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The Challenging World of 4K HDR Streaming
The Challenging World of 4K HDR Streaming

In 2018, overall 4K TV sales passed the 200 million mark with an estimated trade value of more than $85 billion. 4K is quickly becoming a required standard for consumers on the market for a new TV.

It used to be that simply having 4K capabilities was enough of a selling point for TV manufacturers, content owners and streaming platforms. It’s no wonder then that the aforementioned companies are looking to further differentiate themselves with new and exciting technologies and capabilities.

One of these relatively new and exciting technologies is HDR. It stands for High Dynamic Range and it’s a new breed of screens able to get more dynamic images out of a display - bright whites get brighter, deep blacks get darker and deeper, and overall the colors just pop more.

On a standard display, 4K included, everything below a certain brightness is the same shade. An HDR display goes further with better brightness levels and larger color gamut (more available colors) allowing the viewer to tell the difference between things that are really dark and something that is just dark.

Whenever a new technology emerges, it brings about change and new challenges. Changes in hardware and software, but also content protection along with technical and other challenges.

HDR Challenges
Differences of image quality between standard and high dynamic range (HDR) video

HDR places considerable constraints on the hardware used for playback for both the screen it’s displayed on and the player doing the playback, how its all connected and more.

The single biggest variable in the HDR effect is the quality of the screen. Better quality screens support more brightness levels (in nits) and thus are able to produce better HDR effect. But this is not the only challenge.

Video Standards

There are two main 4K HDR standards in use today:

  • HDR10
  • Dolby Vision

HDR10 is free-to-use for manufacturers and every HDR supporting TV screen can decode it as well as every HDR streamer stream it. 99.99% of HDR content has an HDR10 version of it.

Dolby Vision, on the other hand, is a proprietary standard licensed by Dolby and it comes with a license fee. That license fee does include a service whereby Dolby helps with getting the most out of the technology. Because of the license fee, there is less content available, but all the major studios still support and use it.

From a technical perspective, the only difference that matters between these two standards is how they deal with color and brightness metadata. HDR10 uses static metadata - color and brightness are set for the entire movie, while Dolby Vision supports dynamic metadata enabling scene-by-scene and even frame-by-frame settings for those.

Another difference is the maximum brightness. HDR10 tops out at 1000 nits, while Dolby supports up-to 10 000 nits of brightness.

In short, Dolby Vision is able to produce better-looking visuals with its use of dynamic metadata and higher brightness. Still, HDR10s static use of it produces content that is still leaps and bounds ahead of standard video. Any HDR content simply looks better than standard-definition video, no matter the standard used.

HLG - HDR For Broadcasting

While HDR is more common for streaming video, there is a recognized HDR standard developed by BBC and NHK specifically for use in live broadcasting - Hybrid Log-Gamma or HLG for short. It’s a royalty-free standard that, unlike other HDR standards, is backward compatible with non-HDR or standard dynamic range displays.

It’s still rare to see broadcasts done in HLG, but support from device manufacturers is gaining speed and broadcast trials are being held in different regions around the world. For example, last year’s Champions League final was broadcast in HDR by BTSport. The TV network has committed itself to show up to 70 live events in HDR per season.

Codec Support & Streaming

With the massive increase in file size for 4K HDR videos, comes another problem - compression for streaming. Existing codecs like the widely used H.264 is simply not good enough to enable 4K HDR streaming. The files are still too big.

This is were new codecs like HEVC (High Efficiency Video Coding), better known as H.265, and VP9 come into play. They’re both around twice as efficient as H.264 and thus are suitable streaming 4K HDR content. Both of these codecs support HDR10, Dolby Vision and HLG.

File size and streaming support become especially important in disconnected scenarios on different vessels like airplanes with their seatback devices and BYOD (Bring Your Own Device) support. In July 2019, ANA became the first commercial airline to launch 4K TVs on airplanes. While it currently does not support HDR, it’s only a matter of time.

Hardware Support
Differences between human eye dynamic range color & contrast and standard TV screen and high dynamic range TV screen color and contrast

Leaving aside the fact that 4K has 4-times the pixels of Full HD and thus enormous file sizes which put constraints on physical hard drive space required for storing those files, 4K HDR has other hardware requirements. Hardware support has three sides - the screen, the device/player doing the playback and the cable connecting them.

As a first step, the content must be available in 4K HDR by the content provider and accessible by the user. Not only available but also encoded in an HDR standard that the hardware used can use.

The screen
It’s not enough for a screen to have 4K resolution to be able to support 4K HDR. As HDR is all about more color and brightness, it adds extra requirements for the screen.

More precisely, support for bigger color gamut i.e bigger range of available colors and better max brightness limit. Depending on these limits, displays can be certified for HDR10 or Dolby Vision.

Not all HDR10 certified screens support Dolby Vision, but all Dolby Vision certified screens support HDR10. This is thanks to higher technical specifications for Dolby supported screens.

The playback device/player
With players, the situation gets a little more complicated. One side of the equation is if the device is technically able to support playback of 4K HDR content in either standard. Next, the question is about the streaming service used and if that particular streaming service supports the device in question.

Not all streaming services support 4K HDR on every device or built-in player in the case of smart TVs. For example, 4K and 4K HDR streaming through Netflix is only available on specific TV models, streaming devices, and computers. On Windows 10, it only works the Edge browser and Netflix app.

Reasons for this are mainly DRM and content protection related. More on this later.

The connection
The final piece of the puzzle is the connection between the screen and the playback device/player. With smart TVs with built-in apps, the situation is clear - it either supports 4K HDR streaming or not.

With “external” players, as in players separate from the screen, it’s the cable that determines playback capabilities. 4K HDR streaming requires that the cable to be HDMI 2.0b certified and support the HDCP 2.2 standard - the latest evolution of copy protection. HDCP is not DRM, it simply provides a secure link between a source and a display.

For it all to work, the screen, device, and the cable must be HDMI 2.0b certified and support HDCP 2.2.

Which brings us to DRM. As said earlier, HDCP is not DRM. DRM content protection is another topic all on its own with 4K HDR content.

“Hardware” DRM

4K HDR content is the highest quality content that has ever been available for consumer use and thus content owners are keen to use and indeed require that the highest DRM protection levels available are used.

That highest level of DRM protection is better known as "hardware" DRM. This means that all content processing, cryptography, and control is performed within the Trusted Execution Environment (TEE) of the supported device’s processor.

Emphasize on a supported processor. Not all processors support this. When the said hardware is connected via HDCP 2.2 supporting cable to the playback screen, "hardware" DRM is achieved and content is allowed to be shown in 4K HDR.

Apart from hardware support, another side of the story is the DRM service you’re using. The service has to support “hardware” DRM and the technologies (WideVine, PlayReady, FairPlay) your system requires.

One such service is Axinom DRM. Our DRM solution has enabled prominent media, broadcast, and telecommunications organizations in reaching a global audience with their content. With the right mix of robustness, scalability, and extensibility, Axinom fulfills viewer expectations in offering a choice of content and device support.

Multi-key DRM
Technical drawing on single VS multiple key DRM differences from a technical perspective.

With “hardware” DRM, all the hard work of processing and cryptography is done by on-board processors. This puts a considerable strain on the hardware and as it’s not needed or required for content below 4K and 4K HDR quality - it doesn’t make sense to use everywhere.

Instead, adaptive streaming and multi-key DRM are used to optimize hardware use and network congestion. What this means is that different quality of the same content (540p, 1080p, 4K, 4K HDR, etc) use different DRM levels, encryption keys, and methods.

Multiple key DRM is not the same as multi-DRM. Whereas multi-DRM integrates DRM solutions from different vendors (Apple FairPlay, Microsoft Widevine, Google PlayReady) as efficiently as possible, DRM with multiple keys is about making content protection more granular, flexible and secure.

As with “hardware” DRM support, multiple key DRM requires a DRM service that supports it. A service such as Axinom CMS that provides a unified, end-to-end workflow with a high level of automation.

It’s highly customizable and extensible and can be adapted to project needs, handle all content types, is interoperable with numerous third-party services and is frontend agnostic.

We support all major DRM methodologies and standards - multi-DRM, multi-key DRM, “hardware” DRM. Together with Axinom CMS, we provide a unified and highly automated end-to-end workflow that is highly customizable and extendable.

To learn more about Axinom products and services, get in touch by using the chat below!