Archiving video data

[Brian MacWhinney]

Dear Info-CHILDES,

  About a week ago, Erika Hoff posted a message to info-childes outlining
the results from a query about how to best archive video data.  The
suggested method involved the use of CD-ROMs to store data in either
QuickTime or some other compressed format.  I think the idea was that, once
this was done, you could then recycle your original media.
  I would like to point out some potentially serious problems with this
approach to video archiving.  If the goal of the archiving is only to
maintain some basic in-house record that will never be modified in any way,
then the CD-ROM solution is a good one.  After all, the price of CD-ROMs now
has fallen so extremely, that they are about at the level of the diskette of
five years ago.  (By the way, current prices of 10 cents a disk are an
aberration and they will soon rise back to about 30 cents a disk.)  However,
if the project has other potential goals, then CD-ROM archiving has some
problems.
  When one archives data on CD-ROM, it has to be in some compressed format
such as MPEG, Sorensen, or QuickTime.  Raw video data is huge, perhaps as
much as 40 times as big as compressed data. So archiving raw data on CD-ROM
is not a possibility.
  Why would one want to archive raw data?  Let me suggest four reasons (all
based on hard-won personal experience):
1. Editing.  You may want to create a sample of your data based on segments
for playback to classes and colleagues.  Once you have compressed your data,
this is no longer possible.
2. Changing format.  New compression schemes continue to emerge.  Once you
have compressed in one, you can't reverse that compression and switch to
another better format.
3. Changes within format.  Often I find that I didn't map stereo channels
correctly or didn't select the right compression options.  If I throw away
my raw video, none of these errors can be repaired.
4. If you created a transcript and linked it to a video in CLAN and then
went back to change something, all of the links you created will be wrong.

So, what is the solution?  The alternative is to also keep the raw data on
the mini-DV tapes on which it was recorded.  If the original was VHS, the
best method is to first take the VHS to mini-DV and then use the mini-DV as
the archive.  For this scheme to work, you have to rely on good archiving of
your editing script file in your editing program (Final Cut, Premiere,
iMovie).  If you archive this list, you can always just reload the mini-DV
cassette and redigitize the movie.  If you do this, all of the links you
created in CLAN for the time values in your movie will still be good.

So, it seems to me that, if your data is important to you, if you are the
type of person who ever makes a mistake, and if your project has sufficient
funds, the best archiving method relies on keeping the mini-DV and the
accompanying edit script file, as well as the compressed product on CD-ROM.
If you never make mistakes, never change formats, never plan to work with
other projects, and don't have enough funds, then CD-ROM archiving without
mini-DV archiving is OK.

--Brian MacWhinney