One of the most common issues that I encounter
is when a technician or system engineer over-designs the video system. Case in point: I was evaluating a fairly simple system for a client, in which a converter box was used to change an SDI camera input into an analog signal, before the signal was connected to a seamless switcher. The converter was used in order to save a couple of dollars by not ordering the seamless switcher’s SDI input option.
A few key issues can result from the use of this converter, including the addition of video latency (delay) into the system, and a reduction in image quality. But the biggest reason for not taking this path is that it adds one more point of failure into the overall system. Every piece of gear and every additional adapter within a signal chain represents one more place where an issue can arise. This also means that when an issue does occur, it will take that much longer to track down the weak link.
Troubleshooting 101
The one basic axiom that I teach involves running down an issue in the video system:
Always check the five dollar part, before you fix the fifty thousand dollar part.
This axiom is pure common sense, and we all nod our heads as we read it. However, I can guarantee you that before the week is over, I’ll take a call for some poor soul who’s been chasing an issue for the last four hours --only to discover that the (insert your cable of choice here) has failed. With that basic idea in mind, every time we add an adapter, widget or hardware piece in the signal chain, we exponentially add to the system’s complexity.
The best system is the one with the least amount of “moving” parts. In my opinion, the perfect video system for any event is as follows:
source ( cable ( switcher/processor ( cable ( display device
The cables should be adapter free, with the correct terminations on each side for perfect device-to-cable connections. With this simple system, you’ve minimized your possible points of failure, but when you complicate the path by adding pieces, you proportionally add more opportunities to postpone your cold drink at 6 PM.
Prosio’s Patented Design Rules
The following rules are by no means the all-inclusive guidelines for video system design, but they’re a great place to start when pulling your system together.
Rule One: Use a switcher or display device that includes the required connectors for your source signals. Avoid using adapters or widgets in order to make the system work.
For example, if you have SDI camera signals, use a system with built-in SDI capability
Rule Two: If you need to drive multiple displays, use a switcher or processor with multiple main (or AUX) feeds. Avoid the use of loopthru connectors on display gear.
This rule reduces the need for external distribution amplifiers. Loop connections are typically not boosted or re-clocked, and may also have limited signal strength.
Rule Three: Use cables with the correct connectors on each end.
The big issue here is with the VGAto- 5xBNC adapters. If you can use a “direct” cable without an adapter, you’ll reduce noise as well as failure points.
Rule Four: Digital. Run digital signals whenever you can.
Because digital video cables are very particular in signal resolution, bandwidth and quality, they either work -- or they don’t. There are no intermediate issues.
Rule Five: Follow the path of least resistance.
Avoid double scaling, avoid extra processing, and avoid anything that can potentially alter the signal more than is absolutely required.
There, that was easy. Now, please print and post the above rules in a conspicuous location.
Take a Moment and Breathe
There are many more “best practices” that tend to get overlooked when we design systems, and when we encounter hurdles, it’s very easy to get caught up in the particulars, yet overlook the possible simple paths around the obstacle. Sometimes, the quickest way to complete the job is to take a coffee break and get a little perspective on the job at hand.
