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 Why is DV such a pervasive video format? Because it delivers significantly higher quality, significantly better and more reliable performance, and all that at incredibly low cost. |
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It's the network, stupid! Remember: The codec sits in the camcorder or VCR! You have already paid for it. With DV, the video is already captured and compressed. All you have to do is to copy the digital data to your computer via the Firewire. This isn't "capture," it's a data transmission. Think of your camcorder connected to your computer by a high speed network and you get the idea. The Firewire interface board in the computer can be quite inexpensive. Even the first generation Firewire boards coming to market cost less than $1000. Expect this price to drop rather quickly. Also expect the Firewire connector to migrate to other peripherals, like a disk controller, or even the motherboard. Texas Instruments already sells a laptop with built-in Firewire. Down to the shirts: The Adaptec/DPS Spark: Announced for $1000, now selling "naked" for $699.- |
High Quality, High Performance, Low Cost. High quality: With analog video, noise can enter at any point of the path. And usually, once noise has entered, noise will stay. There's tape noise. The cable that routes the video to the capture card can pick up noise. The capture card usually picks up a lot of noise, because it sits in a very noisy environment: In the computer. Going back out to tape adds noise yet again. Noise doesn't just degrade the picture, it also degrades the compression process. Because a codec treats noise as information, it dutifully stores the noise. Which results in high data rates. Those of use who survived the years of analog video on the computer got used to thinking that anything better than 5 Megabytes/second or less than 4 tx compression is good. This is true in most of the cases, but not all. Those of us lucky enough to own very high quality equipment quickly realized: A very clean video signal actually lends itself better to compression. It can compressed more, it can tolerate a lower data rate and still look better. Why? Because it was free of noise in the first place. By compressing the video at the point of origin (in the camcorder, behind the lens), DV avoids noise altogether. High performance: Analog video usually compresses at a varying rate. If the content is complicated, the data rate goes up. Owners of Premiere can actually watch this process by using a feature called Movie Analysis. It usually shows spikes in the data rate during complicated scenes, such as transitions. These spikes can lead to data stalls on playback. The video zips along nicely, suddenly a spike comes down the pike, spike exceeds the bandwidth of the computer and bang, playback hangs. DV uses a steady rate of around 3.7 Megabyte/second. This is a no-brainer for a moderately fast system with a decent hard drive. There are no spikes in the data stream, ergo no bumps in the road to good playback. Low cost: A good capture board can be an expensive thing, and
some of use have amassed quite a collection over the years. As new
ones emerge, driver support for the old ones dries up. Will it ever end?
Yes: Let's forget about capture boards altogether. With DV, capture and
compression happens right behind the lens..
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