Upload
dayo
View
45
Download
0
Embed Size (px)
DESCRIPTION
This presentation can be downloaded from the HPA online website, or mailto: [email protected] (it includes notes and hidden sheets). Extended Color Gamut for Consumers - the Display side. Presented by: Jeroen Stessen. Philips Applied Technologies. - PowerPoint PPT Presentation
Citation preview
This presentation can be downloaded from the HPA online website,
or mailto: [email protected](it includes notes and hidden sheets)
PHILIPSPHILIPS
PHILIPS
Presented by: Jeroen Stessen
Philips Applied TechnologiesDigital Systems & Technology Eindhoven
HPA Tech Retreat 2007 Rancho Mirage – Wednesday 2007-01-31
Extended Color Gamut for Consumers - the Display side
PHILIPS
HPA Tech Retreat 2007 3Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
OutlineWhat is a color gamut
Color gamuts for some displays
Color space conversion
Gamut mapping
Signal processing chain
Image results
Conclusions
PHILIPS
HPA Tech Retreat 2007 4Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
the solution
the problem
PHILIPS
HPA Tech Retreat 2007 5Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
What is a color gamut
PHILIPS
HPA Tech Retreat 2007 6Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
CIE-1931 (x,y) color space 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
,xhhxpj
The border of humanly visible colors (5 nm )Pointer gamut
of surface colors
The horseshoe
gamut covers all visible colors,
the Pointer gamut covers all practical
colors
The background colors are
incorrect, for orientation only
What is a color gamuty
x
PHILIPS
HPA Tech Retreat 2007 7Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
,,xhhxpjx7p
Pointer gamutof surface colors
The standard TV color
gamut does not cover all
surface colors, but
we have been happy with it for 50 years,
and this gamut is easy to reproduce
What is a color gamut
ITU-Rec.709standard TV
y
x
G
B
R
PHILIPS
HPA Tech Retreat 2007 8Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
The digital cinema
reference projector
gamut is good !
Lacking only some cyan
What is a color gamut
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
,,,xhhxpjx7pxdp
Digital Cinemareference (DLP)
ITU-Rec.709standard TV
Pointer gamutof surface colors
y
G
B
R
x
PHILIPS
HPA Tech Retreat 2007 9Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
X
The digital cinema XYZ signal gamutis more than everything
Many codes are never used
What is a color gamut
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ytp
,,,xhhxpjx7pxtp x
y
Y
Z
ITU-Rec.709standard TV
Digital CinemaXYZ signal
Pointer gamutof surface colors
PHILIPS
HPA Tech Retreat 2007 12Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
What is a color gamut
Gamut is 3D:
For each surface color
there is a theoretical maximum
brightness,it is 100%only for a
white surface
white = 100%
“wide gamut”
“bright gamut”
PHILIPS
HPA Tech Retreat 2007 13Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
What is a color gamut
Illustrations byT. Matsumoto et al, Sony Corp. for SID
ITU-Rec.709 standard TV
incomplete coverage
xvYCC wide color gamut TV
more than complete coverage
white = 100% white = 109%
Gamut is 3D:
Maximum luminance for
each color point, compared
with the Munsell color
cascade of known surface
colors(the Pointer
gamut in 3D)
PHILIPS
HPA Tech Retreat 2007 15Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
Color gamuts for some displays
PHILIPS
HPA Tech Retreat 2007 16Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Color gamuts for some displays
This triangular
color gamut is the
de-facto standard for practically every TV or computer display in the world
Also used by sRGB
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
,,xhhxpjx7p
Pointer gamutof surface colors
ITU-Rec.709standard TV
y
x
PHILIPS
HPA Tech Retreat 2007 17Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
The reference gamut for
digital cinema is defined by
a TI DLP projector
It is clearly larger than
standard TV, able to
reproduce more colors
Color gamuts for some displays
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
,,,xhhxpjx7pxdp
Digital Cinemareference (DLP)
ITU-Rec.709standard TV
y
This is the current Digital Cinema gamut
x
PHILIPS
HPA Tech Retreat 2007 18Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
ynp
,,,,xhhxpjx7pxdpxnp
The NTSC gamut is not
a standard for any TV, it is obsolete, but it is still much referred to:
“the gamut of this display is nnn% of the NTSC area”
Color gamuts for some displays
“100% NTSC”display
Digital Cinemareference (DLP)
y
x
ITU-Rec.709standard TV
PHILIPS
HPA Tech Retreat 2007 21Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
An LCD with a “wide color gamut” CCFL backlight for“91% NTSC” color gamut
Improved red and green primaries, but worse blue than Rec.709
Color gamuts for some displays
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
ys91p
,,,,xhhxpjx7pxdpxs91
p
Digital Cinemareference (DLP)
“91% NTSC”LCD
y
x
ITU-Rec.709standard TV
PHILIPS
HPA Tech Retreat 2007 22Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
An LCD with a novel LED backlight for
an impressive color gamut
The saturation
for yellow is not as high as Digital Cinema
Color gamuts for some displays
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
yqp
,,,,xhhxpjx7pxdpxqp
LED-backlitLCD
Digital Cinemareference (DLP)
y
x
ITU-Rec.709standard TV
PHILIPS
HPA Tech Retreat 2007 23Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
With 3 RGB lasers we can
make an almost perfect color gamut
Novalux and COLOR are making the
lasers today
Color gamuts for some displays
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
ycp
ylp
,,,,,xhhxpjx7pxdpxcpxlp
532nm
3-primarylaser displays
Digital Cinemareference (DLP)
y
ITU-Rec.709standard TV
This could be the next Digital Cinema gamut !
621nm
x
628nm
465nm
447nm
PHILIPS
HPA Tech Retreat 2007 25Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
Color space conversion
PHILIPS
HPA Tech Retreat 2007 27Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
If you don’t do anything then you’ll get the wrong color gamut of the standard TV
display
Color space conversion
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
,,,xhhxpjx7pxdp
Source gamut: Digital Cinema
Target gamut: standard TV
Example:y
Bx
G
R
PHILIPS
HPA Tech Retreat 2007 28Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
With color space conversion
we aim to getthe correct
colors of the digital cinema display back
(if possible)
Color space conversion
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
y7p
ydp
,,,xhhxpjx7pxdp
y
Bx
Example:
Source gamut: Digital Cinema
Target gamut: standard TV
G
R
PHILIPS
HPA Tech Retreat 2007 29Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Block diagram:
Use the gamma functions from the transmission standard (709)o for an xvYCC source we must use the symmetrical gamma function
The CSC matrix is only a single 3x3 matrix o it has a dominant diagonal, because it converts RGBRGBo it must have sufficient accuracy, because of linear-light RGB data
Color space conversion
gamma inv. gamma
c c cc c cc c c
c c cc c cc c c
color space conversion matrix
XYZ
RGB
RGB
R’G’B’
R’G’B’
source displayXYZ = absolute and linear-light color space
PHILIPS
HPA Tech Retreat 2007 30Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Color space conversionCalculation example:
o simplification: a white point of D6500 is assumed on both sides
0.487 0.266 0.1980.229 0.692 0.0790.000 0.045 1.044
3.241 −1.537 −0.499−0.969 1.876 0.042 0.056 −0.204 1.057
XYZ
RGB
RGB
source color space display color space
gamma inv. gammacolor space conversion matrix
RGB
RGB
R’G’B’
R’G’B’
=
absolute color space
1.225 −0.225 0.000−0.042 1.042 0.000−0.020 −0.079 1.098
PHILIPS
HPA Tech Retreat 2007 31Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Interpretation:
Negative RGB values < 0 are illegal on the input of the displayo because displaying negative light is physically impossibleo in the given example, the top center coefficient of -0.225
creates the biggest problem:
A 100% Digital-Cinema Green source color (via xvYCC) wants to make a -23% red light output on a standard display
o clipping negative signals to zero is one solution o the generic solution is called gamut mapping (more later)
Color space conversion
Rout 1.225 −0.225 0.000 Rin
Gout = −0.042 1.042 0.000 * Gin
Bout −0.020 −0.079 1.098 Bin
PHILIPS
HPA Tech Retreat 2007 32Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Interpretation:
Positive RGB values > 100% are also a problem on the displayo they want to overdrive the display, causing ugly clipping artefactso in the given example, the top left coefficient of 1.225
creates the biggest problem:
A 100% Digital-Cinema Red source color (via xvYCC) wants to make a 123% red light output on a standard display
o a simple linear signal attenuation would prevent such problemso i.e. the entire signal can be attenuated to 91% (gamma domain)
Color space conversion
Rout 1.225 −0.225 0.000 Rin
Gout = −0.042 1.042 0.000 * Gin
Bout −0.020 −0.079 1.098 Bin
PHILIPS
HPA Tech Retreat 2007 34Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Color space conversionConclusion:
Color space conversion can be mathematically correcto linear problem linear solutiono it is just a 3x3 matrix in linear-light domaino it works perfectly
Conversion to a smaller color gamut can create illegal RGB signals < 0, negative light, underflow
o impossible colors gamut mapping (more later)
Conversion to a smaller color gamut can also create problematic RGB signals > 100%, overflow
o only a problem of scale attenuation
PHILIPS
HPA Tech Retreat 2007 35Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
Gamut mapping
PHILIPS
HPA Tech Retreat 2007 36Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Gamut mapping
First example
A standard television
display has a smaller color gamut than
Digital Cinema
What are the consequences
?
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
y7p
,,,xhhxpjxdpx7p
Standardtelevision
display
y
G
B
Digital Cinemareference
x
R
PHILIPS
HPA Tech Retreat 2007 37Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Example: a Digital Cinema signal on a standard TV display
Starting from a Digital Cinema RGB signal, then from source to display we must apply this color space correction matrix:
o Watch the negative coefficients in 4 places…
Gamut mapping
Rout 1.225 −0.225 0.000 Rin
Gout = −0.042 1.042 0.000 * Gin
Bout −0.020 −0.079 1.098 Bin
PHILIPS
HPA Tech Retreat 2007 38Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
y7p
,,,xhhxpjxdpx7p
It is a problem on all 3 sides
(R,G,B)
Outside the display gamut one or more of the RGB
drive signals go negative
Gamut mapping
G<0
y
x
Display gamut
Source gamut
R<0
G>0
R>0
B<0
B>0
PHILIPS
HPA Tech Retreat 2007 39Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
y7p
,,,xhhxpjxdpx7p
The green area needs only color
space conversion
!
Gamut mappingy
x
This part can berendered correctly
G>0
R>0
B>0
PHILIPS
HPA Tech Retreat 2007 40Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
y7p
,,,xhhxpjxdpx7p
This part isunreachable !
The red area needs gamut
mapping,to substitute something
for the unreachable
colors!
Gamut mappingy
x
R<0
G<0
B<0
PHILIPS
HPA Tech Retreat 2007 41Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
y7p
,,,xhhxpjxdpx7p
Gamut mapping is an age-old
artistic process,
the choice of substitute colors is
subjective !
Note: this is usually not
about natural colors
Gamut mapping
?
?
y
x
G>0
R>0
B>0
Shift towards thedisplay gamut
?
PHILIPS
HPA Tech Retreat 2007 42Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
y7p
,,,xhhxpjxdpx7p
Gamut mapping
Gamut mapping(subjective choice)
Gamut mapping summary
Color spaceconversion
(objective math)
y
x
PHILIPS
HPA Tech Retreat 2007 44Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Gamut mapping
Second example, a LED-backlit LCD panel
The display’s wide color
gamut differs from the digital cinema wide color gamut
What are the consequences
?
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
y
G
Digital Cinemareference
x
R
B
LED-backlitLCD
PHILIPS
HPA Tech Retreat 2007 45Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Gamut mappingExample: a Digital Cinema signal on an LCD with LED-backlight
Starting from a Digital Cinema RGB signal, then from source to display we must apply this color space correction matrix:
o Watch the negative coefficients on the bottom row (= Bout) …
A wider display gamut makes our problems easier
Rout 0.810 0.168 0.022 Rin
Gout = 0.041 0.958 0.001 * Gin
Bout −0.017 −0.049 1.066 Bin
PHILIPS
HPA Tech Retreat 2007 46Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
Outside the display gamut only the Blue drive signals
goes negative
Gamut mappingy
x
Display gamut
Source gamut
G>0
R>0
B<0
B>0
PHILIPS
HPA Tech Retreat 2007 47Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
The green area needs only color
space conversion
!
Gamut mappingy
x
B>0
This part can berendered correctly
PHILIPS
HPA Tech Retreat 2007 48Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
!
Gamut mappingy
x
The red area needs gamut
mapping,to substitute something
for the unreachable
colors
B<0
This part isunreachable !
PHILIPS
HPA Tech Retreat 2007 49Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
Shift towards thedisplay gamut
Gamut mapping is an age-old
artistic process,
the choice of substitute colors is
subjective !
?
??
Gamut mappingy
x
B>0
PHILIPS
HPA Tech Retreat 2007 50Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
This part is not asked for
The yellow area is not asked for,
but there is a temptation to fill it up by
“gamut” “extension”
LED red isso beautiful…
Gamut mappingy
x
G>0
R>0
?
?R<0
G<0
?
PHILIPS
HPA Tech Retreat 2007 51Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
yhh
ypj
ydp
yqp
,,,xhhxpjxdpxqp
Gamut mappingy
Nothing (or somegamut extension)
Color spaceconversion
(objective math)
Gamut mapping(subjective choice)
Gamut mapping summary
x
PHILIPS
HPA Tech Retreat 2007 54Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
Signal processing chain
PHILIPS
HPA Tech Retreat 2007 55Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamut
source gamut
Signal processing chain
XYZsensor
CSCmatrix
gamutmap 1 ...
Rec.709display
Y’CbCr processing & channel
Standard TVgamut
CameraXYZ or wide RGB
native displaygamut
Rec.709display
Rec.709
=
the only
A legacy chain with only Rec.709 compliant components
Rec.709 gamut
inverse...
Rec.709 gamut
PHILIPS
HPA Tech Retreat 2007 56Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamut
source gamut
Signal processing chainAn xvYCC wide gamut chain with a wide gamut display
XYZsensor
CSCmatrix
gamutmap 1 ...
wide gamutdisplay
gamutmap 2
inverse...
Y’CbCr processing & channel
Digital Cinemagamut
CameraXYZ or wide RGB
native displaygamut
DCIdisplay
xvYCC+
=
dominant
not dominant
CSCmatrix
CSCmatrix
xvYCC gamut
xvYCC gamut
PHILIPS
HPA Tech Retreat 2007 57Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
source gamut
Signal processing chain
XYZsensor
CSCmatrix
gamutmap 1 ...
Y’CbCr processing & channel
Digital Cinemagamut
CameraXYZ or wide RGB
DCIdisplay
xvYCC+not dominant
dominant
CSCmatrix
A mixed chain with a legacy Rec.709 display (compatibility)
display gamut
Rec.709display
gamut
CLIPinverse
...
native displaygamut
xvYCC gamut ?<
xvYCC gamut
PHILIPS
HPA Tech Retreat 2007 58Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
receiver-side gamut mapping
larger source gamut
Signal processing chain
XYZsensor
CSCmatrix
gamutmap 1 ...
wide gamutdisplay
gamutmap 2
inverse...
Y’CbCr processing & channel
Digital Cinemagamut
CameraXYZ or wide RGB
DCIdisplay
xvYCC+
CSCmatrix
CSCmatrix
xvYCC signal & processing
What’s new in a wide gamut chain with a wide gamut display:
digital cinema reference display
PHILIPS
HPA Tech Retreat 2007 59Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
display gamutsource gamut
Outline
color space
conversion
gamutmapping
display
image processing
imagesource
Image results
PHILIPS
HPA Tech Retreat 2007 61Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Block diagram for simulation of gamut mapping algorithms:
“DC”image
CSCmatrix
gamutmap
inversematrix
“DC”display
“DC”display 0a, 0b
Image results
=M
1.225
0.042
0.02
0.225
1.042
0.079
0
0
1.098
=M 1
0.822
0.033
0.017
0.178
0.967
0.072
0
0
0.911
1, 2, 3a, 3b
referencedisplay gamutsource gamut
resulta gamut bottleneck
PHILIPS
HPA Tech Retreat 2007 62Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Image resultsResult 0a: ORIGINAL IMAGE (assume that this is the full DC gamut)
PHILIPS
HPA Tech Retreat 2007 63Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Image resultsResult 1: dumb clipping of R’,G’,B’ to 0 and to 255 (worst case legacy)
PHILIPS
HPA Tech Retreat 2007 65Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Image resultsResult 2: dumb clipping of R’,G’,B’ to 0 , plus global attenuation (0.92x)
PHILIPS
HPA Tech Retreat 2007 66Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Image resultsResult 3a: advanced gamut mapping including global attenuation (0.92x)
PHILIPS
HPA Tech Retreat 2007 67Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Image resultsResult 3b: another advanced gamut mapping, with attenuation (0.92x)
PHILIPS
HPA Tech Retreat 2007 68Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Image resultsResult 0b: ORIGINAL IMAGE (now attenuated by the same factor 0.92x)
PHILIPS
HPA Tech Retreat 2007 70Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
OutlineWhat is a color gamut
Color gamuts for some displays
Color space conversion
Gamut mapping
Signal processing chain
Image results
Conclusions
PHILIPS
HPA Tech Retreat 2007 71Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
ConclusionsThe Digital Cinema standard is a good wide color gamut sourceThe xvYCC standard is good for wide color gamut transmissions Wide color gamut display technology is still evolving Mathematically correct color space conversion properly
connects everything together
But due to the variety of display gamuts, it is inevitable that some gamut mapping be done at the display side
o different strategies for RGB<0 and RGB>1 problems !
Decent gamut mapping has a modest effect on the output image o and the effect of gamut mapping will become less as the
color gamuts of consumer displays continue to grow larger
PHILIPS
HPA Tech Retreat 2007 72Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
ConclusionsConsumer displays want to receive Wide Color Gamut programs
o receiver-side Color Space Conversion and some minor Gamut Mapping can be OK
o even if the outer colors are slightly modified by the gamut mapping o thanks to xvYCC it works well, even if the source gamut is undefinedo and xvYCC ensures compatibility with Rec.709 legacy receivers
Without wide color gamut programs the receivers will apply more gamut extension (and more, and more…)
o the color gamut of the scene is limited by the source, and then expanded back to wide gamut by the receiver
o with much less predictable results (guessing at the original colors) o wide color gamut is a very important feature in the display marketo today’s wide gamut displays are promoted with exaggerated colors o the temptation to show off a wider color gamut is irresistible
PHILIPS
HPA Tech Retreat 2007 73Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
ConclusionsPlease produce and distribute wide color gamut programs !
o and we will display them as best as we can
Thank you for your attention
I will be available for questions, discussion, a drink, …
This entire presentation is available in electronic formo with notes and hidden sheets
PHILIPS
HPA Tech Retreat 2007 74Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
Contact information
Jeroen Stessen
Philips Applied Technologies Digital Systems & Technology Building SFJ-5 Glaslaan 2 NL 5616 LW Eindhoven The Netherlands
[email protected] http://www.apptech.philips.com/
PHILIPS
HPA Tech Retreat 2007 Jeroen Stessen - Philips Applied Technologies - 2007-01-31
PHILIPS
This presentation can be downloaded from the HPA online website,
or mailto: [email protected](it includes notes and hidden sheets)