Chapter 1

70 Everything You Ever Wanted to Know About DVD
by using one channel of the analog track for AC-3 or both channels of
the digital track for DTS. DVDs use the same Dolby Digital surround
sound, usually at a higher data rate of 448 kbps, and can optionally
include DTS (at data rates up to 1536 kbps compared to laserdiscs’
1411 kbps, but in practice DTS data rates are often 768 kbps). DVD
players convert Dolby Digital to Dolby Surround. The downmixing,
combined with the effects of compression, often results in lower-quality
sound than from laserdisc Dolby Surround tracks.
• Video DVDs usually have better video. Laserdiscs suffer from degradation
inherent in analog storage and in the composite NTSC or PAL
video signal. DVDs use digital video, and even though it’s heavily compressed
most professionals agree that, when properly and carefully
encoded, it’s virtually indistinguishable from studio masters. This
doesn’t mean that the video quality of a DVD is always better than a
laserdisc. Only that it can be better. Also keep in mind that the average
television is of insufficient quality to show much difference between
laserdiscs and DVDs. Home theater systems or high-definition TVs
(HDTVs) are needed to take full advantage of the improved quality.
• Resolution In numerical terms, a DVD has 345,600 pixels
(720�480), which is 1.3 times the 272,160 pixels of a laserdisc
(567�480). A widescreen DVD has 1.7 times the pixels of a letterboxed
laserdisc (or 1.3 times an anamorphic laserdisc). As for lines of
horizontal resolution, a DVD has about 500, whereas a laserdisc has
about 425 (more info is covered in “What Do Lines of Resolution
Mean?” in Chapter 3, “DVD Technical Details”). In analog output signal
terms, a typical luma frequency response maintains a full amplitude
between 5.0 and 5.5 MHz. This is below the 6.75 MHz native
frequency of the MPEG-2 digital signal. The chroma frequency
response is half that of luma, and the laserdisc frequency response
usually begins to fall off at 3 MHz. (All figures are for NTSC, not PAL.)
• Legacy titles Some movies on laserdisc will probably never appear
on DVD.
• Availability DVD players and discs are available for purchase and
rental in thousands of outlets and on the Internet. Laserdisc players
and discs are becoming hard to find.
• Price Low-cost DVD players are cheaper than the cheapest
laserdisc player. Most movies on DVD cost less than on laserdisc.
• Restrictions For those outside the United States, regional coding
(refer to “What Are Regional Codes, Country Codes, or Zone Locks?”
in Chapter 1) is a definite drawback to DVDs. For some people, Macrovision
copy protection (refer to “What Are the Copy Protection