From: David P. Hayes
Newsgroups: alt.video.dvd,alt.video.laserdisc
Date: Tuesday, November 04, 1997 10:54 PM
Ralph Barbagallo <rbarbaga@cs.uml.edu> wrote in article
<63otvn$qru$1@jupiter.cs.uml.edu>…
> You still have to admit, it is irritating no matter how short
> the break is. … Even
> worse is having to swap discs on a multi-disc film. I hate it! …
> I hope DVD players eventually have RAM in them so it spools the
> movie out of RAM while some sort of carousel mech is swapping the discs
> so you're totally uninterrupted. What's the bandwitdh of DVD? 10mb/sec?
> So 64MB of RAM should be enough to buffer the video while changing
> discs?
A carousel mechanism within DVD players is an idea that I considered a natural, too.
But instead of having RAM store buffer until a single laser-beam has had the second disc transported to it, why not have an additional laser beam? The laser beams are cheap. You'll find at your discount home-electronic superstore boombox CD/cassette players for $49. Sony has a terrific portable CD/cassette/AM-FM unit that at discount can be had at $70. And obviously the laser beams themselves cost only a fraction of this.
The two laser beams could swap turns playing discs--just as movie projectors do in theaters, and just as slide projectors are sometimes rigged up to do at presentations. Those slide projectors are the perfect model for DVD player manufacturers to follow. Just as carousels have worked to transport separate rectangles of images atop slide projectors, so too could a jukebox arrangement be used in DVD. Better still--and following from the jukebox analogy--the 5" discs can be within a single carousel for easy loading by the user, with the mechanism using computer technology to keep track of which disc slot is to next be played and which laser beam to deliver the disc to.
There is another advantage to this idea: movies and programs of such niche appeal that they don't warrant the expense of vast compression, can be spread to multiple discs. (The savings in mastering costs would more than offset the additional cost of manufacturing the small number of additional discs. The need to do this, however, presupposes that mastering costs won't come down considerably--although advances in compression technology may quickly bring more economical procedures. See posts by others for more information on this.) What will it matter if a title is on several discs if the viewer is no more aware of the changeover from disc to disc than he typically is at a movie theater?
(The above presumes that movies would be on single sides of multiple discs. If both sides of the disc are used, then (a) players would have to have laser beams of both sides of each disc-play chamber (and thus four laser beams); (b) multiple-disc movies would have to be configured so that at the end of each side the machine goes to the next disc and does not return to the previous disc until later, after the dormant laser beam or disc has been repositioned (the playing sequence here would be much like that used on some multiple-LP phonograph records, wherein an opera might have side 1 sharing a disc with side 4, side 5 sharing with 2, and side 3 sharing with 6); or (c) for affected titles, movies be released on single-sided discs.)
Incidentally, I am one of those laserdisc owners who has not switched over (principally over the paltry selection of older films, although HDTV and possible obsolescence figure in), yet I am happy that the possibility outlined here eliminates yet another thorn used against DVD: that too little data is left after compression for the picture to appear real. With a few discs per title, DVD can have as many little pits as a single LD has--and yet without side breaks, rot (on single-sided discs, anyway, as single-siders don't need an internal layer of glue), or analog-video problems.
David Hayes
Return to Table of Contents
Go to next article