Documentation/media/uapi/v4l/pixfmt-002.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 ******************************
   4 Single-planar format structure
   5 ******************************
   6
   7 .. tabularcolumns:: |p{4.0cm}|p{2.5cm}|p{11.0cm}|
   8
   9 .. c:type:: v4l2_pix_format
  10
  11 .. cssclass:: longtable
  12
  13 .. flat-table:: struct v4l2_pix_format
  14     :header-rows:  0
  15     :stub-columns: 0
  16     :widths:       1 1 2
  17
  18
  19     -  .. row 1
  20
  21        -  __u32
  22
  23        -  ``width``
  24
  25        -  Image width in pixels.
  26
  27     -  .. row 2
  28
  29        -  __u32
  30
  31        -  ``height``
  32
  33        -  Image height in pixels. If ``field`` is one of ``V4L2_FIELD_TOP``,
  34           ``V4L2_FIELD_BOTTOM`` or ``V4L2_FIELD_ALTERNATE`` then height
  35           refers to the number of lines in the field, otherwise it refers to
  36           the number of lines in the frame (which is twice the field height
  37           for interlaced formats).
  38
  39     -  .. row 3
  40
  41        -  :cspan:`2` Applications set these fields to request an image
  42           size, drivers return the closest possible values. In case of
  43           planar formats the ``width`` and ``height`` applies to the largest
  44           plane. To avoid ambiguities drivers must return values rounded up
  45           to a multiple of the scale factor of any smaller planes. For
  46           example when the image format is YUV 4:2:0, ``width`` and
  47           ``height`` must be multiples of two.
  48
  49     -  .. row 4
  50
  51        -  __u32
  52
  53        -  ``pixelformat``
  54
  55        -  The pixel format or type of compression, set by the application.
  56           This is a little endian
  57           :ref:`four character code <v4l2-fourcc>`. V4L2 defines standard
  58           RGB formats in :ref:`rgb-formats`, YUV formats in
  59           :ref:`yuv-formats`, and reserved codes in
  60           :ref:`reserved-formats`
  61
  62     -  .. row 5
  63
  64        -  enum :c:type::`v4l2_field`
  65
  66        -  ``field``
  67
  68        -  Video images are typically interlaced. Applications can request to
  69           capture or output only the top or bottom field, or both fields
  70           interlaced or sequentially stored in one buffer or alternating in
  71           separate buffers. Drivers return the actual field order selected.
  72           For more details on fields see :ref:`field-order`.
  73
  74     -  .. row 6
  75
  76        -  __u32
  77
  78        -  ``bytesperline``
  79
  80        -  Distance in bytes between the leftmost pixels in two adjacent
  81           lines.
  82
  83     -  .. row 7
  84
  85        -  :cspan:`2`
  86
  87           Both applications and drivers can set this field to request
  88           padding bytes at the end of each line. Drivers however may ignore
  89           the value requested by the application, returning ``width`` times
  90           bytes per pixel or a larger value required by the hardware. That
  91           implies applications can just set this field to zero to get a
  92           reasonable default.
  93
  94           Video hardware may access padding bytes, therefore they must
  95           reside in accessible memory. Consider cases where padding bytes
  96           after the last line of an image cross a system page boundary.
  97           Input devices may write padding bytes, the value is undefined.
  98           Output devices ignore the contents of padding bytes.
  99
 100           When the image format is planar the ``bytesperline`` value applies
 101           to the first plane and is divided by the same factor as the
 102           ``width`` field for the other planes. For example the Cb and Cr
 103           planes of a YUV 4:2:0 image have half as many padding bytes
 104           following each line as the Y plane. To avoid ambiguities drivers
 105           must return a ``bytesperline`` value rounded up to a multiple of
 106           the scale factor.
 107
 108           For compressed formats the ``bytesperline`` value makes no sense.
 109           Applications and drivers must set this to 0 in that case.
 110
 111     -  .. row 8
 112
 113        -  __u32
 114
 115        -  ``sizeimage``
 116
 117        -  Size in bytes of the buffer to hold a complete image, set by the
 118           driver. Usually this is ``bytesperline`` times ``height``. When
 119           the image consists of variable length compressed data this is the
 120           maximum number of bytes required to hold an image.
 121
 122     -  .. row 9
 123
 124        -  enum :c:type:`v4l2_colorspace`
 125
 126        -  ``colorspace``
 127
 128        -  This information supplements the ``pixelformat`` and must be set
 129           by the driver for capture streams and by the application for
 130           output streams, see :ref:`colorspaces`.
 131
 132     -  .. row 10
 133
 134        -  __u32
 135
 136        -  ``priv``
 137
 138        -  This field indicates whether the remaining fields of the
 139           struct :c:type:`v4l2_pix_format`, also called the
 140           extended fields, are valid. When set to
 141           ``V4L2_PIX_FMT_PRIV_MAGIC``, it indicates that the extended fields
 142           have been correctly initialized. When set to any other value it
 143           indicates that the extended fields contain undefined values.
 144
 145           Applications that wish to use the pixel format extended fields
 146           must first ensure that the feature is supported by querying the
 147           device for the :ref:`V4L2_CAP_EXT_PIX_FORMAT <querycap>`
 148           capability. If the capability isn't set the pixel format extended
 149           fields are not supported and using the extended fields will lead
 150           to undefined results.
 151
 152           To use the extended fields, applications must set the ``priv``
 153           field to ``V4L2_PIX_FMT_PRIV_MAGIC``, initialize all the extended
 154           fields and zero the unused bytes of the
 155           struct :c:type:`v4l2_format` ``raw_data`` field.
 156
 157           When the ``priv`` field isn't set to ``V4L2_PIX_FMT_PRIV_MAGIC``
 158           drivers must act as if all the extended fields were set to zero.
 159           On return drivers must set the ``priv`` field to
 160           ``V4L2_PIX_FMT_PRIV_MAGIC`` and all the extended fields to
 161           applicable values.
 162
 163     -  .. row 11
 164
 165        -  __u32
 166
 167        -  ``flags``
 168
 169        -  Flags set by the application or driver, see :ref:`format-flags`.
 170
 171     -  .. row 12
 172
 173        -  enum :c:type:`v4l2_ycbcr_encoding`
 174
 175        -  ``ycbcr_enc``
 176
 177        -  This information supplements the ``colorspace`` and must be set by
 178           the driver for capture streams and by the application for output
 179           streams, see :ref:`colorspaces`.
 180
 181     -  .. row 13
 182
 183        -  enum :c:type:`v4l2_quantization`
 184
 185        -  ``quantization``
 186
 187        -  This information supplements the ``colorspace`` and must be set by
 188           the driver for capture streams and by the application for output
 189           streams, see :ref:`colorspaces`.
 190
 191     -  .. row 14
 192
 193        -  enum :c:type:`v4l2_xfer_func`
 194
 195        -  ``xfer_func``
 196
 197        -  This information supplements the ``colorspace`` and must be set by
 198           the driver for capture streams and by the application for output
 199           streams, see :ref:`colorspaces`.