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- <title>Image Formats</title>
-
- <para>The V4L2 API was primarily designed for devices exchanging
-image data with applications. The
-<structname>v4l2_pix_format</structname> and <structname>v4l2_pix_format_mplane
-</structname> structures define the format and layout of an image in memory.
-The former is used with the single-planar API, while the latter is used with the
-multi-planar version (see <xref linkend="planar-apis"/>). Image formats are
-negotiated with the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video
-capturing and output, for overlay frame buffer formats see also
-&VIDIOC-G-FBUF;.)</para>
-
-<section>
- <title>Single-planar format structure</title>
- <table pgwide="1" frame="none" id="v4l2-pix-format">
- <title>struct <structname>v4l2_pix_format</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>width</structfield></entry>
- <entry>Image width in pixels.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>height</structfield></entry>
- <entry>Image height in pixels. If <structfield>field</structfield> is
- one of <constant>V4L2_FIELD_TOP</constant>, <constant>V4L2_FIELD_BOTTOM</constant>
- or <constant>V4L2_FIELD_ALTERNATE</constant> 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).</entry>
- </row>
- <row>
- <entry spanname="hspan">Applications set these fields to
-request an image size, drivers return the closest possible values. In
-case of planar formats the <structfield>width</structfield> and
-<structfield>height</structfield> 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, <structfield>width</structfield> and
-<structfield>height</structfield> must be multiples of two.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>pixelformat</structfield></entry>
- <entry>The pixel format or type of compression, set by the
-application. This is a little endian <link
-linkend="v4l2-fourcc">four character code</link>. V4L2 defines
-standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref
-linkend="yuv-formats" />, and reserved codes in <xref
-linkend="reserved-formats" /></entry>
- </row>
- <row>
- <entry>&v4l2-field;</entry>
- <entry><structfield>field</structfield></entry>
- <entry>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 <xref linkend="field-order" />.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>bytesperline</structfield></entry>
- <entry>Distance in bytes between the leftmost pixels in two
-adjacent lines.</entry>
- </row>
- <row>
- <entry spanname="hspan"><para>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 <structfield>width</structfield> 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.</para><para>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.</para><para>When the image format is planar the
-<structfield>bytesperline</structfield> value applies to the first
-plane and is divided by the same factor as the
-<structfield>width</structfield> 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 <structfield>bytesperline</structfield> value
-rounded up to a multiple of the scale factor.</para>
-<para>For compressed formats the <structfield>bytesperline</structfield>
-value makes no sense. Applications and drivers must set this to 0 in
-that case.</para></entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>sizeimage</structfield></entry>
- <entry>Size in bytes of the buffer to hold a complete image,
-set by the driver. Usually this is
-<structfield>bytesperline</structfield> times
-<structfield>height</structfield>. When the image consists of variable
-length compressed data this is the maximum number of bytes required to
-hold an image.</entry>
- </row>
- <row>
- <entry>&v4l2-colorspace;</entry>
- <entry><structfield>colorspace</structfield></entry>
- <entry>This information supplements the
-<structfield>pixelformat</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>priv</structfield></entry>
- <entry><para>This field indicates whether the remaining fields of the
-<structname>v4l2_pix_format</structname> structure, also called the extended
-fields, are valid. When set to <constant>V4L2_PIX_FMT_PRIV_MAGIC</constant>, 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.
-</para>
-<para>Applications that wish to use the pixel format extended fields must first
-ensure that the feature is supported by querying the device for the
-<link linkend="querycap"><constant>V4L2_CAP_EXT_PIX_FORMAT</constant></link>
-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.</para>
-<para>To use the extended fields, applications must set the
-<structfield>priv</structfield> field to
-<constant>V4L2_PIX_FMT_PRIV_MAGIC</constant>, initialize all the extended fields
-and zero the unused bytes of the <structname>v4l2_format</structname>
-<structfield>raw_data</structfield> field.</para>
-<para>When the <structfield>priv</structfield> field isn't set to
-<constant>V4L2_PIX_FMT_PRIV_MAGIC</constant> drivers must act as if all the
-extended fields were set to zero. On return drivers must set the
-<structfield>priv</structfield> field to
-<constant>V4L2_PIX_FMT_PRIV_MAGIC</constant> and all the extended fields to
-applicable values.</para></entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>flags</structfield></entry>
- <entry>Flags set by the application or driver, see <xref
-linkend="format-flags" />.</entry>
- </row>
- <row>
- <entry>&v4l2-ycbcr-encoding;</entry>
- <entry><structfield>ycbcr_enc</structfield></entry>
- <entry>This information supplements the
-<structfield>colorspace</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- <row>
- <entry>&v4l2-quantization;</entry>
- <entry><structfield>quantization</structfield></entry>
- <entry>This information supplements the
-<structfield>colorspace</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- <row>
- <entry>&v4l2-xfer-func;</entry>
- <entry><structfield>xfer_func</structfield></entry>
- <entry>This information supplements the
-<structfield>colorspace</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-</section>
-
-<section>
- <title>Multi-planar format structures</title>
- <para>The <structname>v4l2_plane_pix_format</structname> structures define
- size and layout for each of the planes in a multi-planar format.
- The <structname>v4l2_pix_format_mplane</structname> structure contains
- information common to all planes (such as image width and height) and
- an array of <structname>v4l2_plane_pix_format</structname> structures,
- describing all planes of that format.</para>
- <table pgwide="1" frame="none" id="v4l2-plane-pix-format">
- <title>struct <structname>v4l2_plane_pix_format</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>sizeimage</structfield></entry>
- <entry>Maximum size in bytes required for image data in this plane.
- </entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>bytesperline</structfield></entry>
- <entry>Distance in bytes between the leftmost pixels in two adjacent
- lines. See &v4l2-pix-format;.</entry>
- </row>
- <row>
- <entry>__u16</entry>
- <entry><structfield>reserved[6]</structfield></entry>
- <entry>Reserved for future extensions. Should be zeroed by drivers and
- applications.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <table pgwide="1" frame="none" id="v4l2-pix-format-mplane">
- <title>struct <structname>v4l2_pix_format_mplane</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>width</structfield></entry>
- <entry>Image width in pixels. See &v4l2-pix-format;.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>height</structfield></entry>
- <entry>Image height in pixels. See &v4l2-pix-format;.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>pixelformat</structfield></entry>
- <entry>The pixel format. Both single- and multi-planar four character
-codes can be used.</entry>
- </row>
- <row>
- <entry>&v4l2-field;</entry>
- <entry><structfield>field</structfield></entry>
- <entry>See &v4l2-pix-format;.</entry>
- </row>
- <row>
- <entry>&v4l2-colorspace;</entry>
- <entry><structfield>colorspace</structfield></entry>
- <entry>See &v4l2-pix-format;.</entry>
- </row>
- <row>
- <entry>&v4l2-plane-pix-format;</entry>
- <entry><structfield>plane_fmt[VIDEO_MAX_PLANES]</structfield></entry>
- <entry>An array of structures describing format of each plane this
- pixel format consists of. The number of valid entries in this array
- has to be put in the <structfield>num_planes</structfield>
- field.</entry>
- </row>
- <row>
- <entry>__u8</entry>
- <entry><structfield>num_planes</structfield></entry>
- <entry>Number of planes (i.e. separate memory buffers) for this format
- and the number of valid entries in the
- <structfield>plane_fmt</structfield> array.</entry>
- </row>
- <row>
- <entry>__u8</entry>
- <entry><structfield>flags</structfield></entry>
- <entry>Flags set by the application or driver, see <xref
-linkend="format-flags" />.</entry>
- </row>
- <row>
- <entry>&v4l2-ycbcr-encoding;</entry>
- <entry><structfield>ycbcr_enc</structfield></entry>
- <entry>This information supplements the
-<structfield>colorspace</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- <row>
- <entry>&v4l2-quantization;</entry>
- <entry><structfield>quantization</structfield></entry>
- <entry>This information supplements the
-<structfield>colorspace</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- <row>
- <entry>&v4l2-xfer-func;</entry>
- <entry><structfield>xfer_func</structfield></entry>
- <entry>This information supplements the
-<structfield>colorspace</structfield> and must be set by the driver for
-capture streams and by the application for output streams,
-see <xref linkend="colorspaces" />.</entry>
- </row>
- <row>
- <entry>__u8</entry>
- <entry><structfield>reserved[7]</structfield></entry>
- <entry>Reserved for future extensions. Should be zeroed by drivers
- and applications.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-</section>
-
- <section>
- <title>Standard Image Formats</title>
-
- <para>In order to exchange images between drivers and
-applications, it is necessary to have standard image data formats
-which both sides will interpret the same way. V4L2 includes several
-such formats, and this section is intended to be an unambiguous
-specification of the standard image data formats in V4L2.</para>
-
- <para>V4L2 drivers are not limited to these formats, however.
-Driver-specific formats are possible. In that case the application may
-depend on a codec to convert images to one of the standard formats
-when needed. But the data can still be stored and retrieved in the
-proprietary format. For example, a device may support a proprietary
-compressed format. Applications can still capture and save the data in
-the compressed format, saving much disk space, and later use a codec
-to convert the images to the X Windows screen format when the video is
-to be displayed.</para>
-
- <para>Even so, ultimately, some standard formats are needed, so
-the V4L2 specification would not be complete without well-defined
-standard formats.</para>
-
- <para>The V4L2 standard formats are mainly uncompressed formats. The
-pixels are always arranged in memory from left to right, and from top
-to bottom. The first byte of data in the image buffer is always for
-the leftmost pixel of the topmost row. Following that is the pixel
-immediately to its right, and so on until the end of the top row of
-pixels. Following the rightmost pixel of the row there may be zero or
-more bytes of padding to guarantee that each row of pixel data has a
-certain alignment. Following the pad bytes, if any, is data for the
-leftmost pixel of the second row from the top, and so on. The last row
-has just as many pad bytes after it as the other rows.</para>
-
- <para>In V4L2 each format has an identifier which looks like
-<constant>PIX_FMT_XXX</constant>, defined in the <link
-linkend="videodev">videodev2.h</link> header file. These identifiers
-represent <link linkend="v4l2-fourcc">four character (FourCC) codes</link>
-which are also listed below, however they are not the same as those
-used in the Windows world.</para>
-
- <para>For some formats, data is stored in separate, discontiguous
-memory buffers. Those formats are identified by a separate set of FourCC codes
-and are referred to as "multi-planar formats". For example, a YUV422 frame is
-normally stored in one memory buffer, but it can also be placed in two or three
-separate buffers, with Y component in one buffer and CbCr components in another
-in the 2-planar version or with each component in its own buffer in the
-3-planar case. Those sub-buffers are referred to as "planes".</para>
- </section>
-
- <section id="colorspaces">
- <title>Colorspaces</title>
-
- <para>'Color' is a very complex concept and depends on physics, chemistry and
-biology. Just because you have three numbers that describe the 'red', 'green'
-and 'blue' components of the color of a pixel does not mean that you can accurately
-display that color. A colorspace defines what it actually <emphasis>means</emphasis>
-to have an RGB value of e.g. (255,&nbsp;0,&nbsp;0). That is, which color should be
-reproduced on the screen in a perfectly calibrated environment.</para>
-
- <para>In order to do that we first need to have a good definition of
-color, i.e. some way to uniquely and unambiguously define a color so that someone
-else can reproduce it. Human color vision is trichromatic since the human eye has
-color receptors that are sensitive to three different wavelengths of light. Hence
-the need to use three numbers to describe color. Be glad you are not a mantis shrimp
-as those are sensitive to 12 different wavelengths, so instead of RGB we would be
-using the ABCDEFGHIJKL colorspace...</para>
-
- <para>Color exists only in the eye and brain and is the result of how strongly
-color receptors are stimulated. This is based on the Spectral
-Power Distribution (SPD) which is a graph showing the intensity (radiant power)
-of the light at wavelengths covering the visible spectrum as it enters the eye.
-The science of colorimetry is about the relationship between the SPD and color as
-perceived by the human brain.</para>
-
- <para>Since the human eye has only three color receptors it is perfectly
-possible that different SPDs will result in the same stimulation of those receptors
-and are perceived as the same color, even though the SPD of the light is
-different.</para>
-
- <para>In the 1920s experiments were devised to determine the relationship
-between SPDs and the perceived color and that resulted in the CIE 1931 standard
-that defines spectral weighting functions that model the perception of color.
-Specifically that standard defines functions that can take an SPD and calculate
-the stimulus for each color receptor. After some further mathematical transforms
-these stimuli are known as the <emphasis>CIE XYZ tristimulus</emphasis> values
-and these X, Y and Z values describe a color as perceived by a human unambiguously.
-These X, Y and Z values are all in the range [0&hellip;1].</para>
-
- <para>The Y value in the CIE XYZ colorspace corresponds to luminance. Often
-the CIE XYZ colorspace is transformed to the normalized CIE xyY colorspace:</para>
-
- <para>x = X / (X + Y + Z)</para>
- <para>y = Y / (X + Y + Z)</para>
-
- <para>The x and y values are the chromaticity coordinates and can be used to
-define a color without the luminance component Y. It is very confusing to
-have such similar names for these colorspaces. Just be aware that if colors
-are specified with lower case 'x' and 'y', then the CIE xyY colorspace is
-used. Upper case 'X' and 'Y' refer to the CIE XYZ colorspace. Also, y has nothing
-to do with luminance. Together x and y specify a color, and Y the luminance.
-That is really all you need to remember from a practical point of view. At
-the end of this section you will find reading resources that go into much more
-detail if you are interested.
-</para>
-
- <para>A monitor or TV will reproduce colors by emitting light at three
-different wavelengths, the combination of which will stimulate the color receptors
-in the eye and thus cause the perception of color. Historically these wavelengths
-were defined by the red, green and blue phosphors used in the displays. These
-<emphasis>color primaries</emphasis> are part of what defines a colorspace.</para>
-
- <para>Different display devices will have different primaries and some
-primaries are more suitable for some display technologies than others. This has
-resulted in a variety of colorspaces that are used for different display
-technologies or uses. To define a colorspace you need to define the three
-color primaries (these are typically defined as x,&nbsp;y chromaticity coordinates
-from the CIE xyY colorspace) but also the white reference: that is the color obtained
-when all three primaries are at maximum power. This determines the relative power
-or energy of the primaries. This is usually chosen to be close to daylight which has
-been defined as the CIE D65 Illuminant.</para>
-
- <para>To recapitulate: the CIE XYZ colorspace uniquely identifies colors.
-Other colorspaces are defined by three chromaticity coordinates defined in the
-CIE xyY colorspace. Based on those a 3x3 matrix can be constructed that
-transforms CIE XYZ colors to colors in the new colorspace.
-</para>
-
- <para>Both the CIE XYZ and the RGB colorspace that are derived from the
-specific chromaticity primaries are linear colorspaces. But neither the eye,
-nor display technology is linear. Doubling the values of all components in
-the linear colorspace will not be perceived as twice the intensity of the color.
-So each colorspace also defines a transfer function that takes a linear color
-component value and transforms it to the non-linear component value, which is a
-closer match to the non-linear performance of both the eye and displays. Linear
-component values are denoted RGB, non-linear are denoted as R'G'B'. In general
-colors used in graphics are all R'G'B', except in openGL which uses linear RGB.
-Special care should be taken when dealing with openGL to provide linear RGB colors
-or to use the built-in openGL support to apply the inverse transfer function.</para>
-
- <para>The final piece that defines a colorspace is a function that
-transforms non-linear R'G'B' to non-linear Y'CbCr. This function is determined
-by the so-called luma coefficients. There may be multiple possible Y'CbCr
-encodings allowed for the same colorspace. Many encodings of color
-prefer to use luma (Y') and chroma (CbCr) instead of R'G'B'. Since the human
-eye is more sensitive to differences in luminance than in color this encoding
-allows one to reduce the amount of color information compared to the luma
-data. Note that the luma (Y') is unrelated to the Y in the CIE XYZ colorspace.
-Also note that Y'CbCr is often called YCbCr or YUV even though these are
-strictly speaking wrong.</para>
-
- <para>Sometimes people confuse Y'CbCr as being a colorspace. This is not
-correct, it is just an encoding of an R'G'B' color into luma and chroma
-values. The underlying colorspace that is associated with the R'G'B' color
-is also associated with the Y'CbCr color.</para>
-
- <para>The final step is how the RGB, R'G'B' or Y'CbCr values are
-quantized. The CIE XYZ colorspace where X, Y and Z are in the range
-[0&hellip;1] describes all colors that humans can perceive, but the transform to
-another colorspace will produce colors that are outside the [0&hellip;1] range.
-Once clamped to the [0&hellip;1] range those colors can no longer be reproduced
-in that colorspace. This clamping is what reduces the extent or gamut of the
-colorspace. How the range of [0&hellip;1] is translated to integer values in the
-range of [0&hellip;255] (or higher, depending on the color depth) is called the
-quantization. This is <emphasis>not</emphasis> part of the colorspace
-definition. In practice RGB or R'G'B' values are full range, i.e. they
-use the full [0&hellip;255] range. Y'CbCr values on the other hand are limited
-range with Y' using [16&hellip;235] and Cb and Cr using [16&hellip;240].</para>
-
- <para>Unfortunately, in some cases limited range RGB is also used
-where the components use the range [16&hellip;235]. And full range Y'CbCr also exists
-using the [0&hellip;255] range.</para>
-
- <para>In order to correctly interpret a color you need to know the
-quantization range, whether it is R'G'B' or Y'CbCr, the used Y'CbCr encoding
-and the colorspace.
-From that information you can calculate the corresponding CIE XYZ color
-and map that again to whatever colorspace your display device uses.</para>
-
- <para>The colorspace definition itself consists of the three
-chromaticity primaries, the white reference chromaticity, a transfer
-function and the luma coefficients needed to transform R'G'B' to Y'CbCr. While
-some colorspace standards correctly define all four, quite often the colorspace
-standard only defines some, and you have to rely on other standards for
-the missing pieces. The fact that colorspaces are often a mix of different
-standards also led to very confusing naming conventions where the name of
-a standard was used to name a colorspace when in fact that standard was
-part of various other colorspaces as well.</para>
-
- <para>If you want to read more about colors and colorspaces, then the
-following resources are useful: <xref linkend="poynton" /> is a good practical
-book for video engineers, <xref linkend="colimg" /> has a much broader scope and
-describes many more aspects of color (physics, chemistry, biology, etc.).
-The <ulink url="http://www.brucelindbloom.com">http://www.brucelindbloom.com</ulink>
-website is an excellent resource, especially with respect to the mathematics behind
-colorspace conversions. The wikipedia <ulink url="http://en.wikipedia.org/wiki/CIE_1931_color_space#CIE_xy_chromaticity_diagram_and_the_CIE_xyY_color_space">CIE 1931 colorspace</ulink> article
-is also very useful.</para>
- </section>
-
- <section>
- <title>Defining Colorspaces in V4L2</title>
- <para>In V4L2 colorspaces are defined by four values. The first is the colorspace
-identifier (&v4l2-colorspace;) which defines the chromaticities, the default transfer
-function, the default Y'CbCr encoding and the default quantization method. The second
-is the transfer function identifier (&v4l2-xfer-func;) to specify non-standard
-transfer functions. The third is the Y'CbCr encoding identifier (&v4l2-ycbcr-encoding;)
-to specify non-standard Y'CbCr encodings and the fourth is the quantization identifier
-(&v4l2-quantization;) to specify non-standard quantization methods. Most of the time
-only the colorspace field of &v4l2-pix-format; or &v4l2-pix-format-mplane; needs to
-be filled in. Note that the default R'G'B' quantization is full range for all
-colorspaces except for BT.2020 which uses limited range R'G'B' quantization.</para>
-
- <table pgwide="1" frame="none" id="v4l2-colorspace">
- <title>V4L2 Colorspaces</title>
- <tgroup cols="2" align="left">
- &cs-def;
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Details</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_COLORSPACE_DEFAULT</constant></entry>
- <entry>The default colorspace. This can be used by applications to let the
- driver fill in the colorspace.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry>
- <entry>See <xref linkend="col-smpte-170m" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_REC709</constant></entry>
- <entry>See <xref linkend="col-rec709" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry>
- <entry>See <xref linkend="col-srgb" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_ADOBERGB</constant></entry>
- <entry>See <xref linkend="col-adobergb" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_BT2020</constant></entry>
- <entry>See <xref linkend="col-bt2020" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_DCI_P3</constant></entry>
- <entry>See <xref linkend="col-dcip3" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry>
- <entry>See <xref linkend="col-smpte-240m" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry>
- <entry>See <xref linkend="col-sysm" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry>
- <entry>See <xref linkend="col-sysbg" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry>
- <entry>See <xref linkend="col-jpeg" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_COLORSPACE_RAW</constant></entry>
- <entry>The raw colorspace. This is used for raw image capture where
- the image is minimally processed and is using the internal colorspace
- of the device. The software that processes an image using this
- 'colorspace' will have to know the internals of the capture device.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table pgwide="1" frame="none" id="v4l2-xfer-func">
- <title>V4L2 Transfer Function</title>
- <tgroup cols="2" align="left">
- &cs-def;
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Details</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_XFER_FUNC_DEFAULT</constant></entry>
- <entry>Use the default transfer function as defined by the colorspace.</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_709</constant></entry>
- <entry>Use the Rec. 709 transfer function.</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_SRGB</constant></entry>
- <entry>Use the sRGB transfer function.</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_ADOBERGB</constant></entry>
- <entry>Use the AdobeRGB transfer function.</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_SMPTE240M</constant></entry>
- <entry>Use the SMPTE 240M transfer function.</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_NONE</constant></entry>
- <entry>Do not use a transfer function (i.e. use linear RGB values).</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_DCI_P3</constant></entry>
- <entry>Use the DCI-P3 transfer function.</entry>
- </row>
- <row>
- <entry><constant>V4L2_XFER_FUNC_SMPTE2084</constant></entry>
- <entry>Use the SMPTE 2084 transfer function.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table pgwide="1" frame="none" id="v4l2-ycbcr-encoding">
- <title>V4L2 Y'CbCr Encodings</title>
- <tgroup cols="2" align="left">
- &cs-def;
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Details</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_YCBCR_ENC_DEFAULT</constant></entry>
- <entry>Use the default Y'CbCr encoding as defined by the colorspace.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_601</constant></entry>
- <entry>Use the BT.601 Y'CbCr encoding.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_709</constant></entry>
- <entry>Use the Rec. 709 Y'CbCr encoding.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_XV601</constant></entry>
- <entry>Use the extended gamut xvYCC BT.601 encoding.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_XV709</constant></entry>
- <entry>Use the extended gamut xvYCC Rec. 709 encoding.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_SYCC</constant></entry>
- <entry>Use the extended gamut sYCC encoding.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_BT2020</constant></entry>
- <entry>Use the default non-constant luminance BT.2020 Y'CbCr encoding.</entry>
- </row>
- <row>
- <entry><constant>V4L2_YCBCR_ENC_BT2020_CONST_LUM</constant></entry>
- <entry>Use the constant luminance BT.2020 Yc'CbcCrc encoding.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table pgwide="1" frame="none" id="v4l2-quantization">
- <title>V4L2 Quantization Methods</title>
- <tgroup cols="2" align="left">
- &cs-def;
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Details</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_QUANTIZATION_DEFAULT</constant></entry>
- <entry>Use the default quantization encoding as defined by the colorspace.
-This is always full range for R'G'B' (except for the BT.2020 colorspace) and usually
-limited range for Y'CbCr.</entry>
- </row>
- <row>
- <entry><constant>V4L2_QUANTIZATION_FULL_RANGE</constant></entry>
- <entry>Use the full range quantization encoding. I.e. the range [0&hellip;1]
-is mapped to [0&hellip;255] (with possible clipping to [1&hellip;254] to avoid the
-0x00 and 0xff values). Cb and Cr are mapped from [-0.5&hellip;0.5] to [0&hellip;255]
-(with possible clipping to [1&hellip;254] to avoid the 0x00 and 0xff values).</entry>
- </row>
- <row>
- <entry><constant>V4L2_QUANTIZATION_LIM_RANGE</constant></entry>
- <entry>Use the limited range quantization encoding. I.e. the range [0&hellip;1]
-is mapped to [16&hellip;235]. Cb and Cr are mapped from [-0.5&hellip;0.5] to [16&hellip;240].
-</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </section>
-
- <section>
- <title>Detailed Colorspace Descriptions</title>
- <section id="col-smpte-170m">
- <title>Colorspace SMPTE 170M (<constant>V4L2_COLORSPACE_SMPTE170M</constant>)</title>
- <para>The <xref linkend="smpte170m" /> standard defines the colorspace used by NTSC and PAL and by SDTV
-in general. The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>.
-The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and
-the white reference are:</para>
- <table frame="none">
- <title>SMPTE 170M Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.630</entry>
- <entry>0.340</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.310</entry>
- <entry>0.595</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.155</entry>
- <entry>0.070</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <para>The red, green and blue chromaticities are also often referred to
-as the SMPTE C set, so this colorspace is sometimes called SMPTE C as well.</para>
- <variablelist>
- <varlistentry>
- <term>The transfer function defined for SMPTE 170M is the same as the
-one defined in Rec. 709.</term>
- <listitem>
- <para>L' = -1.099(-L)<superscript>0.45</superscript>&nbsp;+&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&le;&nbsp;-0.018</para>
- <para>L' = 4.5L&nbsp;for&nbsp;-0.018&nbsp;&lt;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
- <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&ge;&nbsp;0.018</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = -((L'&nbsp;-&nbsp;0.099)&nbsp;/&nbsp;-1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&le;&nbsp;-0.081</para>
- <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;-0.081&nbsp;&lt;&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
- <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with
-the following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
- <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
-clamped to the range [-0.5&hellip;0.5]. This conversion to Y'CbCr is identical to the one
-defined in the <xref linkend="itu601" /> standard and this colorspace is sometimes called BT.601 as well, even
-though BT.601 does not mention any color primaries.</para>
- <para>The default quantization is limited range, but full range is possible although
-rarely seen.</para>
- </section>
-
- <section id="col-rec709">
- <title>Colorspace Rec. 709 (<constant>V4L2_COLORSPACE_REC709</constant>)</title>
- <para>The <xref linkend="itu709" /> standard defines the colorspace used by HDTV in general.
-The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>. The default
-Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_709</constant>. The default Y'CbCr quantization is
-limited range. The chromaticities of the primary colors and the white reference are:</para>
- <table frame="none">
- <title>Rec. 709 Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.640</entry>
- <entry>0.330</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.300</entry>
- <entry>0.600</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.150</entry>
- <entry>0.060</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <para>The full name of this standard is Rec. ITU-R BT.709-5.</para>
- <variablelist>
- <varlistentry>
- <term>Transfer function. Normally L is in the range [0&hellip;1], but for the extended
-gamut xvYCC encoding values outside that range are allowed.</term>
- <listitem>
- <para>L' = -1.099(-L)<superscript>0.45</superscript>&nbsp;+&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&le;&nbsp;-0.018</para>
- <para>L' = 4.5L&nbsp;for&nbsp;-0.018&nbsp;&lt;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
- <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;L&nbsp;&ge;&nbsp;0.018</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = -((L'&nbsp;-&nbsp;0.099)&nbsp;/&nbsp;-1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&le;&nbsp;-0.081</para>
- <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;-0.081&nbsp;&lt;&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
- <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the following
-<constant>V4L2_YCBCR_ENC_709</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.2126R'&nbsp;+&nbsp;0.7152G'&nbsp;+&nbsp;0.0722B'</para>
- <para>Cb&nbsp;=&nbsp;-0.1146R'&nbsp;-&nbsp;0.3854G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4542G'&nbsp;-&nbsp;0.0458B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
-clamped to the range [-0.5&hellip;0.5].</para>
- <para>The default quantization is limited range, but full range is possible although
-rarely seen.</para>
- <para>The <constant>V4L2_YCBCR_ENC_709</constant> encoding described above is the default
-for this colorspace, but it can be overridden with <constant>V4L2_YCBCR_ENC_601</constant>, in which
-case the BT.601 Y'CbCr encoding is used.</para>
- <para>Two additional extended gamut Y'CbCr encodings are also possible with this colorspace:</para>
- <variablelist>
- <varlistentry>
- <term>The xvYCC 709 encoding (<constant>V4L2_YCBCR_ENC_XV709</constant>, <xref linkend="xvycc" />)
-is similar to the Rec. 709 encoding, but it allows for R', G' and B' values that are outside the range
-[0&hellip;1]. The resulting Y', Cb and Cr values are scaled and offset:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;(219&nbsp;/&nbsp;256)&nbsp;*&nbsp;(0.2126R'&nbsp;+&nbsp;0.7152G'&nbsp;+&nbsp;0.0722B')&nbsp;+&nbsp;(16&nbsp;/&nbsp;256)</para>
- <para>Cb&nbsp;=&nbsp;(224&nbsp;/&nbsp;256)&nbsp;*&nbsp;(-0.1146R'&nbsp;-&nbsp;0.3854G'&nbsp;+&nbsp;0.5B')</para>
- <para>Cr&nbsp;=&nbsp;(224&nbsp;/&nbsp;256)&nbsp;*&nbsp;(0.5R'&nbsp;-&nbsp;0.4542G'&nbsp;-&nbsp;0.0458B')</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The xvYCC 601 encoding (<constant>V4L2_YCBCR_ENC_XV601</constant>, <xref linkend="xvycc" />) is similar
-to the BT.601 encoding, but it allows for R', G' and B' values that are outside the range
-[0&hellip;1]. The resulting Y', Cb and Cr values are scaled and offset:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;(219&nbsp;/&nbsp;256)&nbsp;*&nbsp;(0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B')&nbsp;+&nbsp;(16&nbsp;/&nbsp;256)</para>
- <para>Cb&nbsp;=&nbsp;(224&nbsp;/&nbsp;256)&nbsp;*&nbsp;(-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B')</para>
- <para>Cr&nbsp;=&nbsp;(224&nbsp;/&nbsp;256)&nbsp;*&nbsp;(0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B')</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are clamped
-to the range [-0.5&hellip;0.5]. The non-standard xvYCC 709 or xvYCC 601 encodings can be used by
-selecting <constant>V4L2_YCBCR_ENC_XV709</constant> or <constant>V4L2_YCBCR_ENC_XV601</constant>.
-The xvYCC encodings always use full range quantization.</para>
- </section>
-
- <section id="col-srgb">
- <title>Colorspace sRGB (<constant>V4L2_COLORSPACE_SRGB</constant>)</title>
- <para>The <xref linkend="srgb" /> standard defines the colorspace used by most webcams
-and computer graphics. The default transfer function is <constant>V4L2_XFER_FUNC_SRGB</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_SYCC</constant>. The default Y'CbCr
-quantization is full range. The chromaticities of the primary colors and the white
-reference are:</para>
- <table frame="none">
- <title>sRGB Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.640</entry>
- <entry>0.330</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.300</entry>
- <entry>0.600</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.150</entry>
- <entry>0.060</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <para>These chromaticities are identical to the Rec. 709 colorspace.</para>
- <variablelist>
- <varlistentry>
- <term>Transfer function. Note that negative values for L are only used by the Y'CbCr conversion.</term>
- <listitem>
- <para>L' = -1.055(-L)<superscript>1/2.4</superscript>&nbsp;+&nbsp;0.055&nbsp;for&nbsp;L&nbsp;&lt;&nbsp;-0.0031308</para>
- <para>L' = 12.92L&nbsp;for&nbsp;-0.0031308&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;0.0031308</para>
- <para>L' = 1.055L<superscript>1/2.4</superscript>&nbsp;-&nbsp;0.055&nbsp;for&nbsp;0.0031308&nbsp;&lt;&nbsp;L&nbsp;&le;&nbsp;1</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = -((-L'&nbsp;+&nbsp;0.055)&nbsp;/&nbsp;1.055)<superscript>2.4</superscript>&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;-0.04045</para>
- <para>L = L'&nbsp;/&nbsp;12.92&nbsp;for&nbsp;-0.04045&nbsp;&le;&nbsp;L'&nbsp;&le;&nbsp;0.04045</para>
- <para>L = ((L'&nbsp;+&nbsp;0.055)&nbsp;/&nbsp;1.055)<superscript>2.4</superscript>&nbsp;for&nbsp;L'&nbsp;&gt;&nbsp;0.04045</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the following
-<constant>V4L2_YCBCR_ENC_SYCC</constant> encoding as defined by <xref linkend="sycc" />:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.2990R'&nbsp;+&nbsp;0.5870G'&nbsp;+&nbsp;0.1140B'</para>
- <para>Cb&nbsp;=&nbsp;-0.1687R'&nbsp;-&nbsp;0.3313G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4187G'&nbsp;-&nbsp;0.0813B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are clamped
-to the range [-0.5&hellip;0.5]. The <constant>V4L2_YCBCR_ENC_SYCC</constant> quantization is always
-full range. Although this Y'CbCr encoding looks very similar to the <constant>V4L2_YCBCR_ENC_XV601</constant>
-encoding, it is not. The <constant>V4L2_YCBCR_ENC_XV601</constant> scales and offsets the Y'CbCr
-values before quantization, but this encoding does not do that.</para>
- </section>
-
- <section id="col-adobergb">
- <title>Colorspace Adobe RGB (<constant>V4L2_COLORSPACE_ADOBERGB</constant>)</title>
- <para>The <xref linkend="adobergb" /> standard defines the colorspace used by computer graphics
-that use the AdobeRGB colorspace. This is also known as the <xref linkend="oprgb" /> standard.
-The default transfer function is <constant>V4L2_XFER_FUNC_ADOBERGB</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>. The default Y'CbCr
-quantization is limited range. The chromaticities of the primary colors and the white reference
-are:</para>
- <table frame="none">
- <title>Adobe RGB Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.6400</entry>
- <entry>0.3300</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.2100</entry>
- <entry>0.7100</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.1500</entry>
- <entry>0.0600</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <variablelist>
- <varlistentry>
- <term>Transfer function:</term>
- <listitem>
- <para>L' = L<superscript>1/2.19921875</superscript></para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = L'<superscript>2.19921875</superscript></para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
-following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
- <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
-clamped to the range [-0.5&hellip;0.5]. This transform is identical to one defined in
-SMPTE 170M/BT.601. The Y'CbCr quantization is limited range.</para>
- </section>
-
- <section id="col-bt2020">
- <title>Colorspace BT.2020 (<constant>V4L2_COLORSPACE_BT2020</constant>)</title>
- <para>The <xref linkend="itu2020" /> standard defines the colorspace used by Ultra-high definition
-television (UHDTV). The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_BT2020</constant>.
-The default R'G'B' quantization is limited range (!), and so is the default Y'CbCr quantization.
-The chromaticities of the primary colors and the white reference are:</para>
- <table frame="none">
- <title>BT.2020 Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.708</entry>
- <entry>0.292</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.170</entry>
- <entry>0.797</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.131</entry>
- <entry>0.046</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <variablelist>
- <varlistentry>
- <term>Transfer function (same as Rec. 709):</term>
- <listitem>
- <para>L' = 4.5L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
- <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
- <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
-following <constant>V4L2_YCBCR_ENC_BT2020</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.2627R'&nbsp;+&nbsp;0.6780G'&nbsp;+&nbsp;0.0593B'</para>
- <para>Cb&nbsp;=&nbsp;-0.1396R'&nbsp;-&nbsp;0.3604G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4598G'&nbsp;-&nbsp;0.0402B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
-clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.</para>
- <para>There is also an alternate constant luminance R'G'B' to Yc'CbcCrc
-(<constant>V4L2_YCBCR_ENC_BT2020_CONST_LUM</constant>) encoding:</para>
- <variablelist>
- <varlistentry>
- <term>Luma:</term>
- <listitem>
- <para>Yc'&nbsp;=&nbsp;(0.2627R&nbsp;+&nbsp;0.6780G&nbsp;+&nbsp;0.0593B)'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>B'&nbsp;-&nbsp;Yc'&nbsp;&le;&nbsp;0:</term>
- <listitem>
- <para>Cbc&nbsp;=&nbsp;(B'&nbsp;-&nbsp;Yc')&nbsp;/&nbsp;1.9404</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>B'&nbsp;-&nbsp;Yc'&nbsp;&gt;&nbsp;0:</term>
- <listitem>
- <para>Cbc&nbsp;=&nbsp;(B'&nbsp;-&nbsp;Yc')&nbsp;/&nbsp;1.5816</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>R'&nbsp;-&nbsp;Yc'&nbsp;&le;&nbsp;0:</term>
- <listitem>
- <para>Crc&nbsp;=&nbsp;(R'&nbsp;-&nbsp;Y')&nbsp;/&nbsp;1.7184</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>R'&nbsp;-&nbsp;Yc'&nbsp;&gt;&nbsp;0:</term>
- <listitem>
- <para>Crc&nbsp;=&nbsp;(R'&nbsp;-&nbsp;Y')&nbsp;/&nbsp;0.9936</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Yc' is clamped to the range [0&hellip;1] and Cbc and Crc are
-clamped to the range [-0.5&hellip;0.5]. The Yc'CbcCrc quantization is limited range.</para>
- </section>
-
- <section id="col-dcip3">
- <title>Colorspace DCI-P3 (<constant>V4L2_COLORSPACE_DCI_P3</constant>)</title>
- <para>The <xref linkend="smpte431" /> standard defines the colorspace used by cinema
-projectors that use the DCI-P3 colorspace.
-The default transfer function is <constant>V4L2_XFER_FUNC_DCI_P3</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_709</constant>. Note that this
-colorspace does not specify a Y'CbCr encoding since it is not meant to be encoded
-to Y'CbCr. So this default Y'CbCr encoding was picked because it is the HDTV
-encoding. The default Y'CbCr quantization is limited range. The chromaticities of
-the primary colors and the white reference are:</para>
- <table frame="none">
- <title>DCI-P3 Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.6800</entry>
- <entry>0.3200</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.2650</entry>
- <entry>0.6900</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.1500</entry>
- <entry>0.0600</entry>
- </row>
- <row>
- <entry>White Reference</entry>
- <entry>0.3140</entry>
- <entry>0.3510</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <variablelist>
- <varlistentry>
- <term>Transfer function:</term>
- <listitem>
- <para>L' = L<superscript>1/2.6</superscript></para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = L'<superscript>2.6</superscript></para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y'CbCr encoding is not specified. V4L2 defaults to Rec. 709.</para>
- </section>
-
- <section id="col-smpte-240m">
- <title>Colorspace SMPTE 240M (<constant>V4L2_COLORSPACE_SMPTE240M</constant>)</title>
- <para>The <xref linkend="smpte240m" /> standard was an interim standard used during
-the early days of HDTV (1988-1998). It has been superseded by Rec. 709.
-The default transfer function is <constant>V4L2_XFER_FUNC_SMPTE240M</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_SMPTE240M</constant>.
-The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and the
-white reference are:</para>
- <table frame="none">
- <title>SMPTE 240M Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.630</entry>
- <entry>0.340</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.310</entry>
- <entry>0.595</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.155</entry>
- <entry>0.070</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <para>These chromaticities are identical to the SMPTE 170M colorspace.</para>
- <variablelist>
- <varlistentry>
- <term>Transfer function:</term>
- <listitem>
- <para>L' = 4L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.0228</para>
- <para>L' = 1.1115L<superscript>0.45</superscript>&nbsp;-&nbsp;0.1115&nbsp;for&nbsp;0.0228&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = L'&nbsp;/&nbsp;4&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L'&nbsp;&lt;&nbsp;0.0913</para>
- <para>L = ((L'&nbsp;+&nbsp;0.1115)&nbsp;/&nbsp;1.1115)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.0913</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
-following <constant>V4L2_YCBCR_ENC_SMPTE240M</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.2122R'&nbsp;+&nbsp;0.7013G'&nbsp;+&nbsp;0.0865B'</para>
- <para>Cb&nbsp;=&nbsp;-0.1161R'&nbsp;-&nbsp;0.3839G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.4451G'&nbsp;-&nbsp;0.0549B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Yc' is clamped to the range [0&hellip;1] and Cbc and Crc are
-clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.</para>
- </section>
-
- <section id="col-sysm">
- <title>Colorspace NTSC 1953 (<constant>V4L2_COLORSPACE_470_SYSTEM_M</constant>)</title>
- <para>This standard defines the colorspace used by NTSC in 1953. In practice this
-colorspace is obsolete and SMPTE 170M should be used instead.
-The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>.
-The default Y'CbCr quantization is limited range.
-The chromaticities of the primary colors and the white reference are:</para>
- <table frame="none">
- <title>NTSC 1953 Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.67</entry>
- <entry>0.33</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.21</entry>
- <entry>0.71</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.14</entry>
- <entry>0.08</entry>
- </row>
- <row>
- <entry>White Reference (C)</entry>
- <entry>0.310</entry>
- <entry>0.316</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <para>Note that this colorspace uses Illuminant C instead of D65 as the
-white reference. To correctly convert an image in this colorspace to another
-that uses D65 you need to apply a chromatic adaptation algorithm such as the
-Bradford method.</para>
- <variablelist>
- <varlistentry>
- <term>The transfer function was never properly defined for NTSC 1953. The
-Rec. 709 transfer function is recommended in the literature:</term>
- <listitem>
- <para>L' = 4.5L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
- <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
- <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
-following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
- <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
-clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.
-This transform is identical to one defined in SMPTE 170M/BT.601.</para>
- </section>
-
- <section id="col-sysbg">
- <title>Colorspace EBU Tech. 3213 (<constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant>)</title>
- <para>The <xref linkend="tech3213" /> standard defines the colorspace used by PAL/SECAM in 1975. In practice this
-colorspace is obsolete and SMPTE 170M should be used instead.
-The default transfer function is <constant>V4L2_XFER_FUNC_709</constant>.
-The default Y'CbCr encoding is <constant>V4L2_YCBCR_ENC_601</constant>.
-The default Y'CbCr quantization is limited range.
-The chromaticities of the primary colors and the white reference are:</para>
- <table frame="none">
- <title>EBU Tech. 3213 Chromaticities</title>
- <tgroup cols="3" align="left">
- &cs-str;
- <thead>
- <row>
- <entry>Color</entry>
- <entry>x</entry>
- <entry>y</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row>
- <entry>Red</entry>
- <entry>0.64</entry>
- <entry>0.33</entry>
- </row>
- <row>
- <entry>Green</entry>
- <entry>0.29</entry>
- <entry>0.60</entry>
- </row>
- <row>
- <entry>Blue</entry>
- <entry>0.15</entry>
- <entry>0.06</entry>
- </row>
- <row>
- <entry>White Reference (D65)</entry>
- <entry>0.3127</entry>
- <entry>0.3290</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <variablelist>
- <varlistentry>
- <term>The transfer function was never properly defined for this colorspace.
-The Rec. 709 transfer function is recommended in the literature:</term>
- <listitem>
- <para>L' = 4.5L&nbsp;for&nbsp;0&nbsp;&le;&nbsp;L&nbsp;&lt;&nbsp;0.018</para>
- <para>L' = 1.099L<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&le;&nbsp;L&nbsp;&le;&nbsp;1</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = L'&nbsp;/&nbsp;4.5&nbsp;for&nbsp;L'&nbsp;&lt;&nbsp;0.081</para>
- <para>L = ((L'&nbsp;+&nbsp;0.099)&nbsp;/&nbsp;1.099)<superscript>1/0.45</superscript>&nbsp;for&nbsp;L'&nbsp;&ge;&nbsp;0.081</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>The luminance (Y') and color difference (Cb and Cr) are obtained with the
-following <constant>V4L2_YCBCR_ENC_601</constant> encoding:</term>
- <listitem>
- <para>Y'&nbsp;=&nbsp;0.299R'&nbsp;+&nbsp;0.587G'&nbsp;+&nbsp;0.114B'</para>
- <para>Cb&nbsp;=&nbsp;-0.169R'&nbsp;-&nbsp;0.331G'&nbsp;+&nbsp;0.5B'</para>
- <para>Cr&nbsp;=&nbsp;0.5R'&nbsp;-&nbsp;0.419G'&nbsp;-&nbsp;0.081B'</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>Y' is clamped to the range [0&hellip;1] and Cb and Cr are
-clamped to the range [-0.5&hellip;0.5]. The Y'CbCr quantization is limited range.
-This transform is identical to one defined in SMPTE 170M/BT.601.</para>
- </section>
-
- <section id="col-jpeg">
- <title>Colorspace JPEG (<constant>V4L2_COLORSPACE_JPEG</constant>)</title>
- <para>This colorspace defines the colorspace used by most (Motion-)JPEG formats. The chromaticities
-of the primary colors and the white reference are identical to sRGB. The transfer
-function use is <constant>V4L2_XFER_FUNC_SRGB</constant>. The Y'CbCr encoding is
-<constant>V4L2_YCBCR_ENC_601</constant> with full range quantization where
-Y' is scaled to [0&hellip;255] and Cb/Cr are scaled to [-128&hellip;128] and
-then clipped to [-128&hellip;127].</para>
- <para>Note that the JPEG standard does not actually store colorspace information.
-So if something other than sRGB is used, then the driver will have to set that information
-explicitly. Effectively <constant>V4L2_COLORSPACE_JPEG</constant> can be considered to be
-an abbreviation for <constant>V4L2_COLORSPACE_SRGB</constant>, <constant>V4L2_YCBCR_ENC_601</constant>
-and <constant>V4L2_QUANTIZATION_FULL_RANGE</constant>.</para>
- </section>
-
- </section>
-
- <section>
- <title>Detailed Transfer Function Descriptions</title>
- <section id="xf-smpte-2084">
- <title>Transfer Function SMPTE 2084 (<constant>V4L2_XFER_FUNC_SMPTE2084</constant>)</title>
- <para>The <xref linkend="smpte2084" /> standard defines the transfer function used by
-High Dynamic Range content.</para>
- <variablelist>
- <varlistentry>
- <term>Constants:</term>
- <listitem>
- <para>m1 = (2610 / 4096) / 4</para>
- <para>m2 = (2523 / 4096) * 128</para>
- <para>c1 = 3424 / 4096</para>
- <para>c2 = (2413 / 4096) * 32</para>
- <para>c3 = (2392 / 4096) * 32</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>Transfer function:</term>
- <listitem>
- <para>L' = ((c1 + c2 * L<superscript>m1</superscript>) / (1 + c3 * L<superscript>m1</superscript>))<superscript>m2</superscript></para>
- </listitem>
- </varlistentry>
- </variablelist>
- <variablelist>
- <varlistentry>
- <term>Inverse Transfer function:</term>
- <listitem>
- <para>L = (max(L'<superscript>1/m2</superscript> - c1, 0) / (c2 - c3 * L'<superscript>1/m2</superscript>))<superscript>1/m1</superscript></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </section>
- </section>
-
- <section id="pixfmt-indexed">
- <title>Indexed Format</title>
-
- <para>In this format each pixel is represented by an 8 bit index
-into a 256 entry ARGB palette. It is intended for <link
-linkend="osd">Video Output Overlays</link> only. There are no ioctls to
-access the palette, this must be done with ioctls of the Linux framebuffer API.</para>
-
- <table pgwide="0" frame="none">
- <title>Indexed Image Format</title>
- <tgroup cols="37" align="center">
- <colspec colname="id" align="left" />
- <colspec colname="fourcc" />
- <colspec colname="bit" />
-
- <colspec colnum="4" colname="b07" align="center" />
- <colspec colnum="5" colname="b06" align="center" />
- <colspec colnum="6" colname="b05" align="center" />
- <colspec colnum="7" colname="b04" align="center" />
- <colspec colnum="8" colname="b03" align="center" />
- <colspec colnum="9" colname="b02" align="center" />
- <colspec colnum="10" colname="b01" align="center" />
- <colspec colnum="11" colname="b00" align="center" />
-
- <spanspec namest="b07" nameend="b00" spanname="b0" />
- <spanspec namest="b17" nameend="b10" spanname="b1" />
- <spanspec namest="b27" nameend="b20" spanname="b2" />
- <spanspec namest="b37" nameend="b30" spanname="b3" />
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Code</entry>
- <entry>&nbsp;</entry>
- <entry spanname="b0">Byte&nbsp;0</entry>
- </row>
- <row>
- <entry>&nbsp;</entry>
- <entry>&nbsp;</entry>
- <entry>Bit</entry>
- <entry>7</entry>
- <entry>6</entry>
- <entry>5</entry>
- <entry>4</entry>
- <entry>3</entry>
- <entry>2</entry>
- <entry>1</entry>
- <entry>0</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row id="V4L2-PIX-FMT-PAL8">
- <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry>
- <entry>'PAL8'</entry>
- <entry></entry>
- <entry>i<subscript>7</subscript></entry>
- <entry>i<subscript>6</subscript></entry>
- <entry>i<subscript>5</subscript></entry>
- <entry>i<subscript>4</subscript></entry>
- <entry>i<subscript>3</subscript></entry>
- <entry>i<subscript>2</subscript></entry>
- <entry>i<subscript>1</subscript></entry>
- <entry>i<subscript>0</subscript></entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </section>
-
- <section id="pixfmt-rgb">
- <title>RGB Formats</title>
-
- &sub-packed-rgb;
- &sub-sbggr8;
- &sub-sgbrg8;
- &sub-sgrbg8;
- &sub-srggb8;
- &sub-sbggr16;
- &sub-srggb10;
- &sub-srggb10p;
- &sub-srggb10alaw8;
- &sub-srggb10dpcm8;
- &sub-srggb12;
- </section>
-
- <section id="yuv-formats">
- <title>YUV Formats</title>
-
- <para>YUV is the format native to TV broadcast and composite video
-signals. It separates the brightness information (Y) from the color
-information (U and V or Cb and Cr). The color information consists of
-red and blue <emphasis>color difference</emphasis> signals, this way
-the green component can be reconstructed by subtracting from the
-brightness component. See <xref linkend="colorspaces" /> for conversion
-examples. YUV was chosen because early television would only transmit
-brightness information. To add color in a way compatible with existing
-receivers a new signal carrier was added to transmit the color
-difference signals. Secondary in the YUV format the U and V components
-usually have lower resolution than the Y component. This is an analog
-video compression technique taking advantage of a property of the
-human visual system, being more sensitive to brightness
-information.</para>
-
- &sub-packed-yuv;
- &sub-grey;
- &sub-y10;
- &sub-y12;
- &sub-y10b;
- &sub-y16;
- &sub-y16-be;
- &sub-y8i;
- &sub-y12i;
- &sub-uv8;
- &sub-yuyv;
- &sub-uyvy;
- &sub-yvyu;
- &sub-vyuy;
- &sub-y41p;
- &sub-yuv420;
- &sub-yuv420m;
- &sub-yuv422m;
- &sub-yuv444m;
- &sub-yuv410;
- &sub-yuv422p;
- &sub-yuv411p;
- &sub-nv12;
- &sub-nv12m;
- &sub-nv12mt;
- &sub-nv16;
- &sub-nv16m;
- &sub-nv24;
- &sub-m420;
- </section>
-
- <section id="depth-formats">
- <title>Depth Formats</title>
- <para>Depth data provides distance to points, mapped onto the image plane
- </para>
-
- &sub-z16;
- </section>
-
- <section>
- <title>Compressed Formats</title>
-
- <table pgwide="1" frame="none" id="compressed-formats">
- <title>Compressed Image Formats</title>
- <tgroup cols="3" align="left">
- &cs-def;
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Code</entry>
- <entry>Details</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row id="V4L2-PIX-FMT-JPEG">
- <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry>
- <entry>'JPEG'</entry>
- <entry>TBD. See also &VIDIOC-G-JPEGCOMP;,
- &VIDIOC-S-JPEGCOMP;.</entry>
- </row>
- <row id="V4L2-PIX-FMT-MPEG">
- <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry>
- <entry>'MPEG'</entry>
- <entry>MPEG multiplexed stream. The actual format is determined by
-extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see
-<xref linkend="mpeg-control-id" />.</entry>
- </row>
- <row id="V4L2-PIX-FMT-H264">
- <entry><constant>V4L2_PIX_FMT_H264</constant></entry>
- <entry>'H264'</entry>
- <entry>H264 video elementary stream with start codes.</entry>
- </row>
- <row id="V4L2-PIX-FMT-H264-NO-SC">
- <entry><constant>V4L2_PIX_FMT_H264_NO_SC</constant></entry>
- <entry>'AVC1'</entry>
- <entry>H264 video elementary stream without start codes.</entry>
- </row>
- <row id="V4L2-PIX-FMT-H264-MVC">
- <entry><constant>V4L2_PIX_FMT_H264_MVC</constant></entry>
- <entry>'M264'</entry>
- <entry>H264 MVC video elementary stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-H263">
- <entry><constant>V4L2_PIX_FMT_H263</constant></entry>
- <entry>'H263'</entry>
- <entry>H263 video elementary stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-MPEG1">
- <entry><constant>V4L2_PIX_FMT_MPEG1</constant></entry>
- <entry>'MPG1'</entry>
- <entry>MPEG1 video elementary stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-MPEG2">
- <entry><constant>V4L2_PIX_FMT_MPEG2</constant></entry>
- <entry>'MPG2'</entry>
- <entry>MPEG2 video elementary stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-MPEG4">
- <entry><constant>V4L2_PIX_FMT_MPEG4</constant></entry>
- <entry>'MPG4'</entry>
- <entry>MPEG4 video elementary stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-XVID">
- <entry><constant>V4L2_PIX_FMT_XVID</constant></entry>
- <entry>'XVID'</entry>
- <entry>Xvid video elementary stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-VC1-ANNEX-G">
- <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_G</constant></entry>
- <entry>'VC1G'</entry>
- <entry>VC1, SMPTE 421M Annex G compliant stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-VC1-ANNEX-L">
- <entry><constant>V4L2_PIX_FMT_VC1_ANNEX_L</constant></entry>
- <entry>'VC1L'</entry>
- <entry>VC1, SMPTE 421M Annex L compliant stream.</entry>
- </row>
- <row id="V4L2-PIX-FMT-VP8">
- <entry><constant>V4L2_PIX_FMT_VP8</constant></entry>
- <entry>'VP80'</entry>
- <entry>VP8 video elementary stream.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </section>
-
- <section id="sdr-formats">
- <title>SDR Formats</title>
-
- <para>These formats are used for <link linkend="sdr">SDR</link>
-interface only.</para>
-
- &sub-sdr-cu08;
- &sub-sdr-cu16le;
- &sub-sdr-cs08;
- &sub-sdr-cs14le;
- &sub-sdr-ru12le;
-
- </section>
-
- <section id="pixfmt-reserved">
- <title>Reserved Format Identifiers</title>
-
- <para>These formats are not defined by this specification, they
-are just listed for reference and to avoid naming conflicts. If you
-want to register your own format, send an e-mail to the linux-media mailing
-list &v4l-ml; for inclusion in the <filename>videodev2.h</filename>
-file. If you want to share your format with other developers add a
-link to your documentation and send a copy to the linux-media mailing list
-for inclusion in this section. If you think your format should be listed
-in a standard format section please make a proposal on the linux-media mailing
-list.</para>
-
- <table pgwide="1" frame="none" id="reserved-formats">
- <title>Reserved Image Formats</title>
- <tgroup cols="3" align="left">
- &cs-def;
- <thead>
- <row>
- <entry>Identifier</entry>
- <entry>Code</entry>
- <entry>Details</entry>
- </row>
- </thead>
- <tbody valign="top">
- <row id="V4L2-PIX-FMT-DV">
- <entry><constant>V4L2_PIX_FMT_DV</constant></entry>
- <entry>'dvsd'</entry>
- <entry>unknown</entry>
- </row>
- <row id="V4L2-PIX-FMT-ET61X251">
- <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry>
- <entry>'E625'</entry>
- <entry>Compressed format of the ET61X251 driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-HI240">
- <entry><constant>V4L2_PIX_FMT_HI240</constant></entry>
- <entry>'HI24'</entry>
- <entry><para>8 bit RGB format used by the BTTV driver.</para></entry>
- </row>
- <row id="V4L2-PIX-FMT-HM12">
- <entry><constant>V4L2_PIX_FMT_HM12</constant></entry>
- <entry>'HM12'</entry>
- <entry><para>YUV 4:2:0 format used by the
-IVTV driver, <ulink url="http://www.ivtvdriver.org/">
-http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the
-kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename>
-</para></entry>
- </row>
- <row id="V4L2-PIX-FMT-CPIA1">
- <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry>
- <entry>'CPIA'</entry>
- <entry>YUV format used by the gspca cpia1 driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-JPGL">
- <entry><constant>V4L2_PIX_FMT_JPGL</constant></entry>
- <entry>'JPGL'</entry>
- <entry>JPEG-Light format (Pegasus Lossless JPEG)
- used in Divio webcams NW 80x.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SPCA501">
- <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry>
- <entry>'S501'</entry>
- <entry>YUYV per line used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SPCA505">
- <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry>
- <entry>'S505'</entry>
- <entry>YYUV per line used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SPCA508">
- <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry>
- <entry>'S508'</entry>
- <entry>YUVY per line used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SPCA561">
- <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry>
- <entry>'S561'</entry>
- <entry>Compressed GBRG Bayer format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-PAC207">
- <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry>
- <entry>'P207'</entry>
- <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-MR97310A">
- <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry>
- <entry>'M310'</entry>
- <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-JL2005BCD">
- <entry><constant>V4L2_PIX_FMT_JL2005BCD</constant></entry>
- <entry>'JL20'</entry>
- <entry>JPEG compressed RGGB Bayer format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-OV511">
- <entry><constant>V4L2_PIX_FMT_OV511</constant></entry>
- <entry>'O511'</entry>
- <entry>OV511 JPEG format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-OV518">
- <entry><constant>V4L2_PIX_FMT_OV518</constant></entry>
- <entry>'O518'</entry>
- <entry>OV518 JPEG format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-PJPG">
- <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry>
- <entry>'PJPG'</entry>
- <entry>Pixart 73xx JPEG format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SE401">
- <entry><constant>V4L2_PIX_FMT_SE401</constant></entry>
- <entry>'S401'</entry>
- <entry>Compressed RGB format used by the gspca se401 driver</entry>
- </row>
- <row id="V4L2-PIX-FMT-SQ905C">
- <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry>
- <entry>'905C'</entry>
- <entry>Compressed RGGB bayer format used by the gspca driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-MJPEG">
- <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry>
- <entry>'MJPG'</entry>
- <entry>Compressed format used by the Zoran driver</entry>
- </row>
- <row id="V4L2-PIX-FMT-PWC1">
- <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry>
- <entry>'PWC1'</entry>
- <entry>Compressed format of the PWC driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-PWC2">
- <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry>
- <entry>'PWC2'</entry>
- <entry>Compressed format of the PWC driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SN9C10X">
- <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry>
- <entry>'S910'</entry>
- <entry>Compressed format of the SN9C102 driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SN9C20X-I420">
- <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry>
- <entry>'S920'</entry>
- <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-SN9C2028">
- <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry>
- <entry>'SONX'</entry>
- <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-STV0680">
- <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry>
- <entry>'S680'</entry>
- <entry>Bayer format of the gspca stv0680 driver.</entry>
- </row>
- <row id="V4L2-PIX-FMT-WNVA">
- <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry>
- <entry>'WNVA'</entry>
- <entry><para>Used by the Winnov Videum driver, <ulink
-url="http://www.thedirks.org/winnov/">
-http://www.thedirks.org/winnov/</ulink></para></entry>
- </row>
- <row id="V4L2-PIX-FMT-TM6000">
- <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry>
- <entry>'TM60'</entry>
- <entry><para>Used by Trident tm6000</para></entry>
- </row>
- <row id="V4L2-PIX-FMT-CIT-YYVYUY">
- <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry>
- <entry>'CITV'</entry>
- <entry><para>Used by xirlink CIT, found at IBM webcams.</para>
- <para>Uses one line of Y then 1 line of VYUY</para>
- </entry>
- </row>
- <row id="V4L2-PIX-FMT-KONICA420">
- <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry>
- <entry>'KONI'</entry>
- <entry><para>Used by Konica webcams.</para>
- <para>YUV420 planar in blocks of 256 pixels.</para>
- </entry>
- </row>
- <row id="V4L2-PIX-FMT-YYUV">
- <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry>
- <entry>'YYUV'</entry>
- <entry>unknown</entry>
- </row>
- <row id="V4L2-PIX-FMT-Y4">
- <entry><constant>V4L2_PIX_FMT_Y4</constant></entry>
- <entry>'Y04 '</entry>
- <entry>Old 4-bit greyscale format. Only the most significant 4 bits of each byte are used,
-the other bits are set to 0.</entry>
- </row>
- <row id="V4L2-PIX-FMT-Y6">
- <entry><constant>V4L2_PIX_FMT_Y6</constant></entry>
- <entry>'Y06 '</entry>
- <entry>Old 6-bit greyscale format. Only the most significant 6 bits of each byte are used,
-the other bits are set to 0.</entry>
- </row>
- <row id="V4L2-PIX-FMT-S5C-UYVY-JPG">
- <entry><constant>V4L2_PIX_FMT_S5C_UYVY_JPG</constant></entry>
- <entry>'S5CI'</entry>
- <entry>Two-planar format used by Samsung S5C73MX cameras. The
-first plane contains interleaved JPEG and UYVY image data, followed by meta data
-in form of an array of offsets to the UYVY data blocks. The actual pointer array
-follows immediately the interleaved JPEG/UYVY data, the number of entries in
-this array equals the height of the UYVY image. Each entry is a 4-byte unsigned
-integer in big endian order and it's an offset to a single pixel line of the
-UYVY image. The first plane can start either with JPEG or UYVY data chunk. The
-size of a single UYVY block equals the UYVY image's width multiplied by 2. The
-size of a JPEG chunk depends on the image and can vary with each line.
-<para>The second plane, at an offset of 4084 bytes, contains a 4-byte offset to
-the pointer array in the first plane. This offset is followed by a 4-byte value
-indicating size of the pointer array. All numbers in the second plane are also
-in big endian order. Remaining data in the second plane is undefined. The
-information in the second plane allows to easily find location of the pointer
-array, which can be different for each frame. The size of the pointer array is
-constant for given UYVY image height.</para>
-<para>In order to extract UYVY and JPEG frames an application can initially set
-a data pointer to the start of first plane and then add an offset from the first
-entry of the pointers table. Such a pointer indicates start of an UYVY image
-pixel line. Whole UYVY line can be copied to a separate buffer. These steps
-should be repeated for each line, i.e. the number of entries in the pointer
-array. Anything what's in between the UYVY lines is JPEG data and should be
-concatenated to form the JPEG stream. </para>
-</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table frame="none" pgwide="1" id="format-flags">
- <title>Format Flags</title>
- <tgroup cols="3">
- &cs-def;
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_PIX_FMT_FLAG_PREMUL_ALPHA</constant></entry>
- <entry>0x00000001</entry>
- <entry>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) </entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </section>