Skip to main content

NAB 2009: NBCU, Fox Tout AFD Progress

Click here for complete coverage of the 2009 NAB Show

Las Vegas -- As they head to NAB, engineers from NBC Universal and Fox say they are happy with the industry's adoption of Active Format Description (AFD) technology. AFD directs how downconversion equipment, such as a professional receiver at a cable headend or a consumer digital-to-analog converter, formats broadcasters' widescreen HDTV pictures for display on 4:3 standard-definition TV sets.

The technology ensures that the standard-definition version of an HD program or commercial is viewed in the aspect ratio the program producer originally intended. It allows producers and directors to use the full widescreen canvas that HD production provides, without worrying about important parts of the picture being cut off when displayed on a 4:3 analog set. But for AFD to work, it has to be supported throughout the entire transmission chain through which a show travels—which means producers, programmers and multichannel operators all have to be on board.

NBC, which has been using AFD internally in its production chain since 2005, teamed last spring with station groups Hearst-Argyle and Tribune to form the AFD Ready Initiative, which was intended to raise awareness of AFD among manufacturers and multichannel operators. It also gave demonstrations of the technology at last year's NAB show; Fox, PBS and Cox Broadcasting have since joined the group. More than 20 professional manufacturers have agreed to support AFD in their products, including encoder and receiver manufacturers and makers of data insertion equipment. And several consumer electronics manufacturers have included AFD capability in their digital-to-analog converter boxes.

More important, say NBCU and Fox, is that cable and satellite operators have generally agreed to support AFD, and many cable headends and local signal collection sites have already installed professional receiver/decoders that recognize the AFD codes in the networks' HD signals.

“Last year at NAB, one of the main efforts was to just promote and help people understand what AFD is,” says Clarence Hau, production systems architect and DTV transition lead for NBCU. “Within that 12-month period, we have been extremely happy with how it has all progressed.”

Local NBC stations have installed new equipment to support AFD as part of a major move to a new MPEG-4-based, all-HD program distribution system called Skypath HD, which the network has rolled out to its 200-odd affiliates and owned stations over the past seven months. KXAS Dallas, for example, uses a Tandberg RX1290 integrated receiver/decoder to receive the MPEG-4 satellite signal and decode it to baseband HD-SDI without removing the AFD information (which is located in the Vertical Ancillary Data part of the signal). That HD-SDI signal is then fed into a Harmonic ATSC encoder to compress it for local over-the-air broadcast, as well as for fiber distribution to multichannel operators Charter Cable and Verizon FiOS.

Charter and Verizon use AFD-compliant professional receiver/downconverters from Tandberg and Sencore, respectively, to create a downconverted standard-definition NTSC version of KXAS' signal that is delivered to their standard-def customers. DirecTV captures KXAS' off-air ATSC HD signal, then uses an AFD-compliant Sencore receiver/downconverter to derive an NTSC version for SD distribution. And KXAS itself uses a Miranda downconverter, under AFD control, to deliver an NTSC version of its signal over fiber to Time Warner Cable.

Fox began delivering AFD information within its HD feed last month as it prepares to move to all-HD program distribution by September using an MPEG-2-based system from Motorola. Fox pre-encodes its HD signals in a bitrate suitable for local broadcast; local stations don't decompress the signal back to baseband, but instead use MPEG-2 splicers to insert local graphics and commercials.

Fox has upgraded its encoders to inject AFD data, and encouraged stations to buy AFD insertion devices to transmit AFD information in local HD content they broadcast, such as hi-def syndicated fare. So far, the network has enjoyed good support from its cable and satellite partners, says Jim DeFelippis, senior VP of digital television technologies and standards for Fox. Implementing AFD has eliminated problems in some markets where local stations had their branding bugs cut off by cable operators doing a straight center-cut of HD programming.

“We have had really close communications with DirecTV and some of the cable MSOs, and they do have the equipment,” DeFelippis says. “[AFD implementation] is going to be on an MSO-by-MSO basis, much as it is with the local stations. But quite frankly, they're looking for the AFD signal being there, which is good news for us.”

E-mail comments