One of the the most talked about issues at this year’s NAB Show was AFD, or Active Format Description. AFD is a means by which any TV program is “flagged” with information instructing an encoder or TV set on how to frame the image. It is, many say, a vital ingredient as the digital transition approaches, for AFD will allow producers, networks and local stations to frame a given program (or even a segment of a program or commercial) as a letterboxed or center-cut image on a standard definition set. It also has implications for HD screens in how they will present 4:3 images.
Art Allison, director of advanced engineering at the NAB Science and Technology Division, calls AFD “The tool to let your picture match your display.”
(For a more detailed explanation of AFD, how it works and what it accomplishes, see Jerry Whitaker’s ATSC Update: “Using AFD to Resolve Aspect Ratio Discrepancy,” in the July 12, 2006, issue of TV Technology
.) STANDARD SUPPORT
Today, all the standards and recommendations are in place. SMPTE 2016-1 outlines AFD for production. ATSC A/53, Part 4 covers transmission. And the CEA’s CEB16 makes recommendations for consumer products.
More and more products are appearing in the marketplace to support AFD. and the FCC issued what is being called its 2007 “New Year’s Eve Report and Order,” which strongly suggests voluntary compliance with the standard among broadcasters.
“The food chain is complete, end-to-end,” said Patrick Waddell manager of standards and regulatory issues for Harmonic, who chairs ATSC TSG/S6 on video/audio encoding. “The infamous ‘postage stamp’ [the TV image shown with black bars on both top and bottom] will increasingly become something of the past.”
AFD allows the aspect ratio of a TV image to be changed from 16:9 to 4:3—and even to 14:9 at the receiver. Data can be added to the signal as early as at the camera, or as late as at the point of encoding for broadcast. Cable and satellite services can “read” the signal and pass the appropriate framing to both HD and SD customers. And consumer receivers and converter boxes can use the data to provide the optimal aspect ratio for the home TV set.
While AFD allows for changing aspect ratio on nearly a frame-by-frame basis (it actually works with GOP), most see it being used for individual programs. For example, a show produced and broadcast in 16:9 would be seen in widescreen on HD receivers and could automatically be cropped to 4:3 for standard definition receivers, or the AFD could tell the receiver to show it in letterbox on those SD sets.
As NAB’s Graham Jones who chairs the ATSC Planning Committee explains, “if a format converter changes 4:3 to 16:9 and adds bars on each side, the format converter will automatically insert the AFD.” This tells SD receivers to drop the “pillar bars” and fill the screen.
“A broadcaster can signal that this is 4:3 protected, so the 4:3 set takes a center cut,” Allison said. “It can signal, ‘no, this has stuff in the edges, so I want you to letterbox it on a 4:3.’”NOT UNIVERSAL JUST YET
While AFD exists in more and more equipment, it is still far from being broadly implemented and, at this point, is not being delivered to MSOs, satellite providers, or consumer TV sets. AFD was not required to be included in the first generation of the government-sponsored digital converter boxes.
At this point many believe AFD is vital; others disagree.
NBC Universal has been at the forefront of demonstrating, explaining and implementing AFD internally.
“As it stands right now, we [NBC] are originating and using AFD in all our HD-originated content,” said Ian Trombley, executive vice president for Media Distribution Services. “We’ve been doing this since 2005.”
NBC Universal teamed with Miranda for a highly visible demonstration at the 2008 NAB Show, and an “AFD Ready Initiative” has been launched by NBC Universal, Hearst-Argyle Television and Tribune Broadcasting Co. To date, more than 20 manufacturers have announced support for the initiative.
“The digital transition exposes a whole lot of interesting dilemmas,” Trombley said. “This is about showing the industry more solidarity around the concept of the adoption of AFD.”
Brian Markwalter, vice president of technology and standards for the Consumer Electronics Association agrees. “Broadcasters have figured out there is an obvious benefit to them,” he said. “CEA has released a bulletin of recommended practices and at this point, it’s up to the broadcasters to start sending [AFD] and receiver manufacturers to start putting it in.”THERE ARE SKEPTICS
But not everyone believes that AFD is the answer to SD/HD, 4:3/16:9 framing issues. Bob Seidel, vice president of engineering and advanced television for CBS Corp., said there are no plans to implement AFD in CBS or CW programming. In fact, if a program is provided to the networks with AFD flags, “We’ll probably strip it out, just because we can’t predict what will happen,” he said.
Instead, CBS is telling its advertisers and program suppliers that all of the HD content they deliver must be protected for a 4:3 centercut.
NBC Universal is making the same request. “We’ve made the decision that to protect our consumers, to protect our advertisers, to protect the program content, we’re going to adopt a near-term strategy of going center cut,” Trombley said. “We want to make sure that everyone is protected going through this.”
“If we don’t start adopting AFD now, then we’ll never be able to make a good conversion to this process in a year or two,” he said.
Bruce Jacobs, chief technologist for Twin Cities Public Television, also agrees that there’s “a lot of benefit” with AFD. However, PBS is looking at letterboxing for short-term conversion.
“Most of our HD content was presumed letterbox,” Jacobs said. “Even Newshour is produced assuming letterbox downconversion with graphics all the way out to the edges.”
Jacobs said the industry can benefit greatly by using it internally. “And there is a lot of benefit for distribution from networks to stations when a show needs to be downconverted,” he said.
At this juncture, it appears that education is as much a goal of AFD proponents as is implementation.
“Last year, when you talked about AFD, they never heard of it,” Jacobs said.
However awareness of AFD has grown dramatically, especially as a result of this year’s NAB Show. But that awareness is far from universal.
“It’s a learning process,” Jones said. “We’re at the beginning of the learning curve.”