HD production

John Luff gives insight into how he designs HD studios. This tutorial answers questions such as: What is needed to build an HD studio? Can the equipment be both HD and SD? Or, is specialized HD-only processing preferred
Author:
Publish date:


Turner Entertainment recently launched an HD version of its TNT channel to coincide with its newly upgraded HD facility. Photo courtesy Turner Entertainment and AZCAR.

It’s all about resolution…or is it? During the last year, HD production volume has exploded. Literally hundreds of HD cameras have been sold, many to the live entertainment market. New cable networks seem to come online almost weekly, and an all-HD DBS provider is trying to make a go of it in an SD world. Driven by market forces in consumer electronics, as well as a desire to grab market share early and hold it for the long term, programmers are increasing cost and quality in the expectation of future returns on investments. Turner Entertainment recently launched an HD version of TNT. ESPN gave its infrastructure an HD makeover and will broadcast more than 100 live HD events this year (see Broadcast Engineering, June 2004). FOX and CBS plan to commit to HD sports for the fall of 2004 — with FOX building out an HD affiliate distribution system for the first time this fall.

Is resolution the driver? From a marketing perspective, it is. With ESPN and FOX joining the 720p camp in 2003, the 720p vs. 1080i argument continues unabated. Also, several other factors have proved to be defining issues for those making the leap from SD to HD production systems. Interestingly, graphics, which one might think could be created cheaply in software-based systems, have lagged behind cameras and other more complicated electronics.

Aspect ratio is one of the most critical core issues. The good news for SD program services is that 4:3 aspect ratio content will continue to drive revenue. The bad news is that mixing any two aspect ratios can get messy. Think about a service that wants to distribute a live event such as the 2004 British Open. For North American HD consumption, as well as the Japanese, 16:9 HD is preferred. For European distribution, PAL Plus (625/50i 16:9, sometimes converted from 4:3 as 14:9 aspect ratio) is needed. For the North American SD market, 525/59.94i in 4:3 aspect ratio is a mandate. This means that standards conversion, frame rate conversion and aspect ratio conversion all must be done while preserving high technical quality. Even more importantly in this context, no less than three aspect ratios are required (4:3, 16:9 and perhaps 14:9). If graphics are added in the normal production process, they will be compromised in at least two of the three aspect ratios. As a result, productions are done with separate switching of 4:3 and 16:9, with 14:9 being a compromised subset of the 16:9 broadcast if derived by the end user from the 625/50i 4:3 broadcast.


The production control area of the Center for Disease Control’s HD press room in Atlanta is equipped with all-HD equipment including Evertz’s conversion and signal processing systems, and Panasonic’s AK-HC900 720p cameras and AJ-HD1700 archive video recorder. Photo courtesy Digital Systems Technology.

For instance, lower thirds, which are left-justified and end at the right side of the frame, must be reframed for two additional uses. Perhaps a single format can be agreed upon that has different appearances in the three potential output formats. But adding moving graphics with sound effects, and trying to get the effect to appear correctly in two (or more) aspect ratios is not so simple. Timing the audio to have the right “motivation” in two different screens can also be dicey.

Consider the technical complications of switching two programs from one panel. First, all of the sources must be available in the respective chassis and, most likely, must be mapped to the same physical inputs. This includes POV cameras, graphics and key channels, any still stores or other fixed graphics, and specialty graphics. The next step is to get the moving graphics and the DVE channels lined up and timed to appear on screen perfectly (a left push on in 16:9 might arrive earlier than a left push on in 4:3, with audio out of sync). Then deal with the fact that the two switchers and DVE channels might have different electrical length, which can affect the overall sync of the program’s audio.

Flat-screen displays create another pernicious effect. They are not “real-time devices,” and have in fact had a frame delay built in as well. What then is the right audio sync? What the director sees? What the viewer receives? Consider that the camera signals are a frame late on the monitors, the switcher is a frame or two long, and the output plasma is perhaps a frame later still. What is the correct audio sync for the control room? Will it bother the production staff that the camera on the line monitor is out of sync with the camera direct monitor? Probably not, because it is a problem that cannot be fixed easily.

One might think that the control room should have the exact audio from the output broadcast. Consider the fact that almost no control rooms are the shape or dimensions of the home listening environment. It is not trivial to create a sound field in that space that works for the full production staff. Most production teams have settled on perhaps a stereo feed for the control room, maybe augmented with the LFE channel. It is much easier to create a broad sound field that is uniform in stereo than in 5.1, especially in wide rooms that are not very deep — mobile unit control rooms, for example. After decades of experience designing and working in control rooms, we are in need of new experience to turn the capability of HDTV into reality. Understanding the features the technology offers can offer insights into implementation and the best use of the considerable power of this relatively new medium.

John Luff is senior vice president of business development for AZCAR.