Documentation/media/uapi/v4l/vidioc-enum-fmt.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_ENUM_FMT:
   4
   5 *********************
   6 ioctl VIDIOC_ENUM_FMT
   7 *********************
   8
   9 Name
  10 ====
  11
  12 VIDIOC_ENUM_FMT - Enumerate image formats
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. c:function:: int ioctl( int fd, VIDIOC_ENUM_FMT, struct v4l2_fmtdesc *argp )
  19     :name: VIDIOC_ENUM_FMT
  20
  21
  22 Arguments
  23 =========
  24
  25 ``fd``
  26     File descriptor returned by :ref:`open() <func-open>`.
  27
  28 ``argp``
  29
  30
  31 Description
  32 ===========
  33
  34 To enumerate image formats applications initialize the ``type`` and
  35 ``index`` field of struct :c:type:`v4l2_fmtdesc` and call
  36 the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers
  37 fill the rest of the structure or return an ``EINVAL`` error code. All
  38 formats are enumerable by beginning at index zero and incrementing by
  39 one until ``EINVAL`` is returned.
  40
  41 .. note::
  42
  43    After switching input or output the list of enumerated image
  44    formats may be different.
  45
  46
  47 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
  48
  49 .. c:type:: v4l2_fmtdesc
  50
  51 .. flat-table:: struct v4l2_fmtdesc
  52     :header-rows:  0
  53     :stub-columns: 0
  54     :widths:       1 1 2
  55
  56     -  .. row 1
  57
  58        -  __u32
  59
  60        -  ``index``
  61
  62        -  Number of the format in the enumeration, set by the application.
  63           This is in no way related to the ``pixelformat`` field.
  64
  65     -  .. row 2
  66
  67        -  __u32
  68
  69        -  ``type``
  70
  71        -  Type of the data stream, set by the application. Only these types
  72           are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
  73           ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
  74           ``V4L2_BUF_TYPE_VIDEO_OUTPUT``,
  75           ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
  76           ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`.
  77
  78     -  .. row 3
  79
  80        -  __u32
  81
  82        -  ``flags``
  83
  84        -  See :ref:`fmtdesc-flags`
  85
  86     -  .. row 4
  87
  88        -  __u8
  89
  90        -  ``description``\ [32]
  91
  92        -  Description of the format, a NUL-terminated ASCII string. This
  93           information is intended for the user, for example: "YUV 4:2:2".
  94
  95     -  .. row 5
  96
  97        -  __u32
  98
  99        -  ``pixelformat``
 100
 101        -  The image format identifier. This is a four character code as
 102           computed by the v4l2_fourcc() macro:
 103
 104     -  .. row 6
 105
 106        -  :cspan:`2`
 107
 108           .. _v4l2-fourcc:
 109
 110           ``#define v4l2_fourcc(a,b,c,d)``
 111
 112           ``(((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))``
 113
 114           Several image formats are already defined by this specification in
 115           :ref:`pixfmt`.
 116
 117           .. attention::
 118
 119              These codes are not the same as those used
 120              in the Windows world.
 121
 122     -  .. row 7
 123
 124        -  __u32
 125
 126        -  ``reserved``\ [4]
 127
 128        -  Reserved for future extensions. Drivers must set the array to
 129           zero.
 130
 131
 132
 133 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
 134
 135 .. _fmtdesc-flags:
 136
 137 .. flat-table:: Image Format Description Flags
 138     :header-rows:  0
 139     :stub-columns: 0
 140     :widths:       3 1 4
 141
 142
 143     -  .. row 1
 144
 145        -  ``V4L2_FMT_FLAG_COMPRESSED``
 146
 147        -  0x0001
 148
 149        -  This is a compressed format.
 150
 151     -  .. row 2
 152
 153        -  ``V4L2_FMT_FLAG_EMULATED``
 154
 155        -  0x0002
 156
 157        -  This format is not native to the device but emulated through
 158           software (usually libv4l2), where possible try to use a native
 159           format instead for better performance.
 160
 161
 162 Return Value
 163 ============
 164
 165 On success 0 is returned, on error -1 and the ``errno`` variable is set
 166 appropriately. The generic error codes are described at the
 167 :ref:`Generic Error Codes <gen-errors>` chapter.
 168
 169 EINVAL
 170     The struct :c:type:`v4l2_fmtdesc` ``type`` is not
 171     supported or the ``index`` is out of bounds.