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Re: arsclist Digital knowledge preservation
At 09:33 AM 6/18/2002 -0700, Richard L. Hess wrote:
We are having this precise discussion in the AMIA (Association of Moving
Image Archivists) mailing list where it is heretical to suggest any form
of lossy compression. On the other hand, we've had many analog systems
that provide lossy storage to the original signal.
We have also had the discussion here that the CD Audio Red Book standard
isn't good enough for archival purposes and we need higher resolution,
although many of us are happily transferring sound to uncompressed,
44.1/16 CDs.
One thing to consider in selecting a format to store to is that it is
truly as lossless as possible for the vast majority of material contained
in the archive. On the other hand, the format has to be well-supported
with the anticipation that players will be available long into the future.
There is lossless compression available for digital audio. Two options are
MonkeysAudio (my choice) and Shorten. I verified that there were no losses
by compressing a file, uncompressing it, and comparing the result with the
original. They are identical at the bit level. However, the available
compression is only of the order of a factor of two. Whether that is
sufficient to be worthwhile and whether the code is likely to be available
indefinitely or for different platforms are factors in the choice. For my
purposes, lossless as well as lossy compression has its place.
I do not know the bitrates that are being coded to for the MP3 audio files
mentioned in this post, but the difference between 192Mb/s MP3s and mono
WAV files at 44.1/16 is about 1:3.7. I'm wondering if the savings of $7.00
and seven discs is worth the additional compression. These figures relate
to making Red-Book audio CDs. The difference would be $3.00 and three
discs if there were mono WAV files on the CDROM.
One important item to consider for audio transfers is that the cost of the
final media is only a very small percentage of the final transfer cost.
The biggest single cost is the staff to do the transfer as that staff
needs to be skilled in making the transfer and in all of the arcane
optimizations that must be done to (and the mechanical pre-processing that
must be done before) the analog reproduction chain.
The cost of the medium per se is no longer a substantial issue. The cost of
managing it - storing, indexing, accessing - is far greater in practice.
Note that in many contexts I refer to the MP3 discs as catalogues of the
originals. Thought of in that light, their role is easier to recognize.
They are (cross-)indexed representations of the archival material. Fidelity
is sufficient for the purpose just as a catalogue of an art exhibit is
sufficient for its purpose - and no one would confuse the representation in
the catalogue with the original.
The good news, however, is that a large collection of items are being
made accessible and being preserved in at least one form for future
generations. I believe that our grandchildren will be happier if more is
saved, albeit at SLIGHTLY lower quality than if only the pinnacle of
quality is saved and many things were lost.
Accessibility is critical here, IMHO. Even the dedicated scholar will be at
an advantage if he has a catalogue of the holdings of a repository
sufficient to determine the value in the repository. The student or casual
researcher may be content with the catalogue instead of visiting the
repository and satisfying the conditions for access to the original.
There is a fallacy common to mathematics and geography: confusing the map
with the territory. The catalogue is not the source material; it is a
representation of the source sufficient for limited purposes and designed
to serve those purposes. Even if the high-fidelity, lossless file is
accessible, it may not be as useful for most purposes as a much smaller
one. On historical material, a 32 Kbps MP3 may serve most users better than
a 1.4 or 2.8 Mbps WAV. It will certainly be easier to distribute, hence to
access.
Mike
mrichter@xxxxxxx
http://www.mrichter.com/
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