The Fox Network is honing down the process of delivering HD signals to affiliates. When the network goes live with 720p programming this fall, Fox affiliates will be the first among commercial stations that will not have to convert the HD feed to baseband for inserting local content.
"This is the first time someone is choosing to deliver HD in this way," Setos said. "This is very cutting edge. This keeps the signal from having to go to baseband, which maintains signal integrity," said Andy Setos, executive vice president, News Corp. news technology group and Fox president of engineering.
The distribution of HD to affiliates centers on the Terayon BP-5100 broadcast platform, dubbed the "Fox Splicer."
"The Fox Splicer is a specific implementation of the BP-5100 platform," said Andrew Steele, senior director of business development for the digital video solutions group at Terayon. "Fox is using two specific features of the box initially-MPEG splicing and logo overlay. What really gets to the heart of the value of the product is that we do splicing and logo insertion without decoding and re-encoding [the signal] in the HD environment. Since we do this in the digital stream, we maintain the native HD picture quality. For HD, the quality of the picture is where the value is."
Steele said there are other features of the platform that Fox may decide to use in the future, like statistical multiplexing multiple HD and SD streams as well as data streams.
Part of the Fox-specific design includes a general purpose input/output panel to aid Thomson Grass Valley-which announced its partnership with Fox in late January-in tying the BP-5100 with other pieces of technology at the affiliates, like master control and scheduling systems.
Thomson will be responsible for the systemization and deployment of the HD distribution system to affiliates.
"[Thomson] Grass Valley is putting the package together, assembling it, and installing it at the affiliates and doing maintenance. They are the general contractor and there are specific sets of subcontractors like Terayon. But Thomson is accountable to make it work for us," Setos said.
Steele said Triveni Digital was also part of the equation.
"We've developed a Triveni interface related around file and data transfer [from Fox's Network Center]," he said. "The BP-5100 will act as a data receiver for whatever Fox may choose to download. It gives them remote monitoring and a way to manage the platform, download logos to each box or upgrade software without sending out a person onsite."
The MPEG-2 signal Fox will distribute to its affiliates via satellite from Los Angeles will be a compressed broadcast-ready MPEG stream. Affiliates will be able to switch between local and network HD signals via the Fox Splicer and insert logos while remaining in the MPEG ASI domain.
Currently, the majority of stations receive a digital MPEG stream from a network, then convert it to baseband before monitoring, switching local material and inserting logos. Once done, the HD baseband signal is then re-encoded to an ATSC-compliant ASI MPEG stream for terrestrial transmission.
This process involves at a minimum two decode/encode cycles, and more if contribution from live events are included. But multiple decode/encode cycles have their price.
"The problem with compression is that if you are not careful and don't have enough headroom, the quality goes down very quickly," Setos said. "If you use 20 Mbps for each, it would look grossly unacceptable [after the third pass]." This can produce MPEG artifacts like pixelation and blockiness.
To rectify this, the network would have to distribute at a higher bit rate, or "start high" as Setos said, to preserve quality through the decode/encode cycles to the final delivery to the consumer at a lower bit rate. That, too, would come at a price.
"The cost of distribution for contribution goes up to buy a lot of bandwidth," Setos said.
For Fox, the Splicer approach has multiple advantages.
"We will save tons of money since we won't have to buy as many transponders, and we assure quality," Setos said. The two concepts are usually at odds with each other.
At the same time, affiliates benefit by saving money, since the package includes a logo inserter which the affiliates can use for both network and local feeds. The ability to provide on-screen branding in the MPEG domain was an important criteria in the system design, Setos said.
Another benefit to the affiliate is that the station doesn't have to buy an HD switcher and other HD baseband equipment, except an upconverter, unless they do local HD programming.
Most of the Fox affiliates are using an upconverter now anyway, "and most have upconverters that can be outfitted for HD," Setos said.
While some of the 197 Fox affiliates do originate local HD programming, most do not, Setos observed.
"So this helps them enter the HD landscape with less of an investment. They can use a traditional master control and take the output through an upconverter [to] the Fox Splicer system," he said.
The system will include a Tandberg Television TT1280 HD decoder to monitor video and audio quality, captioning, and other network feed attributes.
"This is so the affiliates can see the incoming feed, logo, and information about what's coming, before the broadcast," Setos said.
Developing the distribution system was a struggle, he said.
"There was no off-the-shelf product. In two or three years there will be, but now it was very hard. We worked on these ideas for about nine months and saw the benefits."
Setos contacted Terayon, a leader in MPEG splicing with offerings mainly for satellite and cable operators. After Terayon ascertained that they were interested in the project, "we hooked them up with Thomson and it really blossomed," Setos said. "Terayon, Fox and Thomson were responsible for drafting and executing the core splicer which didn't exist until we asked for it."
Terayon's Steele noted that the BP-5100 was an evolution of its "Cherry-
Picker" technology for digital program and ad insertion, statistical multiplexing, grooming, and rate shaping.
"We brought those features like logo inserter to the table as part of the product," Steele said.
Setos predicted that the MPEG splicing technology will take on a larger and larger role in the processing of HD video over the next few years.