Looking good

Grooming gathers importance in cable's digital headend Good grooming is becoming an important part of presenting an attractive digital TV package.

It wasn't always that way. But as digital matures and offerings proliferate, the technologies used to compress and deliver those signals become more complex, and the subscriber universe grows, there must be something in the headend that grooms out the unnecessary bits and straightens the ones delivered to end users.

"Once upon a time, all the digital signals that existed were encoded in place. If you were going to put out a digital signal, you would encode a baseband signal, compress it and then transmit it to the set-top box, whether that be satellite or cable," said Geoff Hillier, product market director in Harmonic's convergence systems division.

That was fine when there wasn't that much programming and the subscribers weren't too fussy, Hillier said.

The next step, he said, was to economize: group the signals in a package such as AT&T's Headend In The Sky and Time Warner Cable's Athena, send that package of signals to the headend and push it out as a "digital tier." To make it even more economical - because transponder space is expensive - those signals were statistically multiplexed to take advantage of peaks and valleys in bit value.

Suddenly, cable operators found themselves receiving a block of statistically multiplexed channels that they force-fed to consumers by passing it along as a package. To make matters worse, because the material was statistically multiplexed, there was not an easy way of inserting local programming - or advertising - that used constant bit-rate (CBR) encoding into that ever-changing stream without quality control issues.

"When you encode your own material locally, you have the ability to choose the bit rates and how you want those to be groomed," Hillier said.

CBRs, though, are not the most efficient way to package digital streams, especially when there's more than one stream in the group. Thus, even locally encoded programming - including advertising - began using statistical multiplexing to jam more bits and improve quality.

Watching this market evolve, traditional headend equipment vendors started picking up specialized stat multiplexing companies. Harmonic, for one, acquired DiviCom's digital headend business from C-Cube Microsystems and incorporated its technology into Harmonic's headend system.

"We found that you could get roughly a third more picture services in the same bandwidth," Hillier said. "People have moved from CBR to [variable bit-rate/stat mux] because of the bandwidth efficiency."

Nevertheless, there's a headend nightmare brewing there. To alleviate it, Harmonic and competitors Terayon Communication Systems and Cisco Systems devised - or more accurately, purchased - technologies that assisted in the grooming process.

Terayon's CherryPicker - acquired when Terayon bought Imedia - is arguably the grandfather of all grooming devices. To its current owners, that's a plus; to its competitors, it's an opportunity because it potentially is not as up-to-date as other products.

"The CherryPicker is able to achieve mild bit-rate reduction," Hillier said. "We're able to significantly alter bit rate, so you can change bit rate significantly."

Cisco also took aim at the Cherry-Picker. "I keep an eye on the Cherry-Picker technology," said Michael Suever, video products manager for Cisco's cable business group. "We have superior density and processing capabilities."

That technology isn't something Cisco developed; it came along when the acquisitive company bought V-Bits.

"What I call advanced multiplexing capabilities are bit-rate reduction, digital splicing and statistical multiplexing," Suever said. "All three vendors offer those capabilities."

Cisco, he said, takes it a step further by using digital signal processing (DSP) in its chips, as opposed to the more common application specific integrated circuits (ASICs).

"We have a lot more interesting volume curve for processing power," he said. "The issue with our competitors is that to get more streams, you have to put more ASIC streams in. It's kind of a one-to-one relationship. For ours, we typically do two streams of rate reduction per DSP chip, and that's going to scale into much greater processing power in the future."

There, buried amid the hype, is the main factor impacting grooming systems: the future. The need is growing today, but it's not something that has cable operators banging down doors to get the technology to insert local programming or advertising material into digital streams.

As other companies move into the grooming space, Terayon's strategy is to demonstrate that the functionality of the CherryPicker can become the hub of digital video, said Stephen King, senior vice president and general manager of Terayon's digital video systems group.

That functionality goes beyond typical digital needs to interactive TV. That's where Terayon's Advanced Television Enhancement Forum, or ATVEF, comes in.

"We're starting to act as a platform for interactive television," King said. "When you think of interactive television, there are very few applications where you want to produce the same data at the same time or for the same geography as the video."

Nevertheless, this programming comes to the interactive headend encrypted into the digital stream, he said. CherryPicker, he added, will break out those ATVEF triggers and replace them with more content-specific applications.

"For applications like the Discovery Channel, you might want to point to a different zoo Web site for a documentary," King said. "There needs to be a place in the headend where the video and data are synchronized. That synchronization takes place in the Cherry-Picker."

That's even farther out than digital ad insertion.

"Most people rolling out interactive TV haven't gotten to this point yet," King said. "They're just trying to roll out how to have a wrapper around a video or have a separate area for Web-based traffic."

Terayon, though, is going a step further. "We're saying in the future when you go to pull that [programming] out, you're going to want to pull out associated data. When you change a language track, you want a different URL," he said. "Because we're managing the video in the compressed domain, we can remove those [ATVEF] triggers. We can also remove and replace those triggers with a local ATVEF trigger."

That's tomorrow. Today's operator is more concerned with grooming out unwanted digital content and inserting local content, including - in the not-too-distant future - advertising. The latter is particularly interesting to companies such as SeaChange International, which has worked with Terayon and other major statistical multiplexer splicer vendors, said Joseph Ambeault, advertising systems director for SeaChange.

SeaChange's relationship with Terayon is "very close," Ambeault said, but he noted that SeaChange will work with multiple vendors to ensure that ads and other local programming it receives and encodes can be inserted into digitally multiplexed streams. "We're in field trials with [Terayon] doing some more intense type of insertion events in real-world situations," Ambeault said.

In fact, of all the things that are off in the future, ad insertion may be the closest to being ready for prime time.

"The limiting factor on [ad insertion] is the number of digital set-top boxes that have been deployed," said Cisco's Suever. "As the transition is made from analog to digital, you'll start to get larger and larger audiences, and it will be a requirement for the MSOs to carry advertising in the digital tier. I think right now, because the digital rollout has been a little slower than most of us expected, there hasn't been a real pressing need or urge."

There is, noted Harmonic's Hillier, yet another area that could stand a little grooming: DSL.

"The same [need for grooming] will happen in the DSL space," he said. "Now people will see [in] our equipment that they can get two services per DSL stream as opposed to the one, and that is going to make the difference for some people."

Maybe sooner, maybe later, but definitely sometime the well-groomed headend will be the norm.

"It gives more flexibility and allows the local programmers to provide balanced lineups that are more interesting to their particular customers instead of doing just one movie tier or something like that," Suever said.