HDR in der Live-Produktion Von der Kamera bis zu einem HDR / SDR kompatiblen Workflow

Transcription

1 HDR in der Live-Produktion Von der Kamera bis zu einem HDR / SDR kompatiblen Workflow Klaus Weber Principal Camera Solutions & Technology

2 Agenda UHD Options & Challenges More Pixel Better Pixel Better Colors HDR in Live Production HDR Standards HDR Workflows Summary

3 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

4 4K resolution UHD Options & Challenges More Pixels 8x more bandwidth than HD 12G 1.5G 1080i 3G 1080p 2160p 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

5 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 Large Aperture Small Aperture Why does it matter more in 4K acquisition? In 4K acquisition the resolution loss hurts two F-stops earlier than in HD!

6 UHD Options & Challenges 4K and lens diffraction 5µm pixel Native HD Acceptable performance Optimal performance Optimal performance F8.0 F4.0 F2.0 Poor performance Acceptable performance Optimal performance 2.5µm pixel Native 4K

7 UHD Options & Challenges 4K and lens diffraction Optical Resolution LP/mm 4K 500 HD 250 Focus aberration limit (HD) Focus aberration limit (4K) HD Point of maximum lens resolution 4K Diffraction limit (HD) Diffraction limit (4K) Desired resolution sweet range, 4K sweet range, HD Aperture in f-stops

8 4K resolution Future proof solution Support the trend towards larger screen sizes UHD Benefits More Pixels

9 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 CIE 1931 = Visible colors Pointer s Gamut = Natural colors BT.709 = HDTV standard gamut DCI P3 = Cinema standard gamut BT.2020 = UHD standard gamut Conversion between the different color volumes is a must, but not trivial

10 Extended Color Gamut UHD Benefits Better Colors 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

11 HDR in Live Production

12 Why HDR - For Artistic Reasons High scene contrasts are often requested by the production

13 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

14 Camera-to-Display Transfer Functions OOTF Distribution OETF EOTF 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

15 Camera-to-Display Transfer Functions - SDR OOTF Distribution OETF EOTF

16 HDR Standards - Status Two HDR curves are standardized worldwide for: Production Distribution Presentation SMPTE 2084 / PQ Hybrid Log Gamma / HLG

17 HDR Solutions BBC/NHK Hybrid Log-Gamma In the upper half the signal is mapped in a logarithmic curve The lower half of the HLG signal is close to a regular gamma curve To a SDR monitor the HLG signal look like a regular signal where the knee point is set to a very low level Source: BBC

18 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 nits peak white are supported 10 bit end-to-end are required as minimum

19 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

20 Why a native OETF should be used How applying artistic controls in HDR

21 Why a native OETF should be used Imaging RGB linear in bit Camera System Processing RGB in 34 bit Transmission YC r C b in 10 bit 1.024

22 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

23 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

24 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

25 HDR Workflows HDR workflow with SDR conversion Type of down-mapping define how shading need to be done

26 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

27 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/ p, 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 K 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

28 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