TECHNICAL CORNER:

By Mark Hershey – V.P. of ViewCast Engineering

We’re often asked about what makes an Osprey card a better choice for capturing video than cards designed for Video Editing stations, or general-purpose capture cards found at consumer electronics stores.
We’ve typically responded with various quality, reliability, and design-for-purpose reasons that usually describe the technology of the card. Behind those answers is a balance of very careful design by engineers who truly understand the digital video industry, the selection of very high-quality components, and the carefully-crafted driver software that exposes the card’s features to the user. And, yes, we take pride in tailoring all of these elements expressly for the streaming applications ViewCast and Osprey are known for.

But there are some more subtle design elements that influence the usefulness and applicability of the card that you may not be aware of.

To illustrate, one of our design criteria is 24/7 operation. That’s not just a reliability goal, it also means that the card will likely be fed audio and video continuously, rather than in the “bursts” that an editing suite card would typically be presented. This, in turns, means that there cannot be any drift between audio and video synchronization over very long periods of operation-days, weeks, or even longer-- a particularly challenging but important design goal.

Another Osprey design criteria is called Design for Adversity. In an editing suite, a capture card grabs video and audio samples from a high-cost, high-quality editing deck or other playback device. This playback device is located a foot or two away from the capture card, and delivers flawless audio and video with no electrical ‘challenges’ to the signal. A very simple capture card may work fine in this application. Conversely, in our more typical world, the video input can come from consumer-grade devices like camcorders or off-air receivers that often deliver mis-timed or otherwise impaired video, often located far from the capture card, and delivered by sub-optimum cabling that further distorts the video and audio signals. This impairment also presents challenges that influence the card’s design. The Osprey 530, for example, has a special “chip” that can accept a really mal-formed SDI input and “clean up” ( re-sync) the signal before further processing. In user terms, this simply means you can use long lengths of cruddy SDI cable and the card will still work.

Yet another design criteria is something we call Designed for Live. All Osprey cards are used to capture real-time video, but that video’s characteristics may change on-the-fly, particularly in high-definition broadcast applications where the video aspect ratio and resolution may change many times. You see this at home on your wide-screen HD televisions—you are watching CSI-Miami in HD, then a commercial comes on and the picture changes to 4:3 ratio, then back to 16:9 when the show returns. You don’t think a thing of it…but feed that same input to an ordinary capture card and it’ll drop like a rock the first time the format changes. The new Osprey 700HD handles this just fine…in fact; it can be configured to feed the same signal format to the application software no matter what the incoming SDI video stream looks like. You can even change between SD and HD capture and still keep right on encoding. I should ballyhoo another 700HD feature right about here: Dynamic Logo Positioning. The 700HD lets you superimpose a logo on the video, just like CBS does on CSI-Miami (you know, the CBS Eye in the lower right corner). Most capture cards don’t offer this feature….but the 700HD lets you overlay your own bitmap and automatically resize and reposition it when the incoming video mode changes. Switch the input from standard-definition to any HD mode and the logo adapts accordingly. You won’t see any computer-store cards that do that for you!