by Patrick Feaster, Media Preservation Specialist, Media Digitization and Preservation Initiative, Indiana University
In a previous post, I introduced the Strategic Media Access Resource Team, or “SMARTeam” for short: the intrepid crew responsible for getting audio and video media ready for MDPI to reformat. The preparation work they do involves a number of tasks—each item needs to be physically barcoded, for example—but none is more critical, or more demanding, than sorting by technical characteristics. The efficiency of parallel reformatting depends on having a supply of carriers that can be played on the same equipment with minimal adjustment, and that will each run for roughly the same length of time with no stragglers to hold things up.
Of all the audio and video formats the SMARTeam has had to sort by technical characteristics, the most challenging has been open reel audio tape, partly because of the sheer number of factors in play, and partly because some of the distinctions aren’t visible to the naked eye.
Consider track configuration—how the magnetic signal is arranged on the tape. Does one track take up the whole width of the tape, or are there two different tracks side by side, or four? And if tracks come in pairs, there’s a further question of sound field: are they two halves of a stereo recording, separate mono recordings, or duplicates of the same mono recording? If the metadata for a tape says it’s mono, and you play it as mono, but it’s actually stereo, you won’t notice that anything’s wrong—but you’ll lose all the stereo information. So it’s important to make this call correctly ahead of time and to route each tape to a machine with the right kind of playback head. But the SMARTeam ordinarily relies on quick visual inspections, and if you’re just holding a reel of tape in your hand, different track configurations won’t look any different from one another.
Another important factor is speed, or how fast the tape moved past the head during recording. In the United States, this is generally given in inches per second or “ips.” The options fall into a tidy geometric sequence—30, 15, 7½, 3¾, and so on—and a tape recorded at 15/16 ips will play for thirty-two times as long as a tape recorded at 30 ips, all other things being equal. But you can’t tell the speed of a tape just by looking at it.
Another factor is the tape stock, a distinctive tape formulation identified by company name and product number. Some polyester stocks are known to suffer from sticky shed syndrome, a problem that causes them to stick, squeal, and shed during playback, but which can be cured temporarily by baking at low temperature. We want to separate out all stocks on the sticky-shed list to be routed for baking. Meanwhile, other stocks that occasionally stick and squeal—such as Scotch 175—don’t respond to baking, and it’s not good for a tape to be baked needlessly as certain types may be harmed. We try to separate out these stocks too, so that nobody tries to bake them even if they have problems. Alas, tape stocks can’t always be readily identified. The stock type was usually printed on the containers in which tapes were originally sold, but sometimes tapes have been put in new containers, had their boxes switched around, or otherwise had this information obscured. Thickness can be measured with calipers, and acetate stocks are translucent, but beyond that, the SMARTeam can’t reliably recognize a random tape stock just from its appearance.
Fortunately, the people who recorded open reel tapes often documented details such as track configuration and speed in writing—in fact, many boxes were pre-printed with checkboxes and blanks for keeping track of that information. Sometimes engineers who’d played the tapes in the past took notes about technical characteristics and problems as well. Much of the risk assessment work that preceded MDPI involved collating this data for reference and analysis. When the SMARTeam began sorting open reel tapes for reformatting a couple years ago, these are the sources of information they used.
First up for digitization was a run of Jacobs School of Music performance tapes with wonderfully consistent and well-documented technical specifications. Nearly all of them were recorded at the same speed, and tape stocks and sound fields were mostly consistent by time period. Everything went swimmingly.
But then we moved on to some collections recorded under more varied circumstances, for instance by ethnographers doing fieldwork in various parts of the world. We knew that we’d encounter some tapes with unknown technical specifications and would need to find some way of dealing with those. However, we were surprised at how many tapes with technical metadata present instead had their specifications documented incorrectly. Information we thought we had safely in hand turned out to be wrong, which took a heavy toll on productivity. It was clear we needed to try some new approach to sorting—and that will be the subject of Part Two.