[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
========

.. 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
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
b7e67f6c	18	.. cpp:function:: int ioctl( int fd, int request, struct v4l2_cropcap *argp )
5377d91f	19
586027ce	20
15e7d615	21	Arguments
5377d91f MH	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
5377d91f MH	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
5377d91f MH	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
0579e6e3 MCC	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`.
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
	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
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
	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.
5377d91f MH	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.
5377d91f MH	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
5377d91f MH	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.