Bulletproofing Huge Video Libraries

Distributed VOD Requires Different Tack in Solving Technical Issues

By Todd Spangler -- Multichannel News, 7/26/2010 12:01:00 AM

Cable operators’ heads are filled with visions of video-on-demand services with a breathtaking 50,000 choices — or even more than 100,000.

To get there, MSOs are implementing distributed VOD architectures that would stream the least-popular material from a centralized library while caching frequently accessed content at the “edge” in a local headend. That’s because it doesn’t make sense to store copies of, say, Attack of the Killer Tomatoes! or other “long-tail” content in dozens of locations.

NEW WRINKLES
But such a multi-tier distribution architecture introduces new wrinkles for operators in tracking and resolving VOD glitches.

Although traditional VOD doesn’t scale well, operators over the years have established it as a proven, reliable architecture — and they know how to troubleshoot issues that crop up, said Gino Dion, vice president of strategic solutions for IneoQuest Technologies, a vendor of video-quality measurement tools.

For example, if less than 1% of VOD requests are failing, that’s probably a set-top or service group issue. If that metric is 3% to 5%, it’s likely a configuration issue; i.e., VOD servers don’t have the assets.

“Things go bump in the night on VOD all the time,” Dion said. “Going to this new architecture changes those assumptions quite dramatically.”

Cox Communications plans to start testing a centralized VOD distribution network — dubbed “Stream Through” — before the end of 2010. In that trial, one of the MSO’s divisions will access less-popular content from a large library at its Atlanta data center. Around 2% to 3% of total VOD streams are expected to be served from the central site, according to Louise Wasilewski, Cox’s director of on-demand software.

One issue with that setup is that while the central Stream Through infrastructure will be shared by several back offices, it wouldn’t be under the control of any single one. “That does mean we have to pay attention to troubleshooting issues a little differently,” Wasilewski said.

Cox will also have to modify the way it manages metadata (information about the VOD). For the centralized content, the metadata must be distributed but the MPEG files will remain in Atlanta.

One strategy to ensure MPEG streams reach a subscriber from a central VOD library without any jitter and with predictable latency is to “overprovision” the central servers and the bandwidth connecting the sites, said Tom Rosenstein, vice president of marketing at VOD systems startup Verivue, whose backers include Comcast and Arris.

“The goal is to make everything work together as a real-time solution as much as possible,” he said.

Meanwhile, the servers at the edge shouldn’t be built with off-the-shelf PC components or software, said Edgeware CEO and founder Joachim Roos, whose company makes purpose-built VOD streaming servers. Instead, those devices should be more like multiservice routers that provide wire-speed performance and a real-time operating system.

INHERENT PLUSES
On the other hand, a content distribution network by its very nature theoretically should offer greater reliability, said Jim Owens, Motorola’s senior product marketing manager for on-demand video. “With a CDN, you should have multiple options for delivering that content,” he said.

Cox’s Wasilewski pointed out that the capacity for the shared Atlanta library would be spread across four time zones — so during a peak hour like 8 p.m. on the East Coast, it’s 5 p.m. in the West, smoothing out the demand curve.

Still, a content-distribution network introduces an additional level of complexity. Even in a relatively straightforward single-site VOD environment there are different vendors providing the set-tops, edge QAMs and back-office software that must all be made to work together, IneoQuest’s Dion said.

“There’s a finger-pointing problem,” he said.