Super Bowl LXIV is just a little less wired than it used to be. Since last year’s game, NFL Films has been using a CobraNet digital audio-distribution system running over Cat-5 cabling that has reduced significantly the amount of wire needed to get the signal to international clients. Via an Ethernet network, 48-kHz/20-bit uncompressed audio is transmitted with very low latency and guaranteed synchronous delivery.
According to Steve Fisher, who has supervised distribution of audio throughout the compound for the NFL for two decades, the system sources audio content from CBS’s compound on fiber to the international compound on the opposite end of the stadium. “When the network [audio] reaches our compound,” Fisher explains, “we integrate a monitoring station, an analog conversion station, a transmission station, and distribution network to the international client base.”
That client base numbers more than a dozen on-site, many of which are within the CobraNet spec of 100 m, so signal can move over Cat-5 cabling. For clients farther away, a switched network and GBIC connectors convert the signal to fiber, with a receiving switch at the other end providing more networking capability. The system Fisher manages uses Lance Design ADX-2400 series audio-delay and -distribution units. The CobraNet-compatible boxes provide 24 channels of transmission in each direction over Cat-5, with individually adjustable delay on each output; each ADX unit contains 48 channels of delay (24 on local outputs, 24 on network outputs).
“Perhaps the single biggest benefit to the CobraNet system was its ability to leverage IT-based technology to distribute digital audio at a significant savings over analog audio and all its inherent issues, like grounding, crosstalk, broken wires, and so on,” says Fisher. “Additionally. the network appliance offers greater distributive power than is available over point-to-point fiber-based solutions, and all at lower costs.”
The system also uses DTS Neural’s Surround DownMix technology to take the NFL’s 5.1 audio down to two channels compatible with Dolby and SRS for international broadcasters, who get two versions of the NFL FX mix, with and without commentary in the center channel.
“In the past, we’d use a Dolby E stream with a special mix,” says Fisher. “This year, the [DTS Neural]-encoded stereo pair leaves here and remains untouched till it gets to the viewer overseas, where their systems can reconvert it to 5.1. That really reduces latency issues and gives international viewers access to the same audio as the U.S. Between this and the use of the CobraNet distribution system — something that broadcasters haven’t really used much but are becoming more aware of — moving the audio around has become much more efficient.”
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