Griffis: Dolby Vision’s A`Super Set’ Of All Other 4K HDR Approaches
In the interest of getting an update on the decision-making going on now within various industry standards groups on the future of 4K Ultra HDTV systems that will present picture improvements including inclusion of high dynamic range (HDR) and wide color gamut (WCG), we caught up with Pat Griffis, Dolby Laboratories office of the CTO executive director, to better understand what Dolby is proposing.
In a recent interview with Technicolor’s business development VP, we learned that Dolby Labs was pursuing a closed system, which it calls Dolby Vision, for content development, encoding and display technologies supporting HDR and WCG, which Technicolor and others believe should be open for broadbased development and use.
But Griffis said that it was Dolby that led the charge for HDR and WCG systems in next-generation displays and that several of the technologies it has submitted have already been adopted as standards for industry use.
Read more of our interview with Dolby Labs’ Pat Griffis after the jump:
Q: We’ve heard from Technicolor that Dolby is pursuing a system for HDR that isn’t open to collaboration and designed to work within a closed ecosystem of manufacturers and content providers. How would you describe the HDR formats and systems you would like to see passed within the Ultra HD Alliance (UHDA) and other industry standards setting bodies?
A: Dolby was the first to reintroduce the possibilities of high dynamic range with wider color gamut (or “better pixels”) to the attention of the technical community and industry at large several years ago. Dolby led the effort to create a new set of standards in The Society of Motion Picture and Television Engineers (SMPTE), which define a new HDR Electro-Optic Transfer Function (EOTF) [the process by which digital code words are transferred into visible light] based on how the human eye sees, called the “Perceptual Quantizer” or “PQ” (SMPTE ST-2084), as well as a standard to define the characteristics of the HDR mastering environment ( SMPTE ST-2086).
These standards have been embraced by a number of standards bodies including Blu-ray, MPEG, and now UHDA. Dolby Vision builds on these standards to provide the best possible experience today. We continue to standardize other components of the Dolby Vision technology including our technology to capture and deliver content-scene-based information to improve the mapping of HDR to SDR. As an invited founding member of the UHD Alliance, recognized for our leadership in both audio and imaging technologies, Dolby is working in concert with the Alliance to ensure these technologies, coupled with performance metrics, will deliver a premium entertainment experience throughout the Ultra HD ecosystem from content creation to consumer enjoyment.
Q: What would you like to see approved as an industry standard for HDR, and why is that superior to the solutions sought by others?
A: We would like to see Dolby Vision approved as an industry standard for HDR. We recognized the need for HDR and wider color gamut as key features for the next generation entertainment experience. After years of research and development, investigating the requirements in the market, close cooperation with all six Hollywood studios to define the necessary precision and then spec a future-proof approach, we developed Dolby Vision as an end-to-end ecosystem solution focusing on the best end-consumer experience. Dolby Vision was developed as the highest quality solution capable of up to full 12-bit dynamic range performance and as such, is a super set of all other approaches in the market. As requirements have evolved, Dolby Vision has been refined into a universal playback solution that embraces SDR as well as other HDR formats such as HDR10, which is a base layer format for next generation Blu-ray.
Q: How is Dolby Vision superior to other HDR format proposals being considered for industry adoption?
A: We developed Dolby Vision as a complete end-to-end ecosystem solution while focusing on the best end-consumer experience across a variety of devices and use cases. Dolby Vision is the highest quality HDR solution available capable of up to full 12 bit dynamic range performance with full color capability and as such, is a super set of all other approaches in the market. For stakeholders across the ecosystem, Dolby Vision provides an accurate, compatible, flexible, scalable and future-proof solution.
It also offers a variety of implementation approaches based on use case, bit budget, and market. Specifically, Dolby Vision works with any spatial resolution including 720P, HD, 4K, etc., any video codec (AVC or HEVC), provides a backwards compatible dual-layer, or a non-backwards compatible high-efficiency single-layer option, state of the art tone mapping from HDR to SDR, and, a fully blended HDR to SDR scaling, all of which is being implemented by numerous system-on a- chip (SoC) suppliers. A Dolby Vision solution just works.
Q: Once an HDR format or formats are selected for broad-based distribution, what tools will Dolby have available for postproduction, encoding etc. Can you explain what these tools are, how they will work and how quickly they can be brought up to speed to begin content production processes?
A: Dolby has worked with technology leaders in all parts of the entertainment content ecosystem to enable the necessary technology to create, master, distribute and enjoy Dolby Vision content. The good news is that for scripted workflow, the process remains largely the same, the major changes were to expand the dynamic range in the color suite through new generation of HDR mastering displays which Dolby has developed and enabling the color editing tools to capture and preserve the higher dynamic range information.
Dolby has worked with most of the major color editing tools vendors such as FilmLight, Black Magic, AutoDesk, Digital Vision, etc. to enable Dolby Vision content creation and their solutions are in deployment to create content for major studios like Warner Brothers today. We have also partnered with Deluxe which can provide full-service Dolby Vision mastering. Our approach is to master in the largest color volume possible [color volume is the pallet of all available colors at all allowable intensities. The larger the color volume, the greater the range of both color and contrast]. From that highest quality master, we can derive any needed output version including International Telecommunications Union (ITU) Rec.709 standard dynamic range (SDR) as well as HDR10 and anything in between providing maximum flexibility for the content owner. Dolby Vision uses existing standards such as H.264 and HEVC for distribution which we have already implemented and are deploying with over-the-top (OTT) Internet streaming providers such as VUDU this year. We are also working with all the major compression companies to implement additional commercial solution offerings and are concentrating now on the challenges of real time live HDR distribution.
Q: How will your HDR systems work with wide color gamut material?
A: The Dolby Vision solution is agnostic regarding color primaries and will work with XYZ, ITU Rec. 2020, Digital Cinema Initiative (DCI) P3 Cinema primaries, Rec. 709 or any color primaries the content creator may choose. Of course Dolby Vision also works for Cinema and there are already several movies that have been graded and presented in Dolby Vision including “Tomorrowland” from Disney. As mentioned, our grading process uses high-dynamic range and wide color gamut displays allowing creative professionals to fulfill their artistic intent through the use of a large color palette. Currently, our best displays have a 4000 Cd/M2 (or “Nits”) Cinema Primary (P3) color volume, which 40x brighter than conventional 100 nit CRT’s, and our cinema projector uses a six primary color volume which subsumes nearly 100 percent of the Rec 2020 primary colors.
The resulting files have 12-bit precision across the full pallet of available colors so nothing needs to be “added” to the file. Dolby Vision-enabled Color Grading systems provide features to preserve the artistic intent by capturing metadata to aid in effective mapping to various lower level outputs such as HDR10 or Rec. 709 SDR. This metadata is then preserved throughout the Dolby Vision encoding system for post-produced content, and ultimately decoded in the Dolby Vision-enabled device to maintain artistic intent from the creative to the consumer, while providing the best experience possible for the pedigree of the consumer display device. Such metadata is not required for natural content such as live broadcasts.
Q: What’s Dolby’s position on the dual-layer approach devised for HDR content with backward compatibility? Why is this preferable to some of the other systems being considered?
A: Dolby Vision’s high dynamic range and wide color gamut technology uses a base-layer and an enhancement layer for backward compatibility, or a single-layer offering improved coding efficiency performance when backward compatibility is not necessary. With this approach, some existing infrastructures and encoder/decoder technology may easily adopt Dolby Vision while retaining backward compatibility. In the case of OTT, where there may be petabytes of legacy SDR material already in the cloud with a large installed base of customers, the benefit of backwards compatibility is that content can be sent with an enhancement layer to both legacy and new Dolby Vision-enabled TV’s and the legacy TV will play the SDR layer just like it does today and ignore the HDR layer. The Dolby Vision-enabled TV can take both layers and produce a full quality image. The key benefit is that the enhancement layer only requires on the order of 20-25 percent additional bit-rate over the SDR base layer. For the OTT provider, the ability to repurpose nearly 80 percent of their SDR content for HDR is a huge benefit particularly when you consider the fact that adaptive streaming profiles increase the number of versions of content that must be encoded. Further, the Dolby Vision single layer solution offers improved coding efficiency and will play back on any dual layer enabled Dolby Vision TV, so it offers a future proof migration path as the installed base transitions. Dolby Vision also offers flexibility in precision, for noise free images like animation, CGI and graphics; 12 bits are available to prevent artifacts. For natural content such as live broadcast, we also offer a single layer 10bit solution which is sufficient precision, due to camera noise, to ensure artifacts are below the visible threshold.
Q: How many HDR formats do you ultimately expect to be approved for broad-based use and with which delivery methods?
A: As HDR technology content comes to market, there could be several possible HDR content types available, including Dolby Vision. What’s important to note is that when mastering in Dolby Vision, creatives can master once to the highest quality and can then derive all other industry approved grades from this single distribution master. Therefore, in order to create a simple playback solution, Dolby Vision will support playback from all of these content types, to ensure the best quality experience with Dolby Vision. There is an industry desire for a single-layer HDR solution that works with the existing HEVC Main 10 profile. The new Dolby Vision Single-Layer profile allows for perceived 12-bit fidelity by providing metadata within a 10-bit profile which is used to provide state of the art tone mapping. As a result, Dolby Vision can deliver the best quality compression, quantization and 420 conversion using industry-standard 10-bit HEVC codecs for maximum compatibility. Dolby Vision is an option in Blu-ray offering the highest quality and is being deployed this year via OTT with a full 12-bit backwards compatible dual-layer approach.
Q: Would Dolby consider subsidizing manufacturers or content distributors to see that its system gains market support?
A: Dolby is working directly with the studios to ensure that distribution channels receive content that is already in a Dolby Vision format. We provide distribution-specific encoder technology, depending on whether the distribution is through packaged media, OTT, broadcast, or cinema. The rest of the infrastructure stays the same.
Q: Will streaming or UHD Blu-ray make for better HDR delivery platforms or will it be delivery platform agnostic?
A: The next generation Blu-ray format uses a 10- bit PQ base- layer profile which provides good performance. Dolby Vision builds on this base layer to provide 12-bit precision and increased performance. Both are played out from the disk at bit rates much higher than typical OTT. Some are considering using this Blu-ray HDR base layer as a streaming profile and if so, Dolby Vision can also be added on top of this as base layer in the dual-layer approach as I’ve described. Another method is to provide Dolby Vision as a backwards compatible enhancement layer on top of an SDR base layer as described above. Dolby Vision works fine for either use case. Dolby intends to provide a solution to its partners that can handle any of these use cases and support a single- layer 10-bit approach, which provides significant coding efficiency versus the Blu-ray HDR base layer, an important consideration for bit-rate constrained OTT channels. Also, unlike the Blu-ray HDR base layer, Dolby Vision can also work with the H.264 codec which is an important consideration for portable and cost constrained use cases.
Q: How many camera stops do you expect the final home-delivered HDR solution to support? Are there any particular camera solutions Dolby endorses for HDR capture?
A: In the real world from sunlight to starlight, human beings deal with over 42 f-stops of dynamic range. Our reported scientific research has shown that for both large screen ( i.e. cinematic) as well as small screen (e.g. TV) , the useful dynamic range needed for entertainment content purposes is on the order of 22 f-stops to satisfy the most demanding viewers. Note this is the full end-to-end range for capture purposes and when we consider a specific scene with high peak brightness, the simultaneous contrast needed can generally be lower. Since the majority of movies today are digital, the current trend is to use digital film cameras. Most digital film cameras today will do at least 14 f-stops and some are entering the market with up 18 f-stops of dynamic range.
We have evaluated many cameras but prefer not to make recommendations at this point. What is important to note is that the cameras aren’t the limiting factor; rather, the downstream processing for an 8-bit, 4:2:0, 100 nit max, gamma–based legacy ecosystem is. Our goal is to deliver the largest color volume content possible and we support the SMPTE ST-2084 container which goes from 0 to 10,000 nits in 12-bits with a step-size precision that is below the threshold of visibility anywhere in that end-to-end range. The Dolby Vision ecosystem is designed to enable this level of quality all the way to the end display and then allow the final display to effectively map that content to its native capabilities to provide the best experience possible. This is true for all device classes such as TV’s, tablets, mobile devices etc.
Q: When should we expect to see Dolby Vision content in the marketplace, and do you know if current sets on the market from Sony, Samsung, LG, Panasonic, Philips and others will be able to support it with firmware updates, or do we have to wait for next-generation products including Vizio’s Dolby Vision-supporting Reference Series TVs?
As an end-to-end solution, we have the ecosystem in place to make it easy for new and catalog titles to be mastered in Dolby Vision. We are working with all major studios to deliver Dolby Vision content to the consumer. At CES 2015, we announced several key partnerships. First, Warner Bros. Home Entertainment announced a commitment to creating Dolby Vision content. Warner Bros. has been working with Dolby to re-master library titles and is mastering new home releases in Dolby Vision and the available titles will continue to grow by OTT service launch.
Netflix also publicly committed to delivering Dolby Vision content to the home in 2015. We are excited to be working with Netflix to make this happen, and are especially focused on Netflix original content. Further, our partners in the content creation ecosystem continue to expand in response to growing interest and now include AVID, Digital Vision, Film Light, Autodesk, and Adobe. Those partners demoed Dolby Vision at NAB. Finally, Deluxe, a leading post production facility, is fully up to speed creating Dolby Vision masters for customers. Content mastered using Dolby Vision will also be available via OTT from service providers such as VUDU and eventually via video on demand (VoD).
As for devices, purchasing a new TV or other device will be required, as new models enabled with Dolby Vision will be coming to market throughout the year.
By Greg Tarr
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