Re: [AV Media Matters] let's talk about DV.

[adam@adamwilt.com]

> Can anyone give me any real/concrete info?

DV is surprisingly durable (my comments are about consumer DV; I'll
discuss DVCAM and DVCPRO at the end). I have the tape that was being
used as the floor demo in the VX1000 I bought in October 1995. The
first thing I did was record parallel tests with Hi8 and with BetaSP
(camera recording internally and to an external deck of the other
format. The tests have since been played back perhaps a hundred
times each from the original tape; the DV scenes look exactly like
they did the day they were shot. There has been no visible increase
in dropout or other errors. I wish I could say the same about the
Hi8 or BetaSP test tapes; after perhaps 10-20 playbacks the Hi8 tape
was filled with dropouts and the BetaSP tape didn't hold up much
longer.

This same cassette has been stored in 90+ degree heat, without a
case, dropped on the floor, had its shutter opened to observe the
tape, and has generally been abused. Other parts of this tape have
been re-recorded multiple times, and most of the tape has seen over
50 playbacks. This is the famous cassette that fell into a cup of
hot tea (try that with BetaSP!), and, after carefully dismantling,
rinsing, and air-drying, seems none the worse for wear. I must admit
that the portion of tape that got chewed up in a jammed transport is
no longer playable, but aside from that it plays as if new. Yes, I
still pull it out and thrash it; I want to see what the eventual
limit is.

Nonrecoverable dropouts typically seem to occur one or two times per
tape with the inexpensive Panasonics. The cheap Sonys are a little
better, the pricey Sonys better still (often no noticeable dropouts
for several tapes in a row). This has been the experience of just
about everyone I've spoken with. Most dropouts I see are in
playback; replyaing the tape eliminates 'em. Some do occur during
recording though, and there are unfixable.

I have yet to have any tape-interchange problems as long as tapes
are recorded at SP speed. LP speed is a complete disaster, though;
LP tapes rarely interchange and often don't play back in the
transport that recorded them.

A couple of years ago I took a pratfall on the sidewalk, and my
VX1000 was the first thing to hit the ground. There are two gashes
in the magnesium body as a result. I was afraid I'd trashed the
mechanism, but the tape I had shot earler still played back, and the
tape I shot afterwards is as interchangeable as any other. The low
tape tensions, lightweight and simple transports, and the
auto-tracking servo of DV really seem to add up to a reliable and
robust system.

So far I've not seen any uncorrectable errors in 1394 dubs of DV
tapes. While DV lacks the sophisticated error correction of D-1,
D-5, or DigiBeta, dubs for the most part give identical results. The
only trick, again, is to watch for dropouts during playback, which
are not corrected; 9 times out of 10 redubbing the tape eliminates
the dropout. Bumping to DigiBeta is a nice idea, but impractical for
cost, compatibility, and storage-volume reasons for most DV users.

DVCAM is only more reliable, due to better tape QC and due to the
50% greater track width and pitch. DVCPRO is better still, and the
MP tape used may hold up better over time than the ME tape in DV and
DVCAM.

The DV formats are still young; 4 years old this month as far as
distribution in the USA is concerned. Still, I have yet to hear of a
single case where a DV, DVCAM, or DVCPRO tape failed to play back or
reproduce properly -- as long as LP mode recording was not used.

The immense volume of DV equipment being shipped means that even if
the format were dropped tomorrow, there would be so much gear out
there that  we could find playback/transfer machines for years to
come. Most Sony DV gear will play back DVCAM, and DVCAM gear will
play back DV as well (DVCPRO will usually play back DV and DVCAM
depending on model # and software version).

So while I agree in principle that sloppy analog formats may better
accommodate tape stretching and mechanical variations over time, my
experiences would SO FAR indicate that dubbing to dropout-prone
BetaSP is not a wise idea; keep it 1st-generation digital via 1394
dubs and transfer to another format in the future as circumstances
change. Since digital dubs are so easy to make, and incur no
generation loss, making backups and protection masters is a
no-brainer.

The biggest problem facing DV users is the lingering tape-lubricant
incompatibility between Sony and Panasonic tapes. While this problem
was supposedly solved when Sony reformulated their lubricants in
1997, I still hear about transports jamming when fed a single Sony
after a steady diet of Panasonics, or vice vera. The tricks here
appear to be (a) stick with one brand of tape in a particular
transport, (b) frequently change tape brands so that no single brand
can build up enough gunk in the deck to cause a problem, and/or (c)
clean the heads and guides if you need to change tape brands all of
a sudden. I've been freely interchanging Sony and Panasonic tapes in
my three DV machines all along (even before the reformulation) and
I've yet to have the problem myself, but I rarely run more than 5
hours on a single brand before running at least a few minutes of the
other.

More general DV info at http://www.adamwilt.com/DV.html; but I'm
updating the pages today, so things may be a little inconsistent for
a bit.

Cheers,
Adam Wilt