Pick a Real-time Capture Card for DV

Q. I’ve been thinking about getting a real-time capture card for DV but I’m intimidated by the price of these cards. My computer already has a FireWire card and I am editing with Premiere. I think it would be great if I didn’t have to render anymore. How do I decide on a card?

D. Mendoza

Socorro, NM

A. There are several real-time (RT) capture cards available on the market. While they vary in features and price, all are a magnitude more expensive (costing hundreds of dollars) than generic IEEE 1394 cards (costing just tens of dollars). Each of the former has a hardware chipset that calculates and performs transitions and special effects. Obviously, these transitions and effects require some type of rendering for viewing. Your software, in this case Premiere, usually does this. Until recently, computer CPUs were not fast enough to make these calculations in order for the transitions or FX to display quickly. We got used to frequent pauses while rendering took place. Hardware-based rendering on a real-time card was meant to solve this problem – rendering a two-second transition in less than two seconds.

Now, however, 1GHz to 2GHz CPUs are commonplace and often fast enough to do the work in real time without hardware assistance, provided your software supports real-time effects. Apple Final Cut Pro 3.0, Avid Xpress DV 3.0, Sonic Foundry Vegas Video and many others now support real-time previewing of FX and transitions. Unfortunately, Premiere 6 is not on the real-time preview list. Premiere users, like you, can get real-time previewing today with a real-time hardware card.

Notice the wording, however: real-time previewing. We didn’t say "real-time rendering." While many software products now support real-time previewing, few actually render transitions and FX in real time to the DV format. In other words, yes, you can add an effect and see how it will look in the preview window and even on your NTSC television through your DV camcorder, but no, it is not typically rendered in the DV format or ready to export to the camera or print to tape. For that, you’ll still need to render. But many real-time hardware cards require rendering as well, as they frequently only provide real-time previews.

We don’t want to dissuade you from getting a real-time card; we only want to let you know exactly what you would get. Many of these hardware cards also come with full versions of some very excellent software packages that would cost as much as the card bundles themselves if you bought them separately. Some real-time hardware cards also have multiple inputs/outputs for analog video and audio, including S-video, and have convenient breakout boxes that bring these connections to the front of the computer. At the high end, some cards (e.g. Canopus DV-Storm) do what we’ll call "real-real time," instantly rendering everything (DV, uncompressed, etc.). This would allow you to edit without ever thinking about rendering. There is a continuum here, from cards that do some effects in real-real time to complete systems that do just about everything in real-real time (e.g. Video Toaster 2).

Of course, in a year, this entire discussion will be moot, with real-real time software available for any fast computer. We can hardly wait.

Q. I noticed that the Mini DV and the DVCAM format both have data rates of 25Mbps. If this is true, why is DVCAM considered to be a higher quality, more professional format?

Z.J. Fu

Vancouver, BC, Canada


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A. The DV family of formats (including Mini DV, Digital8, DVCAM and DVCPRO) all have the same data rate of 25Mbps (or roughly 3.6MB per second). Therefore, as you have noticed, the quality is exactly and precisely the same for all four, all other things being equal. There is no doubt that a $4,000 DVCAM or DVCPRO camcorder likely shoots higher-quality video than a $600 Digital8 camcorder, due to things like better optics, number of CCDs and CCD size, but it is not because the format itself is inherently better. You may want to go with DVCAM or DVCPRO for other reasons including a stronger tape format, a more standard way of measuring black. Ultimately it’s the quality of the optics and image sensors that make the biggest difference. It’s the attention to detail that’s put into professional tools.

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