january 27, 2005 1 x’y’z’ color encoding for digital cinema distribution glenn kennel hpa...
TRANSCRIPT
January 27, 2005January 27, 2005 11
X’Y’Z’ Color EncodingX’Y’Z’ Color Encodingfor Digital Cinema Distributionfor Digital Cinema Distribution
Glenn KennelGlenn Kennel
HPA Technology RetreatHPA Technology RetreatJanuary 27, 2005 January 27, 2005
22January 27, 2005January 27, 2005
SMPTE Color AHGSMPTE Color AHG
Prinyar BoonPrinyar Boon
Matt CowanMatt Cowan
Chuck HarrisonChuck Harrison
Jim HoustonJim Houston
George JobloveGeorge Joblove
Glenn KennelGlenn Kennel
Howard LukkHoward Lukk
Tom Maier Tom Maier
Arjun RamamurthyArjun Ramamurthy
Jeremy SelanJeremy Selan
John SilvaJohn Silva
Kaz TsujikawaKaz Tsujikawa
Brad WalkerBrad Walker
Ron WilliamsRon Williams
33January 27, 2005January 27, 2005
Color Image EncodingColor Image Encoding
Choosing a Color Space for the DCDMChoosing a Color Space for the DCDM
Why X’Y’Z’?Why X’Y’Z’?
Color in the Overall WorkflowColor in the Overall Workflow
Color Encoding and DecodingColor Encoding and Decoding
Digital Intermediate WorkflowDigital Intermediate Workflow
Video MastersVideo Masters
ConclusionsConclusions
44January 27, 2005January 27, 2005
Basic Requirements for Basic Requirements for DCDM Color EncodingDCDM Color Encoding
One master shall play on all projectors and One master shall play on all projectors and look the same (device independent)look the same (device independent)Open standard with no licensing feesOpen standard with no licensing feesExtensible to wider color gamut and wider Extensible to wider color gamut and wider contrast in future projectorscontrast in future projectorsFuture masters shall be backward Future masters shall be backward compatible with today’s projectorscompatible with today’s projectorsCan be implemented in today’s mastering Can be implemented in today’s mastering environmentenvironment
55January 27, 2005January 27, 2005
Planning for the FuturePlanning for the Future
Today’s Today’s ProjectorsProjectors
Tomorrow’s Tomorrow’s ProjectorsProjectors
IlluminationIllumination XenonXenon Laser?Laser?
PrimariesPrimaries 33 3 or more?3 or more?
Color GamutColor Gamut Similar to filmSimilar to film Wider gamutWider gamut
ContrastContrast 2000:12000:1 Higher contrastHigher contrast
66January 27, 2005January 27, 2005
Color Space Options ConsideredColor Space Options Considered
R’G’B’R’G’B’ using extended gamut DLP primaries with using extended gamut DLP primaries with Xenon light sourceXenon light source
Parametric R’G’B’-Parametric R’G’B’- R’G’B’ with metadata to R’G’B’ with metadata to define color primaries of Reference Projectordefine color primaries of Reference Projector
Wide gamut R’G’B’Wide gamut R’G’B’ using CIE 1931 XYZ color using CIE 1931 XYZ color primaries- hereby called primaries- hereby called X’Y’Z’X’Y’Z’ Based on international color standardBased on international color standard Explicit device independence, extensibility, backward Explicit device independence, extensibility, backward
compatibility compatibility Robust implementation, not dependent on metadataRobust implementation, not dependent on metadata
77January 27, 2005January 27, 2005 Z X
Y
Visible colors
Displayablecolors
DisplayPrimaries
XYZ encodingSpace (triangle)
Visible and XYZ
88January 27, 2005January 27, 2005
CompressEncryptPackage
Color gradeConform
Store &Play
CinemaProjector
MasteringProjector
DecompressDecrypt
DSM DCPColor
Encoding
Color Management
Color Decoding
CalibratedColor Ref Projector
gamut metadata
DCDM(X’Y’Z’)
DSM:
Digital Source Master
DCP:
Digital Cinema Package
DCDM:
Digital Cinema Distribution Master
Color in the Overall WorkflowColor in the Overall Workflow
January 27, 2005January 27, 2005 99
Mastering ProjectorMastering Projector
(Used in Content Creation (Used in Content Creation or Color Grading)or Color Grading)
1010January 27, 2005January 27, 2005
Mastering Projector PrimariesMastering Projector Primaries
Today, the projectors used in mastering are DLP Today, the projectors used in mastering are DLP CinemaCinemaTMTM projectors, with a color gamut expanded projectors, with a color gamut expanded beyond CCIR 709 to more closely match film beyond CCIR 709 to more closely match film
Encoding Encoding PrimariesPrimaries xx yy u’u’ v’v’
RR 0.68000.6800 0.32000.3200 0.496350.49635 0.525550.52555
GG 0.26500.2650 0.69000.6900 0.098600.09860 0.577670.57767
BB 0.15000.1500 0.06000.0600 0.175440.17544 0.157890.15789
Note: x, y, u’ ,v’ refers to the chromaticity coordinates defined by the CIE.
1111January 27, 2005January 27, 2005
Mastering Projector White PointMastering Projector White Point
Although white point is independent of color encoding,Although white point is independent of color encoding,
A consistent white point target (and tolerances) for A consistent white point target (and tolerances) for mastering and cinema projectors is importantmastering and cinema projectors is important
Considering the installed base of Xenon projectors, we Considering the installed base of Xenon projectors, we recommend a recommend a calibratedcalibrated white point of (0.314, 0.351)white point of (0.314, 0.351), , CCT 6300KCCT 6300K
0.3100
0.3200
0.3300
0.3400
0.3500
0.3600
0.2950 0.3050 0.3150 0.3250 0.3350 0.3450
x
y Daylight curve
D61
DLP
DLP Tolerances
6100
7000
5100
0.314 0.351
Daylight curve
1212January 27, 2005January 27, 2005
Mastering Projector Peak WhiteMastering Projector Peak White
Existing digital cinema practice sets the Existing digital cinema practice sets the peak white at 12 ftL (42 cd/mpeak white at 12 ftL (42 cd/m22))
DCI tests verified that film produces 14 ftL DCI tests verified that film produces 14 ftL for peak whites (with 16 ftL open gate)for peak whites (with 16 ftL open gate) Dmin samples from Technicolor and DeluxeDmin samples from Technicolor and Deluxe
Draft SMPTE standard recommends a Draft SMPTE standard recommends a peak white level of peak white level of 14 ftL (48 cd/m14 ftL (48 cd/m22))
1414January 27, 2005January 27, 2005
Color Encoding ParametersColor Encoding Parameters
CIE XYZ Color PrimariesCIE XYZ Color Primaries
Gamma 1/2.6 Transfer FunctionGamma 1/2.6 Transfer Function
12 bits per channel12 bits per channel
Metadata for downstream gamut mapping- Metadata for downstream gamut mapping- describes color gamut that is used in the describes color gamut that is used in the master master
““Encoding” White PointEncoding” White Point DDEE (1.0,1.0,1.0) is implicit with CIE XYZ (1.0,1.0,1.0) is implicit with CIE XYZ
1515January 27, 2005January 27, 2005
Color Encoding PrimariesColor Encoding Primaries
XYZ color primaries XYZ color primaries (1931 CIE standard)(1931 CIE standard) Device independent, colorimetric representationDevice independent, colorimetric representation Encompasses full color gamutEncompasses full color gamut Luminance isolated to one component (Y)Luminance isolated to one component (Y)
EncodingEncodingPrimariesPrimaries xx yy u’u’ v’v’
XX 1.00001.0000 0.00000.0000 4.00004.0000 0.00000.0000
YY 0.00000.0000 1.00001.0000 0.00000.0000 0.60000.6000
ZZ 0.00000.0000 0.0000.000 0.00000.0000 0.00000.0000
Note: x, y, u’ ,v’ refers to the chromaticity coordinates defined by the CIE.
1616January 27, 2005January 27, 2005
Encoding Color TransformEncoding Color Transform
R’G’B’ color space of Reference Projector is converted R’G’B’ color space of Reference Projector is converted to device-independent X’Y’Z’ color space of DCDM with to device-independent X’Y’Z’ color space of DCDM with a linear space matrixa linear space matrix
DLP
DLP
DLP
B
G
R
Z
Y
X
9074.00471.00000.0
0689.07216.02095.0
1723.02771.04452.0
2.6[ ]
1/2.6
2.6
R’G’B’ RGB XYZ X’Y’Z’
1717January 27, 2005January 27, 2005
Encoding Transfer FunctionEncoding Transfer Function
6.2
1
*4095
P
LCV
Where:
CV is the resulting Code Value for a color component.L is the luminance output in cd/m2
P is 52.39 (extra headroom reserved for future white point changes to accommodate range from D55 to D65).
January 27, 2005January 27, 2005 1818
Color DecodingColor Decodingin the Cinema Projectorin the Cinema Projector
1919January 27, 2005January 27, 2005
Projector Transfer FunctionProjector Transfer Function
P is the peak luminance output (48 cd/m2)
12-bit code valueOutput
Luminance, cd/m2Relative
Luminance Notes4095 48.000 100.000% Peak White3686 36.511 76.065%3276 26.870 55.980%2866 18.980 39.542%2457 12.718 26.497%2048 7.922 16.504%1771 5.429 11.311% 18% Gray1638 4.432 9.233%1228 2.096 4.366%737 0.556 1.158%410 0.121 0.252%288 0.048 0.101% Black 1000:1220 0.024 0.050% Black 2000:1168 0.012 0.025% Black 4000:1118 0.005 0.010% Black 10,000:1
6.2
4095*
CV
PL
Projector Transfer Function
0
8
16
24
32
40
48
0 512 1024 1536 2048 2560 3072 3584 4096
Code Value
Lu
min
ance
(cd
/m2)
2020January 27, 2005January 27, 2005
Projector Color TransformProjector Color Transform
X’Y’Z’ color space of DCDM is converted to Projector X’Y’Z’ color space of DCDM is converted to Projector (device specific) RGB color space with a linear matrix(device specific) RGB color space with a linear matrix
Z
Y
X
B
G
R
DLP
DLP
DLP
1009.10876.00412.0
0226.06897.17952.0
4402.00180.12.7254
2.6[ ]
2.6 Light
ModulatorsX’Y’Z’ XYZ RGB
In this example, the decoding matrix is the inverse of the encoding matrix.
January 27, 2005January 27, 2005 2121
Color Processing forColor Processing forDigital IntermediateDigital Intermediate
for both film and digital cinema distributionfor both film and digital cinema distribution
2222January 27, 2005January 27, 2005
DI Option 1DI Option 1
MasteringProjector
Color CorrectionsConforming
DSMRGB Printing Density
Dual 292 R’G’B’ 12 bits
3D Print Film LUTs(for film matching)
Scan Film orImport Digital Images
DCDM
Output to film(Laser Fim Recorder) Film IN
Color EncodingTo X’Y’Z’
Use a 3D LUT in color corrector or external box to mimic film print stock, Use a 3D LUT in color corrector or external box to mimic film print stock, starting with Printing Density source imagesstarting with Printing Density source images
1 1 - Color-corrected master is ready for film output (Printing Density)- Color-corrected master is ready for film output (Printing Density)2 2 - Render (“bake in”) the film LUT when outputting the DCDM; - Render (“bake in”) the film LUT when outputting the DCDM;
Encode color to X’Y’Z’Encode color to X’Y’Z’
1
2
2323January 27, 2005January 27, 2005
DI Option 1bDI Option 1b
MasteringProjector
Color CorrectionsConforming
DSMRGB Printing Density
Dual 292
3D Print Film LUTs(for film matching)
Scan Film orImport Digital Images
DCDM
Output to film(Laser Fim Recorder) Film IN
Color EncodingTo X’Y’Z’
1
2
Put the 3D print film LUT Put the 3D print film LUT inside the Mastering Projectorinside the Mastering Projector- source and color-- source and color-corrected images are Printing Densitycorrected images are Printing Density
1 1 - Color-corrected master is ready for film output (Printing Density)- Color-corrected master is ready for film output (Printing Density)2 2 - Render (“bake in”) the film LUT when outputting the DCDM; - Render (“bake in”) the film LUT when outputting the DCDM;
Encode color to X’Y’Z’Encode color to X’Y’Z’
Render 3D LUTInto DCDM
2424January 27, 2005January 27, 2005
DI Option 2DI Option 2
MasteringProjector
Color CorrectionsConforming
DSMRGB Printing Density
Dual 292
Scan Film orImport Digital Images
DCDM
Output to film(Laser Fim Recorder)
Film IN
Color EncodingTo X’Y’Z’1
2 3D LUT to convert toRGB Printing Density
Perform color corrections from source RGB Printing Density to color-Perform color corrections from source RGB Printing Density to color-corrected R’G’B’ DCDM.corrected R’G’B’ DCDM.
1 1 - Color-corrected images are ready for color encoding to X’Y’Z’.- Color-corrected images are ready for color encoding to X’Y’Z’.2 2 - Use an - Use an (inverse) 3D LUT(inverse) 3D LUT to convert from R’G’B’ DCDM to RGB to convert from R’G’B’ DCDM to RGB
Printing Density in a 2nd pass (for film output).Printing Density in a 2nd pass (for film output).
Color-correctedR’G’B’ DCDM
2525January 27, 2005January 27, 2005
Creating Video MastersCreating Video Masters
Video displays have a smaller color gamut (CCIR 709)Video displays have a smaller color gamut (CCIR 709) Simple colorimetric conversion could result in clipping of out of Simple colorimetric conversion could result in clipping of out of
gamut colorsgamut colors Viewing conditions are also very different; pictures look different Viewing conditions are also very different; pictures look different
on a small display in a dim (10%) surroundon a small display in a dim (10%) surround
In theory, a 3D LUT can be built to convert to CCIR 709 In theory, a 3D LUT can be built to convert to CCIR 709 color gamut, preserving the look of the picturecolor gamut, preserving the look of the picture
Adjusting the transfer function for color appearanceAdjusting the transfer function for color appearance Applying a hue-preserving “soft-clip” for out of gamut colorsApplying a hue-preserving “soft-clip” for out of gamut colors
A trim pass is still necessary to tune color aesthetics and A trim pass is still necessary to tune color aesthetics and frame (pan/scan) the picture for the 4:3 full-frame video frame (pan/scan) the picture for the 4:3 full-frame video versionversion
2727January 27, 2005January 27, 2005
The Reference ProjectorThe Reference Projector
X’Y’Z’ encoding (as used here) is output-referredX’Y’Z’ encoding (as used here) is output-referredFaithful color reproduction depends on Faithful color reproduction depends on careful careful calibrationcalibration of the mastering projector and cinema of the mastering projector and cinema projectorsprojectorsThe environment is also critical (screen quality, The environment is also critical (screen quality, port glass and ambient light must be controlled)port glass and ambient light must be controlled)The Mastering Projector must have the The Mastering Projector must have the best best available blackavailable black level (sequential contrast) level (sequential contrast) Otherwise, the cinema projector may unveil Otherwise, the cinema projector may unveil
unintended details or color errors in the blacks.unintended details or color errors in the blacks.
2828January 27, 2005January 27, 2005
Color Management inColor Management inthe Mastering Processthe Mastering Process
Proprietary color processing (3D LUTs or Proprietary color processing (3D LUTs or otherwise) used to match print film or otherwise) used to match print film or create a unique look may be included in create a unique look may be included in the Mastering Projector, butthe Mastering Projector, butThis proprietary color processing must be This proprietary color processing must be rendered into the DCDM.rendered into the DCDM.Better to put these LUTs in the color Better to put these LUTs in the color corrector or in an external box or software corrector or in an external box or software process.process.
2929January 27, 2005January 27, 2005
X’Y’Z’ Conclusions and Next StepsX’Y’Z’ Conclusions and Next Steps
Robust, device-independent output-referred Robust, device-independent output-referred color encoding definitioncolor encoding definition Independent of display primaries and white pointIndependent of display primaries and white point
Supports future improvements in color gamut Supports future improvements in color gamut and contrast ratioand contrast ratioDCI StEM test provided a proof of conceptDCI StEM test provided a proof of concept Color transforms were independently verified by Color transforms were independently verified by
several companiesseveral companies Next step is to test color matching across different Next step is to test color matching across different
projection technologiesprojection technologies
Color correctors should implement R’G’B’ to Color correctors should implement R’G’B’ to X’Y’Z’ color conversion for DCDM outputX’Y’Z’ color conversion for DCDM output
3030January 27, 2005January 27, 2005
Additional ReferencesAdditional References
Swartz, editor, “Understanding Digital Cinema”Swartz, editor, “Understanding Digital Cinema”
Cowan, et al, Journal SMPTE, September 2004, Cowan, et al, Journal SMPTE, September 2004, “Contrast Sensitivity Experiment to Determine “Contrast Sensitivity Experiment to Determine the Bit Depth for Digital Cinema”the Bit Depth for Digital Cinema”
Draft SMPTE Standard for DCDMDraft SMPTE Standard for DCDM
Draft SMPTE RP for Reference Projector and Draft SMPTE RP for Reference Projector and EnvironmentEnvironment
Draft SMPTE EG for Color ProcessingDraft SMPTE EG for Color Processing