HDR in der Live-Produktion - tu-ilmenau.de · LP/mm 250 200 150 100 50 500 400 300 200 100 2 4 6 8...
Transcript of HDR in der Live-Produktion - tu-ilmenau.de · LP/mm 250 200 150 100 50 500 400 300 200 100 2 4 6 8...
HDR in der Live-Produktion Von der Kamera bis zu einem HDR / SDR kompatiblen Workflow
Klaus Weber Principal Camera Solutions & Technology
Agenda
• UHD Options & Challenges
– More Pixel
– Better Pixel
– Better Colors
• HDR in Live Production
– HDR Standards
– HDR Workflows
• Summary
UHD Options & Challenges
• UHD = a large palette of options to choose from:
– More Pixels
• 4K resolution
• 8x more bandwidth than HD
– Better Pixels
• High Dynamic Range
• Larger contrast in a given signal range
– Better Colors
• Extended Color Gamut
• New (incompatible) mapping of colors
UHD Options & Challenges – More Pixels
• 4K resolution
– 8x more bandwidth than HD
• 4K requires much more resources than HD
– 4x 3G channels in routers, switchers, servers, etc.
• Sensitivity
– 4-times smaller UHD pixel collect 4-times less photons as HD pixels
• If same technology applied at least two f-stop lower sensitivity
1080i 1080p
2160p 3G
12G
1.5G
UHD Options & Challenges – 4K and lens diffraction
• Light rays passing through a small aperture will begin to diverge and
interfere with one another
– This becomes more significant as the size of the aperture decreases, but
occurs to some extent for any aperture or concentrated light source
• Why does it matter more in 4K acquisition?
– In 4K acquisition the resolution loss hurts two F-stops earlier than in HD!
Large Aperture
Small Aperture
UHD Options & Challenges – 4K and lens diffraction
F8.0 F4.0 F2.0
5µm pixel Native HD
2.5µm pixel Native 4K
Acceptable performance Optimal performance Optimal performance
Poor performance Acceptable performance Optimal performance
UHD Options & Challenges – 4K and lens diffraction
Focus aberration limit (HD) Focus aberration limit (4K)
Desired resolution Diffraction limit (HD)
Diffraction limit (4K)
Aperture in f-stops
Optical Resolution LP/mm
250
200
150
100
50
500
400
300
200
100
2 4 6 8 10 12 14 16
4K HD
HD
4K
‘sweet range,’
4K
‘sweet range,’
HD
Point of maximum lens resolution
UHD Benefits – More Pixels
• 4K resolution
– Future proof solution
– Support the trend towards
larger screen sizes
UHD Options & Challenges – Better Colors
• Extended Color Gamut
– New mapping of a larger color volume
• BT.709 HDTV standard does NOT support
capabilities of latest display technology
– Current standard is still based on CRT
displays
• With the new BT.2020 nearly all natural
colors can be reproduced
– With BT.709 only about 69% can be reproduced
• But BT.709 and BT.2020 are NOT compatible with each other
– Conversion between the different color volumes is a must, but not trivial
CIE 1931 = Visible colors
Pointer’s Gamut = Natural colors
BT.709 = HDTV standard gamut
DCI P3 = Cinema standard gamut
BT.2020 = UHD standard gamut
UHD Benefits – Better Colors
• Extended Color Gamut
– Support of the larger color
volume supported by the latest
television screens
• Higher saturated colors can
be reproduced without
clipping
• More natural color
reproduction possible
BT.709 versus BT.2020
Why HDR - For Live
• High contrast scenes are most challenging in live broadcast applications
– Lighting conditions are
typically not under our
control
– Pictures must be perfect
at all times and can’t be
‘fixed in post’
Camera-to-Display Transfer Functions
• OETF => Opto-Electronic transfer function => Camera transfer function
• EOTF => Electro-optical transfer function => Display transfer function
• OOTF => Opto-Optical transfer function => Artistic or rendering intent
EOTF OETF
Distribution
OOTF
Camera-to-Display Transfer Functions - SDR
EOTF OETF
Distribution
OOTF
HDR Standards - Status
• Two HDR curves are standardized worldwide for:
– Production
– Distribution
– Presentation
• SMPTE 2084 / PQ
• Hybrid Log Gamma / HLG
To a SDR monitor the HLG signal look like a regular
signal where the knee point is set to a very low level
HDR Solutions – BBC/NHK Hybrid Log-Gamma
Source: BBC
The lower half of the
HLG signal is close to
a regular gamma curve
In the upper half the
signal is mapped in a
logarithmic curve
HDR Solutions – SMPTE 2084 (Dolby PQ)
• PQ use available bid depth following human eye sensitivity
– The Barten ramp describe the eye sensitivity seeing level differences
• Whatever the bid depth is PQ use it in the most optimum way
delivering the selected dynamic range
– Up to 10.000 nits
peak white are
supported
– 10 bit end-to-end
are required
as minimum
HDR Standards – Requirements / PQ & HLG
• HLG offer more headroom in the darker parts of the image
– But in some of the brighter parts it is even more on the “wrong side”
– Does offer less dynamic range than PQ means its less future proof
• Conversion from one curve into the other add the weak points
of both to each other
– Any HDR
workflow must
avoid any
unnecessary
conversion
Why a native OETF should be used
Processing
RGB in 34 bit
17.179.869.184
Imaging
RGB linear in 14-16 bit
16.384-65.536
Transmission
YCrCb in 10 bit
1.024
Camera System
HDR Workflows – Parallel SDR & HDR workflow
• Native SDR and HDR signals delivered simultaneously by the camera
and processed independently from each other
– Highest flexibility
• Allow optimizing SDR & HDR images independent from each other
– Double workflow require
more resources and add
complexity to the
production
• Might not be acceptable
on longer term
HDR Workflows – Adopted film workflow
• What is a film workflow? “Capture and record everything what might be needed in post”
– In live the time between light reaching the imagers and the
signal gets “On Air” is typically less than 100 msec
– Live workflows currently
support 10 bit signal only
• Conversion from one 10 bit
signal into another 10 bit
signal reduces the
performance of the signal
HDR Workflows – HDR workflow with SDR conversion
• Native 10 bit HDR signals from camera through the production
– For uncompromised HDR image quality
– SDR images are derived by down-mapping the HDR contend
• Require a dependable high quality conversion which can be done with
dynamic or with static
down-mapping
• Both have their strength
and their limitations
– Providing an efficient and
future proof live workflow
HDR Workflows – HDR workflow with SDR conversion
• Type of down-mapping define how shading need to be done
What are the challenges producing HDR?
• In most cases
quite a large
number of up- and
down-mappers are
required
– Requirements
must be
carefully
calculated
upfront to avoid
any shortage
What are the challenges producing HDR?
• Lessons learned from test productions completed since 2014 *
– European Athletics Championships Zurich - August 2014
• First live HDR recordings in PQ/1080p
– Moto GP Final Valencia - November 2014
• First multi camera test in PQ/1080p
– Woman World Cup Soccer Vancouver - June 2015
• Comparing 4K SDR and 1080p in HDR
– Formula 1 several tests during 2016/2017
• 1080p, 4K, SDR, HDR, etc.
– LA Dodgers Baseball Los Angeles - August 2017
• Live production in HLG/1080p with dynamic down-mapping
– Cinderella Ballet at Sadler Wells London - December 2017
• 4K PQ/HLG under extremely challenging lighting conditions
– Red Bull Crashed Ice Saint Paul - January 2018
• Live production in HLG/1080p with SDR static down-mapping * Selected events only
Summary - Understanding HDR, WCG & Workflows
• UHD has a large palette of options to choose from
• HDR (including WCG) is a major topic and for good reasons
– Much improved viewer experience independent from the screen size
• Different HDR workflow are available and all their strength and weaknesses
– Full parallel HDR / SDR workflows
– HDR/SDR workflow using conversion
• Adopted Film Workflow
• Native HDR conversion to SDR