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authorHans Verkuil <hansverk@cisco.com>2017-07-27 04:58:52 -0400
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2017-08-08 06:06:29 -0400
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tree3747a55fcd56ad113103b94a3db34b2c9f7a8285 /Documentation/media/uapi/v4l/pixfmt-v4l2.rst
parent6c2c188f35c61c8eee71ec6d07524ce122c06539 (diff)
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media: media/doc: rename and reorder pixfmt files
After the DocBook conversion a number of pixfmt description files just had a number in the filename (pix-fmt-004, 006, etc) which was not very descriptive. Rename them. Note that pixfmt-008.rst was folded into colorspaces-details.rst, so that file is deleted. It's easier to maintain that way. Also moved the colorspace sections to the end of the chapter. The old order was weird: the "Standard Image Formats" section (an intro into pixel formats) was followed by the colorspace sections instead of the pixel format descriptions. Moving it to the end resolved that issue. Signed-off-by: Hans Verkuil <hansverk@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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+.. -*- coding: utf-8; mode: rst -*-
+
+******************************
+Single-planar format structure
+******************************
+
+.. tabularcolumns:: |p{4.0cm}|p{2.5cm}|p{11.0cm}|
+
+.. c:type:: v4l2_pix_format
+
+.. cssclass:: longtable
+
+.. flat-table:: struct v4l2_pix_format
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+ * - __u32
+ - ``width``
+ - Image width in pixels.
+ * - __u32
+ - ``height``
+ - Image height in pixels. If ``field`` is one of ``V4L2_FIELD_TOP``,
+ ``V4L2_FIELD_BOTTOM`` or ``V4L2_FIELD_ALTERNATE`` then height
+ refers to the number of lines in the field, otherwise it refers to
+ the number of lines in the frame (which is twice the field height
+ for interlaced formats).
+ * - :cspan:`2` Applications set these fields to request an image
+ size, drivers return the closest possible values. In case of
+ planar formats the ``width`` and ``height`` applies to the largest
+ plane. To avoid ambiguities drivers must return values rounded up
+ to a multiple of the scale factor of any smaller planes. For
+ example when the image format is YUV 4:2:0, ``width`` and
+ ``height`` must be multiples of two.
+ * - __u32
+ - ``pixelformat``
+ - The pixel format or type of compression, set by the application.
+ This is a little endian
+ :ref:`four character code <v4l2-fourcc>`. V4L2 defines standard
+ RGB formats in :ref:`rgb-formats`, YUV formats in
+ :ref:`yuv-formats`, and reserved codes in
+ :ref:`reserved-formats`
+ * - enum :c:type::`v4l2_field`
+ - ``field``
+ - Video images are typically interlaced. Applications can request to
+ capture or output only the top or bottom field, or both fields
+ interlaced or sequentially stored in one buffer or alternating in
+ separate buffers. Drivers return the actual field order selected.
+ For more details on fields see :ref:`field-order`.
+ * - __u32
+ - ``bytesperline``
+ - Distance in bytes between the leftmost pixels in two adjacent
+ lines.
+ * - :cspan:`2`
+
+ Both applications and drivers can set this field to request
+ padding bytes at the end of each line. Drivers however may ignore
+ the value requested by the application, returning ``width`` times
+ bytes per pixel or a larger value required by the hardware. That
+ implies applications can just set this field to zero to get a
+ reasonable default.
+
+ Video hardware may access padding bytes, therefore they must
+ reside in accessible memory. Consider cases where padding bytes
+ after the last line of an image cross a system page boundary.
+ Input devices may write padding bytes, the value is undefined.
+ Output devices ignore the contents of padding bytes.
+
+ When the image format is planar the ``bytesperline`` value applies
+ to the first plane and is divided by the same factor as the
+ ``width`` field for the other planes. For example the Cb and Cr
+ planes of a YUV 4:2:0 image have half as many padding bytes
+ following each line as the Y plane. To avoid ambiguities drivers
+ must return a ``bytesperline`` value rounded up to a multiple of
+ the scale factor.
+
+ For compressed formats the ``bytesperline`` value makes no sense.
+ Applications and drivers must set this to 0 in that case.
+ * - __u32
+ - ``sizeimage``
+ - Size in bytes of the buffer to hold a complete image, set by the
+ driver. Usually this is ``bytesperline`` times ``height``. When
+ the image consists of variable length compressed data this is the
+ maximum number of bytes required to hold an image.
+ * - enum :c:type:`v4l2_colorspace`
+ - ``colorspace``
+ - This information supplements the ``pixelformat`` and must be set
+ by the driver for capture streams and by the application for
+ output streams, see :ref:`colorspaces`.
+ * - __u32
+ - ``priv``
+ - This field indicates whether the remaining fields of the
+ struct :c:type:`v4l2_pix_format`, also called the
+ extended fields, are valid. When set to
+ ``V4L2_PIX_FMT_PRIV_MAGIC``, it indicates that the extended fields
+ have been correctly initialized. When set to any other value it
+ indicates that the extended fields contain undefined values.
+
+ Applications that wish to use the pixel format extended fields
+ must first ensure that the feature is supported by querying the
+ device for the :ref:`V4L2_CAP_EXT_PIX_FORMAT <querycap>`
+ capability. If the capability isn't set the pixel format extended
+ fields are not supported and using the extended fields will lead
+ to undefined results.
+
+ To use the extended fields, applications must set the ``priv``
+ field to ``V4L2_PIX_FMT_PRIV_MAGIC``, initialize all the extended
+ fields and zero the unused bytes of the
+ struct :c:type:`v4l2_format` ``raw_data`` field.
+
+ When the ``priv`` field isn't set to ``V4L2_PIX_FMT_PRIV_MAGIC``
+ drivers must act as if all the extended fields were set to zero.
+ On return drivers must set the ``priv`` field to
+ ``V4L2_PIX_FMT_PRIV_MAGIC`` and all the extended fields to
+ applicable values.
+ * - __u32
+ - ``flags``
+ - Flags set by the application or driver, see :ref:`format-flags`.
+ * - enum :c:type:`v4l2_ycbcr_encoding`
+ - ``ycbcr_enc``
+ - This information supplements the ``colorspace`` and must be set by
+ the driver for capture streams and by the application for output
+ streams, see :ref:`colorspaces`.
+ * - enum :c:type:`v4l2_hsv_encoding`
+ - ``hsv_enc``
+ - This information supplements the ``colorspace`` and must be set by
+ the driver for capture streams and by the application for output
+ streams, see :ref:`colorspaces`.
+ * - enum :c:type:`v4l2_quantization`
+ - ``quantization``
+ - This information supplements the ``colorspace`` and must be set by
+ the driver for capture streams and by the application for output
+ streams, see :ref:`colorspaces`.
+ * - enum :c:type:`v4l2_xfer_func`
+ - ``xfer_func``
+ - This information supplements the ``colorspace`` and must be set by
+ the driver for capture streams and by the application for output
+ streams, see :ref:`colorspaces`.