Mixed Signals Looks For Bad Video On The Edge


Murphy's Law is sure to apply when it comes to cable's switched digital video deployments, according to Mixed Signals CEO Eric Conley.

With switched video, quadrature amplitude modulation (QAM) devices now perform functions that used to be handled at the headend — switching, spectrum allocation and multiplexing video signals.

“All of a sudden, the QAMs become a piece of equipment that can break video,” Conley said. “Before [switched video], you had the same copy of every channel going into every hub. Now you have hundreds of switched channels.”

Traditional headend video-monitoring systems, including Mixed Signals' own Sentry product, can't detect products introduced by switched video or video-on-demand systems, because they don't have the horsepower to check all the channels being sent to every single service group.

“You can't decode every channel. It requires too much math,” Conley said. “The challenge is to find a cost-effective way to monitor all the hubs.”

Of course, his company is trying to convince operators that its brand-new product — Sentry Edge — can do just that.

Sentry Edge is designed to sniff out errors that may creep in at the “edge” of the network through switched digital video and video-on-demand deployments.

The device does two things. First, it makes sure that the MPEG-2 streams being delivered by QAMs are structurally sound — i.e., that they are recognizable as video to set-top boxes. It also verifies that the switched video system is delivering the channels that it's supposed to.

Sentry Edge analyzes the video feed coming out of the video combiners, rather than the QAMs themselves. The one-rack-unit device is passive, meaning it simply sits on the side and analyzes the video as it's delivered. Each device currently handles about 15 service groups, and Mixed Signals' goal is to increase the capacity to handle up to 40 service groups.

The Sentry Edge doesn't examine every individual channel, because, as already noted, that would require hardware with more processing power than is economically feasible.

So the unit uses a “smart” prioritization scheme to look at only certain MPEG-2 feeds, based on an MSO's list of critical channels and information from the switched video resource manager components about the most-watched services.

“If I'm an operator, maybe I don't care as much about C-SPAN 3 as I do about ESPN,” Conley said.

The Sentry Edge is designed to monitor the core broadcast channels as well as the switched ones, since SDV could potentially introduce issues with the non-switched lineup, Conley added.

Conley said Sentry Edge has been deployed on a beta trial basis with several MSOs, which he declined to identify. The company expects to launch the product commercially this summer, although Conley said Mixed Signals has not determined pricing yet.

The hub-based Sentry Edge devices are supposed to work in tandem with Mixed Signal's flagship Sentry headend video-monitoring system that identifies various anomalies in MPEG-2 content, such as video freeze and loss of audio.

Other vendors pitching video-quality measurement tools include Symmetricom. Its V-Factor system includes a headend video analyzer, as well as set-top-based software and network probes to compare video with the source to detect problems.