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1.. -*- coding: utf-8; mode: rst -*-
2
3.. _VIDIOC_ENUM_FMT:
4
5*********************
6ioctl VIDIOC_ENUM_FMT
7*********************
8
9Name
10====
11
12VIDIOC_ENUM_FMT - Enumerate image formats
13
14
15Synopsis
16========
17
18.. c:function:: int ioctl( int fd, VIDIOC_ENUM_FMT, struct v4l2_fmtdesc *argp )
19    :name: VIDIOC_ENUM_FMT
20
21
22Arguments
23=========
24
25``fd``
26    File descriptor returned by :ref:`open() <func-open>`.
27
28``argp``
29    Pointer to struct :c:type:`v4l2_fmtdesc`.
30
31
32Description
33===========
34
35To enumerate image formats applications initialize the ``type`` and
36``index`` field of struct :c:type:`v4l2_fmtdesc` and call
37the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers
38fill the rest of the structure or return an ``EINVAL`` error code. All
39formats are enumerable by beginning at index zero and incrementing by
40one until ``EINVAL`` is returned.
41
42.. note::
43
44   After switching input or output the list of enumerated image
45   formats may be different.
46
47
48.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
49
50.. c:type:: v4l2_fmtdesc
51
52.. flat-table:: struct v4l2_fmtdesc
53    :header-rows:  0
54    :stub-columns: 0
55    :widths:       1 1 2
56
57    * - __u32
58      - ``index``
59      - Number of the format in the enumeration, set by the application.
60	This is in no way related to the ``pixelformat`` field.
61    * - __u32
62      - ``type``
63      - Type of the data stream, set by the application. Only these types
64	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
65	``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
66	``V4L2_BUF_TYPE_VIDEO_OUTPUT``,
67	``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
68	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`.
69    * - __u32
70      - ``flags``
71      - See :ref:`fmtdesc-flags`
72    * - __u8
73      - ``description``\ [32]
74      - Description of the format, a NUL-terminated ASCII string. This
75	information is intended for the user, for example: "YUV 4:2:2".
76    * - __u32
77      - ``pixelformat``
78      - The image format identifier. This is a four character code as
79	computed by the v4l2_fourcc() macro:
80    * - :cspan:`2`
81
82	.. _v4l2-fourcc:
83
84	``#define v4l2_fourcc(a,b,c,d)``
85
86	``(((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))``
87
88	Several image formats are already defined by this specification in
89	:ref:`pixfmt`.
90
91	.. attention::
92
93	   These codes are not the same as those used
94	   in the Windows world.
95    * - __u32
96      - ``reserved``\ [4]
97      - Reserved for future extensions. Drivers must set the array to
98	zero.
99
100
101
102.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
103
104.. _fmtdesc-flags:
105
106.. flat-table:: Image Format Description Flags
107    :header-rows:  0
108    :stub-columns: 0
109    :widths:       3 1 4
110
111    * - ``V4L2_FMT_FLAG_COMPRESSED``
112      - 0x0001
113      - This is a compressed format.
114    * - ``V4L2_FMT_FLAG_EMULATED``
115      - 0x0002
116      - This format is not native to the device but emulated through
117	software (usually libv4l2), where possible try to use a native
118	format instead for better performance.
119
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_fmtdesc` ``type`` is not
130    supported or the ``index`` is out of bounds.
131