ARCHIVAL Requirements not the Same as for Acquisition/ Distribution/ Viewing

By Jim Wheeler
June 24, 1999

We are in a digital revolution and archivists are being told to jump on the digital train. Most technical people are advising archivists to transfer their video material to one of the small digital videotape formats, such as DV or DVC-PRO. These formats make nice looking pictures, the cassettes are small, and the cost of the equipment is reasonable.

Or, why not DVD? Anyone who has viewed a movie on DVD has to be impressed with the picture quality.

All of the Post-Production houses have gone digital, so everything that we see on television today has been digitized in some way.

So, if everyone else is switching to digital, why shouldn't archivists?

The simple answer is that archivists have a different agenda than consumers and the people in the broadcast television business. Archivists must select a medium that has the best chance of surviving for many years, AND archivists must select a system that will not alter the recorded material.

There is nothing wrong with digital, per se. Wether or not a particular digital videotape format is adequate as an archival medium depends on the durability of the tape being used and how the audio/video signals are processed.

The main problem with the low-cost digital formats is that they are heavily compressed. That is okay with most people but a no-no for archivists. Also, all of the low-cost formats sample the incoming signal at a low rate and that means that much of the detail is lost. A good sample rate is 10 bit at 4:2:2 and none of the low-cost formats can handle that rate. Additional issues are those of thin tape and the robustness of the cassette.

There are several possible problems with DVD as a video archival medium. One is that DVDs use heavy compression, and compression discards some of the finer details of the original. The second problem is that archivists will use the recordable DVD and there have been no tests that prove that a disc recorded on a machine made by one manufacturer will play on machines made by other manufacturers. There is also the potential problem for DVDs to delaminate. Some DVDs have an adhesive to hold the two halves together and adhesives have a bad habit of coming unglued after a few years.

The main problem with the high-quality digital videotape formats used by the post-production houses is that the equipment is very expensive. The cheapest is D3, and a D3 tape machine costs around $30,000 US. D5 is a great format but a D5 machine costs $60,000-$70,000 US. For most archives, the high price associated with the high-quality digital videotape machines make them unattainable. Digital Betacam is 4:2:2 at 10 bits but it does have some compression.

These prices are for Standard Definition Television (SDTV) which is NTSC, PAL, and SECAM. You can double or triple the price if you want a High Definition Television (HDTV) machine. In the HDTV world, Panasonic has a modified D5 that records 1080i HDTV, Toshiba has a D6 machine that records 1080i, and Sony has a 1080i machine.

Why isn't there a good archival digital videotape format? The answer is that consumer and broadcast television are the big markets--not archives. There are only two companies making videotape recorders and they are Sony and Matsushita (Panasonic and JVC). For them to manufacture a machine for the archival market, they must be convinced that there is a market there. To show that would require a survey that would indicate how many machines would be sold over X years at a cost of Y dollars each.

Until there is a good archival digital videotape format, it is best to stay with analog. Betacam-SP is the best of the analog formats, but some of the cheaper Betacam-SP machines have quality problems.

For acquisition, distribution, and viewing, several of the digital videotape formats would work. If you do not have a technical person on your staff who can assess the pros and cons of each of the low-cost digital videotape formats, a call to the chief engineer at a local TV station should do it.