diff options
Diffstat (limited to 'Documentation/DocBook/media/v4l/pixfmt.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/pixfmt.xml | 2003 |
1 files changed, 0 insertions, 2003 deletions
diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml b/Documentation/DocBook/media/v4l/pixfmt.xml deleted file mode 100644 index 5a08aeea4360..000000000000 --- a/Documentation/DocBook/media/v4l/pixfmt.xml +++ /dev/null @@ -1,2003 +0,0 @@ - <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, 0, 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…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, 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…1] describes all colors that humans can perceive, but the transform to -another colorspace will produce colors that are outside the [0…1] range. -Once clamped to the [0…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…1] is translated to integer values in the -range of [0…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…255] range. Y'CbCr values on the other hand are limited -range with Y' using [16…235] and Cb and Cr using [16…240].</para> - - <para>Unfortunately, in some cases limited range RGB is also used -where the components use the range [16…235]. And full range Y'CbCr also exists -using the [0…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…1] -is mapped to [0…255] (with possible clipping to [1…254] to avoid the -0x00 and 0xff values). Cb and Cr are mapped from [-0.5…0.5] to [0…255] -(with possible clipping to [1…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…1] -is mapped to [16…235]. Cb and Cr are mapped from [-0.5…0.5] to [16…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> + 0.099 for L ≤ -0.018</para> - <para>L' = 4.5L for -0.018 < L < 0.018</para> - <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for L ≥ 0.018</para> - </listitem> - </varlistentry> - </variablelist> - <variablelist> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = -((L' - 0.099) / -1.099)<superscript>1/0.45</superscript> for L' ≤ -0.081</para> - <para>L = L' / 4.5 for -0.081 < L' < 0.081</para> - <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 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' = 0.299R' + 0.587G' + 0.114B'</para> - <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…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…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> + 0.099 for L ≤ -0.018</para> - <para>L' = 4.5L for -0.018 < L < 0.018</para> - <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for L ≥ 0.018</para> - </listitem> - </varlistentry> - </variablelist> - <variablelist> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = -((L' - 0.099) / -1.099)<superscript>1/0.45</superscript> for L' ≤ -0.081</para> - <para>L = L' / 4.5 for -0.081 < L' < 0.081</para> - <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 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' = 0.2126R' + 0.7152G' + 0.0722B'</para> - <para>Cb = -0.1146R' - 0.3854G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.4542G' - 0.0458B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…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…1]. The resulting Y', Cb and Cr values are scaled and offset:</term> - <listitem> - <para>Y' = (219 / 256) * (0.2126R' + 0.7152G' + 0.0722B') + (16 / 256)</para> - <para>Cb = (224 / 256) * (-0.1146R' - 0.3854G' + 0.5B')</para> - <para>Cr = (224 / 256) * (0.5R' - 0.4542G' - 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…1]. The resulting Y', Cb and Cr values are scaled and offset:</term> - <listitem> - <para>Y' = (219 / 256) * (0.299R' + 0.587G' + 0.114B') + (16 / 256)</para> - <para>Cb = (224 / 256) * (-0.169R' - 0.331G' + 0.5B')</para> - <para>Cr = (224 / 256) * (0.5R' - 0.419G' - 0.081B')</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are clamped -to the range [-0.5…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> + 0.055 for L < -0.0031308</para> - <para>L' = 12.92L for -0.0031308 ≤ L ≤ 0.0031308</para> - <para>L' = 1.055L<superscript>1/2.4</superscript> - 0.055 for 0.0031308 < L ≤ 1</para> - </listitem> - </varlistentry> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = -((-L' + 0.055) / 1.055)<superscript>2.4</superscript> for L' < -0.04045</para> - <para>L = L' / 12.92 for -0.04045 ≤ L' ≤ 0.04045</para> - <para>L = ((L' + 0.055) / 1.055)<superscript>2.4</superscript> for L' > 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' = 0.2990R' + 0.5870G' + 0.1140B'</para> - <para>Cb = -0.1687R' - 0.3313G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.4187G' - 0.0813B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are clamped -to the range [-0.5…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' = 0.299R' + 0.587G' + 0.114B'</para> - <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…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 for 0 ≤ L < 0.018</para> - <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for 0.018 ≤ L ≤ 1</para> - </listitem> - </varlistentry> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = L' / 4.5 for L' < 0.081</para> - <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 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' = 0.2627R' + 0.6780G' + 0.0593B'</para> - <para>Cb = -0.1396R' - 0.3604G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.4598G' - 0.0402B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…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' = (0.2627R + 0.6780G + 0.0593B)'</para> - </listitem> - </varlistentry> - </variablelist> - <variablelist> - <varlistentry> - <term>B' - Yc' ≤ 0:</term> - <listitem> - <para>Cbc = (B' - Yc') / 1.9404</para> - </listitem> - </varlistentry> - </variablelist> - <variablelist> - <varlistentry> - <term>B' - Yc' > 0:</term> - <listitem> - <para>Cbc = (B' - Yc') / 1.5816</para> - </listitem> - </varlistentry> - </variablelist> - <variablelist> - <varlistentry> - <term>R' - Yc' ≤ 0:</term> - <listitem> - <para>Crc = (R' - Y') / 1.7184</para> - </listitem> - </varlistentry> - </variablelist> - <variablelist> - <varlistentry> - <term>R' - Yc' > 0:</term> - <listitem> - <para>Crc = (R' - Y') / 0.9936</para> - </listitem> - </varlistentry> - </variablelist> - <para>Yc' is clamped to the range [0…1] and Cbc and Crc are -clamped to the range [-0.5…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 for 0 ≤ L < 0.0228</para> - <para>L' = 1.1115L<superscript>0.45</superscript> - 0.1115 for 0.0228 ≤ L ≤ 1</para> - </listitem> - </varlistentry> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = L' / 4 for 0 ≤ L' < 0.0913</para> - <para>L = ((L' + 0.1115) / 1.1115)<superscript>1/0.45</superscript> for L' ≥ 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' = 0.2122R' + 0.7013G' + 0.0865B'</para> - <para>Cb = -0.1161R' - 0.3839G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.4451G' - 0.0549B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Yc' is clamped to the range [0…1] and Cbc and Crc are -clamped to the range [-0.5…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 for 0 ≤ L < 0.018</para> - <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for 0.018 ≤ L ≤ 1</para> - </listitem> - </varlistentry> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = L' / 4.5 for L' < 0.081</para> - <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 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' = 0.299R' + 0.587G' + 0.114B'</para> - <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…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 for 0 ≤ L < 0.018</para> - <para>L' = 1.099L<superscript>0.45</superscript> - 0.099 for 0.018 ≤ L ≤ 1</para> - </listitem> - </varlistentry> - <varlistentry> - <term>Inverse Transfer function:</term> - <listitem> - <para>L = L' / 4.5 for L' < 0.081</para> - <para>L = ((L' + 0.099) / 1.099)<superscript>1/0.45</superscript> for L' ≥ 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' = 0.299R' + 0.587G' + 0.114B'</para> - <para>Cb = -0.169R' - 0.331G' + 0.5B'</para> - <para>Cr = 0.5R' - 0.419G' - 0.081B'</para> - </listitem> - </varlistentry> - </variablelist> - <para>Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…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…255] and Cb/Cr are scaled to [-128…128] and -then clipped to [-128…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> </entry> - <entry spanname="b0">Byte 0</entry> - </row> - <row> - <entry> </entry> - <entry> </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> |