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Clearer Skies for Hi-Def SNG

As high-definition cameras and editing systems expand into local and national news organizations, networks are eyeing the last hurdle in high-def news: transmitting live stand-ups to the studio using satellite links.

While stations and networks have been shooting HD in the studio for years, high-definition satellite newsgathering, or HD SNG, is still in its relative infancy. ABC and NBC have done some uplinks for their morning shows that broadcast in HD. CNN has been doing an increasing percentage of uplinks in the U.S.—though not internationally—since launching its high-def service last fall. But the vast majority of satellite feeds remain in standard-def.

There are several reasons. Networks have been slower to roll out high-definition camcorders in the field than local stations, mainly because changing to a new format across multiple bureaus and far-flung satellite trucks is a logistical challenge. Hi-def satellite feeds have also required up to twice the capacity of standard-def feeds, making HD SNG expensive. This has forced producers to either cut the overall quantity of feeds to support higher picture quality, or lease more capacity. And the high rate of compression needed to fit HD into a satellite slot introduces more latency, or delay, than in SD feeds, which can make a back-and-forth Q&A with a field correspondent difficult.

“There's no question that for HD the last big hurdle is links,” says Fox President of Engineering Andy Setos. New technologies are emerging that might make HD SNG more of an everyday occurrence. DVB-S2 8-PSK is an advanced modulation technique that can deliver more megabits per a given amount of satellite capacity than traditional modulation. And MPEG-4 advanced compression is 50% more efficient than legacy MPEG-2 compression systems. Finally, encoder manufacturers are also improving the latency of their HD products to the point that video and audio delays are comparable to standard-def feeds.

Low-Latency Solution

CBS, for example, thinks it has identified a solution that will allow it to transmit high-definition feeds in the same satellite slots it previously used for standard-def. The network began testing a low-latency MPEG-4 encoder from Japanese manufacturer Fujitsu last fall over fiber links, and Fujitsu has now improved the latency to the point where it can be successfully used over satellite transmissions.

According to Bob Seidel, vice president of engineering and advanced technology for CBS, the Fujitsu IP-9500e MPEG-4 AVC encoder can operate with a latency as low as 300 milliseconds. Combining that with the standard latency for satellite transmission gives a total delay of about 550 milliseconds, or about half-a-second, which Seidel says is just slightly more than the lag for CBS's standard-def feeds. That is a big difference from the type of MPEG-4 encoders used for cable network distribution, which have a latency of anywhere from two to four seconds.

“It's a breakthrough technology,” says Seidel. What's more, the Fujitsu encoder can deliver high-quality HD pictures at a bit rate of 9-10 megabits per second, which is about the same amount of throughput (10.3 Mbps) that can be pushed through a standard 5 megahertz satellite slot using DVB-S2 modulation. By comparison, CBS had been using DVB-S QPSK modulation and MPEG-2 compression to deliver standard-def feeds at about 5 Mbps in the same space.

According to CBS, the Fujitsu MPEG-4 encoder delivers picture quality at 9 Mbps that is equivalent to a 25 Mbps MPEG-2 stream coming from the network's Sony XDCAM HD camcorders. Using the encoder in combination with advanced modulation should allow CBS to fit a 1080i HD feed into the same satellite space it was previously using for SD transmissions. CBS could then theoretically fit up to 10 HD feeds in a 54 mhz transponder.

CBS has tested a complete HD SNG system based on the Fujitsu encoder, a Newtec DVB-S2 modulator and a Sencore integrated receiver decoder in its CBS Newspath trucks, and plans to use it later this year for hi-def field coverage of the 2008 presidential election and other major news events.

Harmonic is marketing the Fujitsu product to U.S. broadcasters. The product isn't cheap—it lists for $49,950, roughly twice the price of the type of MPEG-4 encoders sold for distribution applications. But John Pittas, a consultant in Fujitsu's video and broadcast technology group, expects it to take off.

“What we're enabling is within an existing standard-def SD channel, to put the HD in and go,” says Pittas.

CNN and MPEG-2 Compression

While CBS is focused on MPEG-4 for HD SNG, CNN has already moved forward with MPEG-2 compression to provide HD uplinks on a regular basis, though they still represent less than 10% of CNN's 250 daily incoming satellite feeds. CNN is using low-latency MPEG-2 encoders from Tandberg and dedicates two standard-def slots, or about 10.5 MHz of satellite bandwidth, to each HD feed. CNN uses DVB-S2 modulation to increase the throughput across that space segment, and is able to deliver HD at a bit rate of about 16 Mbps.

The network's current HD SNG setup delivers good picture quality, says Frank Barnett, vice president of CNN Satellites and Transmissions, even after the multiple concatenations of compression involved with routing signals to Atlanta and then on to New York. CNN went with MPEG-2 mainly because low-latency MPEG-4 encoders weren't commercially available when the network was making technology decisions for the September 2007 launch of CNN HD.

Ten of CNN's 17 Ku-band SNG trucks are now equipped to handle HD feeds, as is the network's new “Election Express” bus. CNN also has two HD “flight cases” to quickly add HD encoding capability to a truck for special events, as well as HD-capable fiber feeds from Washington to New York. CNN Newsbeam, which leases satellite space segment to CNN Newsource's 800-plus domestic television affiliates, can also supply an HD path, consisting of two 5.5 MHz slots, to affiliates who want to do a live HD uplink.

“We're willing to segment our bandwidth for people to do HD. It's just a matter of allocating what bandwidth they want,” says Barnett.

CNN has successfully tested MPEG-4 and Barnett is impressed with the bandwidth savings it could realize, but notes that he would “have to ask for a bunch of capital to do it.” Right now, CNN is not that capacity-constrained, says Barnett, as it has a number of transponders on SES Americom's AMC-3 and AMC-5 birds.

Another cable network that doesn't mind using a little more satellite capacity to support HD SNG is The Weather Channel HD, with its first live HD uplink from Miami Beach scheduled for June 2 to coincide with the launch of its HD studio. The network has upgraded its Southeast-based “Sprinter” SNG unit to HD to cover the hurricane season with Panasonic P2 HD HPX-2000 camcorders, Canon HD lenses and a Tandberg HD MPEG-2 encoder.

Instead of using a 6 MHz slice of satellite capacity, as it does for SD feeds today, The Weather Channel HD will use a 9 MHz segment combined with DVB-S2 8-PSK modulation to deliver HD pictures compressed at around 15.8 Mbps.

“It looks really good,” says Nathan Smith, the network's vice president of broadcast operations, who admits that the true test will be trying to deliver quality HD live pictures during a real hurricane.

The network's SNG trucks in New York and Chicago won't be converted to HD until 2009. For now, those units will shoot live shots in widescreen SD and upconvert them.

Station group Hearst-Argyle is already using the widescreen SD approach for its SNG efforts. Hearst-Argyle leases its own 36 MHz transponder to support 10 simultaneous SD feeds; 75% of the time it is using all of that capacity, says vice president of engineering Marty Faubell, and sometimes demand is so high it turns to affiliate satellite services like CBS Newspath and ABC's ABSAT as an “overflow valve.”

While several Hearst-Argyle stations already do HD newscasts, including WCVB Boston, WESH Orlando and KMBC Kansas City, Faubell is reluctant to dive into the world of HD SNG because of the tradeoffs involved—either less available feed paths, or extra bandwidth costs. Five minutes of satellite time on a 5 MHz slot generally costs around $50, and Faubell isn't keen on doubling his satellite costs to $100 for the same period of time just to support HD.