Monday, May 23, 2005

Videotape Preservation Handbook by Jim Wheeler

Wheeler, Jim. Videotape Preservation Handbook. 2002. (PDF, 28 pages)

According to Wheeler's opening paragraph, his handbook is meant to be a resource for archivists, librarians, and others who oversee collections of videotapes. His first point (which is starting to sound familiar) is that magnetic tape should not be considered a long-term storage medium. Why? The medium itself, and the equipment needed to play it. His recommendation: "Migration must be considered element of all long-term archival plans."

Wheeler separates two kinds of restoration: 1) physical restoration, and 2) content restoration. The first involves "actions to stabilize and return a deteriorated or damaged tape as nearly as possible to its original condition." The second uses "video and audio enhancement techniques" to a copy (not the original).

The second section gives a brief history of videotape, its physical properties of tape (backcoat, substrate, binder, magnetic coating), life expectancy, and common problems such as sticky-shed syndrome, bad playback signals, edge damage or warped tape, and unstable video.

1956- First usable videotape recorder 2” Quad (Ampex)
Used to delay network TV programs for various time zones.
1969- Open reel video tape recorders in Japan ½”
EIAJ (Electronic Industries Association of Japan) standard. Affordable
1971- First successful cassette machine (VTR) ¾” U-Matic (Sony)
1975- First successful VCR for the home (VCR) ½” Betamax (Sony)
1976- VHS introduced ½” VHS (JVC)
1978- Type C open reel tape; replaced quad machines 1” open-reel tape
1987- Digital videotape recorder introduced D-1
Only top-of-the-line production studios used these.
1995- New digital videotape recorder formats used for industry and educational
markets.

There’s three impressive lists under Figures One-Three in the back of the Wheeler manual. Figure One gives the formats for analog videotape from 1956 to 1989. The columns give the year the format was introduced, the tape width (varies from 8 mm and 1/4” to 2 inches in width), whether it was open reel or cassette, its usages (either professional, industrial/educational, or consumer), an obsolescence rating (extinct, critically endangered, endangered, threatened, or OK), originating company, and any comments.

Figure Two gives formats for digital videotape from 1986 to 1996. the categories given include name, year of introduction, makers, tape width (.25” to .75”), tape thickness, hours per cassette, tape type (iron, metal particle, metal evaporated), compression, bits, and quantization.

Figure Three is a graph of format categories under which analog and digital videotape can be categorized; either composite or component.

Wheeler points out that VHS “is an analog format to make videotaped recording affordable to everyone, and it was not designed with high resolution and long life in mind.” Oh, boy. There are industrial VCRs, which are better than consumer brands. Another format called S-VHS (a component, analog system) is a little better than VHS (composite, analog)—but that’s no longer made. Wheeler discusses Betacam-SP which has been considered an archival format in the past.

The parts:
1) Backcoat: Thin carbon-black backcoat that minimizes electrostatic charge, to help maintain a uniform tape pack, and to prevent slippage.
2) Basefilm (Substrate): Our favorite: PET! Different thicknesses from original quad tapes to the most recent ones.
3) Binder- the jello
4) Magnetic coating- the fruit floating in the jello. Types of magnetic coating include: iron oxide (rust, used in quad tapes), cobalt-doped iron oxide tapes (Type C tapes), MP (metal particle) tapes for digital video and Hi-8.

For alleviating the problem of bad playback signal, Wheeler recommends cleaning the tap guides, adjusting the tape tension, or playing the tape on another tape recorder. Sometimes older formats will not work on machines intended for newer formats. He cites the example of High-Band Quad not being compatible with low-band quad. For “unstable video”, in the case of tearing, vertical rolling, or jiggling, Wheeler recommends “using a video processor or a time-based corrector to make the video stable.”

The sections on preservation management, includes recommendations for care and handling, reformatting, environment control, and emergencies. There’s also a useful glossary of frequently used terms—many of these terms I’ve learned for audio preservation. But not helical scan recording, coercitivity, magnetic remanence, or some other magnetism terms. Why didn’t I do better in physics in high school! Ack! Some other figures in the back show a cross section of magnetic tape, a graph of constant absolute humidity curves vs. relative humidity (looks like isoperm theory to me), and a comparison of data bytes per minute/hour of video.

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