4K and Beyond: Technical Challenges and Opportunities. An InfoComm International White Paper

Transcription

1 4K and Beyond: Technical Challenges and Opportunities An InfoComm International White Paper

2 Copyright 2015 InfoComm International All rights reserved. Printed in the United States of America Published by InfoComm International, Waples Mill Road, Suite 200, Fairfax, VA No part of this work may be used, reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without prior agreement and written permission from InfoComm International. The contents of this work are subject to revision without notice due to continued progress in methodology, design, installation and manufacturing in the audiovisual industry. This material is provided as is, without warranty of any kind, respecting the contents of this work, including but not limited to implied warranties for this work s quality, performance, merchantability or fitness for any particular purpose. InfoComm International shall not be liable to the purchaser, user or any other entity with respect to any liability, loss or damage caused directly or indirectly by this work.

3 Table of Contents Acknowledgments... iii Executive Summary... 1 The 4K Puzzle... 2 Visual Acuity and Optimum Viewing Distance... 3 Frame and Refresh Rates... 5 Color Depth and Contrast Ratio... 7 To Compress or Not to Compress?... 8 Content Protection Infrastructure Designing for 4K Needs Assessment Network Assessment System Design Implementation Challenges HDMI 2.0 vs Signal-Integrity Issues The Trouble With HDCP Device Support K in the Real World Multiwindowing on a Single Display and Scaling 4K Across Multiple Displays Projection Mapping Videoconferencing Security Visualization i

4 Simulation Peering Into the Future Conclusion References... 28

5 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Acknowledgments InfoComm International would like to thank the following industry experts for their generous contribution of time and knowledge: Timothy Albright, CTS, DMC-E, EAVA, Director of Operations, Innovad Ken Eagle, Director of Field Training/Technical Sales, Atlona Dave Fluegeman, Director of Simulation, Barco Mike Garrido, Senior Product Manager, 3 DLP Projectors, Christie Digital Paul Harris, CEO, Aurora Multimedia HDBaseT Alliance Nathan Hicks, CTS-D, Consultant, K2 Audio Erik Iversen, Product Manager, Image Processing, Barco Justin Kennington, Technology Manager, DigitalMedia, Crestron Electronics Phil Laney, Director of Visualization and Simulation, Digital Projection Sander Phipps, Product Manager, Professional Display Group, Sony Electronics iii

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7 Executive Summary When high-definition TVs (HD or 1080p) first entered the market, only three HDTV channels were available. Fast forward five years, the number of channels grew to 40. Today, over 20 years since the HD breakthrough, most streamed content is available in HD and many consumers also own HD media players. The AV industry knew that 1080p would become a standard, but it didn t happen overnight. The 4K specification promises significant improvements in the image and video viewing experience over 1080p, with quadruple the number of pixels and 64 times the number of colors. However, 4K system design currently presents many challenges, including the lack of content, infrastructure, and processing power. For example, if anywhere between a 4K source and a 4K display a product is not capable of handling 4K resolution whether it is an input card, transmitter, or cable that product creates a bottleneck. System designers have to ensure that every component in a 4K path is capable of 4K. 4K has been fodder for transition polemics and propositions for roughly a year and a half. In the absence of stable infrastructure, vendors want to know how they can build a system today that would allow them to take advantage of 4K down the road. And if they do, what pieces of the infrastructure can they use right now? How do they know and communicate to end users which system components they may have to replace within five years of implementation? Before 4K can become widespread, there have to be applications that require it. The challenge with 4K today is that there aren t many applications that couldn t exist without it. One could argue that it is display manufacturers who need 4K to succeed, because sales of 1080p systems have peaked. And to spur sales, they have to begin pushing 4K products. In this way, product is perceived as the main driver of 4K adoption, rather than the need for product. However, it is easy to see the immersive value of 4K in a variety of applications, from multiwindow displays, to projection mapping, to simulation and visualization. And some end users are already reaping the benefits of smoother video and much greater detail. The goal of this white paper is to dispel myths surrounding 4K technology, present the theoretical and practical parameters of its capabilities, and explain which applications can harness 4K today and in the future. 1

8 The 4K Puzzle The 4K Puzzle The term 4K is generally used to refer to video signals with a horizontal resolution on the order of 4,000 pixels. To be technically accurate, 4K is a resolution of 4,096 pixels horizontally by 2,160 pixels vertically, which is 8.8 million pixels. This is a cinematic standard for 4K film projection (Digital Cinema Initiatives [DCI] 4K) and carries a specific aspect ratio that is not used for commercial or consumer displays. Previous generations of video resolutions were described by the vertical resolution (i.e., 1080p refers to a signal with 1080 vertical lines). Had the naming convention for standard definition (SD) and HD been used, 4K video might instead have been referred to as 2160p. What a lot of video consumers do not realize is that DCI 4K is a 17:9 aspect ratio, whereas most displays today including those supporting 720p, 1080i, and 1080p are built for a 16:9 aspect ratio (see table 1). Because essentially all sources and displays have used this aspect ratio, manufacturers and integrators have seen an era of relative simplicity. For several years, there has been no need to accommodate various other aspect ratios. 4K brought with it a challenge of managing two different standard resolutions. Table 1 4K aspect ratios Resolution Aspect Ratio Common Name :1 (~17:9) 4K Digital Cinema Initiatives (DCI) :1 (16:9) Ultra HD (UHD) In 2014, International Telecommunication Union s Radiocommunication Sector (ITU-R) defined an alternative, ultra high-definition (UHD) resolution that would fit a 4K-like image into the standard display ratio. Such an image has 7 percent fewer pixels in the horizontal aspect. On the left and right edges, 3.5 percent of pixels are eliminated without compression or stretching so the image would have a 16:9 ratio (see figure 1). Figure 1 Ultra high-definition vs. Digital Cinemas Initiative resolution (courtesy of Crestron) 2

9 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES In Recommendation BT (popularly known as Rec. 2020), ITU-R defines two UHD television resolutions: (4K) and (8K). The recommendation further confirms that UHDTV applications require system parameters that go beyond the levels of HDTV (Rec. 709, 1993) larger screens, higher spatial/temporal resolutions, a wider color gamut, and a wider dynamic range. Most of the 4K recording equipment today records natively in DCI 4K. The chipsets in those devices are built for native 4K. Usually, when they are writing to the disc, the chipsets record in the 16:9 aspect ratio instead. Considering the sparse need for DCI 4K, 16:9 UHD chipsets are becoming the norm. Manufacturers are building recording devices either in the 16:9 UHD aspect ratio or DCI 4K (with some type of internal conversion). DCI 4K devices are then cropping the image horizontally and writing the result to disc. Adding to the complexity of having two 4K resolutions is the existence of other resolutions between 2K (2,048 1,080) and 4K. Quad HD resolution is pixels and most popular in the mass consumer market because it is the HD resolution ( ) multiplied by 4 exactly (see figure 2). Figure 2 Comparison of video resolutions (courtesy of Crestron) Resolutions and are becoming popular on some high-end source devices, such as the MacBook Pro, high-end Windows laptops, and even some mobile devices. The problem is, even though those resolutions are not actually 4K they are not 4,000 pixels wide they require more bandwidth than 2K and 1080p. Displaying those resolutions, therefore, requires 4K-class switching and distribution gear. The following sections take apart the 4K puzzle, explaining the various components of the UHD signal and user experience. We begin with some constants defined by the limits of human visual acuity. Visual Acuity and Optimum Viewing Distance Human visual acuity describes the limits of human vision in terms of the finest details the eye can perceive. Visual acuity is described by an angle, specifically the angle formed between the retina and the edges of something being viewed. A person with good vision (20/20) can perceive detail down to around 1 arcminute. An arcminute is 1/60 of one degree. 3

10 The 4K Puzzle The reason smaller details can be seen more clearly when they are viewed at a shorter distance is because close objects consume a larger angle of the viewer s vision, not because the object actually becomes larger. To determine a basic guideline for optimum viewing distance, a display is placed far enough that the viewer cannot see individual pixels so that they are smaller than one arcminute but not much farther than that; otherwise, the display would show detail the viewer would not be able to perceive. Consequently, the optimum viewing distance depends entirely on the visual acuity of the viewer (assumed to be 1 arcminute) and the size of the individual pixels (essentially the overall size of the display divided by the total number of pixels). The following formula from RCA Commercial Electronics helps to determine the viewing distance for commercial applications: VD = NHR NVR 2 DS + 1 CVR tan 1 60 Where: VD is viewing distance (in inches) DS is display's diagonal size (in inches) NHR is display's native horizontal resolution (in pixels) NVR is display's native vertical resolution (in pixels) CVR is vertical resolution of the video being displayed (in pixels) tan is tangent, in this case, of one arcminute (1/60 of one degree) Using the formula for a 1080p video on a 42-inch display, the pixels disappear at around 65.5 inches (166 centimeters [cm]) from the viewer: VD = tan 1 60 = 65.5 Doubling the horizontal and vertical resolution of this display (to or 4K) cuts the optimal viewing distance approximately by half, to 32.8 inches (83 cm). VD = tan 1 60 =

11 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Doubling the diagonal screen size will double the optimal viewing distance. So, at 4K, on an 84- inch display, optimal viewing distance is again around 65.5 inches or 5.45 feet (1.66 meters [m]). VD = tan 1 60 = 65.5 These facts taken together suggest that the HD technology already produces an indiscernible-pixel image for some viewers. However, when viewers sit closer to displays, they likely will begin to discern the difference between pixels. And that is where the 4K resolution becomes beneficial. Ultimately, the decision to invest in 4K should be driven by application and need. For applications where 4K makes a lot of sense, see section 4K in the Real World. Frame and Refresh Rates While spatial resolution is the width and height of the displayed image measured in pixels, temporal resolution or frame rate is the number of frames (images) displayed per second. For testing purposes, watching high-frame-rate content in slow motion reveals more detail without blur, whereas lower frame-rate content shows discernible artifacts. The 4K format originally entered the market at 30 frames per second (fps) in order to keep the data rate manageable. As the market progressed to High-Definition Multimedia Interface (HDMI) 2.0, 4K at 60 fps became possible. Before the advent of 4K, the video world had been operating at 60 fps for many years. This frame rate is the current limit in display technologies. The human eye is capable of discerning a much higher frame rate, leaving room for further technological advancement. Delivering video at 60 fps generates a data rate of 4.46 gigabits per second (Gbps). The 4K resolution requires moving much more data at a rate sufficient for smooth viewing. A fourfold increase in pixels increases the required data rate by a factor of four. By comparison, the highest broadly accepted version of HDMI version 1.4 supports a maximum data rate of 10.2 Gbps, including overhead. It is important to distinguish the difference between frame rates and refresh rates. Refresh rate is the frequency at which a screen updates, measured in hertz (Hz). The higher the refresh rate, the less noticeable flicker. A refresh rate of 60 Hz means that the screen draws 60 images per second. However, because displays currently cannot handle frame rates above 60 fps, a display with a 120-Hz refresh rate would upconvert that signal to 120 Hz using motion interpolation. Motion interpolation is a type of processing that adds frames between the original frames. The intended effect is more fluid motion. This does not mean that the signal would gain a higher frame rate. When played in slow motion, such signal would show distortion. Note that projectors can accommodate higher refresh rates. The problem is finding sources that can run those higher refresh rates and have the bandwidth to provide to that projector. Digital light processing (DLP) projectors are capable of running frame rates of up to 480 fps. The following table shows some output choices along with supported resolutions and frame rates. 5

12 The 4K Puzzle Table 2 Output resolutions and refresh rates Output Standard Resolutions and Frame Rates (fps) Digital Visual Interface (DVI) High-Definition Multimedia Interface (HDMI) (version 2.0) DisplayPort (version 1.3 plus High Bit Rate [HBR] 3) (version 1.3) HDBaseT USB Type-C (if all 4 lanes are used) Mobile High-Definition Link (MHL) (version 3.0) The main advantage of higher refresh rates is that they can reduce smear, jitter, and some of the artifacts seen in fast-moving imagery. For static images or basic video needs, a lower refresh rate (30 Hz) does not produce noticeable artifacts. Integration and rental and staging markets, however, want to be able to provide higherend still and moving-image solutions, and 60 Hz provides the smoother image for their video display needs. Consumers of 120 Hz come from the visualization and simulation markets. They use cameras and computers that generate very high-resolution images at least 4K. Other consumers of high refresh rates include areas of research, such as oil exploration. They need to be able to see the details from the probes and distinguish between different colors. This is also where bit depth comes into play (discussed in the next section). Processing 4K at higher refresh rates requires faster chips and faster, larger system memory. This increases the cost of 4K. Once the computer industry begins using the chips to support highrefresh-rate 4K, the price of 4K for everybody is expected to go down. 1 Data at 10.2 Gbps 2 Data up to 20 Gbps 3 Connecting mobile devices to TVs 6

13 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Color Depth and Contrast Ratio Resolution is just one component of image quality. Color depth and contrast ratio can be more important than the amount of pixels in a signal. 4K resolution, coupled with better control of the color gradient, provides a smoother-looking image. Color depth is measured in bits. Higher bit depths provide more information, particularly in dark images. They allow for a truer reproduction of the incoming color, with sharper color detail and definition. When yellow and orange are shown side by side, for example, the viewer can begin to see the differences. The red, green, and blue (RGB) bytes making up a video pixel can be separated into brightness (or luma) and color (or chroma) components, which are called YUV in the analog and YCbCr in the digital realm. Y represents the luma level, and UV and CbCr are blue and red chroma components (see figure 3). These components correspond to an x:x:x scheme in a digital video sample. Figure 3 Chroma and luma components of color resolution (courtesy of Crestron) Each pixel in the current Rec. 709 TV system is composed of three 8-bit color channels. Combining all three primary colors at each pixel allows for as many as 2 8*3 or 16,777,216 different colors, or true color. This is referred to as 24 bits per pixel. Below 24 bits or 4:4:4, the color quality begins to drop. Sixteen-bit color results in a 2 8 * 2 or 65,536-color palette. For more information about chroma, bandwidth, and compression, see section To Compress or Not to Compress? The new Rec specifies 10 bits and 12 bits per color. Ten bits would yield 2 10*3 or 30 bits per pixel, which is 1,073,741,824 colors. Manufacturers are working on display solutions that would approach this color gamut, which currently can be achieved only with RGB laser projectors. One of the technologies showing progress with the Rec color gamut is quantum dots. They are currently used on a limited number of displays, particularly hybrid liquid crystal displays (LCDs). Quantum dots are tiny manmade crystals or semiconductors that sit behind each LCD pixel and control the way the light is created. Precise control of quantum dots at manufacturing enables the 7

14 The 4K Puzzle dots to emit light at any wavelength in the visible spectrum. Technology developer and licensor Nanosys is aiming to achieve this goal with Quantum-Dot Enhancement Film (QDEF) technology. High dynamic range (HDR) is an imaging technology that produces images with a greater range of light and color than conventional imaging. HDR with respect to displays refers to modulating the light source to achieve a higher color range. HDR combined with 4K brings the viewer a step closer to the luminance range available in the actual recorded scene. The latest advancements in LED backlighting and panel technologies have made HDR more plausible on the display side. And, on the projector side, the development of alternative light sources, such as laser phosphor technologies, allow HDR implementation because their color spectral output is wider than that of conventional lamp technology. Matching the source to the display is crucial for achieving full color depth, and so is adjusting the optics for contrast ratio. In simulation applications, accurate representation of the real-world contrast makes the biggest impact. For example, a simulator pilot or driver will not be able to properly test in nighttime conditions if color black is not represented correctly. Commercial airline simulators are rated in the same manner as the actual aircraft, and first flight officers get certified to fly using flight simulators. A Federal Aviation Administration (FAA) inspector will fail a flight simulator that does not reproduce the darkest nighttime conditions. To Compress or Not to Compress? In the absence of an adequate infrastructure bandwidth to support 4K signals, compression of the video stream is often necessary. 4K compression is available today, but when should it be used? For examples of uncompressed video, see section 4K in the Real World. Two basic categories of compression are lossless and lossy. Lossless compression is accomplished through algorithms that allow data to be reconstructed from the compressed data in the original form. Lossy compression means reducing the original data to the extent where the original information cannot be fully restored when the video is decompressed. The difference between the original and the lossy version are called artifacts. Note that HDMI 1.4 supports lossless 4K at 30 fps or less with 8-bit color or less, while HDMI 2.0 supports lossless 4K in many more formats. See table 3 for more detail. However, this is distinct from lossless compression. Considering that humans have always been more tolerant of changes in color resolution than in brightness resolution, a compression strategy called chroma subsampling made sense for use first in analog and later in digital video. Subsampling reduces color resolution by half or more by sending chroma values less frequently than luma values, as shown in figure 4. 8

15 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES 4:4:4 4:2:2 4:2:0 Y Y Y U U U 8 8 V V V bits per pixel 16 bits per pixel 12 bits per pixel Figure 4 Chroma subsampling The 4:4:4 notation in essence means that the luminance and chrominance components have the same sample rate and that no chroma subsampling is applied. When applied, chroma subsampling transmits luminance information at full resolution and chrominance at lower resolutions. To transmit 4K video at 60 fps below 9 Gbps, color information is compressed to 4:2:0, resulting in a resolution. One set of algorithms is used to remove image data and another set is applied in order to interpret the data and view it on the monitor. Those steps take time. Such delay is called compression latency. Note that latency is not a function of lossless vs. lossy formats but a function of the codec delay, transport delay, and delay caused by other processing. When it comes to latency tolerance in AV applications, image-magnification (IMAG) applications exhibit the least tolerance for latency; videoconferencing applications have a very low tolerance for latency; and video playback and remote video have a relatively high tolerance for latency. Image accuracy and motion without delay are crucial in rental and staging, live events, and simulation applications. A simultaneous broadcast of a CEO speaking at a live event should not be even a half second behind, lest it distract the audience. Surgeons have to be able to receive video in real time while performing a surgery. For these reasons, live events and simulation markets continue to rely on uncompressed video. 4K integration is deemed successful if the viewers are interacting with the video without noticing or thinking about it. This represents an exceptional 4K experience. In conference rooms, 4K content is usually sourced from computers, videoconferencing systems, and cameras. At the moment, streamed uncompressed 4K video requires too much bandwidth to be displayed. In order to achieve acceptable throughput, streamed 4K video requires compression. To meet the parameters of 4K technology, compression standards depend on technology 9

16 The 4K Puzzle development and testing by the silicon market and manufacturers. Part of the challenge with 4K is figuring out how to improve existing codecs and design new ones that can deliver a high-quality 4K image with low latency. The following are a few algorithm sets or codecs competing or coexisting in the 4K market. Currently, H.264 or MPEG-4 Part 10, Advanced Video Coding (MPEG-4 AVC), is the most widely used lossy codec. While it does support 4K, it still consumes a lot of bandwidth. The succeeding codec, H.265 or High Efficiency Video Coding (HEVC), can provide about 50 percent bandwidth savings compared with H.264 s bandwidth usage. However, it is not widely accepted yet. Netflix already produces 4K video using H.265. The streaming device, whether it is a computer, TV, or a set-top box, has to have an H.265 decoder installed to display it. (Another, less efficient, option for viewing on computers is decoding software.) The adoption of H.265 is moving slowly simply because the development of decoding hardware takes time. H.265 is not the only contender in the area of 4K compression. VESA recently released a low-ratio Advanced Display Stream Compression (A-DSC) for display links. Display links pertain to connections between computers and monitors, set-top boxes and TVs, and application processors and display panels. According to VESA, DisplayPort 1.3 will be able to support 8K video at 60 fps and 24-bit color using a 2:1 compression ratio, or 30-bit color using a low 2.5:1 compression ratio. The intended result is visually lossless image quality. VESA has released a call for technology in an effort to standardize the coding system. At the time of writing, the VESA Display Stream Compression Task Group is evaluating test models. Google s VP9 is an Internet-based open-source encoder used by YouTube, many browsers, and recently 4K TVs as well. The codec improves on the previous version, VP8, adding support for 10- bit and 12-bit depth, 4:2:2 and 4:4:4 chroma subsampling. It cuts the size of video in half and now also prioritizes the sharpest image features to allow for a crisper and block-free video. The medical, simulation, and live events markets all require minimum latency, exceptionally highquality images, and low-to-zero compression. And some manufacturers are not waiting for ubiquitous compression standards; they develop their own hardware-based compression for broadcast and security and monitoring markets. Content Protection In 2000, Intel Corp. created a method of encrypting discs for Blu-ray and other types of digital standard devices to prevent illegal content reproduction. High-definition bandwidth content protection (HDCP) creates a secure pathway from one device to another, and from the source to the destination. If a proper key exchange does not occur for decryption inside the receiving device, the content is unusable. HDCP may be used by any content owner to protect their recorded video. Because of HDCP and its rules, the content from a Sony Pictures Blu-ray cannot be sent to a recording device. All Apple computers and a lot of Windows PCs can recognize HDCP support in the monitor or system they are plugged into and turn on HDCP. Displaying copyright-protected 4K material may require a set of products that are compliant with the new HDCP 2.2 specification, including players, cabling, switching devices, and the audio/video 10

17 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES receiver (AVR). In other words, an HDCP 2.2-protected video will not display on the screen if there is a compliance break in any part of the chain. Infrastructure Today s video systems continue to use HDMI cabling, a technology that was developed for the 1080p resolution. The AV industry is attempting to augment this technology to support 4K signals. The results of these attempts reveal a dire need for a new solution that would surpass the capabilities of Category cabling and adequately respond to much larger bandwidth requirements without supplemental engineering. Ultimately, the infrastructure decision depends on the application that is driving the need for 4K. A 4K signal may generate between 3.5 and 20 Gbps of data. HDMI 1.4 and HDBaseT peak at 10.2 Gbps and the latest version of HDMI, 2.0, supports up to 18 Gbps of data. HDMI 2.0 requires version support from the source, through cabling and transmission devices, to the display. Furthermore, an HDMI cable can reliably achieve the upper bandwidth limit only over a short distance 40 to 50 feet (12.2 to 15.2 meters [m]) maximum or 25 feet (7.6 m). Distributed applications that require longer cable length fall back to HDBaseT (limited to 10.2 Gbps), and at best achieve uncompressed 4K at 60 fps and 8-bit color with 4:2:0 chroma subsampling. One benefit of Category cable, however, is power over Ethernet (PoE), which enables delivering more than 90 watts of power over copper cabling. For example, for a staging show, a single copper cable could power the display and deliver the content, eliminating the need to run a separate electrical line. Some solutions require full, uncompressed, signal to take advantage of all 4K qualities. Simulators, which require uncompressed content, generally are self-contained. Image generators, projectors, and display structures are all built and designed within the limits of copper because the components are collocated in the same environment and do not require remote connection. In live events, the industry is seeing a lot more optical fiber especially for 4K requirements. Optical fiber provides benefits that could solve the bandwidth problem, but the industry has not implemented it yet. Multimode fiber cable supplies the bandwidth of 100 Gbps and length of at least 328 feet (100 m), while singlemode cable can distribute 40 Gbps over the length of at least miles (40 kilometers [km]). Optical fiber could also be combined with IP solutions, in which case no compression would be required. Instead of having to use a proprietary switch, such a solution could utilize a standard fiber Ethernet switch. By comparison albeit running over standard LAN cable HDBaseT requires its own matrix and transmitter receivers. Although HDBaseT is packet based (T-packets), it is not IP based and does not run on a standard IP platform. In the absence of fiber, Category cable, preferably CAT-6a or CAT-7 are recommended for distribution of 4K content with HDBaseT. 11

18 The 4K Puzzle In some cases, end users may be interested in implementing 4K but own legacy CAT-5e or CAT-6 and are not able to afford retrofits. They could implement a 4K system, with limitations, as follows: Using a class A HDBaseT chipset for a 1080p signal or lower can provide 328 feet (100 m) or the full use of the specification the cable is CAT-5e, CAT-6, or CAT-7. But, if the bandwidth increases due to a resolution above 1080p, the older cable (i.e., CAT-5 or CAT- 6) will limit the system to a maximum of about 238 feet (70 m). Specification 2.0 of the technology increases this distance to 295 feet (90 m). However, CAT-6a shielded or CAT-7 cable could provide the full 328 feet (100 m) distance. HDBaseT also offers a class B chipset, which is more budget friendly and carries a shorter distance specification than the class A chipset. Using the class B chipset and a 1080p signal over CAT-6a shielded or CAT-7 cable, the end user would still get the full 230 feet (70 m). In an older installation, over CAT-5e or CAT-6 cable, the distance is going to drop down to a max of 197 feet (60 m). But, if the bandwidth requirements increase, the class B chipset and CAT-6a or CAT-7 cable will provide 130 feet (40 m) of distance. Dropping down to CAT-5 or CAT-6, the system is going to be limited to a maximum of 115 feet (35 m). Note that these distance assertions are vulnerable to compromises such as electromagnetic interference (EMI) and cable damage (e.g., pinching, cutting, bending, and stretching). 12

19 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Designing for 4K The best way to think about designing a 4K system is to take stock of the principles that are not affected by 4K. Recall the discussion about visual acuity. What has to change when a 1080p image is swapped out with a 4K image on the same 42-inch TV? The optimum viewing distance. The following questions help to determine the variables in a 4K project: What is the goal of this 4K project? What does the end user need to be able to see? What infrastructure is required to support this amount of data? Which type of display or projector does the end user want to use? Which type of receiver and processors are suitable for this system? Based on the end user s needs, designers look at the available products and their constraints, and then extrapolate the limitations the solution might impose. Consider, for example, an encoder box that accepts 4K. The specification might state that it can support UHD signal at 60 fps with 4:2:0 chroma subsampling and 30 fps with 4:4:4 chroma subsampling. And, that could be limiting depending on the end user s needs. Ultimately, the only way to make sure that end users are satisfied with the result regardless of the underlying parameters is to allow them to have an interactive experience with the solution in real time, with different types of content. That might not mean they will choose 4K. In an educational facility, 4K may not necessarily improve the flow of information or the quality of meetings. In a highend institution, it may provide a level of polish that conveys high stature or overall quality of the institution. And live events and simulation applications will require uncompressed 4K video. The following section describes the workflow of a 4K design project. Needs Assessment Assuming the end user is interested in 4K, it is important to clarify which sources, resolutions, color depth, application, frequency, and bandwidth they expect to use, and identify whether or not their infrastructure and budget will support them. Designers should take the following steps: Evaluate the application. In an application such as K-12 education environment, color quality is going to be important, but not in the range of color depth required in art gallery image reproduction or simulation video applications. Identify the switching-system requirements. The players, content, and sources determine the requirements of a switching system between the source and the end points. End users may or may not require the full detail of 4K resolution. They may require a higher refresh rate to achieve a seamless and smooth image on the screen. Likewise, they might benefit from 10-bit or 12-bit color depth but, in most cases, are limited by transmission 13

20 Designing for 4K media to 8-bit color. As noted in the Infrastructure section, HDBaseT can distribute content over 328 feet (100 m) via Category cable. However, its bandwidth is limited to 4K at 10.2 Gbps. One of the things integrators designing for 4K run into is legacy cabling that does not meet the 4K bandwidth requirements. This is especially a concern when reusing Category cable for applications with HDBaseT. Using products with a class A chipset allows transmission over longer distance using the older line than using the value-based class B chipset. Identify the bandwidth requirements. Once the end user understands the characteristics and differences among the resolutions, designers have to determine how much bandwidth is required to transmit the most bandwidth-intensive signal required. Greater color depth, resolution, and refresh rate will improve the quality of the display system but require more bandwidth. The differences among 24 Hz, 30 Hz, 60 Hz, and 120 Hz are quite large. Refreshing the pixels on a screen 60 times per second rather than 30 times per second is going to essentially double the bandwidth requirements. However, it will be capable of reproducing smoother motion. Choose a transport model. When it comes to design, there are two models to consider the current AV-centric model and the emerging, network-based, model. - The current AV model does not necessarily pose bandwidth issues from a design standpoint. The products and their specifications will show if they support a given resolution, color depth, and chroma subsampling. It is the manufacturers burden to determine the bandwidth capabilities of their products. - Designers have to inspect the IT infrastructure and decide in cooperation with the IT department if a single set of switches will handle both AV and IT traffic or dedicate a switch stack that will handle AV traffic. A recommended approach is to consider the upcoming demands of AV on the switches and standardize the design with enough bandwidth to accommodate future growth. The next section discusses these issues in greater depth. Identify stream distribution requirements. An end user may want to be able to stream a shareholders meeting, a sporting event or a commencement ceremony. A streaming distribution system, consisting of stream encoders and transcoder stream processor, may be used to address the distribution of content to users outside the organization (see figure 5). 14

21 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Figure 5 A streaming distribution system (courtesy of K2 Audio) Network Assessment Bandwidth is easier to plan for with a dedicated AV system than a networked AV system. Manufacturers of dedicated AV switching solutions provide guidance for creating a system that is not bandwidth constrained. With a networked AV system, the stress will vary depending on the number and type of video streams, as well as the network topology. To determine bandwidth requirements, a recommended approach is to define a most taxing use case based on the video streams and network topology employed. The system is then subjected to that state and evaluated by playing video content for any dropouts, pixilation, and compression artifacts. If the 4K video system is collocated with other traffic on a network, emulating high usage states for the rest of the network is useful as well. Video may display properly if no other systems are in use, but simultaneous operation of workstations and servers could compromise video quality and continuity. The configuration of multicast traffic and network topology could then be fine-tuned. Next, integrators select either products that can deliver uncompressed performance or products that create compression. They might structure the network bandwidth according to quality requirements, but it may be necessary to work with a given bandwidth, say 500 Mbps, and adjust video quality to fit within this constraint. The amount of compression applied to the video can be configured directly on the encoder. However, more compression means lower quality. The next step is to conceive a system and demonstrate the technology. 15

22 Designing for 4K System Design Ultimately, 4K signal distribution is similar to pre-4k environments. The network-based model is discussed in detail below, but the figures have been annotated to show similarities to the AVcentric model. If the end user has only one room that requires AV switching, such as two wall plate inputs and a projector, and wants to be able to switch between the inputs and the projector, all three devices could be plugged into a single switch (see figure 6). This is an example of an isolated AV system that does not require being connected to a distributed infrastructure. Figure 6 Designing a single-room 4K environment (courtesy of K2 Audio) If the end user has 10 conference rooms and wants the ability to take one conference room s video and send it to all of the other conference rooms, each room could have its own switch separate from the IT network. Then centrally, the designer could specify an additional AV network switch and, using a star configuration, connect it via copper or optical fiber to each of the individual switches. Now all of the AV switching could be accomplished without using the main IT switch stack. If the end user wants to use part of the main IT network for their AV traffic, rather than having an AV network switch, connections from the 10 rooms would be plugged into a separate network switch or directly into the IT s data closet network switches. 16

23 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Figure 7 shows the source-to-sink requirements to interconnect two and three spaces, respectively. Figure 7 Designing a single- and multiroom 4K environment (courtesy of K2 Audio) 17

24 Designing for 4K Note that these diagrams are simplified examples. Network topology may significantly differ in practice. Before accepting the system, the system verifier should perform standard color and brightness verification of the display. By playing a variety of sources, including still images and video, they observe the screen to see if downscaling or other artifacts are introduced along the way. By testing the proximity to the display where image and video viewing becomes an indiscernible pixel experience, they can verify that the end user is receiving the full performance expected from the screen. Implementation Challenges The biggest technical challenge with 4K is confusion about refresh rate and color space, discussed in The 4K Puzzle section. The second thing many end users discover is that, because many originally acquired 4K displays did not provide HDMI 2.0, they are limited to delivering 4K at 30 fps. And they are not compatible with HDCP 2.2, which will cause issues with displaying premium content. HDMI 2.0 vs. 1.4 The speed at which a full frame of pixels fits into one 60th of a second (i.e., one refresh cycle) is called a pixel clock. The HDMI 1.4 pixel clock can reach up to 340 MHz and pass 4K at 30 fps. HDMI 2.0 allows the pixel clock to go up to 600 MHz and pass 4K signals at 60 fps with 4:4:4 color space, but not past 8 bits. It also allows 4K at 60 fps and 12 bits but with the 4:2:0 chroma subsampling. Table 3 from HDMI highlights in red the 4K formats supported by HDMI 2.0. Table 3 4K formats supported by HDMI Frame Rate 8-bit 10-bit 12-bit 16-bit 4K@24 4K@25 4K@30 RGB 4:4:4 RGB 4:4:4 RGB 4:4:4 4:2:2 RGB 4:4:4 4K@50 4K@60 RGB 4:4:4 4:2:0 4:2:0 4:2:2 4:2:0 4:2:0 For most end users, color space is not going to make much difference, specifically for video playback. Computer users, especially in the visualization and simulation applications, generally require the 4:4:4 color space because their applications do not tolerate color shift. Choice of transmission method has to be carefully evaluated during the needs assessment. 18

25 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Signal-Integrity Issues Another challenge designers must contend with is that signal-integrity requirements for 4K video are significantly higher than those of 1080p. The two main signal integrity issues are related to voltage and time. In simple terms, a couple of volts is a 1 and no volts is a 0. If 1s and 0s begin to get closer together in terms of how much voltage is applied, the difference begins to shrink and the signal begins to shift in time, left to right on the screen. This anomaly is called jitter. Another disturbance affected by power is voltage drop or sag, which affects the video data and signal quality. To verify signal integrity and specific bandwidth, it is not enough to test for continuity. Oscilloscopes and network testing equipment can be used to verify that crimps from end to end and data integrity across all the pairs meet the specification and confirm there is no crosstalk, jitter, and other effects. The Trouble With HDCP When a source (e.g., a Blu-ray player) initiates HDCP communication, it presents a master key to the display. If the display responds with a public key, the source device provides a session key that enables communication and begins transmitting the content. HDCP can add to the processing time due to decryption. A bigger problem is that different HDCP versions are not backward compatible and the HDCP 1.4 specification cannot be upgraded to the 2.2 specification, posing a big challenge. To pass the encrypted content, all of the matrix switches have to support HDCP 2.2. Manufacturers provide a user control that can send a message from the switch input to the source stating that the switch does not support HDCP. The source then determines based on the content if protection is required. If it is a PowerPoint slideshow, for example, the file will be displayed; if it is an itunes movie, the source will not route it. If the display continues to show an HDCP error message, testing the system with encrypted and non-encrypted content helps to determine the source of the problem. Device Support One of the biggest challenges with 4K is taking high-resolution content from the source to the display. The higher the level of compression, the more of the original color value is lost. And 4K file sizes remain large regardless of the amount of compression. As a result, the cabling has been one of the most difficult elements of a 4K system to manage due to unrelenting bandwidth constraints. Simple things like the inability of DisplayPort to run full 4K bandwidth over a single cable make implementing a 4K projector into a large public viewing space difficult. Ultimately, many components required to support full 4K capabilities chipsets, routers and switchers, scalers, and transmitters remain a work in progress. End users need to be able to use mixed formats and mixed resolutions, so that, for example, they can show some 4K HDR type content and PowerPoint in a single usable image. 19

26 Designing for 4K A mix of legacy and new technology, as well as end users who are pushing the envelope, exists across the AV industry s markets, even in low-latency applications. A simulation site may have a mix of the old and new equipment blended and held together by a processor or host controller. Many end users want to be able to combine new technology and displays with older devices. Screen management systems (figure 8) allow the user to combine various resolutions and signal types into a single display. These types of systems will convert color space, upscale or downscale resolutions, and allow for video and computer signals to be displayed simultaneously. Such systems also allow the end user to choose from a variety of sources to be displayed. They enable upgrades to future signal interfaces, without replacing the entire system. Figure 8 Screen management system (courtesy of Barco) 20

27 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES 4K in the Real World Any application that relies on the ability to process and synthesize large amounts of information has a real-world use case for 4K. The new specification benefits a variety of applications, small and large. Even before the pro-av industry transitions completely to 4K, there is an opportunity to take advantage of so-called tweener resolutions. Source devices such as the MacBook Pro, some Windows PCs, and the top end of mobile phones and tablets all have native operating resolutions in the 2.5-to-3K range that require 4K equipment to be displayed. Applications as simple as computer-aided design (CAD) or content sharing in a collaboration setting can benefit from the 4K image quality. Beyond these simple examples, specialized applications such as visualization, whether it is medical imaging, oil and gas exploration, or longterm financial stock charting, can now be seen in larger depth of detail. The following section covers some 4K applications where users are grasping the full benefit of higher resolution, higher color depth, and faster refresh rate. Multiwindowing on a Single Display and Scaling 4K Across Multiple Displays End users can display four 1080p signals on a 4K screen capable of multiwindowing. A multiimage display makes it possible to fit four instances of 2K content on a 4K display without any loss of resolution. And a 2 2 videowall using 1080p screens can split 4K content and provide four native pixel-for-pixel 1080p screens. Alternatively, a 3 3 video wall using 720p-class resolution can split 4K content over nine native-resolution displays. When daisy-chaining a 4K signal to multiple displays that scale to show part of the image, it is important to verify that 4K is supported on all display interfaces. Otherwise, an independent signal will need to be routed to each display either from the source or a windowing processor. Likewise, HDCP may not support daisy-chaining to multiple displays, so this item should also be verified. Figure 9 shows a videowall with a multiwindowing capability. Such displays can be layered in zones to show different sources of information and enhance collaboration. 21

28 4K in the Real World Figure 9 A multiwindowing display at Stanford University (courtesy of Christie Digital) And on the projector side, a multichannel projector system that used to employ four 1080p projectors to fill a large screen can now be swapped out for a single 4K projector. That eliminates the need for edge blending, color matching, and achieving correct geometry. However, at this time, 4K on a single projector is most commonly achieved using four discrete 2K-class video signals rather than a single 4K video signal, due to transport technology limitations. This is similar to the multiwindowing display discussed above. Projection Mapping 4K projectors provide the same benefits as 4K displays, including a wider color gamut and smoother and more lifelike images. Moreover, 4K creates many opportunities for projecting onto nontraditional surfaces owing to the 4K projectors power to emit the light of 40,000 lumens (or 60,000 lumens if they are laser projectors). Figure 10 Projection mapping at Festival of Lights in Lyon France (courtesy of Christie Digital) 22

29 4K AND BEYOND: TECHNICAL CHALLENGES AND OPPORTUNITIES Brighter 4K projectors are quite popular in projection mapping (see figure 10) because fewer projectors are required than in comparable HD applications. This improvement not only produces a more immersive experience, but also positively impacts the bottom line less equipment means lower equipment cost, as well as lower power and signal distribution. Videoconferencing One of the pain points with videoconferencing is zooming. A 1080p camera relies on the mechanics or lens for zooming purposes. With 4K cameras, electronic capabilities obviate the need for mechanical zooming. Also, the higher the resolution, the easier it becomes to implement facial recognition, which may be used to identify videoconference participants. Security The security market does not have latency requirements and requires the ability to send small packets of data to different end points. Because a 4K camera allows wider angles and digital zooming capabilities, moving from point A to point B in an image becomes easier. The camera is always pointed in the right direction, allows digital zoom into the area of interest, and eliminates the need for robotics. Visualization Visualization consists of processing and analyzing large data sets. Oil and gas industries use satellite maps overlaid with data collected by the oil exploration machinery, such as acoustic transducers. Oil and gas industries collect terabytes of data from ground or oil samples and sonar sampling. The combined data helps to discover salt domes pushed up by natural gas and concealing oil underneath. The same type of data is then used to determine the appropriate oil extraction technique. And high-resolution and accurate color displays assist with visualization of ground hardness and softness based on different color variations. In the medical applications, data is typically analyzed from x-rays, CAT scans, and PET scans. In other markets, such as automotive design, where a 1:1 scale on an immersive powerwall or similar display is used to look at an automobile in 3D or 2D, fine detail and true color reproduction are vital. Smaller pixel structure allows for smoother object rendering (see figure 11). For example, blending three 4K projectors can generate a 12,000-pixel image, which allows the end user to see a large amount of data at an even finer level of detail. 23