zhou@brazil.psych.purdue.edu (Albert Zhou) (01/14/91)
A while ago, I posted an article in another newsgroup asking about the memory capacity of laser disk. Currently, laser disks used by computers typically have a few hundred Meg bytes. However, according to my computation, if a laser disk stores uncompressed digitalized pictures, its memory capacity has to be much higher (consider a 90-minute movie. it needs to store 25x60x90 pictures). Does anyone know the mechanism of storing pictures in video disk?
clouds@ccwf.cc.utexas.edu (Kathy Strong) (01/14/91)
In article <11678@j.cc.purdue.edu> zhou@brazil.psych.purdue.edu (Albert Zhou) writes: >A while ago, I posted an article in another newsgroup asking about the >memory capacity of laser disk. Currently, laser disks used by computers >typically have a few hundred Meg bytes. However, according to my >computation, if a laser disk stores uncompressed digitalized pictures, >its memory capacity has to be much higher (consider a 90-minute movie. >it needs to store 25x60x90 pictures). Does anyone know the mechanism >of storing pictures in video disk? Sorry, laserdiscs don't work that way. They do not store information digitally, but rather in an analog form. To answer your original question, CAV (constant angular velocity) videodisks, the kind usually used in multimedia and interactive videodisk, hold 30 minutes (54,000 frames) of video, while CLV (constant linear velocity) disks, more often used for movies, hold 60 minutes (108,000 frames) of video per side. --K . -- ........................................................................... : Kathy Strong : "Try our Hubble-Rita: just one shot, : : (Clouds moving slowly) : and everything's blurry" : : clouds@ccwf.cc.utexas.edu : --El Arroyo : :..........................................................................:
rjn@hpfcso.HP.COM (Bob Niland) (01/14/91)
re: > Does anyone know the mechanism of storing pictures in video disk?
The video is analog. The composite video signal is used to modulate an FM
carrier over the range 7.6 MHz (sync tip) to 9.3 MHz (white level). The
resulting sine wave is amplitude modulated by the two analog FM audio
subcarriers and the combined digital audio subcarrier, then clipped. The
resulting square waves are recorded as pits and lands more or less as is.
Crudely put, the analog video signal is represented in the frequency of the
pit stream, and the various audio channels are represented by duty-cycle
modulation of the pit stream.
Regards, Hewlett-Packard
Bob Niland Internet: rjn@hpfcrjn.FC.HP.COM 3404 East Harmony Road
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