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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
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Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+******************************
+Single-planar format structure
+******************************
+
+.. tabularcolumns:: |p{4.0cm}|p{2.6cm}|p{10.7cm}|
+
+.. 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`. If the application sets the
+ flag ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
+ this field for a capture stream to request a specific colorspace
+ for the captured image data. If the driver cannot handle requested
+ conversion, it will return another supported colorspace.
+ The driver indicates that colorspace conversion is supported by setting
+ the flag V4L2_FMT_FLAG_CSC_COLORSPACE in the corresponding struct
+ :c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
+ * - __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`. If the application sets the
+ flag ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
+ this field for a capture stream to request a specific Y'CbCr encoding
+ for the captured image data. If the driver cannot handle requested
+ conversion, it will return another supported encoding.
+ This field is ignored for HSV pixelformats. The driver indicates that
+ ycbcr_enc conversion is supported by setting the flag
+ V4L2_FMT_FLAG_CSC_YCBCR_ENC in the corresponding struct
+ :c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
+ * - __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`. If the application sets the flag
+ ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set this
+ field for a capture stream to request a specific HSV encoding for the
+ captured image data. If the driver cannot handle requested
+ conversion, it will return another supported encoding.
+ This field is ignored for non-HSV pixelformats. The driver indicates
+ that hsv_enc conversion is supported by setting the flag
+ V4L2_FMT_FLAG_CSC_HSV_ENC in the corresponding struct
+ :c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
+ * - }
+ -
+ * - __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`. If the application sets the flag
+ ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
+ this field for a capture stream to request a specific quantization
+ range for the captured image data. If the driver cannot handle requested
+ conversion, it will return another supported quantization.
+ The driver indicates that quantization conversion is supported by setting
+ the flag V4L2_FMT_FLAG_CSC_QUANTIZATION in the corresponding struct
+ :c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
+ * - __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`. If the application sets the flag
+ ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
+ this field for a capture stream to request a specific transfer function
+ for the captured image data. If the driver cannot handle requested
+ conversion, it will return another supported transfer function.
+ The driver indicates that xfer_func conversion is supported by setting
+ the flag V4L2_FMT_FLAG_CSC_XFER_FUNC in the corresponding struct
+ :c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
+
+.. tabularcolumns:: |p{6.8cm}|p{2.3cm}|p{8.2cm}|
+
+.. _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)
+ * .. _`v4l2-pix-fmt-flag-set-csc`:
+
+ - ``V4L2_PIX_FMT_FLAG_SET_CSC``
+ - 0x00000002
+ - Set by the application. It is only used for capture and is
+ ignored for output streams. If set, then request the device to do
+ colorspace conversion from the received colorspace to the requested
+ colorspace values. If the colorimetry field (``colorspace``, ``xfer_func``,
+ ``ycbcr_enc``, ``hsv_enc`` or ``quantization``) is set to ``*_DEFAULT``,
+ then that colorimetry setting will remain unchanged from what was received.
+ So in order to change the quantization, only the ``quantization`` field shall
+ be set to non default value (``V4L2_QUANTIZATION_FULL_RANGE`` or
+ ``V4L2_QUANTIZATION_LIM_RANGE``) and all other colorimetry fields shall
+ be set to ``*_DEFAULT``.
+
+ To check which conversions are supported by the hardware for the current
+ pixel format, see :ref:`fmtdesc-flags`.