10 Remedies for Everyday Video Problems

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J u l y / a u g u s t 2 0 1 2 | 10 Remedies foR eveRyday video PRoblems A3

Ì REmEdy #1

what is ambient light? simply, put, it’s the light that doesn’t come from the projector. it’s a problem for commercial spaces because in many applications, high levels of ambient light are required—in order to achieve their purposes, houses of wor-ship, classrooms, meeting rooms, lobbies all require a sig-nificant amount of ambient light.

the problem is that high ambient light in a space reduces the contrast level of the image as it’s perceived on the screen, and thus makes it hard to see. tech-nically, the screen is reflecting both the light produced by the projector and the ambient light existing in the space.

once the decision has been made to use a projection system (versus a flat-panel), the next question is front projection versus rear projection. rear projection requires space behind the screen which varies between a few feet to many feet, depending on the system used. if you have the space, rear projection solves most ambient light issues,

since you can control the amount of ambi-ent light in that space, and it won’t compete with the light from the projector.

if front projection is required, there are things you can do to control it or minimize its effect on the quality of the projected image:

1. Control the lightsunlight streaming in through glass win-dows is the most common source of exces-sive ambient light. many AV control systems now have the capability to control motorized shades, blinds or blackout curtains when the projector is activated.

the second most common source of ambient light is generated by room light-ing, which may be required in order for people to see meeting materials or other participants while they view projected con-tent. Lighting dimmers can also be added to the AV control system. Also, make sure that light fixtures near the screen (either on adjacent walls or the ceiling) can be controlled separately from the other fix-tures in the room. reducing light near the screen will reduce the contrast ratio, making the image easier to see.

2. SCreen loCationthe key consideration for placement

of projection screen place-ment is to locate the screen as far as possible from obvi-ous light sources like win-dows or skylights.

3. SCreen SeleCtion new front projection screen technologies have emerged that can reproduce excel-lent images, even under challenging ambient light

conditions. most of these screen mate-rials attempt to reflect more of the pro-jected light compared to ambient light. screens that are described as “high con-trast”—like grey screens—will work bet-ter than matte surfaces. Another screen material feature a “lens” design that diverts ambient light away from the seat-ing area, while reflecting on –axis light (presumably the light directly projected from the projector) to the audience. the only drawback for this technology may be a more narrow angle of reflection and thus, seating area.

4. ProjeCtor SeleCtion in the old days, before LcD and DLP pro-jection, crt projectors simply weren’t capable of producing enough light to compete with the sun. today, as a result of better light engines, lamp technolo-gies, and screens, economically achieving adequate projector brightness is rarely an issue. in fact, a bigger issue is when AV designers choose an overpowered projec-tor in attempt to overcome ambient light. higher brightness does not increase con-trast ratio; in fact, it may reduce it. the negative effect on image quality is almost always worse than the ambient light itself.

Projection for Venues with Ambient Light

+ KiSS (Keep it Simple)

1. Darken the room.

2. if you can’t darken the room, use rear-projection.

3. if you can’t rear project, minimize light near the screen.

4. for rear or front projection, use a screen technology that reduces ambient light at the screen.

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Here’s the scenario: An executive brings her laptop into the meeting room, connects the video cable that’s been provided at the lec-tern and (after a few presses of the Function buttons) there’s an image on both the laptop and the external display (or projector). The “problem” is, the image doesn’t entirely fill the screen. Panic, finger-pointing, and/or technology rage ensues.

There could be two reasons for this, and they are related, but different: aspect ratio and image resolution.

Aspect ratio refers to the width-to-height ratio of an image. We live in a world of many standards, so there’s not one single aspect ratio that’s common among all source devices and display devices. The most common ones today are “wide-screen” 16:9 (or 16:10 for Apple displays) and 4:3. Resolution refers to the actual pixel count of the display, expressed as the number of horizontal pixels by the number of vertical pixels. A resolution of 1366 x 768

therefore has an aspect ratio of 16:9 (or 1.78 to 1); so does a resolution of 1920 x 1080. Simple math. “Native resolution” of a display refers to the fixed resolution of its imaging device, which could be an active matrix display on a laptop or the imaging engine in a digital projector. Most displays are able to inform the source of its native resolution using extended display identifi-cation data (EDID).

First, the bottom line: The only true way to avoid this problem is to use a source device with the same native resolution as the display device. But since this isn’t always possible, video signal processing offers a few solutions (sort of).

Scaling is signal processing that alters the size (or resolution) of an image to fit the pixel size (or native resolution) of a dis-play device, without changing its shape (or aspect ratio).

But when the aspect ratio of the image produced by the source (like a laptop with

a 4:3 aspect ratio) does not match the aspect ratio of the display device’s native resolution, the image doesn’t completely fill the shape of the display, and you see the “black bars” (which are not really black bars, but the result of no image data being sent to that part of the screen) along the sides or top and bottom of the display.

Most digital displays have built-in scal-ing circuitry which allows you to get rid of the “black bars”, but not without a tradeoff.

The remote control units for many dis-play devices have a “zoom” or “image size” button. You can lose the bars by “zooming” the image to expand it horizontally (for a 4:3 source image on a 16:9/16:10 display) or vertically (for a 16:9/16:10 source image on a 4:3 display)—but you’ll lose image content from the top and bottom or sides.

Some scaling circuitry can also expand the image, stretching a 4:3 source image horizontally so it fills a 16:9 frame. But the image will appear distorted.

A common real-world example of the aspect ratio problem is displaying a Pow-erPoint slideshow that was created in 4:3 on a 16:9 display. While changing the Page Setup from 4:3 to 16:9 or 16:10 will re-size text without much problem, Microsoft has yet to offer a “scaling” function for graphics or photos. Until they do, the only solution is to re-set or re-size each image individually.

Ì Remedy #2

Aspect RAtiosWhen the Source content DoeSn’t Match the DiSplay’S ForMat, What Do you Do?

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Ì REmEdy #3

DeALing with content ProtecteD source mAteriAL

the digital revolution is undeniably the most pervasive issue in AV today. Vast improvements in sound and visual quality are the most obvious benefits, but there are drawbacks too, especially for com-mercial AV applications. Digital AV has historically been driven by the consumer electronics industry and content creators. because digital signals are theoretically perfect copies of the original and so easy to duplicate, extensive copy protection schemes, along with an entire economy of devices and organization to enforce them, have emerged. the most prevalent scheme is high-bandwidth Digital content Projec-tion (hDcP). hDcP was developed with no consideration of commercial AV applica-tions. After all, most pre-recorded content like films and music are transmitted from one source to one display or audio system, right? not always in commercial AV, where users often want to include “protected con-tent” in their presentations. in addition, the most popular signal transmission technol-ogies have hDcP in their core specification, which in turn, require the use of hDcP-compliant components. the bottom line is that over the last several years, hDcP has been the number one source of headaches

for commercial AV system designers. here are some of the most common head-aches—along with their aspirin.

1. BlaCK SCreenAll components are connected, powered on, but there’s no image on the display. this could be due to a “bad cable” or one that’s too long; in either case, signal deg-radation can prevent the exchange of eDiD (extended display identification data), which tells the source the optimal video parameters for the display. solution: if the components all have hDmi interfaces, be sure to use only good-quality, high-speed hDmi cables.

Another cause could be the presence of a non-hDcP compliant device in the signal chain. All hDmi and DisplayPort interfaces support hDcP, but not all DVi interfaces do. if any component in your system supports hDmi, then all of them must or no signal will be passed. if you’ve got one component with a DVi interface, it’s possible that the component does not support hDcP, and is preventing the key exchange that’s required to pass the signal. solution: make sure every component from source to display is “hDcP compliant”.

2. SnoWy iMagein the days of analog broadcasting, we used to call this “snow” due to poor reception. with digital signal transmission, it means that you’re actually looking content protec-tion in action; the “snow” is encrypted video. Like “black screen”, it can happen when your display (or any active component, like an extender or a splitter, used in the transmis-sion) doesn’t support hDcP. the display, in turn, isn’t able to decrypt the video stream. solution: check for hDcP compliance of all components, and replace if necessary.

3. SWitChing DelaySthis headache is unique to commercial AV because rarely does a residential installa-tion require the use of switchers or video routers. the problem is that whenever a newly-connected device is sense in the signal transmission (as happens when the source or display is switched) a new round of key exchanges and authentication must be negotiated, and that takes time. solu-tion: some manufacturers have taken steps to minimize switching time and speed up the key exchange process by maintaining continuous authentication among hDcP-compliant components.

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Ì REmEdy #4

ViDeo connector incomPAtibiLitythis issue has to be the source of more user headaches than any other in the world of video. Video connector standards are like the weather in new england; if you don’t like it, just wait a minute, it’ll change. the only difference is that many old interface standards never seem to go away completely—like hav-ing a rainstorm, snow, tornado, and blue sky all at the same time.

of course, there are technical (and com-mercial) reasons for this, but at the end of the day, it’s the tech manager or presenter who often pays the price for the constantly chang-ing connector issue.

hoW DiD We get here?first, it’s helpful to distinguish between video formats, standards, and connectors. before digital, VgA (developed by ibm in 1987) was the most common video signal format, and it was considered “standard” although it was never adopted by an official standards-making body. for many years, most Pcs output VgA, and displays and other sources accepted it. VgA uses the common De-15 connector, still seen on many Pcs.

that’s all changing with digital video signal formats. for commercial AV appli-cations, the most common digital formats are DVi, hDmi, DisplayPort, and sDi. within each format, there are multiple variants and connector types.

in 2010, intel, AmD and Pc makers Dell, Lenovo, samsung, and Lg announced that they would phase out VgA con-nectors (or ports) by 2015. their rea-soning is that digital formats such as DisplayPort and hDmi allow for slim-mer laptop designs and higher reso-lution with deeper color than VgA. earlier this year, analyst firm nPD in-stat released a report stating that DVi ports will also disappear from

Pcs over the next five years, setting the stage for “standardization” on hDmi and DisplayPort.

there are several other sev-eral issues driving the phase out of VgA and DVi interfaces. one is

that VgA does not allow for content protection, so it may be phased out

due to digital content license agreements. A more practice issue for manufacturers and users is the size of the connectors: VgA and DVi connectors with thumb screws are dif-ficult and sometimes impossible to accom-modate in the latest ultra-slim notebook and netbook designs, and connecting and secur-ing these cables to monitors is difficult in confined spaces.

So Why Do We Still neeD tWo Digital interFaCeS? DisplayPort and hDmi are very different tech-nically, and each has a different product focus. hDmi is the de-facto standard in home the-atre and is used widely on hDtVs, and some Pcs and monitors include hDmi to enable connectivity with hDtVs and other consumer electronics gear. DisplayPort is focused on Pc, monitor, and projector applications as a replacement for DVi and VgA where high per-formance is critical, and allows backwards and forwards compatibility over standard cables. the DisplayPort connector is com-patible with hDmi signals, enabling product interoperability. And, to make content pro-ducers happy, DisplayPort 1.2 supports hDcP

v1.3, ensuring that protected content such as blu-ray Disc movies may be easily viewed over a DisplayPort connection that includes hDcP support.

Be PrePareDwhile there is no one best plan to avoid the connector conundrum, the best advice is to be prepared. whenever possible, try to determine the connector type of all possible sources and displays before any installation project or ad hoc presentation. check to see if there are matching connectors on installed AV devices (projectors, flat panels, switchers) and connectivity interfaces (pop-up access panels or wall plates, etc.). if you’re lucky, the issue is resolved with a single format cable of the appropriate length.

when that is not possible, there are three courses of action:

1. use adaptors: Adaptors provide the simplest solution, but with digital video sig-nal transmission, there can be drawbacks too. for example, don’t expect to get audio from a DVi connector (it’s video only). Also, most adaptors are passive devices, and won’t convert from digital to analog.

2. use an active Device: A very common scenario in which connectors present prob-lems are group presentations, where multiple presenters each bring their own laptop. but combining multiple formats is considerable easier than it used to be, by using presentation switchers. A presentation switcher accepts and scales a wide range of video signals to a com-

mon, high-resolution output rate.3. Check alternate inputs on downstream device: many display devices like video projectors offer several input options. instead of concentrating on making the con-nection work at the source end, try working backwards and check to see options are available on the next device in the chain.

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in the early days of computing, the term multiplatform was straightforward: ms-Dos/windows or mac. today, with many different operating sys-tems, device form factors, delivery options and providers, multi-platform is most often defined with the ambiguous (and often overstated if not downright mislead-ing) phrase “any device, anywhere, any time.” the reality is that we have a long way to go before multi-platform evolves to omni-platform.

As computing, communication and pre-sentation technologies have converged, so have the number of platforms proliferated. today’s tech landscape is one of multiple standards and interoperability issues, making it difficult for technology manag-ers to keep ahead of advances in technol-ogy and the needs of their end-users.

for enterprise video content delivery, however, the smoke may be clearing on video platform delivery options. one of the

key platform distinctions is the type of device used for viewing.

PCSthe bottom line here is that Adobe’s flash is the dominant

software for viewing online video on Pcs. if you want to view

video on a Pc, chances are you’ll continue to use flash Player to do it.

MoBile DeviCeSfor mobile devices, it looks like htmL5 is king. there was a significant momen-tum shift in the fall of 2011, when Adobe announced that they would stop the future development of flash on mobile platforms. instead, they’ll work with developers to cre-ate Apps for the various mobile platforms. According to their official announcement dated november 9, 2011:

“htmL5 is now universally supported on major mobile devices, in some cases exclusively. this makes htmL5 the best solution for creating and deploying con-

tent in the browser across mobile plat-forms. we are excited about this, and will continue our work with key players in the htmL community, including google, Apple, microsoft and rim, to drive htmL5 innovation they can use to advance their mobile browsers.

some observers like streaming Learning center’s jan ozer believe that this sets the stage for a windows/mac style dichotomy, which should be welcome news to video content developers and consumers alike.

“streaming producers are going to need a plug-in based option for several more years, and flash is the obvious choice,” says ozer. “flash on the desktop isn’t going away any time soon. it just feels like in the mobile space, Adobe decided if they couldn’t pro-vide a good experience, for whatever rea-son, and it didn’t make sense to provide a bad experience.”

for the content consumer, it means it is less likely that you’ll receive the “this for-mat is not supported” brick wall when you try to watch a video.

Ì REmEdy #5

muLtiPLAtform onLine ViDeo DeLiVery

crEStroncrestron.cominfo

format options continue to grow, as are the multiple platforms for playback. 4K resolution will soon become the standard viewers expect from online video providers, according to crestron, which is why they are moving aggressively to support, manage, and distribute it.

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transcending and bridging all other cur-rent tech trends is the explosion of mobile devices and demand for functionality of every kind on mobile platform. in 2011, more smartphones and laptops were shipped than Pcs and laptops. As a result, tech users are demanding increasing capabil-ity from their mobile devices. the collision of streaming and mobility is transforming the traditional models of location based or scheduled learning and training.

According a wainhouse research report, “As smart phones and tablets become increasingly pervasive [among students], educational institutions are increasingly being asked to deliver content to or otherwise harness the power of those devices for mobile learning (m-Learning).” the trend is not lim-ited to education; for any training or learning environment, mobile delivery is becoming an expectation. can vendors deliver it?

MoBility ChallengeSstreaming to mobile devices is becoming fairly common, but there are still some limi-tations.

Bandwidth. Although compression algorithms are improving all the time,

bandwidth continues to be an issue and expectations for higher quality (hD) view-ing experiences and multiple streams drive increasing bandwidth requirements.

Connection stability. since mobile devices are mobile by definition, moving in and out of coverage areas continues to present a problem for stable connection to a local wifi area or 3g/4g coverage.

As mobile device processing power increases, the major limitation among devices simply comes down to screen size; it’s difficult to view more than one stream at a time. Larger mobile devices, like tablets, are a better choice for decoding and viewing multiple streams or easily switching between them.

MoBile aPPSLearning software companies like tegrity offer mobile apps that allow you to record, search, and stream content mobile devices. tegrity campus, a fully automated lecture capture solution streams content to the tegrity mobile App over the air, so there’s no need for the student to first connect to a computer in order to download con-tent. blackboard recently announced the

beta launch of blackboard collaborate mobile, an interactive mobile app for their collaboration software.

harDWare venDorS aDD MoBility

Although apps may provide an efficient, streamlined approach

for mobile viewing, it’s also possible to view streams optimized for mobile devices on web browsers. many of the traditional (and non-traditional) streaming providers are offering solutions. streaming hardware vendors are also getting into the mobile act. Last year, sonic foundry released media-site 6, the most recent version of its lec-ture capture platform that allows users to view live or on-demand streams on mobile devices using htmL5 and h.264. it includes a feature they call “automatic device detec-tion” which determines what type of device you’re using, then provides the optimal for-mat for that device. haivision’s Viper is a compact integrated appliance for capturing, streaming, reviewing, distributing, and pub-lishing multiple hD h.264 streams simul-taneously to any desktop, laptop, or mobile device. And AV control provider crestron now offers captureLive hD, an end-to-end lecture capture and streaming solution that can stream content to mobile devices.

Feature WiSh liStno matter which system you use, you’ll want to be sure their platform uses adap-tive streaming (also known as adaptive bit rate streaming), a technique that enables the optimum streaming video viewing expe-rience for a diverse range of devices over a broad set of connection speeds by detect-ing the user’s bandwidth and cPu capac-ity and adjusting the stream accordingly. while adaptive streaming has been in use for some time, it has become more impor-tant for mobile streaming because of the inherent limitations of wireless networks. Protocols from Apple (httP Live streaming or hLs), microsoft (smooth streaming), and Adobe (httP Dynamic streaming) all use a form of adaptive streaming.

Ì REmEdy #6

extenDing webcAsts & Lecture cAPture to mobiLe DeVices

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mobile video delivery is becoming an expectation to users in just about every vertical market. image courtesy of the AV design and integration firm conference technologies inc. (conferencetech.com).

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one of the key issues that distinguishes commercial AV from residential AV is the distance of signal transmission. it’s one thing to connect a three-meter hDmi inter-connect cable from a blu-ray player to an hDtV; it’s quite another to run an AV signal from a distribution closet to every meeting room on a corporate or university campus.

for long distance AV signal transmission, there are basically four choices; 1) coax, 2) category cabling, 3) fiber optic cabling, and 4) wireless. All of these have distance limitations depending on the quality of the cable and/or electronics, signal strength, type of signal, quality of connectors and terminations, and other factors. signal attenuation is the primary determinant of a cable or wireless signal’s distance limit. for analog signals, attenuation results in a gradual deterioration of the audio or video signal, along with increased noise. for digi-tal signals, some loss of signal quality will be noticeable, but a more likely limit indica-tion will be a complete loss of transmission.

Coaxtwo-conductor coaxial cabling has been the backbone of broadcast and AV cabling infrastructure for over 80 years. coax is still prevalent for video signal transmission up to about 300 feet. using active line driv-ing electronics, you can extend distances to up to around 1,000 with reasonable quality. but variances in the quality of manufactur-ing can result in performance degradation especially at longer distance. there are many types of coaxial cable, typically dif-ferentiated by “rg” (radio guide) number.

Attenuation is a key specification for all coax cables, and most cable manufacturers will specify attenuation loss in decibels per foot. the longer the coax cable, the greater the loss, but loss is also frequency dependent.

for digital signal transmission (sDi) with coax cable, you can send a composite video signal up to 2,700 feet at low bandwidth (143 mbps) with the right type of cable. but at higher bandwidths for hD signals, distance limitations are typically several hundred feet.

Category CaBlingthe American national standards institute and electronic industries Association (Ansi/eiA) have created standards that specify “cat-egories” of unshielded and shielded twisted pair cabling, which is more commonly asso-ciated with networking applications. today, it’s also commonly used for long distance AV signal transmission. it’s an attractive alterna-tive for many reasons, including 1) it’s cheap (compared to coaxial), 2) it’s small and easy to work with in the field, 3) it’s commonly pre-wired in many buildings, and 4) shielded twisted pair cabling provides some immu-nity to electromagnetically induced “noise”. high-resolution signals can be sent an aver-age of two to three times farther over twisted pair cabling compared to coaxial. extended distance transmission is achieved using an “active” electronic signal transmitter/receiver pair to convert the signal from AV formats (DVi, hDmi, VgA, etc.) to a balanced signal that’s optimized for twisted pair cabling. other types of signal processing can also be included (peaking, level, equalization, etc.) to ensure signal integrity over long distances.

FiBer oPtiCfor long distance cable signal transmis-sion, nothing beats fiber optic cabling. After all, it’s what runs communication signals between continents, across oceans. but just like any other transmission medium, as distance increases, opportunity for signal degradation also increases. And, like other long distance media, it requires signal con-verters at both ends. fiber optic cabling is available two basic types: multimode and single mode. single mode fiber is smaller in diameter, more expensive, but can transmit up to 18 miles (30 km).

in addition to external transmitters/

Ì REmEdy #7

Long DistAnce ViDeo signAL trAnsmission

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infothe opticomm-emcore hDmx is a video format converter and matrix switch (any input to any output). it can connect to any source DVi, hDmi or 3g hD-sDi/hD-sDi/sDi and send the output to the fiber monitor.

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Ì REmEdy #8

changing content is one thing; creating it and quickly getting on the display—sometimes called “dynamic content updating”—is a bit more of a challenge. the key is to put the control and access in the hands of the technology manager, instead of relying on a third-party service provider.

Digital signage provider mvix offers cloud-based approach for media storage—allowing you upload, download, or edit content anywhere with an internet connection. most of their clients use PowerPoint to create basic digital signage content. changes can be made at a moment’s notice, and as soon as content is changed and saved, it is immediately pushed to digital signage player wherever it lives on a network.

one of the simplest solutions comes from edina, mn-based AV integrator Alpha Video. their cast-net system uses a “fill out the form” web page approach to information creation which allows non-technical employees to update information from anywhere there’s a network connection. And, the castnet web interface is set up for use on a mobile device. An end-user can log into the castnet interface and make updates to the content from any mobile device with a web browser.

of course, live data feeds to digital signage players can add an element of dynamic content updat-ing without any direct action required by technology managers. tightrope media systems’ carousel Digital signage, for example, allows you to easily create twitter, rss, weather or news bulletins that will automatically appear and update on the display network. this type of content is especially criti-cal in environments like hospitals or school campuses.

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content creAtion on the go

receivers, some manufacturers build the optic conversion capability right into AV components. for example, transport solutions provider opticomm enables “fiber to the monitor”, by offering a direct input module for display manufacturers to allow direct fiber optic input—no exter-nal receiver to power and install.

WireleSSwireless signal transmission in AV is most commonly associated with microphones. but for video signal transmission, it’s a different story. most AV providers would love nothing more than to forego the labor and expense of running cable to displays. but the simple truth is, the technology is not to the point where we can give up the cable entirely yet, especially not for reliable hD video signal transmission in commercial AV applications. for some security applications, you can transmit video camera images up to several hun-dred feet using rf converters, but there are bandwidth and signal quality trade-offs. gefen offers a variety of wireless AV solutions.

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Ì REmEdy #9

this one of the most basic questions in all of AV. over the years, there have been many ways to answer it, including complicated formulas with variants depending on mul-tiple factors. the main concern is to fit the screen to the audience size and the room.

how do you know when the screen size is adequate? it depends on the image to be viewed. note that “image size” and “screen size” are not necessarily the same thing. the image is the relevant content on the screen that people need to see, and it may occupy only 50 to 75 percent of the screen area; the screen is the maximum physi-cal display area. Despite this technicality, for most screen size calculations, we use screen and image size to mean the same thing.

there’s no simpler explanation of proper image size than the one found in info-comm’s book, the basics of Audio and Visual systems Design: “A projected image is sized correctly when the most distant viewer can comfortably read characters, numerals, and other symbols that have been prepared in accordance with proper graphic standards.” focusing on the image content first gives us a test to use once we think we’ve determined the best screen size.

bigger is not always better; for most commercial AV applications, an “immer-sive” experience is not the objective. even for the so-called “telepresence” experience, human images shouldn’t appear larger than actual life-size. it is possible to overwhelm the human visual system with data, which impairs the communication of information.

4-6-8 ruleone of the oldest and most reli-able rules of thumb to deter-mine image size is the “4-6-8 rule”, which states that the farthest viewer should be no farther from the screen than some multiple of the image height. that multiple depends on the type of content being displayed.

for graphics or detailed drawings, the farthest viewer should be no more than 4 times the image height from the screen. for data or numbers, the farthest viewer should be no more than 6 times the image height, and for video content, no more than 8 times image height. by focus-ing on the image height as the guideline (as opposed to diagonal or width), it removes screen’s aspect ratio from the equation.

iDeal SCreen DiMenSionSonce you’ve determine the screen height, the width is then dictated by the aspect ratio you want to use. for 16:9 aspect ratio, mul-tiply the height by 1,78; for 4:3 aspect ratio, multiply height by 1.33.

remember that sitting too close to the screen can be as detrimental as too far; the closest audience member should be about 1.5 times the height of the screen.

seating layout can also affect viewing. on a flat floor, optimal viewing for the farthest row requires the bottom of the screen to be positioned above the heads of seated audi-

ence members in the closest row, which is usually 4 to 4.5 feet from the floor. Also, the top of the screen should be at least 6 inches from the ceiling.

the real WorlDwhile these formulas and guidelines are fine for calculating the ideal screen size, in many cases achieving the ideal is lim-ited by a pre-determined ceiling height or seating layout. if you don’t have the option to size the screen according to the distance to the farthest viewer, con-sider multiple screens, positioned within the distance to viewer guidelines. often, stage left and right screens with a dupli-cate image will get closer to ideal for the farthest viewer, simply by reducing the viewing angle.

�FURTHEST GENERAL VIEWING DISTANCE�

8x SCREEN HEIGHT

PREFERRED VIEWING AREA�90 DEGREES VIEWING CONE CENTER OF SCREEN

ACCEPTABLE VIEWING AREA�45 DEGREES OFF THE EDGE OF THE SCREEN

CLOSEST VIEWER�1x IMAGE WIDTH

FURTHEST INSPECTION VIEWING DISTANCE�4x SCREEN HEIGHT

FURTHEST DETAIL VIEWING DISTANCE�6x SCREEN HEIGHT

SEATING AREAS

mAtching imAge size to AuDience size—how big Does it neeD to be?

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1. extreMe teMPeratureSone way to keep displays cool in a hot environment is to use an enclosure that includes thermostatically controlled air-conditioning, much like we use in build-ings. but this has drawbacks which include increased power consumption, size, and the need to draw outside air in—which may also draw dirt, dust, moisture and other harm-ful elements. Atlanta-based manufactur-ing resources international (mri) offers enclosed displays that use a system they call “coolVu”, which relies on what they call a “closed-loop cooling system”. All sensi-tive components are contained in a sealed environment which is air-cooled as a single unit by low noise/low power fans.

the same enclosure used for cooling systems can be insulated to retain heat in extreme cold temperatures. normally, the small amount of heat generated by an LcD can maintain the internal temperature within operating limits, but in extreme cold weather a small heating element may be used.

2. ProteCt the DiSPlay FroM the environMentthe national electrical manufacturers Asso-ciation (nemA) has developed standards for electronic equipment enclosures. for out-door digital signage, the required standard is nemA 4. nemA type 4 enclosures offer several types of protection: 1) it prevents people from touching hazardous parts; 2) it provides some protection of the equipment inside the enclosure from ingress of solid foreign objects (falling dirt and windblown dust), 3) it protects against the ingress of water (rain, sleet, snow, splashing water, and hose directed water); and 4) it also ensures the external formation of ice on the enclosure will not damage the device inside. Also, nemA 4x, commonly used in outdoor environments, provides additional protection

against corrosion.

3. Dealing With Sunlightthe quality of an image on any display depends on many factors, but chief among them is brightness. but in an outdoor environment, a display can’t pos-sibly compete with the 1.6 billion nits produced by the sun. some LcD panels are capable of produc-ing 1500 nits or more, but battling brightness with brightness is not always the solution. Another critical factor in outdoor viewing circum-stance is contrast. contrast ratio is the ratio of luminance between the brightest “white” and the darkest “black” that can be produced on a display. most display manufactur-ers will cite their contrast ratio per-formance; but unfortunately, like many specification numbers that are used to sell audio and video products, they can be deceiving in the hands of overzealous mar-keters. comparing display based on published contrast ratio num-bers is difficult and can be mis-leading because there are many ways to measure it, state it, and almost impossible to verify in the real world. the bottom line: for outdoor digital signage, you want the highest contrast ratio possible, but be wary of contrast ratio claims over 1,000:1—there is some scientific evidence that suggest the human eye just can’t detect contrast any higher than this.

Perceived contrast can also be increased by locating the display in a shaded area pro-tected from direct sunlight—for example, under the eaves of a building structure. this can also balance out the changing conditions caused by sun and intermittent clouds during the course of a day.

Another approach is to use a special “transreflective” overlay film applied to the screen. these films are designed to reflect ambient light (from sunlight for example) from screen’s surface. the drawback is that they typi-cally have insufficient transmis-sive luminance, which means that when the sunlight level fluc-tuates (like when a cloud passes

by), it may be harder to see images on the screen.

4. vanDalProoFingmost enclosures for use with outdoor digital signage displays include a locking mechanism to prevent theft. but protect-ing the display from senseless damage is another problem. clear polycarbonate front panels (like Lexan) are one way to pro-tect the display, but it’s easily scratched. Another technique is offered by chilin solu-tions. using a Dupont process called “Ver-tak optical bonding”, the company bonds a sheet of cover glass to the display using optically transparent adhesive and a spe-cialized process.

samsung’s oL46b (left) is an all-in-one outdoor display and enclosure. cybertouch’s outdoor digital signage solution (above) withstands the sun and rain (and vandals).

Ì REmEdy #10oPtimizing outDoor DigitAL signAge

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