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34 Everything You Ever Wanted to Know About DVD<br />
tracks on their PAL discs instead of MPEG audio tracks. Because of PAL’s<br />
higher resolution, the movie usually takes more space on the disc than the<br />
NTSC version. See <strong>Chapter</strong> 3 for more details.<br />
Actually, three types of DVD players exist if you count computers. Most<br />
DVD PC software and hardware can play both NTSC and PAL video, as well<br />
as both Dolby Digital and MPEG audio. Some PCs can only display the<br />
converted video on the computer monitor, but others can output it as a<br />
video signal for a TV.<br />
The bottom line is that NTSC discs (with Dolby Digital audio) play on over<br />
95 percent of DVD systems worldwide. PAL discs play on very few players<br />
outside of PAL countries, irrespective of regions.<br />
What About Animation on DVD?<br />
Doesn’t It Compress Poorly?<br />
Some people claim that animation, especially hand-drawn cell animation<br />
such as cartoons and anime, does not compress well with MPEG-2 or even<br />
ends up larger than the original. Other people claim that animation is simple<br />
so it compresses better. Neither is true.<br />
Supposedly the “jitter” between frames caused by differences in the<br />
drawings or in their alignment causes problems. An animation expert at Disney<br />
pointed out that this doesn’t happen with modern animation techniques.<br />
And even if it did, the motion estimation feature of MPEG-2 would<br />
compensate for it.<br />
Because of the way MPEG-2 breaks a picture into blocks and transforms<br />
them into frequency information, it can have a problem with the sharp<br />
edges common in animation. This loss of high-frequency information can<br />
show up as “ringing” or blurry spots along edges (called the Gibbs effect).<br />
However, at the data rates commonly used for DVD, this problem does not<br />
usually occur.<br />
Why Do Some Discs Require Side Flipping?<br />
Can’t DVDs Hold Four Hours per Side?<br />
Even though DVD’s dual-layer technology (see “What Are the Sizes and<br />
Capacities of DVDs?” in <strong>Chapter</strong> 3) enables over four hours of continuous<br />
playback from a single side, some movies are split over two sides of a disc,<br />
requiring that the disc be flipped partway through. Most “flipper” discs are<br />
made because producers are too lazy to optimize the compression or make<br />
a dual-layer disc. Better picture quality is a cheap excuse for increasing the
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