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.. -*- coding: utf-8; mode: rst -*-
.. _VIDIOC_ENUM_FMT:
*********************
ioctl VIDIOC_ENUM_FMT
*********************
*man VIDIOC_ENUM_FMT(2)*
Enumerate image formats
Synopsis
========
.. c:function:: int ioctl( int fd, int request, struct v4l2_fmtdesc *argp )
Arguments
=========
``fd``
File descriptor returned by :ref:`open() <func-open>`.
``request``
VIDIOC_ENUM_FMT
``argp``
Description
===========
To enumerate image formats applications initialize the ``type`` and
``index`` field of struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` and call
the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers
fill the rest of the structure or return an EINVAL error code. All
formats are enumerable by beginning at index zero and incrementing by
one until EINVAL is returned.
Note that after switching input or output the list of enumerated image
formats may be different.
.. _v4l2-fmtdesc:
.. flat-table:: struct v4l2_fmtdesc
:header-rows: 0
:stub-columns: 0
:widths: 1 1 2
- .. row 1
- __u32
- ``index``
- Number of the format in the enumeration, set by the application.
This is in no way related to the ``pixelformat`` field.
- .. row 2
- __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_CAPTURE_MPLANE``,
``V4L2_BUF_TYPE_VIDEO_OUTPUT``,
``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`.
- .. row 3
- __u32
- ``flags``
- See :ref:`fmtdesc-flags`
- .. row 4
- __u8
- ``description``\ [32]
- Description of the format, a NUL-terminated ASCII string. This
information is intended for the user, for example: "YUV 4:2:2".
- .. row 5
- __u32
- ``pixelformat``
- The image format identifier. This is a four character code as
computed by the v4l2_fourcc() macro:
- .. row 6
- :cspan:`2`
.. _v4l2-fourcc:
.. code-block:: c
#define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))
Several image formats are already defined by this specification in
:ref:`pixfmt`. Note these codes are not the same as those used
in the Windows world.
- .. row 7
- __u32
- ``reserved``\ [4]
- Reserved for future extensions. Drivers must set the array to
zero.
.. _fmtdesc-flags:
.. flat-table:: Image Format Description Flags
:header-rows: 0
:stub-columns: 0
:widths: 3 1 4
- .. row 1
- ``V4L2_FMT_FLAG_COMPRESSED``
- 0x0001
- This is a compressed format.
- .. row 2
- ``V4L2_FMT_FLAG_EMULATED``
- 0x0002
- This format is not native to the device but emulated through
software (usually libv4l2), where possible try to use a native
format instead for better performance.
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_fmtdesc <v4l2-fmtdesc>` ``type`` is not
supported or the ``index`` is out of bounds.
.. ------------------------------------------------------------------------------
.. This file was automatically converted from DocBook-XML with the dbxml
.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
.. from the linux kernel, refer to:
..
.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
.. ------------------------------------------------------------------------------
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