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A Tale of Two HDs... - AvNetwork.com

A Tale of Two HDs...

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Just this past week, I encountered a few questions about which HD (high definition) format to use for a given situation. This brings up a good point: technically, what is HD, and what is perceived HD? For example, over the past few years, end users and technicians have told me that they’re using “HD DVD” — only to discover that they’re actually running standard definition DVD with a 16x9 letterbox image.

High and Higher Def
What most consumers (and thus end users) perceive as HD is any display that uses a 16x9 (or 1.77:1) aspect ratio. This is clearly evident by the slew of monitors at your local electronics shop that have unique resolutions, such as 1365x780. Coupled with the marketing notion that anything with more resolution than NTSC is HIGHer DEFinition (and thus HD), you can see how the confusion snowballs .

Based on SMPTE standards, HD signals include 480p, 720p, 1080i, and 1080p. Most broadcast HD signals are either transmitted in 1080i or 720p. Sports-heavy broadcasters tend to use the 720p signal to reduce motion artifacts. In either case, the bandwidth required to transmit either of these signals is very similar. True, 1080p transmission requires much more bandwidth, and it is still a ways off for consumer broadcasting.

When deciding which HD format to utilize for a production, it comes down to two variables: final display device and budget. If the proposed event has a budget that supports the use of higher resolution projectors or displays that can natively run at 1080i, 1080p, or 720p, then by all means, go for it, with my highest recommendation. In many cases, projectors with a 1280x1024 or 1400x1050 native resolution can be set to run at native 720p (1280 x 720). This setting reduces the maximum light output, but nets a true HD resolution. At this point, you can say (without fearing the “Pinocchio” effect), that you are providing a true HD display.

Calculating HD Resolution
If the budget will not support the use of the “larger” projectors or displays, a menu-savvy technician can create a 16x9 resolution within the available pixels. For example, if you’re running a 1024 x 768 projector, you can calculate the “HD” resolution by dividing the horizontal pixel count by 1.77. This calculation (1024/1.77) yields the required vertical resolution of 578.5, but since you can’t create half a pixel on a display, it’s rounded off to 579.

Next, by creating content (or setting any upstream seamless switcher) to the calculated resolution of 1024 x 579, you can create the “HD look” required for the show. This is also true with LED wall displays. Many times, customers will tell me that they have an “HD” LED wall, when in fact they may be using its “perceived” widescreen aspect ratio. To create an actual 1920x1080-pixel LED display would require a much bigger wall, and this can present a challenge from both the budgetary and spatial standpoints.

Managing and Defining
Ultimately, how you manage the tools at hand is what delivers the desired look for your customer. At the outset, always confirm the definition of HD with both the customer and the content creation team. If HD just means a letterbox display, regardless of resolution, then just about any system will achieve the desired results. Even if your delivery system is a laptop set at 800x600, you’ll still achieve a “perceived” HD display with a PowerPoint created in a 16x9 aspect ratio.

Moving forward, the availability of “true HD” players will drive content towards a more standard 1920x1080 format. There will always be exceptions, and we’ll have to adapt to these with agility. These will typically originate from the computer domain, in which display outputs tend to not conform to SMPTE standards. For example, as I type this article, I’m using my laptop’s 1920x1200 “HD” screen. For the savvy user, knowing how to manipulate graphics cards will be critical link in achieving the required output format.

In the end, HD is in the eye of the beholder, whether perceived or actual. The one common factor is that both event-driven and consumerdriven market segments are moving towards the 16x9 (or 1.77:1) widescreen aspect ratio. This trend continues to be reinforced as more and more HD media options are made available for home consumption. Ultimately, for our event-driven marketplace, delivering HD means managing customer expectations based on the budget and the event’s provided equipment.

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