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ABC Shifts Program Distribution To MPEG-4

ABC is converting the distribution of its network programming from an MPEG-2-based system to more bandwidth-efficient MPEG-4 advanced compression using transmission equipment from Tandberg Television.

The migration to MPEG-4 is due to begin next Monday and should be completed by mid-January as a part of ABC's "Accelerated HD Delivery" plan, according to Rich Wolf,  senior vice president of telecommunications and network origination for ABC. Stations will decode the feeds and recompress them in MPEG-2 for local broadcast delivery.

ABC would be the second major North American broadcaster to shift its program distribution to MPEG-4. Mexican broadcaster Televisa made the move to MPEG-4 last May, also using Tandberg gear.

The new MPEG-4 encoders and receivers, combined with DVB-S2 advanced modulation, will allow ABC to transmit three HD feeds in the same slice of satellite capacity that it currently uses to broadcast one HD feed.

"It's three for one in a 36 megahertz transponder," said Wolf, who spoke with B&C Tuesday at the ISCe Satellite Investment Symposium in New York.

The DVB-S2 modulation equipment can theoretically deliver up to 80 megabits per second in one transponder, says Wolf, allowing ABC to send high-quality HD feeds at bit rates of up to 25 Mbps. Going much higher than 25 Mbps with MPEG-4 compression doesn't achieve much of a quality gain, said Wolf, an opinion shared by other network engineers.

Latency can be an issue with MPEG-4 signals, but Wolf said ABC's goal is to achieve the same level of latency it currently has with MPEG-2 signals.

Although the network is shifting to MPEG-4 for program distribution, ABC's satellite newsgathering (SNG) operations will remain in MPEG-2 for the near future. ABC, which took "World News with Charles Gibson" to HD in August, does about 15% of its newsgathering in HD today, said Wolf, transmitting an MPEG-2 feed at 18 Mbps in an 18 Mhz slice of satellite capacity.

"We'll continue to use the legacy MPEG-2 infrastructure that's there," said Wolf. "The challenge from a space segment perspective is to still do SD and at the same time handle hi-def as well."

Eventually, Wolf would like to see ABC's SNG operations move to MPEG-4, transmitting at an average bit rate of 8 to 10 Mbps, which would allow HD feeds to fit into the same space as today's SD feeds.

CBS has already successfully implemented that approach, using low-latency MPEG-4 encoders from Fujitsu to backhaul satellite feeds from the political conventions in the same bandwidth it previously used for MPEG-2 standard-def feeds.

"That's been good for point-to-point [transmissions]," said Brent Stranathan, vice president of broadcast distribution for CBS. "But I think it will be another few years before local stations are covering a fire with HD SNG."

While CBS will still use satellites to cover breaking news, Stranathan noted that CBS has moved to a heavy use of fiber optic links for major news events like the political conventions and debates. Sports coverage has used fiber for backhauls for years, with satellite links as a backup, and CBS used uncompressed 1.5-gigabit links to bring back feeds of the U.S. Open tennis tournament this summer.

"Sports, I can see moving entirely to fiber," predicted Stranathan.