Originally posted October 8, 2014
Updated December 1, 2015: added 4K video sources
TVs and projectors with four times the resolution of a high-definition Blu-ray movie are quickly becoming the new standard for larger home theater displays. The sources and selection of video material for this new ultra high-definition viewing experience are expanding as well, but let's start with the basics.
A brand new name
Most of us are familiar with the term "1080p" and its variants such as "Full HD", FHD, 1920x1080 pixels, or the more vague descriptor "high def". To assist consumers looking to experience ultra high-definition (UHD) in the home, the Consumer Electronics Association (CEA) recently announced that UHD display devices shall use the branding 4K Ultra HD and 4K Ultra HD Connected.
What qualifies as an ultra HD display?
The CEA characterizes ultra high-definition TVs, monitors, and projectors as display devices that meet the following minimum attributes:
- Display Resolution – Has at least eight million active pixels, with at least 3840 horizontally and at least 2160 vertically.
- Aspect Ratio – Has a width to height ratio of the display’s native resolution of 16:9 or wider.
- Upconversion – Is capable of upscaling HD video and displaying it at ultra high-definition resolution.
- Digital Input – Has one or more HDMI inputs supporting at least 3840x2160 native content resolution at 24p, 30p and 60p frames per second. At least one of the 3840x2160 HDMI inputs shall support HDCP revision 2.2 or equivalent content protection.
- Colorimetry – Processes 2160p video inputs encoded according to ITU-R BT.709 color space and may support wider colorimetry standards.
- Bit Depth – Has a minimum color bit depth of eight bits.
The CEA defines connected ultra high-definition displays as meeting all of the above requirements as well as:
- Video Codec – Decodes IP-delivered video of 3840x2160 resolution that has been compressed using HEVC* and may decode video from other standard encoders.
- Audio Codec – Receives and reproduces, and/or outputs multichannel audio.
- IP and Networking – Receives IP-delivered ultra HD video through a Wi-Fi, Ethernet or other appropriate connection.
- Application Services – Supports IP-delivered ultra HD video through services or applications on the platform of the manufacturer’s choosing.
*High Efficiency Video Compression Main Profile, Level 5, Main tier, as defined in ISO/IEC 23008-2 MPEG-H Part 2 or ITU-T H.265, and may support higher profiles, levels or tiers.
4K in cinema
The CEA's definition of ultra high-definition displays specifies at least a certain number of pixels, a picture shape (aspect ratio) of 16:9/1.78:1 or wider, and the possibility of richer colors. The use of the term "4K" in cinema production means something slightly different than it does in the UHD video world.
For the cinema industry, the Digital Cinema Initiatives (DCI) consortium has defined several 4K formats for various applications that include pixel resolutions of 4096x2160 (1.90:1), 4096x1716 (2.39:1), and 3996x2160 (1.85:1).
DCI also specifies an expanded color palette and advanced compression scheme for these "true 4K" formats that the home user is unlikely to encounter in typical consumer products - at least in the near future. It's understandable that some cinema purists cringe when the terms 4K and UHD are used interchangeably.
Sources of UHD video
Ultra HD video enjoyment is available now albeit with a fairly limited (but growing) selection of content to choose from. How you will experience ultra HD depends on the hardware you own and the services you subscribe to. Here's what you can expect from these current, and soon to be, UHD video providers.
Netflix demonstrated its UHD video streaming service at the 2014 CES and has since found its way into new consumer devices including UHD TVs and set top boxes. Looking to the future, Netflix has indicated that they are working toward improving its ultra high-definition streaming service with increased color precision and higher framerates.
Amazon's 4K Ultra HD Instant Video streaming service has launched (press release) and is currently available on select LG, Samsung, and Sony TVs. More details are available in the Amazon 4K Ultra HD Guide. Amazon has begun streaming UHD video with high dynamic range (HDR) and select TVs from Samsung, LG, and Sony have been software upgraded to support HDR decoding and playback.
The Sony FMP-X10 is an Internet streaming appliance that integrates a 1TB hard drive for local storage. Powered by the company's Video Unlimited 4K service, the FMP-X10 currently lists more than 65 feature films that are available for rent or purchase. Sony recently updated the FMP-X10 to be compatible with any display that features an HDMI v2.0 port that supports HDCP v2.2. Read my review of the Sony FMP-X10.
Owners of newer Samsung UHD TVs can purchase a compatible UHD Video Pack that is decoded through the M-GO streaming video app - this content includes HDR and wide color gamut (WCG) enhanced videos that are currently unavailable by any other means. Samsung SUHD TVs have also been upgraded to support UHD/HDR streaming from Amazon and UHD streaming from YouTube, Netflix, and other popular UHD video applications.
Satellite television provider DirecTV is currently testing limited UHD video delivery with wide deployment scheduled for 2015-16. Cable and fiber TV providers are also in the early testing phase for deploying UHD video services. It seems likely that all of these TV providers will utilize streaming video technology to delivery UHD content to its subscribers.
YouTube also has a growing selection of UHD videos available for streaming, however, not every UHD TV supports UHD YouTube playback at this time and are limited to 1080p streaming quality.
The video streaming service M-GO now offers a growing selection of 4K UHD movies and TV shows. The M-GO app is also used for playback of content purchased on secure storage (with compatible UHD TVs).
Ultraflix is another source of streaming UHD programming that's available on select 2015 Sony, Samsung, Vizio, and Android TV-powered UHD TVs.
Here are a few sources of 4K UHD video material that you are free to explore and download for playback.
Tears of Steel (2012) - a group of warriors and scientists attempt to rescue the world from destructive robots
Sintel (2010) - a woman's search for a dragon that she had once nursed back to health
Big Buck Bunny (2008) - a day in the life of a big bunny named Buck
Demo UHD 3D - a source of various 4K UHD and 3D videos
Ultra Video Group - test sequences
houkouonchi.jp - a directory of 4K UHD material
Not all UHD is created equal
Resolution is only one component of video picture quality. A still picture that is JPEG encoded can be compressed by an arbitrary amount while maintaining the original pixel resolution. Increasing picture compression produces a smaller file size but fine details become increasingly softened and blurred. Likewise, a lightly or uncompressed image will exhibit more detail and clarity along with a larger corresponding file size. The same concept applies to video.
The datastream of Blu-ray video can peak at 40Mbps enabling it to reproduce even the most detailed, quick-moving video imagery with very few compression artifacts. Likewise, 1080p video from Internet streaming services reaches a maximum average bitrate of 5-7Mbps. The current library of Netflix UHD videos average 16Mbps - less than half of Blu-ray's maximum bitrate yet with four times the pixel resolution. Improvements in video compression technology help make HD and UHD video delivery possible, but there is no substitute for pure bitrate to maintain video quality.
Bitrate is king
For the quality conscious home theater enthusiast, video compression is only part of the story. Blu-ray supports multichannel lossless audio at up to 27.7Mbps (48Mbps total for audio and video data) providing a "like you are there" listening experience that is unmatched by any Internet streaming service or DVD video. If you believe that quality audio is at least half of the home theater experience, streaming services have a ways to go to catch up to good ol' Blu-ray.
UHD is a work in progress
Plenty of pitfalls remain for early adopters of UHD gear. A major issue relates to the need for HDCP v2.2 support between an external UHD video source device and UHD display. HDCP v2.2 is a complete break from previous versions, and this means that the entire video pathway must support HDCP v2.2 in order for UHD playback to occur - older gear will most likely not be upgradable to the new HDCP spec. The good folks at Audioholics wrote up an excellent article detailing the current mess that is HDMI v2.0 and HDCP v2.2 and how it relates to current and upcoming home theater gear, and I encourage anyone interested in this subject to give it a careful read.