Description

This article is from the DVD Formats FAQ, by jtfrog@usa.net (Jim Taylor) with numerous contributions by others.

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. Unlike CAV LD,
DVD can't play backwards (it's technically possible, but no current
players can do it).
* 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 has better quality on Dolby Surround soundtracks, which are
stored in uncompressed PCM format. DVD has better quality on Dolby
Digital or music only. LD has 2 audio tracks: analog and digital. DVD
has up to 8 audio tracks. LD uses PCM audio sampled with 16 bits at 44
kHz. DVD LPCM audio can use 16, 20, or 24 bit samples at 48 or 96 kHz
(although PCM won't be 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 the same data rate (384
kbps) but can go up to 448 kbps for better quality, and can optionally
include DTS (at data rates up to 1536 kbps compared to LD's 1411 kbps,
but in practice DTS data rates will probably be lower on DVD than on
LD). DVD players convert Dolby Digital to Dolby Surround. This
conversion (downmix) process can reduce dynamic range. Combined with
the effects of compression, this usually 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.
Nevertheless, this doesn't mean that the video quality of DVD,
especially at first, WILL be 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. The arguments about DVD quality vs. LD quality will
rage for a long time. The only final answer is to compare them side by
side and form your own opinion.
* 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 ~= 500, LD
~= 425, and VHS ~= 240. 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: There are thousands of movies on laserdisc that 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. LD players and
discs are becoming hard to find.
* Price: Low-cost DVD players are cheaper than the cheapest LD player,
and the success of DVD-ROM will inevitably drive the price to the
under-$100 level of CD players. 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.

For more laserdisc info, see Leopold's FAQ at
<http://www.cs.tut.fi/~leopold/Ld/FAQ/index.html>, and Bob Niland's FAQs
and overview at <http://www.frii.com/~rjn/laser/> (overview reprinted from
Widescreen Review magazine).

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