Telairity, a small Santa Clara, Calif., startup specializing in MPEG-4 AVC (Advanced Video Coding) compression, sees a big opportunity in more stations converting their electronic newsgathering (ENG) operations to high-definition. The company has already sold its low-latency MPEG-4 encoders to KTLA Los Angeles, WTVF Nashville and Alabama Public Television for backhauling HD signals, and last month at NAB it launched a new MPEG-4 product aimed specifically at electronic newsgathering helicopters.
MPEG-4 compression is already being used by major networks like CBS and Fox News Channel to transmit HD satellite newsgathering (SNG) feeds in the same satellite capacity they've been using for standard-definition feeds. And Telairity expects that local stations will start adopting the technology for HD microwave links as well.
That's because of the new, smaller microwave channels broadcasters have to contend with as part of the 2 GHz Relocation Process. Sprint Nextel is working with stations to convert their ENG operations from analog to digital microwave technology as part of a $4.8 billion spectrum deal it brokered with the FCC in 2005. While stations get new digital microwave gear as part of the deal, they also wind up with less bandwidth per ENG channel—12 MHz compared with 17 MHz.
Broadcasters operating under the old band plan can easily support HD links from their trucks and helicopters using traditional MPEG-2 compression, even when they split the channel in half to do two simultaneous ENG feeds. In fact, both KTLA and WTVF do HD feeds from their helicopters in split channels using MPEG-2.
WTVF, which has received new NuComm digital microwave radios for its trucks as part of the 2 GHz process but hasn't yet switched to the new frequency plan, currently uses an NTT MPEG-2 encoder and a NuComm radio running 16-QAM modulation in its helicopter. That setup delivers an 18-megabit-per-second (Mbps) HD feed in an 8 MHz “pedestal,” which represents slightly less than half of a split 17 MHz channel. WTVF Chief Engineer Gibson Prichard says the pictures look great.
But once the Nashville market converts to the new 12 MHz band plan, a split channel will only represent 6 MHz. And that's too little capacity to keep using MPEG-2. “One of my goals in the whole 2 gig transition was to be able to deal with the channel splits as we transition to narrower channels,” Prichard says.
So when Landmark-owned WTVF upgraded its news trucks last fall with Sony XDCAM EX cameras to support HD live shots, it made an early move to MPEG-4 by purchasing five Telairity BH8100 MPEG-4 encoders, which list for slightly under $20,000 each. The station also considered MPEG-4 units from Grass Valley and Fujitsu, but Telairity struck the best balance between performance and price, according to Prichard.
To support HD ENG, WTVF also upgraded the analog relays from its ENG receive sites back to the studio, a significant investment that wasn't covered by Sprint Nextel. It installed NuComm Analog Coder modems, which allow hi-def digital signals to be transmitted over an analog microwave link, and Tandberg RX1290 multi-format receiver/decoders to support the MPEG-4 feeds.
Since last fall, the station has been using the Telairity MPEG-4 encoders to deliver HD live feeds at 10 Mbps. While the station could theoretically run those feeds at a higher bit rate under the current ENG frequency plan, it is already running at a bit-rate suitable for a 6 MHz channel because that allows it to also transmit the same video within a 6 MHz satellite slot. WTVF frequently buys occasional-use satellite capacity to transmit live shots because of the Nashville market's challenging terrain, and it has outfitted three of its news trucks with Newtec DVB-S2 modulators to support HD SNG operations.
Prichard says the Telairity units have performed well for both microwave and satellite links, and that the extra latency of MPEG-4 versus MPEG-2 hasn't been a problem, though it initially took a little time for the talent to get used to it. (Telairity says its encoders can run at a latency of as little as 150 milliseconds, though both WTVF and KTLA are running with more latency to ensure top picture quality).
“What we have not done is one satellite shot tossing to another satellite shot, as there's a latency there,” Prichard says. “But the normal program path over MPEG-4 satellite is manageable. Certainly for us, the big challenge is to try to do the whole thing inexpensively.”
In that vein, while WTVF does HD live shots with its XDCAM EX cameras mounted on tripods, it still is producing edited packages in widescreen SD using nine-year-old Sony Betacam SX tape-based camcorders and decks. The station would like to eventually transition its newsgathering to Sony's XDCAM HD disc-based shoulder-mount camcorders, which its photographers prefer for their ergonomics, but is holding off on that investment for now.
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