From 670027c507e99521d416994a18a498def9ef2ea3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?= Date: Sat, 22 Oct 2016 19:31:08 -0300 Subject: Linux-libre 4.8.3-gnu --- Documentation/DocBook/media/v4l/pixfmt.xml | 2003 ---------------------------- 1 file changed, 2003 deletions(-) delete mode 100644 Documentation/DocBook/media/v4l/pixfmt.xml (limited to 'Documentation/DocBook/media/v4l/pixfmt.xml') diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml b/Documentation/DocBook/media/v4l/pixfmt.xml deleted file mode 100644 index 5a08aeea4..000000000 --- a/Documentation/DocBook/media/v4l/pixfmt.xml +++ /dev/null @@ -1,2003 +0,0 @@ - Image Formats - - The V4L2 API was primarily designed for devices exchanging -image data with applications. The -v4l2_pix_format and v4l2_pix_format_mplane - 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 ). 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;.) - -
- Single-planar format structure - - struct <structname>v4l2_pix_format</structname> - - &cs-str; - - - __u32 - width - Image width in pixels. - - - __u32 - height - Image height in pixels. If field is - one of V4L2_FIELD_TOP, V4L2_FIELD_BOTTOM - or V4L2_FIELD_ALTERNATE then height refers to the - number of lines in the field, otherwise it refers to the number of - lines in the frame (which is twice the field height for interlaced - formats). - - - Applications set these fields to -request an image size, drivers return the closest possible values. In -case of planar formats the width and -height applies to the largest plane. To -avoid ambiguities drivers must return values rounded up to a multiple -of the scale factor of any smaller planes. For example when the image -format is YUV 4:2:0, width and -height must be multiples of two. - - - __u32 - pixelformat - The pixel format or type of compression, set by the -application. This is a little endian four character code. V4L2 defines -standard RGB formats in , YUV formats in , and reserved codes in - - - &v4l2-field; - field - Video images are typically interlaced. Applications -can request to capture or output only the top or bottom field, or both -fields interlaced or sequentially stored in one buffer or alternating -in separate buffers. Drivers return the actual field order selected. -For more details on fields see . - - - __u32 - bytesperline - Distance in bytes between the leftmost pixels in two -adjacent lines. - - - Both applications and drivers -can set this field to request padding bytes at the end of each line. -Drivers however may ignore the value requested by the application, -returning width times bytes per pixel or a -larger value required by the hardware. That implies applications can -just set this field to zero to get a reasonable -default.Video hardware may access padding bytes, -therefore they must reside in accessible memory. Consider cases where -padding bytes after the last line of an image cross a system page -boundary. Input devices may write padding bytes, the value is -undefined. Output devices ignore the contents of padding -bytes.When the image format is planar the -bytesperline value applies to the first -plane and is divided by the same factor as the -width field for the other planes. For -example the Cb and Cr planes of a YUV 4:2:0 image have half as many -padding bytes following each line as the Y plane. To avoid ambiguities -drivers must return a bytesperline value -rounded up to a multiple of the scale factor. -For compressed formats the bytesperline -value makes no sense. Applications and drivers must set this to 0 in -that case. - - - __u32 - sizeimage - Size in bytes of the buffer to hold a complete image, -set by the driver. Usually this is -bytesperline times -height. When the image consists of variable -length compressed data this is the maximum number of bytes required to -hold an image. - - - &v4l2-colorspace; - colorspace - This information supplements the -pixelformat and must be set by the driver for -capture streams and by the application for output streams, -see . - - - __u32 - priv - This field indicates whether the remaining fields of the -v4l2_pix_format structure, also called the extended -fields, are valid. When set to V4L2_PIX_FMT_PRIV_MAGIC, it -indicates that the extended fields have been correctly initialized. When set to -any other value it indicates that the extended fields contain undefined values. - -Applications that wish to use the pixel format extended fields must first -ensure that the feature is supported by querying the device for the -V4L2_CAP_EXT_PIX_FORMAT -capability. If the capability isn't set the pixel format extended fields are not -supported and using the extended fields will lead to undefined results. -To use the extended fields, applications must set the -priv field to -V4L2_PIX_FMT_PRIV_MAGIC, initialize all the extended fields -and zero the unused bytes of the v4l2_format -raw_data field. -When the priv field isn't set to -V4L2_PIX_FMT_PRIV_MAGIC drivers must act as if all the -extended fields were set to zero. On return drivers must set the -priv field to -V4L2_PIX_FMT_PRIV_MAGIC and all the extended fields to -applicable values. - - - __u32 - flags - Flags set by the application or driver, see . - - - &v4l2-ycbcr-encoding; - ycbcr_enc - This information supplements the -colorspace and must be set by the driver for -capture streams and by the application for output streams, -see . - - - &v4l2-quantization; - quantization - This information supplements the -colorspace and must be set by the driver for -capture streams and by the application for output streams, -see . - - - &v4l2-xfer-func; - xfer_func - This information supplements the -colorspace and must be set by the driver for -capture streams and by the application for output streams, -see . - - - -
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- Multi-planar format structures - The v4l2_plane_pix_format structures define - size and layout for each of the planes in a multi-planar format. - The v4l2_pix_format_mplane structure contains - information common to all planes (such as image width and height) and - an array of v4l2_plane_pix_format structures, - describing all planes of that format. - - struct <structname>v4l2_plane_pix_format</structname> - - &cs-str; - - - __u32 - sizeimage - Maximum size in bytes required for image data in this plane. - - - - __u32 - bytesperline - Distance in bytes between the leftmost pixels in two adjacent - lines. See &v4l2-pix-format;. - - - __u16 - reserved[6] - Reserved for future extensions. Should be zeroed by drivers and - applications. - - - -
- - struct <structname>v4l2_pix_format_mplane</structname> - - &cs-str; - - - __u32 - width - Image width in pixels. See &v4l2-pix-format;. - - - __u32 - height - Image height in pixels. See &v4l2-pix-format;. - - - __u32 - pixelformat - The pixel format. Both single- and multi-planar four character -codes can be used. - - - &v4l2-field; - field - See &v4l2-pix-format;. - - - &v4l2-colorspace; - colorspace - See &v4l2-pix-format;. - - - &v4l2-plane-pix-format; - plane_fmt[VIDEO_MAX_PLANES] - 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 num_planes - field. - - - __u8 - num_planes - Number of planes (i.e. separate memory buffers) for this format - and the number of valid entries in the - plane_fmt array. - - - __u8 - flags - Flags set by the application or driver, see . - - - &v4l2-ycbcr-encoding; - ycbcr_enc - This information supplements the -colorspace and must be set by the driver for -capture streams and by the application for output streams, -see . - - - &v4l2-quantization; - quantization - This information supplements the -colorspace and must be set by the driver for -capture streams and by the application for output streams, -see . - - - &v4l2-xfer-func; - xfer_func - This information supplements the -colorspace and must be set by the driver for -capture streams and by the application for output streams, -see . - - - __u8 - reserved[7] - Reserved for future extensions. Should be zeroed by drivers - and applications. - - - -
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- Standard Image Formats - - 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. - - 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. - - Even so, ultimately, some standard formats are needed, so -the V4L2 specification would not be complete without well-defined -standard formats. - - 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. - - In V4L2 each format has an identifier which looks like -PIX_FMT_XXX, defined in the videodev2.h header file. These identifiers -represent four character (FourCC) codes -which are also listed below, however they are not the same as those -used in the Windows world. - - 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". -
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- Colorspaces - - '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 means -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. - - 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... - - 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. - - 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. - - 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 CIE XYZ tristimulus 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]. - - The Y value in the CIE XYZ colorspace corresponds to luminance. Often -the CIE XYZ colorspace is transformed to the normalized CIE xyY colorspace: - - x = X / (X + Y + Z) - y = Y / (X + Y + Z) - - 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. - - - 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 -color primaries are part of what defines a colorspace. - - 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. - - 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. - - - 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. - - 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. - - 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. - - 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 not 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]. - - 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. - - 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. - - 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. - - If you want to read more about colors and colorspaces, then the -following resources are useful: is a good practical -book for video engineers, has a much broader scope and -describes many more aspects of color (physics, chemistry, biology, etc.). -The http://www.brucelindbloom.com -website is an excellent resource, especially with respect to the mathematics behind -colorspace conversions. The wikipedia CIE 1931 colorspace article -is also very useful. -
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- Defining Colorspaces in V4L2 - 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. - - - V4L2 Colorspaces - - &cs-def; - - - Identifier - Details - - - - - V4L2_COLORSPACE_DEFAULT - The default colorspace. This can be used by applications to let the - driver fill in the colorspace. - - - V4L2_COLORSPACE_SMPTE170M - See . - - - V4L2_COLORSPACE_REC709 - See . - - - V4L2_COLORSPACE_SRGB - See . - - - V4L2_COLORSPACE_ADOBERGB - See . - - - V4L2_COLORSPACE_BT2020 - See . - - - V4L2_COLORSPACE_DCI_P3 - See . - - - V4L2_COLORSPACE_SMPTE240M - See . - - - V4L2_COLORSPACE_470_SYSTEM_M - See . - - - V4L2_COLORSPACE_470_SYSTEM_BG - See . - - - V4L2_COLORSPACE_JPEG - See . - - - V4L2_COLORSPACE_RAW - 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. - - - -
- - - V4L2 Transfer Function - - &cs-def; - - - Identifier - Details - - - - - V4L2_XFER_FUNC_DEFAULT - Use the default transfer function as defined by the colorspace. - - - V4L2_XFER_FUNC_709 - Use the Rec. 709 transfer function. - - - V4L2_XFER_FUNC_SRGB - Use the sRGB transfer function. - - - V4L2_XFER_FUNC_ADOBERGB - Use the AdobeRGB transfer function. - - - V4L2_XFER_FUNC_SMPTE240M - Use the SMPTE 240M transfer function. - - - V4L2_XFER_FUNC_NONE - Do not use a transfer function (i.e. use linear RGB values). - - - V4L2_XFER_FUNC_DCI_P3 - Use the DCI-P3 transfer function. - - - V4L2_XFER_FUNC_SMPTE2084 - Use the SMPTE 2084 transfer function. - - - -
- - - V4L2 Y'CbCr Encodings - - &cs-def; - - - Identifier - Details - - - - - V4L2_YCBCR_ENC_DEFAULT - Use the default Y'CbCr encoding as defined by the colorspace. - - - V4L2_YCBCR_ENC_601 - Use the BT.601 Y'CbCr encoding. - - - V4L2_YCBCR_ENC_709 - Use the Rec. 709 Y'CbCr encoding. - - - V4L2_YCBCR_ENC_XV601 - Use the extended gamut xvYCC BT.601 encoding. - - - V4L2_YCBCR_ENC_XV709 - Use the extended gamut xvYCC Rec. 709 encoding. - - - V4L2_YCBCR_ENC_SYCC - Use the extended gamut sYCC encoding. - - - V4L2_YCBCR_ENC_BT2020 - Use the default non-constant luminance BT.2020 Y'CbCr encoding. - - - V4L2_YCBCR_ENC_BT2020_CONST_LUM - Use the constant luminance BT.2020 Yc'CbcCrc encoding. - - - -
- - - V4L2 Quantization Methods - - &cs-def; - - - Identifier - Details - - - - - V4L2_QUANTIZATION_DEFAULT - 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. - - - V4L2_QUANTIZATION_FULL_RANGE - 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). - - - V4L2_QUANTIZATION_LIM_RANGE - 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]. - - - - -
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- Detailed Colorspace Descriptions -
- Colorspace SMPTE 170M (<constant>V4L2_COLORSPACE_SMPTE170M</constant>) - The standard defines the colorspace used by NTSC and PAL and by SDTV -in general. The default transfer function is V4L2_XFER_FUNC_709. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_601. -The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and -the white reference are: - - SMPTE 170M Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.630 - 0.340 - - - Green - 0.310 - 0.595 - - - Blue - 0.155 - 0.070 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- 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. - - - The transfer function defined for SMPTE 170M is the same as the -one defined in Rec. 709. - - L' = -1.099(-L)0.45 + 0.099 for L ≤ -0.018 - L' = 4.5L for -0.018 < L < 0.018 - L' = 1.099L0.45 - 0.099 for L ≥ 0.018 - - - - - - Inverse Transfer function: - - L = -((L' - 0.099) / -1.099)1/0.45 for L' ≤ -0.081 - L = L' / 4.5 for -0.081 < L' < 0.081 - L = ((L' + 0.099) / 1.099)1/0.45 for L' ≥ 0.081 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with -the following V4L2_YCBCR_ENC_601 encoding: - - Y' = 0.299R' + 0.587G' + 0.114B' - Cb = -0.169R' - 0.331G' + 0.5B' - Cr = 0.5R' - 0.419G' - 0.081B' - - - - 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 standard and this colorspace is sometimes called BT.601 as well, even -though BT.601 does not mention any color primaries. - The default quantization is limited range, but full range is possible although -rarely seen. -
- -
- Colorspace Rec. 709 (<constant>V4L2_COLORSPACE_REC709</constant>) - The standard defines the colorspace used by HDTV in general. -The default transfer function is V4L2_XFER_FUNC_709. The default -Y'CbCr encoding is V4L2_YCBCR_ENC_709. The default Y'CbCr quantization is -limited range. The chromaticities of the primary colors and the white reference are: - - Rec. 709 Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.640 - 0.330 - - - Green - 0.300 - 0.600 - - - Blue - 0.150 - 0.060 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- The full name of this standard is Rec. ITU-R BT.709-5. - - - Transfer function. Normally L is in the range [0…1], but for the extended -gamut xvYCC encoding values outside that range are allowed. - - L' = -1.099(-L)0.45 + 0.099 for L ≤ -0.018 - L' = 4.5L for -0.018 < L < 0.018 - L' = 1.099L0.45 - 0.099 for L ≥ 0.018 - - - - - - Inverse Transfer function: - - L = -((L' - 0.099) / -1.099)1/0.45 for L' ≤ -0.081 - L = L' / 4.5 for -0.081 < L' < 0.081 - L = ((L' + 0.099) / 1.099)1/0.45 for L' ≥ 0.081 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the following -V4L2_YCBCR_ENC_709 encoding: - - Y' = 0.2126R' + 0.7152G' + 0.0722B' - Cb = -0.1146R' - 0.3854G' + 0.5B' - Cr = 0.5R' - 0.4542G' - 0.0458B' - - - - Y' is clamped to the range [0…1] and Cb and Cr are -clamped to the range [-0.5…0.5]. - The default quantization is limited range, but full range is possible although -rarely seen. - The V4L2_YCBCR_ENC_709 encoding described above is the default -for this colorspace, but it can be overridden with V4L2_YCBCR_ENC_601, in which -case the BT.601 Y'CbCr encoding is used. - Two additional extended gamut Y'CbCr encodings are also possible with this colorspace: - - - The xvYCC 709 encoding (V4L2_YCBCR_ENC_XV709, ) -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: - - Y' = (219 / 256) * (0.2126R' + 0.7152G' + 0.0722B') + (16 / 256) - Cb = (224 / 256) * (-0.1146R' - 0.3854G' + 0.5B') - Cr = (224 / 256) * (0.5R' - 0.4542G' - 0.0458B') - - - - - - The xvYCC 601 encoding (V4L2_YCBCR_ENC_XV601, ) 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: - - Y' = (219 / 256) * (0.299R' + 0.587G' + 0.114B') + (16 / 256) - Cb = (224 / 256) * (-0.169R' - 0.331G' + 0.5B') - Cr = (224 / 256) * (0.5R' - 0.419G' - 0.081B') - - - - 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 V4L2_YCBCR_ENC_XV709 or V4L2_YCBCR_ENC_XV601. -The xvYCC encodings always use full range quantization. -
- -
- Colorspace sRGB (<constant>V4L2_COLORSPACE_SRGB</constant>) - The standard defines the colorspace used by most webcams -and computer graphics. The default transfer function is V4L2_XFER_FUNC_SRGB. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_SYCC. The default Y'CbCr -quantization is full range. The chromaticities of the primary colors and the white -reference are: - - sRGB Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.640 - 0.330 - - - Green - 0.300 - 0.600 - - - Blue - 0.150 - 0.060 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- These chromaticities are identical to the Rec. 709 colorspace. - - - Transfer function. Note that negative values for L are only used by the Y'CbCr conversion. - - L' = -1.055(-L)1/2.4 + 0.055 for L < -0.0031308 - L' = 12.92L for -0.0031308 ≤ L ≤ 0.0031308 - L' = 1.055L1/2.4 - 0.055 for 0.0031308 < L ≤ 1 - - - - Inverse Transfer function: - - L = -((-L' + 0.055) / 1.055)2.4 for L' < -0.04045 - L = L' / 12.92 for -0.04045 ≤ L' ≤ 0.04045 - L = ((L' + 0.055) / 1.055)2.4 for L' > 0.04045 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the following -V4L2_YCBCR_ENC_SYCC encoding as defined by : - - Y' = 0.2990R' + 0.5870G' + 0.1140B' - Cb = -0.1687R' - 0.3313G' + 0.5B' - Cr = 0.5R' - 0.4187G' - 0.0813B' - - - - Y' is clamped to the range [0…1] and Cb and Cr are clamped -to the range [-0.5…0.5]. The V4L2_YCBCR_ENC_SYCC quantization is always -full range. Although this Y'CbCr encoding looks very similar to the V4L2_YCBCR_ENC_XV601 -encoding, it is not. The V4L2_YCBCR_ENC_XV601 scales and offsets the Y'CbCr -values before quantization, but this encoding does not do that. -
- -
- Colorspace Adobe RGB (<constant>V4L2_COLORSPACE_ADOBERGB</constant>) - The standard defines the colorspace used by computer graphics -that use the AdobeRGB colorspace. This is also known as the standard. -The default transfer function is V4L2_XFER_FUNC_ADOBERGB. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_601. The default Y'CbCr -quantization is limited range. The chromaticities of the primary colors and the white reference -are: - - Adobe RGB Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.6400 - 0.3300 - - - Green - 0.2100 - 0.7100 - - - Blue - 0.1500 - 0.0600 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- - - Transfer function: - - L' = L1/2.19921875 - - - - Inverse Transfer function: - - L = L'2.19921875 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the -following V4L2_YCBCR_ENC_601 encoding: - - Y' = 0.299R' + 0.587G' + 0.114B' - Cb = -0.169R' - 0.331G' + 0.5B' - Cr = 0.5R' - 0.419G' - 0.081B' - - - - 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. -
- -
- Colorspace BT.2020 (<constant>V4L2_COLORSPACE_BT2020</constant>) - The standard defines the colorspace used by Ultra-high definition -television (UHDTV). The default transfer function is V4L2_XFER_FUNC_709. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_BT2020. -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: - - BT.2020 Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.708 - 0.292 - - - Green - 0.170 - 0.797 - - - Blue - 0.131 - 0.046 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- - - Transfer function (same as Rec. 709): - - L' = 4.5L for 0 ≤ L < 0.018 - L' = 1.099L0.45 - 0.099 for 0.018 ≤ L ≤ 1 - - - - Inverse Transfer function: - - L = L' / 4.5 for L' < 0.081 - L = ((L' + 0.099) / 1.099)1/0.45 for L' ≥ 0.081 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the -following V4L2_YCBCR_ENC_BT2020 encoding: - - Y' = 0.2627R' + 0.6780G' + 0.0593B' - Cb = -0.1396R' - 0.3604G' + 0.5B' - Cr = 0.5R' - 0.4598G' - 0.0402B' - - - - 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. - There is also an alternate constant luminance R'G'B' to Yc'CbcCrc -(V4L2_YCBCR_ENC_BT2020_CONST_LUM) encoding: - - - Luma: - - Yc' = (0.2627R + 0.6780G + 0.0593B)' - - - - - - B' - Yc' ≤ 0: - - Cbc = (B' - Yc') / 1.9404 - - - - - - B' - Yc' > 0: - - Cbc = (B' - Yc') / 1.5816 - - - - - - R' - Yc' ≤ 0: - - Crc = (R' - Y') / 1.7184 - - - - - - R' - Yc' > 0: - - Crc = (R' - Y') / 0.9936 - - - - 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. -
- -
- Colorspace DCI-P3 (<constant>V4L2_COLORSPACE_DCI_P3</constant>) - The standard defines the colorspace used by cinema -projectors that use the DCI-P3 colorspace. -The default transfer function is V4L2_XFER_FUNC_DCI_P3. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_709. 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: - - DCI-P3 Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.6800 - 0.3200 - - - Green - 0.2650 - 0.6900 - - - Blue - 0.1500 - 0.0600 - - - White Reference - 0.3140 - 0.3510 - - - -
- - - Transfer function: - - L' = L1/2.6 - - - - Inverse Transfer function: - - L = L'2.6 - - - - Y'CbCr encoding is not specified. V4L2 defaults to Rec. 709. -
- -
- Colorspace SMPTE 240M (<constant>V4L2_COLORSPACE_SMPTE240M</constant>) - The 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 V4L2_XFER_FUNC_SMPTE240M. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_SMPTE240M. -The default Y'CbCr quantization is limited range. The chromaticities of the primary colors and the -white reference are: - - SMPTE 240M Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.630 - 0.340 - - - Green - 0.310 - 0.595 - - - Blue - 0.155 - 0.070 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- These chromaticities are identical to the SMPTE 170M colorspace. - - - Transfer function: - - L' = 4L for 0 ≤ L < 0.0228 - L' = 1.1115L0.45 - 0.1115 for 0.0228 ≤ L ≤ 1 - - - - Inverse Transfer function: - - L = L' / 4 for 0 ≤ L' < 0.0913 - L = ((L' + 0.1115) / 1.1115)1/0.45 for L' ≥ 0.0913 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the -following V4L2_YCBCR_ENC_SMPTE240M encoding: - - Y' = 0.2122R' + 0.7013G' + 0.0865B' - Cb = -0.1161R' - 0.3839G' + 0.5B' - Cr = 0.5R' - 0.4451G' - 0.0549B' - - - - 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. -
- -
- Colorspace NTSC 1953 (<constant>V4L2_COLORSPACE_470_SYSTEM_M</constant>) - 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 V4L2_XFER_FUNC_709. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_601. -The default Y'CbCr quantization is limited range. -The chromaticities of the primary colors and the white reference are: - - NTSC 1953 Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.67 - 0.33 - - - Green - 0.21 - 0.71 - - - Blue - 0.14 - 0.08 - - - White Reference (C) - 0.310 - 0.316 - - - -
- 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. - - - The transfer function was never properly defined for NTSC 1953. The -Rec. 709 transfer function is recommended in the literature: - - L' = 4.5L for 0 ≤ L < 0.018 - L' = 1.099L0.45 - 0.099 for 0.018 ≤ L ≤ 1 - - - - Inverse Transfer function: - - L = L' / 4.5 for L' < 0.081 - L = ((L' + 0.099) / 1.099)1/0.45 for L' ≥ 0.081 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the -following V4L2_YCBCR_ENC_601 encoding: - - Y' = 0.299R' + 0.587G' + 0.114B' - Cb = -0.169R' - 0.331G' + 0.5B' - Cr = 0.5R' - 0.419G' - 0.081B' - - - - 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. -
- -
- Colorspace EBU Tech. 3213 (<constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant>) - The 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 V4L2_XFER_FUNC_709. -The default Y'CbCr encoding is V4L2_YCBCR_ENC_601. -The default Y'CbCr quantization is limited range. -The chromaticities of the primary colors and the white reference are: - - EBU Tech. 3213 Chromaticities - - &cs-str; - - - Color - x - y - - - - - Red - 0.64 - 0.33 - - - Green - 0.29 - 0.60 - - - Blue - 0.15 - 0.06 - - - White Reference (D65) - 0.3127 - 0.3290 - - - -
- - - The transfer function was never properly defined for this colorspace. -The Rec. 709 transfer function is recommended in the literature: - - L' = 4.5L for 0 ≤ L < 0.018 - L' = 1.099L0.45 - 0.099 for 0.018 ≤ L ≤ 1 - - - - Inverse Transfer function: - - L = L' / 4.5 for L' < 0.081 - L = ((L' + 0.099) / 1.099)1/0.45 for L' ≥ 0.081 - - - - - - The luminance (Y') and color difference (Cb and Cr) are obtained with the -following V4L2_YCBCR_ENC_601 encoding: - - Y' = 0.299R' + 0.587G' + 0.114B' - Cb = -0.169R' - 0.331G' + 0.5B' - Cr = 0.5R' - 0.419G' - 0.081B' - - - - 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. -
- -
- Colorspace JPEG (<constant>V4L2_COLORSPACE_JPEG</constant>) - 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 V4L2_XFER_FUNC_SRGB. The Y'CbCr encoding is -V4L2_YCBCR_ENC_601 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]. - 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 V4L2_COLORSPACE_JPEG can be considered to be -an abbreviation for V4L2_COLORSPACE_SRGB, V4L2_YCBCR_ENC_601 -and V4L2_QUANTIZATION_FULL_RANGE. -
- -
- -
- Detailed Transfer Function Descriptions -
- Transfer Function SMPTE 2084 (<constant>V4L2_XFER_FUNC_SMPTE2084</constant>) - The standard defines the transfer function used by -High Dynamic Range content. - - - Constants: - - m1 = (2610 / 4096) / 4 - m2 = (2523 / 4096) * 128 - c1 = 3424 / 4096 - c2 = (2413 / 4096) * 32 - c3 = (2392 / 4096) * 32 - - - - Transfer function: - - L' = ((c1 + c2 * Lm1) / (1 + c3 * Lm1))m2 - - - - - - Inverse Transfer function: - - L = (max(L'1/m2 - c1, 0) / (c2 - c3 * L'1/m2))1/m1 - - - -
-
- -
- Indexed Format - - In this format each pixel is represented by an 8 bit index -into a 256 entry ARGB palette. It is intended for Video Output Overlays only. There are no ioctls to -access the palette, this must be done with ioctls of the Linux framebuffer API. - - - Indexed Image Format - - - - - - - - - - - - - - - - - - - - - Identifier - Code -   - Byte 0 - - -   -   - Bit - 7 - 6 - 5 - 4 - 3 - 2 - 1 - 0 - - - - - V4L2_PIX_FMT_PAL8 - 'PAL8' - - i7 - i6 - i5 - i4 - i3 - i2 - i1 - i0 - - - -
-
- -
- RGB Formats - - &sub-packed-rgb; - &sub-sbggr8; - &sub-sgbrg8; - &sub-sgrbg8; - &sub-srggb8; - &sub-sbggr16; - &sub-srggb10; - &sub-srggb10p; - &sub-srggb10alaw8; - &sub-srggb10dpcm8; - &sub-srggb12; -
- -
- YUV Formats - - 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 color difference signals, this way -the green component can be reconstructed by subtracting from the -brightness component. See 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. - - &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; -
- -
- Depth Formats - Depth data provides distance to points, mapped onto the image plane - - - &sub-z16; -
- -
- Compressed Formats - - - Compressed Image Formats - - &cs-def; - - - Identifier - Code - Details - - - - - V4L2_PIX_FMT_JPEG - 'JPEG' - TBD. See also &VIDIOC-G-JPEGCOMP;, - &VIDIOC-S-JPEGCOMP;. - - - V4L2_PIX_FMT_MPEG - 'MPEG' - MPEG multiplexed stream. The actual format is determined by -extended control V4L2_CID_MPEG_STREAM_TYPE, see -. - - - V4L2_PIX_FMT_H264 - 'H264' - H264 video elementary stream with start codes. - - - V4L2_PIX_FMT_H264_NO_SC - 'AVC1' - H264 video elementary stream without start codes. - - - V4L2_PIX_FMT_H264_MVC - 'M264' - H264 MVC video elementary stream. - - - V4L2_PIX_FMT_H263 - 'H263' - H263 video elementary stream. - - - V4L2_PIX_FMT_MPEG1 - 'MPG1' - MPEG1 video elementary stream. - - - V4L2_PIX_FMT_MPEG2 - 'MPG2' - MPEG2 video elementary stream. - - - V4L2_PIX_FMT_MPEG4 - 'MPG4' - MPEG4 video elementary stream. - - - V4L2_PIX_FMT_XVID - 'XVID' - Xvid video elementary stream. - - - V4L2_PIX_FMT_VC1_ANNEX_G - 'VC1G' - VC1, SMPTE 421M Annex G compliant stream. - - - V4L2_PIX_FMT_VC1_ANNEX_L - 'VC1L' - VC1, SMPTE 421M Annex L compliant stream. - - - V4L2_PIX_FMT_VP8 - 'VP80' - VP8 video elementary stream. - - - -
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- -
- SDR Formats - - These formats are used for SDR -interface only. - - &sub-sdr-cu08; - &sub-sdr-cu16le; - &sub-sdr-cs08; - &sub-sdr-cs14le; - &sub-sdr-ru12le; - -
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- Reserved Format Identifiers - - 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 videodev2.h -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. - - - Reserved Image Formats - - &cs-def; - - - Identifier - Code - Details - - - - - V4L2_PIX_FMT_DV - 'dvsd' - unknown - - - V4L2_PIX_FMT_ET61X251 - 'E625' - Compressed format of the ET61X251 driver. - - - V4L2_PIX_FMT_HI240 - 'HI24' - 8 bit RGB format used by the BTTV driver. - - - V4L2_PIX_FMT_HM12 - 'HM12' - YUV 4:2:0 format used by the -IVTV driver, -http://www.ivtvdriver.org/The format is documented in the -kernel sources in the file Documentation/video4linux/cx2341x/README.hm12 - - - - V4L2_PIX_FMT_CPIA1 - 'CPIA' - YUV format used by the gspca cpia1 driver. - - - V4L2_PIX_FMT_JPGL - 'JPGL' - JPEG-Light format (Pegasus Lossless JPEG) - used in Divio webcams NW 80x. - - - V4L2_PIX_FMT_SPCA501 - 'S501' - YUYV per line used by the gspca driver. - - - V4L2_PIX_FMT_SPCA505 - 'S505' - YYUV per line used by the gspca driver. - - - V4L2_PIX_FMT_SPCA508 - 'S508' - YUVY per line used by the gspca driver. - - - V4L2_PIX_FMT_SPCA561 - 'S561' - Compressed GBRG Bayer format used by the gspca driver. - - - V4L2_PIX_FMT_PAC207 - 'P207' - Compressed BGGR Bayer format used by the gspca driver. - - - V4L2_PIX_FMT_MR97310A - 'M310' - Compressed BGGR Bayer format used by the gspca driver. - - - V4L2_PIX_FMT_JL2005BCD - 'JL20' - JPEG compressed RGGB Bayer format used by the gspca driver. - - - V4L2_PIX_FMT_OV511 - 'O511' - OV511 JPEG format used by the gspca driver. - - - V4L2_PIX_FMT_OV518 - 'O518' - OV518 JPEG format used by the gspca driver. - - - V4L2_PIX_FMT_PJPG - 'PJPG' - Pixart 73xx JPEG format used by the gspca driver. - - - V4L2_PIX_FMT_SE401 - 'S401' - Compressed RGB format used by the gspca se401 driver - - - V4L2_PIX_FMT_SQ905C - '905C' - Compressed RGGB bayer format used by the gspca driver. - - - V4L2_PIX_FMT_MJPEG - 'MJPG' - Compressed format used by the Zoran driver - - - V4L2_PIX_FMT_PWC1 - 'PWC1' - Compressed format of the PWC driver. - - - V4L2_PIX_FMT_PWC2 - 'PWC2' - Compressed format of the PWC driver. - - - V4L2_PIX_FMT_SN9C10X - 'S910' - Compressed format of the SN9C102 driver. - - - V4L2_PIX_FMT_SN9C20X_I420 - 'S920' - YUV 4:2:0 format of the gspca sn9c20x driver. - - - V4L2_PIX_FMT_SN9C2028 - 'SONX' - Compressed GBRG bayer format of the gspca sn9c2028 driver. - - - V4L2_PIX_FMT_STV0680 - 'S680' - Bayer format of the gspca stv0680 driver. - - - V4L2_PIX_FMT_WNVA - 'WNVA' - Used by the Winnov Videum driver, -http://www.thedirks.org/winnov/ - - - V4L2_PIX_FMT_TM6000 - 'TM60' - Used by Trident tm6000 - - - V4L2_PIX_FMT_CIT_YYVYUY - 'CITV' - Used by xirlink CIT, found at IBM webcams. - Uses one line of Y then 1 line of VYUY - - - - V4L2_PIX_FMT_KONICA420 - 'KONI' - Used by Konica webcams. - YUV420 planar in blocks of 256 pixels. - - - - V4L2_PIX_FMT_YYUV - 'YYUV' - unknown - - - V4L2_PIX_FMT_Y4 - 'Y04 ' - Old 4-bit greyscale format. Only the most significant 4 bits of each byte are used, -the other bits are set to 0. - - - V4L2_PIX_FMT_Y6 - 'Y06 ' - Old 6-bit greyscale format. Only the most significant 6 bits of each byte are used, -the other bits are set to 0. - - - V4L2_PIX_FMT_S5C_UYVY_JPG - 'S5CI' - 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. -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. -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. - - - - -
- - - Format Flags - - &cs-def; - - - V4L2_PIX_FMT_FLAG_PREMUL_ALPHA - 0x00000001 - The color values are premultiplied by the alpha channel -value. For example, if a light blue pixel with 50% transparency was described by -RGBA values (128, 192, 255, 128), the same pixel described with premultiplied -colors would be described by RGBA values (64, 96, 128, 128) - - - -
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