The Logic Off Topic list

> From: Marvin Humphrey <marvin@...>
> 
> I'm curious about DVDr... Does it work on the same burn-dye-to-imitate-pits
> strategy as CDR?  I like the idea of DVDr, but I'm not sold that
> miniaturized CDr technology boasts the same reliability or longevity as full
> size.

I believe it's phase-change.  Dunno about reliability.  BTW, the AES
(http://www.aes.org) has a working group on archiving and restoration.

> 
>> Longer lifespan than analog tape....
> 
> Hmm.  The problem is that digital degrades so ungracefully.  Shannon's
> theories allow you to predict how much EC overhead you'll need to insulate
> the information from the noise of the "noisy channel", but your calculation
> becomes invalid as the noise in the storage channel increases over time.

Well, the calculation doesn't become invalid, if you account for degradation
over time as well. 


> All of a sudden, the EC fails, and you have dropouts.  Depending on how the
> information is organized, this commonly results in complete dropouts in the
> reconstructed waveform or huge glitching.

True.  But if you have multiple copies, the probablity of them all failing
at the same point decreases exponentially, and since it's digital, as long
as you have a known good copy of every sample, you can perfectly reconstruct
the whole.  While something similar is theoretically possible with analog,
in practice there wouldn't be enough copies around to even try it.

> 
> In contrast, when analog magnetic media goes south, you may get HF loss, or
> warbles, but by and large, the perceptual effects are not as severe.  Also,
> sticky-shed syndrome does not affect all tape formulations.  We just played
> back somebody's acetate tape from the 60s with no conditioning other than
> repack onto a better reel.

True, the graceful degradation is appealing.  I believe some form of disk
holds the longevity record, either acetate or phenolic or something... and
wire recordings.  Vinyl records if properly stored can last way longer than
tape.



> The problem with all of the storage solutions that digital audio sponges off
> the computer industry is that no one in computer R&D has market pressure
> driving them to think about making storage that lasts decades or centuries!

True, but there is a small and growing movement even in the biz sector as
records are digitized, people are starting to wonder what's going to happen
to them.


> It can be done, but will it be done?  Risky thing to assume.

Another approach that I alluded to above is to make many copies at the time,
and ideally distribute them geographically.  THere's more to archiving than
media longevity -- what if the building burns down!


> These Seagate drives with the fluid bearings... your misgivings are in
> regards to short term reliability, I assume.

Well, more like 5-10 year timeframe.  I still have some hard drives in
operation from the 80's!


> But imagine one of those Apple G4 Cubes outfitted with a quiet HD... no fan
> noise, no HD noise (supposedly).  You could actually have one of those in
> the room with you as you record.  A lot of DIYers have been waiting for that
> for a while.

True, it would be nice... until and if solid state memory gets cheap enough!