
	97	- .. row 4
	98
	99	- struct :ref:`v4l2_fract <v4l2-fract>`
	100
	101	- ``pixelaspect``
	102
	103	- This is the pixel aspect (y / x) when no scaling is applied, the
0579e6e3 MCC	104	ratio of the actual sampling frequency and the frequency required
0579e6e3 MCC	105	to get square pixels.
5377d91f	106
0579e6e3 MCC	107	When cropping coordinates refer to square pixels, the driver sets
	108	``pixelaspect`` to 1/1. Other common values are 54/59 for PAL and
	109	SECAM, 11/10 for NTSC sampled according to [:ref:`itu601`].
5377d91f MH	110
	111
	112
	113	.. _v4l2-rect-crop:
	114
	115	.. flat-table:: struct v4l2_rect
	116	:header-rows: 0
	117	:stub-columns: 0
	118	:widths: 1 1 2
	119
	120
	121	- .. row 1
	122
	123	- __s32
	124
	125	- ``left``
	126
	127	- Horizontal offset of the top, left corner of the rectangle, in
0579e6e3	128	pixels.
5377d91f MH	129
	130	- .. row 2
	131
	132	- __s32
	133
	134	- ``top``
	135
	136	- Vertical offset of the top, left corner of the rectangle, in
0579e6e3	137	pixels.
5377d91f MH	138
	139	- .. row 3
	140
	141	- __u32
	142
	143	- ``width``
	144
	145	- Width of the rectangle, in pixels.
	146
	147	- .. row 4
	148
	149	- __u32
	150
	151	- ``height``
	152
	153	- Height of the rectangle, in pixels.
	154
	155
	156
	157	Return Value
	158	============
	159
	160	On success 0 is returned, on error -1 and the ``errno`` variable is set
	161	appropriately. The generic error codes are described at the
	162	:ref:`Generic Error Codes <gen-errors>` chapter.
	163
	164	EINVAL
	165	The struct :ref:`v4l2_cropcap <v4l2-cropcap>` ``type`` is
	166	invalid.