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Posted by Chel van Gennip on 10/05/80 11:45
On Wed, 19 Apr 2006 16:06:44 +0200, Richard Crowley wrote:
> There are both analog and digital methods of recording. There are both
> magnetic and optical (and mechanical) media.
You are missing solid state media (flash). Optical analog media are not so
common anymore. When analog magnetic media became available develepment of
analog optical media (although interesting, see the Fantasound system:
http://www.widescreenmuseum.com/sound/Fantasound1.htm ) stopped
> It would appear that digital is a more reliable method of encoding data
> than analog. For the obvous reasons that it is easier to decode
> semi-degraded information because you know what to expect, etc.
Analog magnetic media have a good degradation characteristic, digital
media have a terrible degradation characteristic but also has good
solutions for error correction. Depending on error correction method used
and the real degradation analog or digital may perform better. As the
error correction mechanism used for digital data is sufficient for real
life errors, digital data normally outperforms analog data.
> I have first-hand experience to show that field-writable optical media
> are not necessarily reliable. And certainly not as reliable as mag tape
> (whether analog or digital).
It is complete nonsense to say "field-writable optical media are certainly
not as reliable as mag tape". It is clear that solid state media are by
far the most reliable field writable media. It is hard to find other media
with an operating temperature range -25C to +85C, an MTBF > 1.000.000H,
extrem resistance to mechanical shocks etc. For archiving digital
solutions with integrety checks, redundancy etc. are the most reliable
solutions.
--
Chel van Gennip
Visit Serg van Gennip's site http://www.serg.vangennip.com
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