Why HDR Provides the Quality OTT Providers Need to Excel
Streaming video services have shown that you don’t need to leave the house or subscribe to a traditional cable service to view premium content, but the video quality may not be consistent. Viewers certainly expect it to be—that's why they purchase new displays, smartphones and tablets that offer higher resolutions and support high dynamic range (HDR). If one OTT provider fails to stream content at that level, consumers may look elsewhere.
From encoding to playback, organizations that make the inevitable switch from SDR to HDR will greatly improve the video quality of experience (QoE). HDR is not yet the norm for streaming video, but most new content is being produced with the technology, which begs the question: why aren’t streaming video services taking advantage of this? Why should anyone have to buy the Blu-ray disc to see content the way it was originally intended when they’re paying good money for OTT providers? HDR is gradually becoming ubiquitous in the general streaming space, but the industry as a whole must catch up. In other words, OTT services will need to provide HDR content to remain competitive. Streaming industry analyst Dan Rayburn believes that HDR will be a key advantage to one or more OTT services and predicts that HDR adoption will accelerate significantly over the next two years.
I concur with his assessment but will also add that HDR will be a notable differentiator for any streaming service that adopts the technology. But not all technology is created equal, and the same can be said about HDR. Designed to provide superior visuals with a greater variety in brightness, contrast, and color accuracy, HDR offers a distinct advantage to streaming video. There are four common encoding standards – HDR10, HDR10+, HLG (hybrid log-gamma) and Dolby Vision – being used to bolster picture quality, but their differences are very important. In order to develop the very best OTT platform possible, it is important to understand these differences. Let’s take a closer look at how HDR works and how the different versions impact the visual quality of the content being streamed.
HDR's Impact on Color
HDR produces darker blacks and brighter whites than standard dynamic range (SDR). It also increases the number of steps between each value of gray, resulting in more shades of that color as well.
In photography, HDR images are created by combining several photos that are taken – each at different exposures and with the amount of light doubled from one to the next – during a burst. In video, HDR uses just one single exposure and instead relies on the power of HDR-compatible displays to ensure the bright parts of the images are really bright and the dark parts remain appropriately dark.
HDR provides a significant improvement in color, a value based on absolute red, green and blue levels regardless of the video format. With a greater range for both color as well as contrast, HDR offers impressive illumination with difficult light. This makes it easier to capture and more accurately display the stunning visuals of images that contain light backgrounds and dark foregrounds.
With all of that in mind, OTT providers are likely to be interested in using HDR as soon as possible. But before they do, they need to review the primary standards currently in use.
The Four Types of HDR
There is no one-size-fits-all HDR solution. Each encoding standard requires different hardware and video content, so it’s unlikely that every need will be fulfilled by a single standard. Instead of picking a “best” of the bunch, let’s instead focus on what each solution has to offer:
HDR10: Advanced by the UHD Alliance, HDR10 adheres to a few notable conventions: it uses the ST2084 Perception Quantization (PQ) curve and the REC.2020 color space. HDR10 also supports TVs with luminosities of 1,000 nits (compared to the 100 nits of SDR TVs) while allowing mastering on monitors with 4,000 nits and support for the future up to 10,000 nits. It is an open, royalty-free standard, which has allowed its popularity to flourish, offers 10bpc (bits per channel) encoding and uses static metadata. Last but not least, HDR10 can be found in virtually any TV that supports HDR, from expensive high-end sets with all the bells and whistles to budget-friendly displays, providing broad consumer reach.
HDR10+: Much like the "plus" added to any number of products, services, solutions, and standards, HDR10+ is essentially an enhanced version of HDR10. With improved picture quality and the option to add an extra layer of data—with the purpose of updating luminance on a scene-by-scene or even frame-by-frame basis—HDR10+ offers some advantages. It also incorporates dynamic metadata, which results in a more efficient tone-mapping process and provides separate information for each scene. With luminance values up to 10,000 nits and resolutions up to 8K, HDR10+ is a strong option. Display manufacturers appreciate the lower price and freedom compared to Dolby Vision, which we’ll discuss next, as it allows them to bring their own strengths and processes into play.
HLG: Co-developed by the BBC and NHK for broadcast applications, HLG uses a hybrid approach for its gamma function. It combines the SDR gamma curve with a logarithmic function for the HDR range, creating a best-of-both-worlds scenario in which HLG content can be viewed as intended on both SDR and HDR-capable monitors. It also allows one video signal to support both HDR and SDR live without the need to grade or use LUTs.
Dolby Vision: With luminance values up to 10,000 nits, dynamic metadata, and 12bpc encoding, Dolby Vision offers the highest quality HDR available. Dolby Vision is also capable of replicating real-life scenes and images to produce more realistic sunrises and other visuals when compared to competing HDR standards. But it is the most demanding standard currently in the market, and Dolby Vision charges a license fee that both content creators and device makers have to pay. If a company can afford to pay for it, the benefits are pretty clear – but it may not be right for everyone.
Storytellers and device manufacturers want to ensure that they deliver the most visually compelling content possible. HDR can help them achieve that, but they must first understand the differences between each of the three leading standards before deciding which to use. That said, even if everyone adopts HDR for all new content and upconverts their old videos from SDR, the quality will still vary.
On the upside, this provides another opportunity for streaming services to stand out by offering the best HDR quality available. I predict OTT providers can – and will – succeed by embracing the technology sooner than later, and by taking the time to do it right from the start. From price and image quality to freedom and flexibility, there are a number of attributes to consider. OTT providers should carefully explore their options and invest in an HDR solution that best suits their needs, as well as the needs of their consumers, while keeping a close eye on competitors’ HDR deployments.
[This is a contributed article from Bitmovin. Streaming Media accepts vendor bylines based solely on their value to our readers.]
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