--- zzzz-none-000/linux-3.10.107/Documentation/DocBook/media/v4l/pixfmt.xml 2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/Documentation/DocBook/media/v4l/pixfmt.xml 2021-02-04 17:41:59.000000000 +0000
@@ -25,7 +25,12 @@
__u32height
- Image height in pixels.
+ 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
@@ -54,7 +59,7 @@
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 details see .
+For more details on fields see .
__u32
@@ -75,13 +80,16 @@
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 largest
+bytesperline value applies to the first
plane and is divided by the same factor as the
-width field for any smaller planes. For
+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.
+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
@@ -97,15 +105,65 @@
&v4l2-colorspace;colorspaceThis information supplements the
-pixelformat and must be set by the driver,
+pixelformat and must be set by the driver for
+capture streams and by the application for output streams,
see .__u32priv
- Reserved for custom (driver defined) additional
-information about formats. When not used drivers and applications must
-set this field to zero.
+ 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 .
@@ -132,16 +190,16 @@
- __u16
+ __u32bytesperlineDistance in bytes between the leftmost pixels in two adjacent
- lines.
+ lines. See &v4l2-pix-format;.
__u16
- reserved[7]
- Reserved for future extensions. Should be zeroed by the
- application.
+ reserved[6]
+ Reserved for future extensions. Should be zeroed by drivers and
+ applications.
@@ -154,12 +212,12 @@
__u32width
- Image width in pixels.
+ Image width in pixels. See &v4l2-pix-format;.__u32height
- Image height in pixels.
+ Image height in pixels. See &v4l2-pix-format;.__u32
@@ -192,11 +250,41 @@
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[11]
- Reserved for future extensions. Should be zeroed by the
- application.
+ reserved[7]
+ Reserved for future extensions. Should be zeroed by drivers
+ and applications.
@@ -239,7 +327,7 @@
In V4L2 each format has an identifier which looks like
PIX_FMT_XXX, defined in the videodev.h header file. These identifiers
+linkend="videodev">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.
@@ -256,345 +344,1173 @@
Colorspaces
- [intro]
+ '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.
+
-
-
-
-
-
- Gamma Correction
-
- [to do]
- E'R = f(R)
- E'G = f(G)
- E'B = f(B)
-
-
-
- Construction of luminance and color-difference
-signals
-
- [to do]
- E'Y =
-CoeffR E'R
-+ CoeffG E'G
-+ CoeffB E'B
- (E'R - E'Y) = E'R
-- CoeffR E'R
-- CoeffG E'G
-- CoeffB E'B
- (E'B - E'Y) = E'B
-- CoeffR E'R
-- CoeffG E'G
-- CoeffB E'B
-
-
-
- Re-normalized color-difference signals
-
- The color-difference signals are scaled back to unity
-range [-0.5;+0.5]:
- KB = 0.5 / (1 - CoeffB)
- KR = 0.5 / (1 - CoeffR)
- PB =
-KB (E'B - E'Y) =
- 0.5 (CoeffR / CoeffB) E'R
-+ 0.5 (CoeffG / CoeffB) E'G
-+ 0.5 E'B
- PR =
-KR (E'R - E'Y) =
- 0.5 E'R
-+ 0.5 (CoeffG / CoeffR) E'G
-+ 0.5 (CoeffB / CoeffR) E'B
-
-
-
- Quantization
-
- [to do]
- Y' = (Lum. Levels - 1) · E'Y + Lum. Offset
- CB = (Chrom. Levels - 1)
-· PB + Chrom. Offset
- CR = (Chrom. Levels - 1)
-· PR + Chrom. Offset
- Rounding to the nearest integer and clamping to the range
-[0;255] finally yields the digital color components Y'CbCr
-stored in YUV images.
-
-
-
-
-
-
- ITU-R Rec. BT.601 color conversion
-
- Forward Transformation
-
-
-int ER, EG, EB; /* gamma corrected RGB input [0;255] */
-int Y1, Cb, Cr; /* output [0;255] */
-
-double r, g, b; /* temporaries */
-double y1, pb, pr;
-
-int
-clamp (double x)
-{
- int r = x; /* round to nearest */
-
- if (r < 0) return 0;
- else if (r > 255) return 255;
- else return r;
-}
-
-r = ER / 255.0;
-g = EG / 255.0;
-b = EB / 255.0;
-
-y1 = 0.299 * r + 0.587 * g + 0.114 * b;
-pb = -0.169 * r - 0.331 * g + 0.5 * b;
-pr = 0.5 * r - 0.419 * g - 0.081 * b;
-
-Y1 = clamp (219 * y1 + 16);
-Cb = clamp (224 * pb + 128);
-Cr = clamp (224 * pr + 128);
-
-/* or shorter */
-
-y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB;
-
-Y1 = clamp ( (219 / 255.0) * y1 + 16);
-Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128);
-Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128);
-
-
- Inverse Transformation
-
-
-int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */
-int ER, EG, EB; /* output [0;255] */
-
-double r, g, b; /* temporaries */
-double y1, pb, pr;
-
-int
-clamp (double x)
-{
- int r = x; /* round to nearest */
-
- if (r < 0) return 0;
- else if (r > 255) return 255;
- else return r;
-}
-
-y1 = (255 / 219.0) * (Y1 - 16);
-pb = (255 / 224.0) * (Cb - 128);
-pr = (255 / 224.0) * (Cr - 128);
-
-r = 1.0 * y1 + 0 * pb + 1.402 * pr;
-g = 1.0 * y1 - 0.344 * pb - 0.714 * pr;
-b = 1.0 * y1 + 1.772 * pb + 0 * pr;
-
-ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */
-EG = clamp (g * 255);
-EB = clamp (b * 255);
-
-
-
-
- enum v4l2_colorspace
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+ 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
- Value
- Description
- Chromaticities
- The coordinates of the color primaries are
-given in the CIE system (1931)
-
- White Point
- Gamma Correction
- Luminance E'Y
- Quantization
-
-
- Red
- Green
- Blue
- Y'
- Cb, Cr
+ Identifier
+ Details
- V4L2_COLORSPACE_SMPTE170M
- 1
- NTSC/PAL according to ,
-
- x = 0.630, y = 0.340
- x = 0.310, y = 0.595
- x = 0.155, y = 0.070
- x = 0.3127, y = 0.3290,
- Illuminant D65
- E' = 4.5 I for I ≤0.018,
-1.099 I0.45 - 0.099 for 0.018 < I
- 0.299 E'R
-+ 0.587 E'G
-+ 0.114 E'B
- 219 E'Y + 16
- 224 PB,R + 128
+ V4L2_COLORSPACE_DEFAULT
+ The default colorspace. This can be used by applications to let the
+ driver fill in the colorspace.
- V4L2_COLORSPACE_SMPTE240M
- 2
- 1125-Line (US) HDTV, see
- x = 0.630, y = 0.340
- x = 0.310, y = 0.595
- x = 0.155, y = 0.070
- x = 0.3127, y = 0.3290,
- Illuminant D65
- E' = 4 I for I ≤0.0228,
-1.1115 I0.45 - 0.1115 for 0.0228 < I
- 0.212 E'R
-+ 0.701 E'G
-+ 0.087 E'B
- 219 E'Y + 16
- 224 PB,R + 128
+ V4L2_COLORSPACE_SMPTE170M
+ See .V4L2_COLORSPACE_REC709
- 3
- HDTV and modern devices, see
- x = 0.640, y = 0.330
- x = 0.300, y = 0.600
- x = 0.150, y = 0.060
- x = 0.3127, y = 0.3290,
- Illuminant D65
- E' = 4.5 I for I ≤0.018,
-1.099 I0.45 - 0.099 for 0.018 < I
- 0.2125 E'R
-+ 0.7154 E'G
-+ 0.0721 E'B
- 219 E'Y + 16
- 224 PB,R + 128
+ See .
- V4L2_COLORSPACE_BT878
- 4
- Broken Bt878 extents
- The ubiquitous Bt878 video capture chip
-quantizes E'Y to 238 levels, yielding a range
-of Y' = 16 … 253, unlike Rec. 601 Y' = 16 …
-235. This is not a typo in the Bt878 documentation, it has been
-implemented in silicon. The chroma extents are unclear.
- ,
- ?
- ?
- ?
- ?
- ?
- 0.299 E'R
-+ 0.587 E'G
-+ 0.114 E'B
- 237 E'Y + 16
- 224 PB,R + 128 (probably)
+ 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
- 5
- M/NTSC
- No identifier exists for M/PAL which uses
-the chromaticities of M/NTSC, the remaining parameters are equal to B and
-G/PAL.
- according to ,
- x = 0.67, y = 0.33
- x = 0.21, y = 0.71
- x = 0.14, y = 0.08
- x = 0.310, y = 0.316, Illuminant C
- ?
- 0.299 E'R
-+ 0.587 E'G
-+ 0.114 E'B
- 219 E'Y + 16
- 224 PB,R + 128
+ See .V4L2_COLORSPACE_470_SYSTEM_BG
- 6
- 625-line PAL and SECAM systems according to ,
- x = 0.64, y = 0.33
- x = 0.29, y = 0.60
- x = 0.15, y = 0.06
- x = 0.313, y = 0.329,
-Illuminant D65
- ?
- 0.299 E'R
-+ 0.587 E'G
-+ 0.114 E'B
- 219 E'Y + 16
- 224 PB,R + 128
+ See .V4L2_COLORSPACE_JPEG
- 7
- JPEG Y'CbCr, see ,
- ?
- ?
- ?
- ?
- ?
- 0.299 E'R
-+ 0.587 E'G
-+ 0.114 E'B
- 256 E'Y + 16
- Note JFIF quantizes
-Y'PBPR in range [0;+1] and
-[-0.5;+0.5] to 257 levels, however Y'CbCr signals
-are still clamped to [0;255].
-
- 256 PB,R + 128
+ See .
- V4L2_COLORSPACE_SRGB
- 8
- [?]
- x = 0.640, y = 0.330
- x = 0.300, y = 0.600
- x = 0.150, y = 0.060
- x = 0.3127, y = 0.3290,
- Illuminant D65
- E' = 4.5 I for I ≤0.018,
-1.099 I0.45 - 0.099 for 0.018 < I
- n/a
+ 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].
+
+
+ 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
@@ -673,6 +1589,7 @@
&sub-srggb8;
&sub-sbggr16;
&sub-srggb10;
+ &sub-srggb10p;
&sub-srggb10alaw8;
&sub-srggb10dpcm8;
&sub-srggb12;
@@ -702,6 +1619,7 @@
&sub-y12;
&sub-y10b;
&sub-y16;
+ &sub-y16-be;
&sub-uv8;
&sub-yuyv;
&sub-uyvy;
@@ -718,6 +1636,7 @@
&sub-nv12m;
&sub-nv12mt;
&sub-nv16;
+ &sub-nv16m;
&sub-nv24;
&sub-m420;
@@ -762,7 +1681,7 @@
V4L2_PIX_FMT_H264_MVC
- 'MVC'
+ 'M264'H264 MVC video elementary stream.
@@ -802,7 +1721,7 @@
V4L2_PIX_FMT_VP8
- 'VP8'
+ 'VP80'VP8 video elementary stream.
@@ -810,6 +1729,20 @@
+
+ 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;
+
+
+
Reserved Format Identifiers
@@ -1038,5 +1971,22 @@
+
+
+
+ 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)
+
+
+