HDR: Which format is which?

HDR: Which format is which?

UHD or ‘Ultra High Definition’ television promises many things, among them high dynamic range (HDR), a wider colour gamut (ie getting closer to the huge range of colours that most people can see), higher frame rates (for super-smooth action, particularly in sport) and higher resolution (4K). Between them, they’re shaking up the TV technology landscape.

In HDR, there are three main standards you’ll have probably heard of. For delivery, the BBC and NHK have developed their Hybrid Log-Gamma system, HLG, while Dolby favour their own Dolby Vision (also known as Dolby PQ). Then, for more domestic delivery, there is also HDR 10.

The principle of using an alternate gamma so that you concentrate the bit-depth where you want the extra range is well established; our eyes do not perceive light the way cameras do. To recap, with a camera, when twice the number of photons hit the sensor, it receives twice the signal (a linear relationship). We, on the other hand, perceive twice the light as being only a fraction brighter — and this is increasingly true at higher light intensities (a nonlinear relationship).

Since gamma encoding redistributes tonal levels closer to how our eyes perceive them, fewer bits are needed to describe a given tonal range. Otherwise, an excess of bits would be devoted to describing the brighter tones (where the camera is relatively more sensitive), and a shortage of bits would be left to describe the darker tones (where the camera is relatively less sensitive). This means gamma encoded images store greyscale more efficiently.

ITU-R BT.2100

It does seem like all of the manufacturers will coalesce around BT.2100, which defines (amongst other things) how you handle the specular highlights: those very bright parts of the picture which really add to the look of pictures.

Specular highlights are typically defined to be >500 Cdm-2, which is much brighter than broadcast white! The idea is that in 10-bit HDR, the tenth bit of dynamic range (all values above 512) represents the highlights, and the other nine bits are akin to the usual video dynamic range.

Delivery formats

There are three delivery formats you need to consider.

HLG

HLG was developed by the BBC and their Japanese counterpart NHK. It is a scene-referred system, just like conventional television, and has been designed with the specific goal of making the transition to HDR easy on broadcasters and production crews – hence its compatibility with SDR, which means that broadcasters can continue to use their existing 10-bit SDI production installations (as with all video, levels are considered dimensionless).

HLG uses relative brightness values to dictate how an image is displayed – the display uses its knowledge of its own capabilities to interpret the relative, scene-referred information. This means that the image can be displayed on monitors with very different brightness capabilities without any impact on the artistic effect of the scene. Because it uses relative values, HLG does not need to carry metadata, and can be used with displays of differing brightness in a wide range of viewing environments.

HLG is supported in Rec. 2100 with a nominal peak luminance of 1000 Cdm-2 (though the BBC have said this is an artificial cap imposed by the monitors they use, and the real figure is more like 4000). It is also supported in HEVC.

Dolby Vision or DolbyPQ (Perceptual Quantiser)

Dolby Vision is the wider set of products that cover both digital cinema and video – Dolby PQ is the element that we’re concerned with. Unlike HLG, DolbyPQ is a display-referred system that uses absolute dimensioned values for the light captured.

The metadata that travels in the SDi payload defines how video levels equate to light levels, and how they should be reproduced at the DolbyPQ display end. The display then reports back to the playback device via EDID to convey its maximum light output.

DolbyPQ supports a maximum brightness of 10,000 Cdm-2.

HDR 10
HDR 10 is another format you’ll have heard of. It’s an open source version of PQ, developed by device manufacturers, but it has a lower video quality, mastered in 10-bit, and only up to 1000 nits cd/m(compared to Dolby’s potential 10,000). It does use metadata, but a far simpler form than Dolby, specifying one luminance level for the entire programme rather than frame by frame.
It’s not backwards compatible either (so can’t be viewed on SDR displays) but because its far more affordable, it’s a popular standard for domestic delivery, particularly on systems where it’s easy to host an SDR version to accompany the HDR (so UHD Blu-rays, set-top boxes and streaming services like Amazon). Sony and Microsoft have also gone down this route for PlayStation 4 and Xbox One S. So while it is big in home cinema, it ultimately has little relevance for the professional production environment.
Dynamic range

All of these formats have greater dynamic range than the human eye (about 14 stops) and SDR video (about six stops) and 10-bit pro SDR (about 10). When HLG footage is displayed on a 1,000 Cdm-2 display with a bit depth of 10 bits per sample, it has a dynamic range of 200,000:1 or 17.6 stops.

HLG also increases the dynamic range by not including the linear part of the conventional gamma curve used by Rec. 601 and Rec. 709. The linear part of the conventional gamma curve was used to limit camera noise in low light video, but is no longer needed with HDR cameras.

DolbyPQ has an even broader dynamic range of around 18 stops, but this is necessary when using display referral as you need to be able to accommodate different types of display and viewing conditions.

Which is right for you?

In a controlled environment like a movie theatre, Dolby Vision makes a lot of sense – it gives you very precise control, can take advantage of more advanced displays, and has a high degree of futureproofing thanks to that whopping 10,000 Cdm-2 upper limit. If you’re in a feature-focused facility with an existing Dolby workflow, it makes a lot of sense to roll out this system to other parts of your pipeline.

However, if your bread and butter jobs come from the BBC and you’re aware that a lot of your viewers will, ultimately, be watching your content in their living room, in the office at lunch or on their iPhone, aligning your setup to their standard seems sensible, as you’ll be in line with a major customer, and the adaptive nature of HLG means it’s well suited to the variety of viewing environments you need to cater for if you’re producing online or television content.

How can we help?

Well, we can make recommendations for acquisition, post-production and delivery of HDR content. We carry cameras, monitors and video interfaces appropriate to HDR workflows, and can often offer demo kit to test in customers’ workflows. To find out more, get in touch with the team on the details below.

If you want to know more, give us a call on 03332 409 306 or email broadcast@Jigsaw24.com. For all the latest news, follow @WeAreJigsaw24 on Twitter, or ‘Like’ us on Facebook.

IBC 2016: Avid demonstrates leadership in emerging IP and UHD workflows

IBC 2016: Avid demonstrates leadership in emerging IP and UHD workflows

At IBC 2016, Avid showcases IP and UHD workflow innovation on the open, interoperable Avid MediaCentral Platform.

Avid today previewed solutions for several converging technologies that are driving significant change for the media industry. By supporting real-time IP signals natively in key components of the Avid MediaCentral Platform, Avid is accelerating the industry’s transition to IP and delivering a unified environment for file-based and live signal-based media workflows that will ease the migration to emerging image formats, including UHD.

“To address the intensifying changes that our industry is facing, we are continuing to invest heavily in key technologies and innovations that are important for customer success,” said Dana Ruzicka, vice president and chief product officer at Avid. “At IBC 2016, we are demonstrating how the open, integrated Avid MediaCentral Platform will accelerate the transition to IP stream-based workflows, and make it possible for customers to create, manage, and deliver UHD content powerfully and efficiently.”

Historically, media companies have relied on specialized technologies for transporting video and audio signals throughout facilities and across geographies. Legacy technologies like coaxial cabling and baseband SDI signals were necessary because IP data networks lacked adequate bandwidth. But rapid technological advancement has made it feasible to pass professional audio and video signals over standard IP networks. Unlike traditional baseband infrastructure, IP networks are intrinsically format agnostic, paving the way for adoption of new formats like UHD. Converging on IP networks for file-based and signal-based traffic will provide media companies with increased flexibility, agility, and lower costs.

New Avid video IP integrations at IBC

Avid will demonstrate support for a variety of emerging IP standards, including SMPTE 2022-6 and VSF TR-03, illustrating how media companies can easily manage the transition to converged IP infrastructure over time. Technology presentations will showcase IP ingest, editing, playout, graphics insertion, and monitoring workflows spanning several Avid products, including Media Composer, Maestro, 3DPlay, and Playmaker.

“The innovative architecture of Avid’s MediaCentral Platform treats all content equally, regardless of its format or source,” said Alan Hoff, Vice President, Market Solutions at Avid. “We are delivering upon our vision to provide a unified, open platform for converged file and signal-based workflows by expanding support for emerging standards like IP and UHD.”

New Avid UHD integrations at IBC

Avid will showcase innovative UHD broadcast solutions that integrate seamlessly with both standard SDI production infrastructure, as well as IP production workflows. The Avid UHD workflow enables broadcasters to deliver richer, sharper content without over-investing in new solutions, and is centered on Media Composer | Software, Interplay | Production, Media | Director, Pro Tools, Avid DNxHR, and Avid NEXIS, along with graphics and replay servers.

Avid is also participating fully in the AIMS alliance and showcasing its interoperability at IBC 2016 with products from other vendors at the IP Interoperability Zone in Hall 8.

For more on the latest IBC releases, take a look at our roundup post, give us a call on 03332 409 306, email broadcast@Jigsaw24.com or pop your details in the form below. For all the latest news, follow @WeAreJigsaw24 on Twitter or ‘Like’ us on Facebook.

CES2016: UHD Alliance present ‘UHD Premium’ standards for UHD and HDR

CES2016: UHD Alliance present ‘UHD Premium’ standards for UHD and HDR

The UHDA, formed a year ago, comprises of the biggest players in the global content creation and distribution industries. Their primary goal is to “Define a next generation premium audio-visual entertainment experience”, and at CES 2016 they have announced their first major step.

The UltraHD Premium ‘standard’ is not a format, like we have from the SMTPE for colour spaces (BT.2020, REC.709 et al), but as explained by UHDA President Hanno Blass – who is chief technology officer at 20th Century Fox – it is “…parameters that define the quality of the experience.” This is great news for content creators and consumers. Those of us looking for a UHD TV in the coming months will start to see this logo being used to show that the model complies with various requirements covering resolution, bit depth and colour spaces.

Blass provided the following details on these specifications that manufactures will have to meet to be legible for licensing the logo onto their devices:

UltraHD Premium Logo
UltraHD Premium Logo

 

“The UHD Alliance has developed three specifications to support the next-generation premium home entertainment experience. The three specifications cover the entertainment ecosystem in the following categories:

– Devices (currently, television displays, with other devices under consideration)

– Distribution

– Content

A high level overview of each technical specification can be found below. Please join the UHD Alliance for full access to all technical and test specifications.

Devices

The UHD Alliance supports various display technologies and consequently, have defined combinations of parameters to ensure a premium experience across a wide range of devices. In order to receive the UHD Alliance Premium Logo, the device must meet or exceed the following specifications:

– Image Resolution: 3840×2160

– Color Bit Depth: 10-bit signal

– Color Palette (Wide Color Gamut)

– Signal Input: BT.2020 color representation

– Display Reproduction: More than 90% of P3 colors

– High Dynamic Range

– SMPTE ST2084 EOTF

– A combination of peak brightness and black level either:

More than 1000 nits peak brightness and less than 0.05 nits black level

OR

More than 540 nits peak brightness and less than 0.0005 nits black level

Distribution

Any distribution channel delivering the UHD Alliance content must support:

– Image Resolution: 3840×2160

– Color Bit Depth: Minimum 10-bit signal

– Color: BT.2020 color representation

– High Dynamic Range: SMPTE ST2084 EOTF

Content Master

The UHD Alliance Content Master must meet the following requirements:

– Image Resolution: 3840×2160

– Color Bit Depth: Minimum 10-bit signal

– Color: BT.2020 color representation

– High Dynamic Range: SMPTE ST2084 EOTF

The UHD Alliance recommends the following mastering display specifications:

– Display Reproduction: Minimum 100% of P3 colors

– Peak Brightness: More than 1000 nits

– Black Level: Less than 0.03 nits

The UHD Alliance technical specifications prioritize image quality and recommend support for next-generation audio.”


These specifications will help consumers choose TV sets and other devices capable of showing the highest quality content which has been created to the same high specifications laid out by the industry leaders.

It will also influence the workflows and technology being chosen by production and post-production companies to make sure their content meets the standards being put together by the UHDA group.

UHDA Board Members at the CES Press Conference. From Left to right: Victor Matsuda (Sony), Masahiro Shinada (Panasonic), Bryan Barber (Warner Home Video), Mike Dunn (Twentieth Century Fox), Ron Sanders (Warner Home Video), Man Jit Singh (Sony), Hanno Basse (Fox), Michael Bonner (Universal), SP Baik (LG), Michael Wise (Universal), KG Lee (Samsung), Mark Turner (Technicolor), and Mahesh Balakrishnan (Dolby)
UHDA Board Members at the CES Press Conference. From left to right: Victor Matsuda (Sony), Masahiro Shinada (Panasonic), Bryan Barber (Warner Home Video), Mike Dunn (Twentieth Century Fox), Ron Sanders (Warner Home Video), Man Jit Singh (Sony), Hanno Basse (Fox), Michael Bonner (Universal), SP Baik (LG), Michael Wise (Universal), KG Lee (Samsung), Mark Turner (Technicolor), and Mahesh Balakrishnan (Dolby)

 

If you want to find out more about how Jigsaw24’s expert consultants can advise you on workflows and technologies around UHD and HDR content capture and creation, please get in touch with our team by emailing broadcast@jigsaw24.com