diff --git a/Documentation/DocBook/media/v4l/biblio.xml b/Documentation/DocBook/media/v4l/biblio.xml
index d2eb79e41a01..7ff01a23c2fe 100644
--- a/Documentation/DocBook/media/v4l/biblio.xml
+++ b/Documentation/DocBook/media/v4l/biblio.xml
@@ -178,6 +178,75 @@ Signal - NTSC for Studio Applications"
1125-Line High-Definition Production"
+
+ sRGB
+
+ International Electrotechnical Commission
+(http://www.iec.ch)
+
+ IEC 61966-2-1 ed1.0 "Multimedia systems and equipment - Colour measurement
+and management - Part 2-1: Colour management - Default RGB colour space - sRGB"
+
+
+
+ sYCC
+
+ International Electrotechnical Commission
+(http://www.iec.ch)
+
+ IEC 61966-2-1-am1 ed1.0 "Amendment 1 - Multimedia systems and equipment - Colour measurement
+and management - Part 2-1: Colour management - Default RGB colour space - sRGB"
+
+
+
+ xvYCC
+
+ International Electrotechnical Commission
+(http://www.iec.ch)
+
+ IEC 61966-2-4 ed1.0 "Multimedia systems and equipment - Colour measurement
+and management - Part 2-4: Colour management - Extended-gamut YCC colour space for video
+applications - xvYCC"
+
+
+
+ AdobeRGB
+
+ Adobe Systems Incorporated (http://www.adobe.com)
+
+ Adobe© RGB (1998) Color Image Encoding Version 2005-05
+
+
+
+ opRGB
+
+ International Electrotechnical Commission
+(http://www.iec.ch)
+
+ IEC 61966-2-5 "Multimedia systems and equipment - Colour measurement
+and management - Part 2-5: Colour management - Optional RGB colour space - opRGB"
+
+
+
+ ITU BT.2020
+
+ International Telecommunication Union (http://www.itu.ch)
+
+ ITU-R Recommendation BT.2020 (08/2012) "Parameter values for ultra-high
+definition television systems for production and international programme exchange"
+
+
+
+
+ EBU Tech 3213
+
+ European Broadcast Union (http://www.ebu.ch)
+
+ E.B.U. Standard for Chromaticity Tolerances for Studio Monitors"
+
+
IEC 62106
@@ -266,4 +335,20 @@ in the frequency range from 87,5 to 108,0 MHz
Version 1, Revision 2
+
+ poynton
+
+ Charles Poynton
+
+ Digital Video and HDTV, Algorithms and Interfaces
+
+
+
+ colimg
+
+ Erik Reinhard et al.
+
+ Color Imaging: Fundamentals and Applications
+
+
diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml b/Documentation/DocBook/media/v4l/pixfmt.xml
index df5b23d46552..ccf6053c1ae4 100644
--- a/Documentation/DocBook/media/v4l/pixfmt.xml
+++ b/Documentation/DocBook/media/v4l/pixfmt.xml
@@ -296,343 +296,1003 @@ in the 2-planar version or with each component in its own buffer in the
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...
-
-
-
- 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.
-
-
-
-
+ 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.
-
- ITU-R Rec. BT.601 color conversion
+ 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.
- Forward Transformation
+ 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].
-
-int ER, EG, EB; /* gamma corrected RGB input [0;255] */
-int Y1, Cb, Cr; /* output [0;255] */
+ The Y value in the CIE XYZ colorspace corresponds to luminance. Often
+the CIE XYZ colorspace is transformed to the normalized CIE xyY colorspace:
-double r, g, b; /* temporaries */
-double y1, pb, pr;
+ x = X / (X + Y + Z)
+ y = Y / (X + Y + Z)
-int
-clamp (double x)
-{
- int r = x; /* round to nearest */
+ 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.
+
- if (r < 0) return 0;
- else if (r > 255) return 255;
- else return r;
-}
+ 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.
-r = ER / 255.0;
-g = EG / 255.0;
-b = EB / 255.0;
+ 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.
-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;
+ 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.
+
-Y1 = clamp (219 * y1 + 16);
-Cb = clamp (224 * pb + 128);
-Cr = clamp (224 * pr + 128);
+ 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.
-/* or shorter */
+ 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.
-y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB;
+ 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.
-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);
-
+ 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].
- Inverse Transformation
+ 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.
-
-int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */
-int ER, EG, EB; /* output [0;255] */
+ 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.
-double r, g, b; /* temporaries */
-double y1, pb, pr;
+ 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.
-int
-clamp (double x)
-{
- int r = x; /* round to nearest */
+ 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.
+
- if (r < 0) return 0;
- else if (r > 255) return 255;
- else return r;
-}
+
+ Defining Colorspaces in V4L2
+ In V4L2 colorspaces are defined by three values. The first is the colorspace
+identifier (&v4l2-colorspace;) which defines the chromaticities, the transfer
+function, the default Y'CbCr encoding and the default quantization method. The second
+is the Y'CbCr encoding identifier (&v4l2-ycbcr-encoding;) to specify non-standard
+Y'CbCr encodings and the third 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 always full range for all colorspaces,
+so this won't be mentioned explicitly for each colorspace description.
-y1 = (Y1 - 16) / 219.0;
-pb = (Cb - 128) / 224.0;
-pr = (Cr - 128) / 224.0;
-
-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
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+ 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_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
+ 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
-
-
- 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_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
-
-
- 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
-
-
- 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
+ See .
+
+
+ V4L2_COLORSPACE_ADOBERGB
+ See .
+
+
+ V4L2_COLORSPACE_BT2020
+ See .
+
+
+ V4L2_COLORSPACE_SMPTE240M
+ See .
+
+
+ V4L2_COLORSPACE_470_SYSTEM_M
+ See .
+
+
+ V4L2_COLORSPACE_470_SYSTEM_BG
+ See .
+
+
+ V4L2_COLORSPACE_JPEG
+ See .
+
+
+ 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' 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 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. 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_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.
+ The V4L2_YCBCR_ENC_601 encoding as described above is the
+default for this colorspace, but it can be overridden with V4L2_YCBCR_ENC_709,
+in which case the Rec. 709 Y'CbCr encoding is used.
+
+
+ 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 / 255) * (0.299R' + 0.587G' + 0.114B') + (16 / 255)
+ Cb = (224 / 255) * (-0.169R' - 0.331G' + 0.5B')
+ Cr = (224 / 255) * (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 encoding can also be used by selecting
+V4L2_YCBCR_ENC_XV709. The xvYCC encodings always use full range
+quantization.
+
+
+
+ Colorspace Rec. 709 (<constant>V4L2_COLORSPACE_REC709</constant>)
+ The standard defines the colorspace used by HDTV in general. 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.
+
+
+ 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 / 255) * (0.2126R' + 0.7152G' + 0.0722B') + (16 / 255)
+ Cb = (224 / 255) * (-0.1146R' - 0.3854G' + 0.5B')
+ Cr = (224 / 255) * (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 non-standard xvYCC 601 encoding can also be used by
+selecting 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 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 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 Y'CbCr encoding is V4L2_YCBCR_ENC_BT2020.
+The default Y'CbCr quantization is limited range. 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' + 0.6789G' + 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 + 0.6789G + 0.0593B)'
+
+
+
+
+
+ B' - Yc' ≤ 0:
+
+ Cbc = (B' - Y') / 1.9404
+
+
+
+
+
+ B' - Yc' > 0:
+
+ Cbc = (B' - Y') / 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 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 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 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 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 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.
+
+