[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).