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The Devil In The DSP

Digital signal processing (DSP) devices impact system design, installation, and operation in a variety of ways, and it's time to fight the demons that followed them into pro AV.

On the other end of the spectrum are the matrix and tab interfaces that require multiple screens that aren't simultaneously viewable to understand how the system is configured. While these devices may be just as capable as those based on the block diagram approach, they're more difficult to learn and document offline. With the block diagram approach, at least there's a chance that someone who isn't trained in the particular DSP software can figure out what the system is doing or could do.

Demons, design, and documentation

But the demon is here to stay, at least for now. Deferred design and deficient documentation are its primary manifestations. The first issue is purely a design phase problem, although the impact appears mostly during installation. The second concept affects design and installation, including people on both sides of AV contracts — AV providers and system owners. And these are just part of the overall impact of digital AV signals, DSP, and data networking on pro AV in recent years. So what are the solutions?

To address deferred design, designers need to understand that system design encompasses the whole system. Virtual devices inside a DSP box need to be designed just as much as the hardware boxes outside it. The simple solution? Develop a complete system design — both inside and outside DSP devices — during the design phase. But it isn't necessarily that simple. We have three options, each with its own issues in today's industry: 1) Create the DSP design in the preferred (or sole source) DSP software for a given device; 2) Draw an analog block diagram representing the signal flow inside the DSP box; or 3) Provide a detailed functional description of what the insides of the DSP box should do. In any case, it's important to address virtual devices during the design phase, rather than at system checkout.

When the project is finished, we need documents — electronic or paper — that provide a technical view of the DSP part of the system that allows for navigation, troubleshooting, and understanding of the installed system — at least as easily as the analog as-builts do. And I don't think I'm just being an old fogey here. I've tried to troubleshoot and operate systems that include very challenging DSP user interfaces. Sure, with sufficient training and experience on the particular DSP device, I can design, navigate, and set up a system offline. But even with experience and training, most DSP devices aren't conducive to complex event planning that may require system reconfiguration or real-time event troubleshooting and system adjustments.

Maybe it's a pipedream, but what if DSP devices — regardless of their built-in user interface —included an option to output documentation in a common, perhaps graphical, format? Maybe it could be a representation of the “analog equivalent.” Maybe it would even allow programming to be translated from one manufacturer's device to another. That would be a start. This kind of documentation would be invaluable in navigating and troubleshooting a complex system, especially during an event when time is short and pressure is high. Screen shots and text file output don't do the trick. Manufacturers: Are you listening?

Ultimately we have to learn to live with and embrace digital technology in all of its forms and its impact on pro AV design and installation. I'm sure it will mean that we have to learn and adapt. But we need to keep good design and integration in mind during the transition, and fight off the demons that are giving us the devil.

FEEDBACK

To comment on this article, email the Pro AV editorial staff at proav@ascendmedia.com.

Tim Cape is a contributing editor for Pro AV, the principal consultant for Atlanta-based technology consulting firm Technitect LLC, and co-author of “AV Best Practices,” published by InfoComm International. He's the current chairman of InfoComm's ICAT consultant's council, and an instructor and presenter in AV technology design and management. Contact him at tim@technitect.com.



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