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[2.7] How does DVD compare to laserdisc?
- Features: DVD has the same basic features as
CLV LD (scan, pause, search) and CAV LD (freeze, slow) and adds
branching, multiple camera angles, parental control, video menus,
interactivity, etc., although some of these features are not available
on all discs.
- Capacity: Single-layer DVD holds over 2 hours,
dual-layer holds over 4 hours. CLV LD holds one hour per side,
CAV holds half an hour. A CAV laserdisc can hold 104,000 still
images. DVD can hold thousands of still pictures accompanied by
hundreds of hours of audio and text.
- Convenience: An entire movie fits on one side
of a DVD, so there's no need to flip the disc or wait for the
player to do it. DVDs are smaller and easier to handle. DVD players
can be portable, similar to CD players. Discs can be easily and
cheaply sent through the mail. On the other hand, laserdiscs have
larger covers for better art and text.
- Noise: Most LD players make a whirring noise
that can be heard during quiet segments of a movie. Most DVD players
are as quiet as CD players.
- Audio: LD can have better quality on Dolby Surround
soundtracks stored in uncompressed PCM format. DVD has better
quality on Dolby Digital or music only (PCM). LD has 2 audio tracks:
analog and digital, whereas DVD has up to 8 audio tracks. LD uses
PCM audio sampled with 16 bits at 44.1 kHz. DVD LPCM audio can
use 16, 20, or 24 bit samples at 48 or 96 kHz (although PCM is
not used with most movies). LD has surround audio in Dolby Surround,
Dolby Digital (AC-3), and DTS formats. 5.1-channel surround sound
is available by using one channel of the analog track for AC-3
or both channels of the digital track for DTS. DVD uses 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 LD's 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 LD Dolby Surround
tracks.
- Video: DVD usually has better video. LD suffers
from degradation inherent in analog storage and in the composite
NTSC or PAL video signal. DVD uses 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 DVD is always
better than LD. Only that it can be better. Also keep in mind
that the average television is of insufficient quality to show
much difference between LD and DVD. Home theater systems or HDTVs
are needed to take full advantage of the improved quality.
- Resolution: In numerical terms DVD has 345,600
pixels (720x480), which is 1.3 times LD's approximately 272,160
pixels (567x480). Widescreen DVD has 1.7 times the pixels of letterboxed
LD (or 1.3 times anamorphic LD). As for lines of horizontal resolution,
DVD has about 500 whereas LD has about 425 (more info in 3.4.1).
In analog output signal terms, typical luma frequency response
maintains full amplitude to between 5.0 and 5.5 MHz. This is below
the 6.75 MHz native frequency of the MPEG-2 digital signal. Chroma
frequency response is one-half that of luma. 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 (see Julien Wilk's Laserdisc
Database).
- Availability: DVD players and discs are available
for purchase and rental in thousands of outlets and on the Internet.
LD players and discs are becoming hard to find.
- Price: Low-cost DVD players are cheaper than
the cheapest LD player. Most movies on DVD cost less than on LD.
- Restrictions: For those outside the US, regional
coding (see 1.10) is a definite drawback of DVD. For some people Macrovision
copy protection (see 1.11) is an annoyance. Laserdisc has no copy protection and
does not have regional differences other than PAL vs. NTSC.
- Recordable: DVD recorders are increasingly affordable.
Laserdisc recording, at a low of $250 per disc, was never available
to general consumers.
For more laserdisc info, see Leopold's FAQ at <www.cs.tut.fi/~leopold/Ld/FAQ/index.html>,
and Bob Niland's FAQs and overview at <www.access-one.com/rjn/laser/laserdisc.html>
(overview reprinted from Widescreen Review magazine).
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