High Hopes for High Dynamic Range (HDR) Video

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High Hopes for High Dynamic Range (HDR) Video

Samsung-JS9500.jpgUltra HD TVs have been on the market for a couple years now, but 2015 may be the year the technology truly makes its move, thanks to the arrival of two technologies that will notably improve color and contrast in these new TVs. Last week, we discussed quantum dots and how they will help expand the color gamut of new UHD TVs. This week, we're going to focus on how high dynamic range (HDR) can dramatically improve contrast, both in UHD source content and display devices.

A display device's dynamic range is the range from its darkest black to its brightest white (also known as contrast ratio). Just as the name suggests, high dynamic range technology expands this range far beyond what we've previously seen, to dramatically improve the TV's contrast and thus make the entire image (including color saturation) look richer and more three-dimensional. You may already be familiar with the term HDR as it is used in cameras and smartphones for taking still photographs. When you enable the HDR function in your camera, the camera actually takes several pictures at different exposures (brightness levels), chooses elements from each, and combines them to create a single image. You can get a great explanation of HDR, and its pluses and minuses for photography, here.

On the video/TV side, the goal of HDR is essentially the same: to capture and reproduce all of the subtle nuances of the image, from its finest black/shadow details to its brightest white/color elements in all their glory. While HDR photographs must�tone-map the end result for display on a standard dynamic range (SDR) display like a PC or smartphone, the current push on the video/TV side is to maintain HDR all the way from the camera to the display.

The first important difference in an HDR display device is its brightness. Today's LED/LCD TVs have ample overall brightness to watch content even in a really bright room. On average, we're talking 300 to 500 nits (or candelas per square meter). HDR requires a significant increase in peak brightness. It's not necessarily about making the whole image brighter; it's about improving the TV's ability to create bright elements that really pop off the screen. Samsung's new flagship SUHD Series, for instance, can reportedly achieve up to 1,000 nits. Sony claims that its X-tended Dynamic Range Pro technology produces three times the brightness of a typical LED/LCD, while Panasonic's Super Bright Panel with Dynamic Range Remaster promises a 40 percent increase in brightness.

Dolby-Vision-sample.jpgOf course, that extra brightness is meaningless to overall dynamic range if the black level increases, too. So another crucial piece of the puzzle for LED/LCD TVs is the use of local dimming to keep the black level in check. The top-shelf HDR-enabled TVs on display at CES (from Samsung, Sony, and Panasonic) use full-array LED backlighting systems with local dimming. Some models were edge-lit with local dimming, but you likely won't get as much precision with that approach. Behind closed doors, LG showed off an HDR-enabled OLED prototype, which is even more enticing because of its innate ability to render an absolute black. Add in the increased peak brightness, and the resulting image was eye-catchingly stunning.

One reason why HDR is exciting is that it provides a benefit you can see right now, with any source material. Most reviewers (myself included) will assert that contrast is the single most important element of an image, far more important than resolution on its own. The step up from a 1080p to a UHD resolution may be difficult to discern on a 65-inch TV, but a big step up in contrast will be very obvious with anything you watch, from an Ultra HD Blu-ray to a 1080p Blu-ray to a 1080i TV broadcast.

That being said, HDR technology will truly blossom when we get HDR-mastered content to go with it. Current TV and Blu-ray standards limit maximum brightness to 100 nits. Dolby Vision HDR technology aims for content that's mastered at up to 4,000 nits. Dolby has been leading the HDR charge for several years now, and Dolby Vision is actually an end-to-end solution, from camera to post-production to distribution to display. Enjoying the high dynamic range, wider color gamut, and 10- or 12-bit color that are all part of Dolby Vision requires Dolby Vision-authored content displayed on a Dolby Vision-enabled TV. Basically, the Dolby Vision information is stored as residual image information, as well as metadata, that compatible TVs can read, and the Dolby Vision content will be optimized upon playback for that TV's capabilities, including its brightness, contrast, and color gamut.


At CES, Dolby and Warner Brothers announced the first crop of DV-enabled titles to be offered in streaming form this year: The Lego Movie, Into the Storm, and Edge of Tomorrow. Netflix plans to support Dolby Vision; at CES, both Netflix and Dolby showed examples of the Netflix series�Marco Polo�in 4K Dolby Vision as an example of what Netflix plans to offer in 2015. As for display partners,�Vizio-Reference.jpgDolby's current partnerships include Philips, Hisense, Toshiba, and Vizio. Back at CES 2014, Vizio showed off its Reference Series Dolby Vision UHD TVs�(shown, right), and those models are expected to ship in the first half of 2015.

You may have noticed that a few TV manufacturers are missing from that list. You know, little-known names like Samsung, Sony, LG, and Panasonic. That's because these manufacturers have developed their own approaches to HDR technology, and they are pushing for a more open standard for future HDR content. For CES, Samsung teamed up with 20th Century Fox to show scenes of Exodus that had been specially mastered with HDR and a wider color gamut. It's worth noting that Netflix reps also spoke about HDR streaming at the Sony and LG press conferences.

After we spoke with one industry rep about the different approaches being taken by Dolby and the TV giants, Jerry Del Colliano immediately said, "I smell format war." Let's hope not, and a couple of encouraging signs suggest that won't be the case. For one, the major TV manufacturers and Dolby are both part of the new UHD Alliance, formed specifically to work out a roadmap to usher in workable UHD standards. That suggests a willingness to work together.

Another positive sign was announced just last week, as the Blu-ray Disc Association revealed more details on the upcoming Ultra HD Blu-ray spec. Advanced Television reported that Ultra HD Blu-ray will support an open-standard HDR platform but will also allow for optional solutions like Dolby Vision. So the different approaches can be incorporated into the format to suit the UHD TV you're using.

There are still plenty of questions surrounding HDR. How many nits of brightness officially "defines" an HDR TV, how many nits does an HDR TV really need, and how many nits are too many for a comfortable viewing experience? It is at least encouraging that all the big players seem to recognize the importance of getting on the same page...and getting there soon.

Additional Resources
Learn more about Dolby Vision on the company's website.
��High Dynamic Range Arrives at CES 2015 at CNET.com.
Hands on With Samsung's New JS9000 SUHD Tizen TVs at Forbes.com.

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