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130 Everything You Ever Wanted to Know About DVD<br />
groove recording, and a 640nm laser, but contrary to initial reports, the<br />
drives were not expected to be able to read DVD-ROM or compatible discs.<br />
There was also FMD (see “What Effect Will FMD Have on DVD?” in<br />
<strong>Chapter</strong> 2). And there are HD formats (see “What’s New with DVD Technology?”<br />
in <strong>Chapter</strong> 6, “Miscellaneous”).<br />
How Long Does DVD Recording Take?<br />
The time it takes to burn a DVD depends on the speed of the recorder and<br />
the amount of data. Playing time of the video may have little to do with<br />
recording time, since a half hour at high data rates can take more space<br />
than an hour at low data rates. A 2x recorder, running at 22 Mbps, can write<br />
a full 4.7G DVD in about 30 minutes. A 4x recorder can do it in about 15<br />
minutes.<br />
NOTE: The -R/RW format often writes a full lead-out to the diameter<br />
required by the DVD spec, so small amounts of data (such as a<br />
very short video clip) may take the same amount of time as large<br />
amounts.<br />
Why Can’t I Take a Screenshot of DVD Video?<br />
Why Do I Get a Pink or Black Square?<br />
Most DVD PCs, even those with software decoders, use video overlay hardware<br />
to insert the video directly into the VGA signal. This an efficient way to<br />
handle the very high bandwidth of full-motion video. Some decoder cards,<br />
such as the Creative Labs Encore Dxr series and the Sigma Designs Hollywood<br />
series, use a pass-through cable that overlays the video into the analog<br />
VGA signal after it comes out of the video display card. Video overlay<br />
uses a technique called colorkey to selectively replace a specified pixel<br />
color (often magenta or near-black) with video content. Anywhere a colorkey<br />
pixel appears in the computer graphics video, it’s replaced by video<br />
from the DVD decoder. This process occurs downstream from the computer’s<br />
video memory, so if you try to take a screenshot (which grabs pixels<br />
from video RAM), all you get is a solid square of the colorkey color.<br />
Hardware acceleration must be turned off before screen capture will<br />
work. This makes some decoders write to standard video memory. Utilities<br />
such as Creative Softworx, HyperSnap, and SD Capture can then grab still<br />
pictures. Some player applications such as PowerDVD and the Windows<br />
Me player can take screenshots if hardware acceleration is turned off.
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