Friday, May 27, 2011

An old adversary returns.

The price of memories (to paraphrase Wendell Phillips) is eternal vigilance.  At least, that's the case if the memories are kept on videotape.  Way back, when a VTR filled a room, and cost (as memory serves) some 50x the annual salary of the engineer who tended it, one opened a tape box with trepidation.   Yes, readers, videotapes were once 2 inches wides, weighed a ton, and did come in a box.  There were essentially two makes:  Scotch and Memorex, and the latter, especially when not a new tape but, a year or so old, could contain a surprise.

The surprise was called, somewhat unimaginatively, the 'white powder' syndrome.  Said powder would be seen coating the top surface of the wound tape, sometimes loose in the box too.   The powder was a byproduct of chemical degradation in the tape -  assumed to be the 'binder' that held the metal oxide layer onto the polymer base of the tape itself.   At the very least, playback could involve frequent drop-outs of the signal, with possible clogging up of the magnetic heads, which entailed a tedious unthreading, spraying and cleaning of both the head assembly and the various guides and rollers that came into contact with the tape.   At worst, there was no playback at all because so much of the oxide had degraded.   This problem is immortalised in the 'White Powder Christmas' (1) and 'Good King Memorex' Christmas tapes of 1970's BBC VT fame - and although there are reports of similar degradation in some 1" archival tapes, I had thought it consigned to history and (literally) fading memories.   Until this week, that is.

In a fascinating report about the near disappearance and resuscitation of the BBC's Domesday 1986 videodisc, Andy Finney writes of the problems of playing a 1980's videotape (the master for the video sequences).   The laservision discs themselves haven't survived too well, either:  even discounting the problems of sourcing a working BBC-Micro based player to read the material, the discs are liable to delamination, rendering them unplayable.  But all's well that ends well, and there's now a 21st Century version of the Domesday material, on a website of course, accessible to all.  Though I have yet to do the sums, I suspect the entire contents of the original project, data and video, would fit comfortably in the SD card of a smartphone, which would have no problem in playing the lot!

Reading about these problems prompted me to check up on a couple of things, primarily the stock of family home videos (8mm video and VHS-C) and look what I found:


VHS-C (actually JVC brand VHS) from 1988





VHS (Sony brand) 1989

The good news is that both tapes were still playable - and have been hastily digitised - without major problems.  But I can't help thinking this was a close-run thing.  Other brands (TDK, Scotch S-VHS, BASF) from the same era don't show the problem.

Lessons for us all - especially if dealing with originals.
- have a quick check visually.  If in doubt, make safety copies.   But be prepared:  if it's VHS for instance, do you still have a VHS cleaning tape? (2)  VHS is no longer a mainstream standard, who knows what will be around in say 5 years time?
- don't assume that once you've made a digital copy, your archive is safe.  Welcome to the world of 'eternal vigilance' as you tend your hard drives, RAIDS, or digital tapes.


Phil

Footnotes:
1.  Despite what you might read on the internet, this is the true derivation of 'White Powder' - it's not a drug-related in-joke aimed at famous names.  Not deliberately anyway.  (That all came much later).
2.  Though I always used to reckon that playing a BASF tape was just as good as using a cleaning tape.  BASF tapes had a reputation for being slightly more abrasive, in my experience.