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 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_fmtdesc *argp )
  19
  20
  21 Arguments
  22 =========
  23
  24 ``fd``
  25     File descriptor returned by :ref:`open() <func-open>`.
  26
  27 ``request``
  28     VIDIOC_ENUM_FMT
  29
  30 ``argp``
  31
  32
  33 Description
  34 ===========
  35
  36 To enumerate image formats applications initialize the ``type`` and
  37 ``index`` field of struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` and call
  38 the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers
  39 fill the rest of the structure or return an ``EINVAL`` error code. All
  40 formats are enumerable by beginning at index zero and incrementing by
  41 one until ``EINVAL`` is returned.
  42
  43 .. note:: After switching input or output the list of enumerated image
  44    formats may be different.
  45
  46
  47 .. _v4l2-fmtdesc:
  48
  49 .. flat-table:: struct v4l2_fmtdesc
  50     :header-rows:  0
  51     :stub-columns: 0
  52     :widths:       1 1 2
  53
  54
  55     -  .. row 1
  56
  57        -  __u32
  58
  59        -  ``index``
  60
  61        -  Number of the format in the enumeration, set by the application.
  62           This is in no way related to the ``pixelformat`` field.
  63
  64     -  .. row 2
  65
  66        -  __u32
  67
  68        -  ``type``
  69
  70        -  Type of the data stream, set by the application. Only these types
  71           are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
  72           ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
  73           ``V4L2_BUF_TYPE_VIDEO_OUTPUT``,
  74           ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
  75           ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`.
  76
  77     -  .. row 3
  78
  79        -  __u32
  80
  81        -  ``flags``
  82
  83        -  See :ref:`fmtdesc-flags`
  84
  85     -  .. row 4
  86
  87        -  __u8
  88
  89        -  ``description``\ [32]
  90
  91        -  Description of the format, a NUL-terminated ASCII string. This
  92           information is intended for the user, for example: "YUV 4:2:2".
  93
  94     -  .. row 5
  95
  96        -  __u32
  97
  98        -  ``pixelformat``
  99
 100        -  The image format identifier. This is a four character code as
 101           computed by the v4l2_fourcc() macro:
 102
 103     -  .. row 6
 104
 105        -  :cspan:`2`
 106
 107
 108           .. _v4l2-fourcc:
 109           .. code-block:: c
 110
 111               #define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))
 112
 113           Several image formats are already defined by this specification in
 114           :ref:`pixfmt`.
 115
 116           .. attention:: These codes are not the same as those used
 117              in the Windows world.
 118
 119     -  .. row 7
 120
 121        -  __u32
 122
 123        -  ``reserved``\ [4]
 124
 125        -  Reserved for future extensions. Drivers must set the array to
 126           zero.
 127
 128
 129
 130 .. _fmtdesc-flags:
 131
 132 .. flat-table:: Image Format Description Flags
 133     :header-rows:  0
 134     :stub-columns: 0
 135     :widths:       3 1 4
 136
 137
 138     -  .. row 1
 139
 140        -  ``V4L2_FMT_FLAG_COMPRESSED``
 141
 142        -  0x0001
 143
 144        -  This is a compressed format.
 145
 146     -  .. row 2
 147
 148        -  ``V4L2_FMT_FLAG_EMULATED``
 149
 150        -  0x0002
 151
 152        -  This format is not native to the device but emulated through
 153           software (usually libv4l2), where possible try to use a native
 154           format instead for better performance.
 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_fmtdesc <v4l2-fmtdesc>` ``type`` is not
 166     supported or the ``index`` is out of bounds.