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In Reply to: Was this laser rot in a laserdisc? posted by John C. - Aussie on April 9, 2003 at 17:14:11:
Generally, my rotted discs will be worse on one side than the other, but this has not been universally true. Rot usually first manifests itself as multi-colored speckles, and if the oxidation becomes bad enough, the picture can become scrambled and the disc unplayable. I believe I only have one side of one disc that has suffered that particular fate, though.Laserdiscs are far more vulnerable to rot and aluminum layer oxidation problems than CDs or DVDs because they have analog picture information. They lack the interweaved data and robust error correction of the digital formats. In fact, the laserdisc format has no real means of replacing lost picture information; hence, the occurence of dropouts and other problems that DVDs are largely immune to. There were also a number of problems related to laserdisc manufacture over the years. Some were due to the pioneering nature of laserdisc, the first consumer optical disc format, but others were simply due to shoddy manufacturing. Rotted discs were still being produced at the Sony pressing facility in Terre Haute, Indiana, well into the 90's.
I do have one disc that a friend sent me that has a weird manifestation of laser rot in that there are little horizontal streaks appearing randomly throughout the picture. On this disc, you can actually see that the aluminum has a mottled appearance from the oxidation.
Rotted discs will also very often have audio problems. Commonly, this will manifest itself as sort of a helicopter like sound, usually more noticeable on the analog FM tracks than on the digital tracks. I do have a few discs where the situation is reversed, though, and I don't know what's going on there.
On NTSC discs, particularly bad ones are DiscoVision titles, Technidisc releases, discs with the LDVS mintmark, and Pioneer Artists 8" discs. I have over 50 eight inch music video discs and would estimate that fully 20% of them have some sort of rot, in most cases, minor to moderate.
Todd
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Follow Ups
- Re: Was this laser rot in a laserdisc? - Lasermeister 18:12:19 04/16/03 (0)
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