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

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 ******************************
   4 Single-planar format structure
   5 ******************************
   6
   7
   8 .. _v4l2-pix-format:
   9
  10 .. flat-table:: struct v4l2_pix_format
  11     :header-rows:  0
  12     :stub-columns: 0
  13     :widths:       1 1 2
  14
  15
  16     -  .. row 1
  17
  18        -  __u32
  19
  20        -  ``width``
  21
  22        -  Image width in pixels.
  23
  24     -  .. row 2
  25
  26        -  __u32
  27
  28        -  ``height``
  29
  30        -  Image height in pixels. If ``field`` is one of ``V4L2_FIELD_TOP``,
  31           ``V4L2_FIELD_BOTTOM`` or ``V4L2_FIELD_ALTERNATE`` then height
  32           refers to the number of lines in the field, otherwise it refers to
  33           the number of lines in the frame (which is twice the field height
  34           for interlaced formats).
  35
  36     -  .. row 3
  37
  38        -  :cspan:`2` Applications set these fields to request an image
  39           size, drivers return the closest possible values. In case of
  40           planar formats the ``width`` and ``height`` applies to the largest
  41           plane. To avoid ambiguities drivers must return values rounded up
  42           to a multiple of the scale factor of any smaller planes. For
  43           example when the image format is YUV 4:2:0, ``width`` and
  44           ``height`` must be multiples of two.
  45
  46     -  .. row 4
  47
  48        -  __u32
  49
  50        -  ``pixelformat``
  51
  52        -  The pixel format or type of compression, set by the application.
  53           This is a little endian
  54           :ref:`four character code <v4l2-fourcc>`. V4L2 defines standard
  55           RGB formats in :ref:`rgb-formats`, YUV formats in
  56           :ref:`yuv-formats`, and reserved codes in
  57           :ref:`reserved-formats`
  58
  59     -  .. row 5
  60
  61        -  enum :ref:`v4l2_field <v4l2-field>`
  62
  63        -  ``field``
  64
  65        -  Video images are typically interlaced. Applications can request to
  66           capture or output only the top or bottom field, or both fields
  67           interlaced or sequentially stored in one buffer or alternating in
  68           separate buffers. Drivers return the actual field order selected.
  69           For more details on fields see :ref:`field-order`.
  70
  71     -  .. row 6
  72
  73        -  __u32
  74
  75        -  ``bytesperline``
  76
  77        -  Distance in bytes between the leftmost pixels in two adjacent
  78           lines.
  79
  80     -  .. row 7
  81
  82        -  :cspan:`2`
  83
  84           Both applications and drivers can set this field to request
  85           padding bytes at the end of each line. Drivers however may ignore
  86           the value requested by the application, returning ``width`` times
  87           bytes per pixel or a larger value required by the hardware. That
  88           implies applications can just set this field to zero to get a
  89           reasonable default.
  90
  91           Video hardware may access padding bytes, therefore they must
  92           reside in accessible memory. Consider cases where padding bytes
  93           after the last line of an image cross a system page boundary.
  94           Input devices may write padding bytes, the value is undefined.
  95           Output devices ignore the contents of padding bytes.
  96
  97           When the image format is planar the ``bytesperline`` value applies
  98           to the first plane and is divided by the same factor as the
  99           ``width`` field for the other planes. For example the Cb and Cr
 100           planes of a YUV 4:2:0 image have half as many padding bytes
 101           following each line as the Y plane. To avoid ambiguities drivers
 102           must return a ``bytesperline`` value rounded up to a multiple of
 103           the scale factor.
 104
 105           For compressed formats the ``bytesperline`` value makes no sense.
 106           Applications and drivers must set this to 0 in that case.
 107
 108     -  .. row 8
 109
 110        -  __u32
 111
 112        -  ``sizeimage``
 113
 114        -  Size in bytes of the buffer to hold a complete image, set by the
 115           driver. Usually this is ``bytesperline`` times ``height``. When
 116           the image consists of variable length compressed data this is the
 117           maximum number of bytes required to hold an image.
 118
 119     -  .. row 9
 120
 121        -  enum :ref:`v4l2_colorspace <v4l2-colorspace>`
 122
 123        -  ``colorspace``
 124
 125        -  This information supplements the ``pixelformat`` and must be set
 126           by the driver for capture streams and by the application for
 127           output streams, see :ref:`colorspaces`.
 128
 129     -  .. row 10
 130
 131        -  __u32
 132
 133        -  ``priv``
 134
 135        -  This field indicates whether the remaining fields of the
 136           :ref:`struct v4l2_pix_format <v4l2-pix-format>` structure, also called the
 137           extended fields, are valid. When set to
 138           ``V4L2_PIX_FMT_PRIV_MAGIC``, it indicates that the extended fields
 139           have been correctly initialized. When set to any other value it
 140           indicates that the extended fields contain undefined values.
 141
 142           Applications that wish to use the pixel format extended fields
 143           must first ensure that the feature is supported by querying the
 144           device for the :ref:`V4L2_CAP_EXT_PIX_FORMAT <querycap>`
 145           capability. If the capability isn't set the pixel format extended
 146           fields are not supported and using the extended fields will lead
 147           to undefined results.
 148
 149           To use the extended fields, applications must set the ``priv``
 150           field to ``V4L2_PIX_FMT_PRIV_MAGIC``, initialize all the extended
 151           fields and zero the unused bytes of the
 152           :ref:`struct v4l2_format <v4l2-format>` ``raw_data`` field.
 153
 154           When the ``priv`` field isn't set to ``V4L2_PIX_FMT_PRIV_MAGIC``
 155           drivers must act as if all the extended fields were set to zero.
 156           On return drivers must set the ``priv`` field to
 157           ``V4L2_PIX_FMT_PRIV_MAGIC`` and all the extended fields to
 158           applicable values.
 159
 160     -  .. row 11
 161
 162        -  __u32
 163
 164        -  ``flags``
 165
 166        -  Flags set by the application or driver, see :ref:`format-flags`.
 167
 168     -  .. row 12
 169
 170        -  enum :ref:`v4l2_ycbcr_encoding <v4l2-ycbcr-encoding>`
 171
 172        -  ``ycbcr_enc``
 173
 174        -  This information supplements the ``colorspace`` and must be set by
 175           the driver for capture streams and by the application for output
 176           streams, see :ref:`colorspaces`.
 177
 178     -  .. row 13
 179
 180        -  enum :ref:`v4l2_quantization <v4l2-quantization>`
 181
 182        -  ``quantization``
 183
 184        -  This information supplements the ``colorspace`` and must be set by
 185           the driver for capture streams and by the application for output
 186           streams, see :ref:`colorspaces`.
 187
 188     -  .. row 14
 189
 190        -  enum :ref:`v4l2_xfer_func <v4l2-xfer-func>`
 191
 192        -  ``xfer_func``
 193
 194        -  This information supplements the ``colorspace`` and must be set by
 195           the driver for capture streams and by the application for output
 196           streams, see :ref:`colorspaces`.