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From: clouds@ccwf.cc.utexas.edu (Kathy Strong)
Newsgroups: comp.ivideodisc
Subject: Re: How much can be put on a videodisc
Keywords: videodisc, size
Message-ID: <39941@ut-emx.uucp>
Date: 19 Nov 90 15:42:34 GMT
References: <10527@ur-cc.UUCP>
Sender: news@ut-emx.uucp
Reply-To: clouds@ccwf.cc.utexas.edu (Kathy Strong)
Lines: 40

In article <10527@ur-cc.UUCP> gest_ss@uhura.cc.rochester.edu (Gavin Stark) 
writes:
>
>Quick question:
>	Does anyone know the maximum number of seconds (or hours) that can
>be put on a videodisc?  Does it depend on things like resolution, recording
>speed etc?  I know nothing about videosic technology but would like to do
>some work with it.
>

Quick answer: there are two types of videodiscs: CAV (constant angular velocity)
and CLV (constant linear velocity). One can hold 54,000 frames per side
(30 min x 60 sec/min x 30 frames/sec) and is VERY fast access; the other has
slower access (as long as three or four seconds) but holds twice as many
frames per side.

Due to my constitututional inability to deal with acronyms, I forget which
is which--but I believe the faster one, the one that has 30 min/side, is the
"standard."

Of course, that's 30 minutes of motion video. Most videodisc programs make
good use of the fact that you can have two to four tracks of audio as
well. Example: seek frame 4000, a still of Terra as seen from space, disable
video passthrough (i.e., "grab" or "freeze" the image), move the heads to 
frame 6000, play 15 seconds of narration from audio track B. One-thirtieth
of a second of video has provided a "picture" for 15 seconds. Careful inter-
spersion of stills with motion video can make a 100-minute show out of a 30-
minute videodisc with no problem at all.

--Kathy

(Help! I feel like I'm the only person talking on this newsgroup...)


-- 
...........................................................................
:   Kathy Strong               :  "Try our Hubble-Rita: just one shot,     :
:  (Clouds moving slowly)      :   and everything's blurry"                :
:   clouds@ccwf.cc.utexas.edu  :                           --El Arroyo     :
:..........................................................................: