Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst - linux - Git at Google

 .. Permission is granted to copy, distribute and/or modify this
 .. document under the terms of the GNU Free Documentation License,
 .. Version 1.1 or any later version published by the Free Software
 .. Foundation, with no Invariant Sections, no Front-Cover Texts
 .. and no Back-Cover Texts. A copy of the license is included at
 .. Documentation/userspace-api/media/fdl-appendix.rst.
 ..
 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

 ******************************
 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.

 	For compressed formats that contain the resolution information encoded
 	inside the stream, when fed to a stateful mem2mem decoder, the fields
 	may be zero to rely on the decoder to detect the right values. For more
 	details see :ref:`decoder` and format descriptions.

 	For compressed formats on the CAPTURE side of a stateful mem2mem
 	encoder, the fields must be zero, since the coded size is expected to
 	be calculated internally by the encoder itself, based on the OUTPUT
 	side. For more details see :ref:`encoder` and format descriptions.
     * - __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:`pixfmt-rgb`, YUV formats in
 	:ref:`yuv-formats`, and reserved codes in
 	:ref:`reserved-formats`
     * - __u32
       - ``field``
       - Field order, from enum :c:type:`v4l2_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
 	number of bytes required by the codec to support the worst-case
 	compression scenario.

 	The driver will set the value for uncompressed images.

 	Clients are allowed to set the sizeimage field for variable length
 	compressed data flagged with ``V4L2_FMT_FLAG_COMPRESSED`` at
 	:ref:`VIDIOC_ENUM_FMT`, but the driver may ignore it and set the
 	value itself, or it may modify the provided value based on
 	alignment requirements or minimum/maximum size requirements.
 	If the client wants to leave this to the driver, then it should
 	set sizeimage to 0.
     * - __u32
       - ``colorspace``
       - Image colorspace, from enum :c:type:`v4l2_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`.
     * - union {
       - (anonymous)
     * - __u32
       - ``ycbcr_enc``
       - Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
         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`.
     * - __u32
       - ``hsv_enc``
       - HSV encoding, from enum :c:type:`v4l2_hsv_encoding`.
         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`.
     * - }
       -
     * - __u32
       - ``quantization``
       - Quantization range, from enum :c:type:`v4l2_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`.
     * - __u32
       - ``xfer_func``
       - Transfer function, from enum :c:type:`v4l2_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`.

 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|

 .. _format-flags:

 .. flat-table:: Format Flags
     :header-rows:  0
     :stub-columns: 0
     :widths:       3 1 4

     * - ``V4L2_PIX_FMT_FLAG_PREMUL_ALPHA``
       - 0x00000001
       - The color values are premultiplied by the alpha channel value. For
         example, if a light blue pixel with 50% transparency was described
 	by RGBA values (128, 192, 255, 128), the same pixel described with
 	premultiplied colors would be described by RGBA values (64, 96,
 	128, 128)
	.. Permission is granted to copy, distribute and/or modify this
	.. document under the terms of the GNU Free Documentation License,
	.. Version 1.1 or any later version published by the Free Software
	.. Foundation, with no Invariant Sections, no Front-Cover Texts
	.. and no Back-Cover Texts. A copy of the license is included at
	.. Documentation/userspace-api/media/fdl-appendix.rst.
	..
	.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

	******************************
	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.

	For compressed formats that contain the resolution information encoded
	inside the stream, when fed to a stateful mem2mem decoder, the fields
	may be zero to rely on the decoder to detect the right values. For more
	details see :ref:`decoder` and format descriptions.

	For compressed formats on the CAPTURE side of a stateful mem2mem
	encoder, the fields must be zero, since the coded size is expected to
	be calculated internally by the encoder itself, based on the OUTPUT
	side. For more details see :ref:`encoder` and format descriptions.
	* - __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:`pixfmt-rgb`, YUV formats in
	:ref:`yuv-formats`, and reserved codes in
	:ref:`reserved-formats`
	* - __u32
	- ``field``
	- Field order, from enum :c:type:`v4l2_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
	number of bytes required by the codec to support the worst-case
	compression scenario.

	The driver will set the value for uncompressed images.

	Clients are allowed to set the sizeimage field for variable length
	compressed data flagged with ``V4L2_FMT_FLAG_COMPRESSED`` at
	:ref:`VIDIOC_ENUM_FMT`, but the driver may ignore it and set the
	value itself, or it may modify the provided value based on
	alignment requirements or minimum/maximum size requirements.
	If the client wants to leave this to the driver, then it should
	set sizeimage to 0.
	* - __u32
	- ``colorspace``
	- Image colorspace, from enum :c:type:`v4l2_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`.
	* - union {
	- (anonymous)
	* - __u32
	- ``ycbcr_enc``
	- Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
	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`.
	* - __u32
	- ``hsv_enc``
	- HSV encoding, from enum :c:type:`v4l2_hsv_encoding`.
	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`.
	* - }
	-
	* - __u32
	- ``quantization``
	- Quantization range, from enum :c:type:`v4l2_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`.
	* - __u32
	- ``xfer_func``
	- Transfer function, from enum :c:type:`v4l2_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`.

	.. tabularcolumns:: \|p{6.6cm}\|p{2.2cm}\|p{8.7cm}\|

	.. _format-flags:

	.. flat-table:: Format Flags
	:header-rows: 0
	:stub-columns: 0
	:widths: 3 1 4

	* - ``V4L2_PIX_FMT_FLAG_PREMUL_ALPHA``
	- 0x00000001
	- The color values are premultiplied by the alpha channel value. For
	example, if a light blue pixel with 50% transparency was described
	by RGBA values (128, 192, 255, 128), the same pixel described with
	premultiplied colors would be described by RGBA values (64, 96,
	128, 128)