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Distributed PA On A Fiber Backbone
Australia's Olympic Park, home to the 2000 Summer Games, showcases the future applications of large-scale distributed systems over a fiber optic backbone.
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Open Platform
In basic overview, the system can be described as a central control front-end networked with several distributed “nodes” via the fiber backbone. But in reality it’s a bit more complicated than that. First, this project marks the first real-world application of Peak Audio’s implementation of Simple Network Management Protocol (SNMP) for addressing all CobraNet devices on the network.

Further, Creative Audio’s latest generation amplifier control/interface module – accommodating SNMP - has been implemented, enabling the dynamic control of CobraNet bundles and channels from the host application.

“Ultimately what this means is that we have an open platform for all CobraNet devices. For the previous installation at Stadium Australia we used Crown IQ software for control of the CobraNet bundles and channels within the amps, but by using SNMP we’ve streamlined the communication process, cutting a layer that’s no longer necessary,” Dodds says. “At a point very soon, I think we’ll also be able to utilize this Peak platform even more efficiently, for example, in terms of matrixing and routing. In this project we have been able to integrate CobraNet products from Peavey, QSC (RAVE) (http://www.qscaudio.com), and our own Creative Audio amplifier modules”

Conceptually, SNMP is simple, yet that belies its sophistication. It has two basic commands: “get a value” and “set a value”. Any CobraNet device on the network runs a piece of software called an SNMP agent, which oversees a collection of variables that represent the state of the device being managed. Within the campus system, the SNMP agents are managed via the Creative Audio software at the system’s central control position.

Control Packages
Officially dubbed the Homebush Bay Operations Center (HBOC), the central control position houses “a conglomeration of computers and bits and pieces that make the whole thing work”, Dodds says. The main audio routing system is a Peavey MediaMatrix 940 running their version 3.1.1 software and outfitted with six CobraNet digital signal processing (DSP) cards.

The heart of the control system, effectively the control server, is an Intel-based PC running under QNX, a ‘real time’ POSIX compliant operating system. This box runs all the processor software such as Creative Audio’s PageServer, which manages all paging requests and priorities, and EventScheduler, which initiates all time-based requests. These two programs also work with the SNMP and MediaMatrix RATC interfaces, which communicate the appropriate requirements to the various amplifier modules and the MediaMatrix itself.

Three additional Intel PCs form the message playback and ‘store and forward’ elements of the system. Each unit is loaded with a new Creative Audio CobraNet-PCI card, capable of simultaneously recording and playing back full bandwidth CobraNet audio. Under control of the WaveDev process, these units supply the playback of scheduled messages and the ability to store and forward live announcements when destination zones are busy. They differ from standard sound cards in that they’re multi-channel and include a direct CobraNet interface.

Messages are created as standard .wav files and are stored on the hard drives of the message PC’s. Capability in this regard is quite impressive, with 24 channels of simultaneous playback capability available along with 8 additional channels dedicated to recording for store and forward, providing an ample queue so that live announcements don’t clash with regularly scheduled messages.

The other primary control element consists of a Windows NT computer, which runs a copy of CobraNet Discovery software along with Crown’s IQ Server. Discovery is the mechanism for assigning IP addresses and managing and updating CobraNet firmware to all system components in the field. All of the CobraNet devices require an IP address to facilitate communication via SNMP. IQ server allows anyone connected to the network with a copy of IQ for Windows to establish communication with the amplifier modules for system setup and monitoring.

“One of the notable things about this system and the SNMP implementation is that in the field, there are 48 local and wireless mic inputs,” Dodds notes. “But in terms of CobraNet channels and traffic, and the size of the MediaMatrix system, we’re restricted to only having 12 of them active at any given time. This means that a key part of the whole management software application is the dynamic assigning of CobraNet bundles and channels addresses to those 12 inputs/wireless mics in use at any given time.”


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