4K Smartphones - Stand and Deliver

In my last post I ventured to predict that 4K displays will become mainstream on high-end smartphones at some point even though they’re unlikely to deliver a better viewing experience for the mobile user on average. To become a game changer, it takes more than just adding a impressive new feature to a device to attain that immersive cinematic experience. What about 4K video content? Is enough readily available? Are the wireless networks and mobile infrastructure in place to transport high-resolution content? What are the effects of 4K displays on the smartphone itself? It’s a tall order to provide a comprehensive picture in a blog, so I’ll attempt providing some vignettes of insight in a question and answer style. We’ll shortly probe the ecosystem from production through to transfer and finally consumption of 4K content to arrive at the bigger picture.

"Looks pretty much like 4K to me"

Seeing the difference

Spicing up the quality of images or video is not only a case of increasing resolution. It’s technical and personal matter at the same time.

What parameters influence the perceived quality of a display?

A combination of technical factors such as the screen size, display resolution, frame rate, color depth, dynamic range, viewing distance and other parameters make up for the quality of the viewing experience. In addition, your own eyesight plays an important role, in particular its ability to distinquish fine details, known as visual acuity. The resulting mix of objective and subjective factors makes it extremely difficult to pinpoint a single metric as being paramount in providing a superior viewing experience.

What does it take to produce 4K broadcast quality content?

Producing 4K content dictates a four times higher resolution than the prevalent HD (high-definition) standard, resulting in 4x the amount of data too. That translates to very expensive equipment in the production chain (cameras, lenses, switchers, encoders, storage disks, editing workstations) so that only a trickle of material is currently shot in 4K. Over time equipment pricing will erode and options will increase. Shooting in 4K will ultimately ensure that content is future proof, spurring on its adoption.

What content is available in 4K resolution to date?

YouTube Netflix, Amazon, Sony, DirectTV, Comcast are just some of the names who boast 4K UHD movies, TV shows, or video clips, all of which have caveats of sorts. A good overview of 4K UHD programming available in the USA currently (December 2014) can be found at Digital Trends. Indeed, it’s quite a limited offering but it’s an incoming tide that’s rising.

Squeezing 4K data

Getting 4K content to the end-user requires high-bandwidth transmission paths. 4K codecs that efficiently compress the material when it is captured (encoder) and decompress it again when viewed (decoder) play a pivotal role in easing bandwidth requirements and the cost of transfer.

What are the transport requirements for 4K video?

As can be seen from the listing of offerings at Digital Trends, most 4K content is streamed over the Internet and requires a 25 Mbps channel. Many experts contend that 36 Mbps is the best channel bandwidth for delivering Ultra HD, whilst others purport that 15 Mbps is sufficient for a decent 4K experience that is also commercially viable. Whatever the case, that’s certainly a lot more compared to delivering a HD (1K) stream at 3 Mbps. It also costs approximately 5x more.

	SD (720 x 576)	HD (1920 x 1080)	UHD (3840 x 2160)
Recommended Internet Speed	3 Mbps	5 Mbps	25 Mbps

Netflix’s recommendations on Internet speed for viewing their movies and TV shows

Why are differing minimum 4K bandwidth requirements quoted by experts?

This depends on the type of content and the codec used for compressing the video footage. For example live sports events with fast moving action will require higher frame rates (more data to encode) for a fluid viewing experience. In addition the encoder used to reduce the data must compress at a faster rate due the live nature of the event. Stated in simple terms, the more time a codec has available, the more it can squeeze the data without sacrificing quality. So it stands to reason that films shot and compressed in the studio require less transport bandwidth than live sports events broadcast on the fly.

What codecs are available for 4K video compression and do they differ in the quality and bit-rate?

Of late there’s been a pitting of solutions between Google’s VP9 that follows an open source approach, and MPEG / ITU groups’ HEVC (High Efficiency Video Codec, also known as H.265). The latter’s previous H.264 (MPEG) codec has been the defacto standard for HD content in the past, but Google is hot on the heels to change this for 4K. Then there’s another initiative from Mozilla and Xiph.org called Daala that claims it will beat both on technical merit. In a future post I’ll attempt to uncover some of the key differences of these codecs in their complexity, delivered quality, achievable bit-rate reduction, available content offerings and devices that support each.

Please, no frame freezes or fallouts

Many of us know how annoying a sudden and unexpected throttling of bandwidth can be, especially when enjoying streamed video or audio. Consistent channel bandwidth is of the essence, so let’s take a look at the options.

What channels are available for transmitting 4K Ultra-HD content?

Several options are available such as satellite, microwave, cellular and fixed networks using cable or DSL. Currently the majority of 4K content is available as video-on-demand (VoD) that is stored and then streamed through fixed networks (cable/DSL) to the end user. On the broadcast TV front, satellite providers like DirectTV and BSkyB will lead the 4K race. Terrestial TV broadcasting will require more time for standards to come into place and availability will largely depend on country initiatives in transitioning to newer technology with Japan and Korea at the forefront.

Will mobile networks have sufficient bandwidth to transmit 4K content?
4G cellular networks typically support download rates of up to 150 Mbps for LTE Cat 5 smartphones that are prevalent on the market . More than enough for one UHD channel at 25 Mbps one would think. Keep in mind though, the cellular broadband network is being shared by many people at the same time. In fact we’re dealing with a top theoretical download speed that most of us won’t ever witness in the real world. Even worse, the data rate may change unexpectedly depending on network usage, and your 4K video may suddenly freeze.

Can Wi-Fi reliably stream 4K video content?

The more recent WiFi standards that employ 40 MHz channel bands (802.11n or 802.11ac) provide sufficient data throughput to support 4K video transmission in theory. In practice however, performance is unpredictable as those of us who have tried streaming HD video at home will know. This is largely due to contention between neighbouring WiFi networks whose data rates start sagging as they counter the chatter of next-door access points on the same frequencies. In addition WiFi microwaves, especially those operating in the 5 MHz band, are attenuated by walls and floors, leading to a 80 - 90 % drop in peak rate compared to the access point being in the same room. In short, uninterrupted video delivery is simply not reliable enough.

What other wireless standards can handle 4K streaming and when will they become available?

Two new standards, WiGig and WirelessHD, are out there and both operate in the 60 GHz band. They are much faster than Wi-Fi 802.11ac or LTE mobile broadband technologies. Their formidable throughput rates (7.5 Gbps for WiGig) are targeted at the wireless delivery of high-definition content. Yet the 60 GHz signals they use cannot penetrate walls. It’s all about connecting computing and entertainment devices in the same room without cables. The idea is to turn mobile devices into media stations that wirelessly dispatch streams to 4K TVs and displays. Devices supporting the new standards are expected to start shipping this year and they will allow uninterrupted wireless streaming of 4K content, albeit in the same room.

Expensive power hogs

Smartphone innovation happens at a mindboggling rate and users often wait for announced models to be released before replacement. Even if 4K is one of those desirable new features, there are other factors to observe.

What are the drawbacks of smartphones with 4K displays?

Power and cost are two inhibitors in the uptake of 4K displays on smartphones. The display is one of the major culprits in draining the battery on a mobile phone and the amount of power consumed is directly related to the size of the display. 4K also means four times more data to store and process. More memory and busier units on the SoC (system-on-chip) will sap precious juice from your phone’s battery even faster. In addition, the display is the component that costs the most in a smartphone. Paying more and having to charge your phone more often don’t speak for a runaway market success.

Can smartphones record 4K video?

The minimum requirement for a smartphone camera to capture 4K content is a camera with at least 8 megapixels (MP) of resolution. Most mid-range devices already sport such pixel magic. But can available smartphones capture and encode 4K video? Suprisingly yes, even though most don’t feature 4K displays. For example, both Apple’s iPhone 6 and 6 Plus models (8 MP camera) support 4K video recording; Samsung’s Galaxy S5 (16 MP camera) and Sony’s Xperia Z2 (20.7 MP camera) both use Qualcomm’s Snapdragon 801 that supports video capture and playback using the HEVC / H.265 codec. In fact, an impressive list of smartphones supporting HEVC can be found at phoneArena.com which are able to record 4K videos.

A nascent technology gaining momentum

What do you do if 4K content is limited, seamless transfer paths still patchy, the first smartphones with 4K displays just around corner, yet many featuring 4K capture available right now? 4K’s marketing machine has the answer and is harping that user-generated 4K content on mobiles will bridge the gap. Smartphones will be the force to bring 4K into the limelight as users record 4K footage and either watch it on 4K TVs or upload it to YouTube. A bulletproof business model or high hopes on an act of faith? Whatever the case, it is apparent that the industry is working its fingers to the bone towards a single new display standard. At some point the law of large numbers will bring down costs and herald in the age of 4K phablets, one way or another, sooner or later. The market research company ABI Research forecasts almost 500 million 4K display-enabled mobile phones to be sold in 2019.

It’s still an HD world out there and will be for quite some time, but 4K UHD is on the move.