Re: Concertolas and Roll Scanning/Digitizing
By Jody Kravitz
Marc,
I'm always interested in new methods of conversion. Do you know what the "straightforward manner" is that is used by Mr. Heyworth ?
Here's a quick (and overly terse) review of what I remember about "roll digitizing projects":
One of the advantages of optical scanning is that you can resolve a spot much smaller than a tracker bar hole. You save the image data and then apply whatever "tracker bar algorithm" suits you later. Remember that on some instruments the tracker bar holes are not identical (some are not the same shape and some come slightly early). The properly adjusted pneumatic reader with micro-switches on the pouches will do a great job on a roll intended for the particular tracker bar, but the "interpretation" is done pneumatically [Wayne Sankhe and others use this method. For good quality control, there is quite a bit of monitoring/adjusting that goes into the process. Its not a "one size fits all" solution. Although Mills Novelty company used wire brushes through the paper to read rolls, (and David Wasson has built a Midi reader for his hand-cut band organ rolls this way) I'm skeptical that wire brushes are a good idea, because of noise (contact bounce) and wear-and-tear on the roll. One of our readers has built a "scanner" by stuffing photo-diodes into the holes of a tracker bar. This system has some problems with translucent paper and doesn't exactly reproduce the behavior of the pneumatic pouches, but is very clever, inexpensive solution. Applying polarizing filters to the system might solve the translucent paper problem. The direct optical scanning approach also has its problems, with ink and other artifacts on/in the paper (word rolls must be scanned from the back). A full-color scanner might provide for correct interpretation in spite of paper artifacts by some clever multi-color lighting scheme. Kravitz/Ames and Zoltan Janosy both have experimented with monochrome optical scanning with good results. Both of those projects had their problems. Zoltan contracted out the scanning, which was both slow and expensive (but very accurate) and Kravitz/Ames used an inexpensive fax scanner (Chinon DS-3000 with modified firmware) but it is slow (40 scans/second), and is not grey-scale. I (Kravitz) have recently purchased a Hewlett-Packard Scanjet 3p, which is 8-bit monochrome (grey-scale) and may be able to scan as fast as 120 lines/second. If its firmware could be modified to scan continuously, it might represent the cost-breakthrough which is needed. I paid $315.00 plus $18.00 for shipping to USA-Flex (mail-order). I did the reverse- engineering on the Chinon Firmware. I'm not sure I want to do another one! I'd be happy to consult/advise anyone who wants to embark on that project. A guy at the MIT medial lab has done two scanning projects, one using a linear CCD array (similar to a fax scanner) and then later using a standard NTSC camcorder and a "frame grabber". He felt that this method allowed him to get the temporal information more easily (all the other methods require some kind of paper speedometer as an auxiliary input the the recording computer). I'm personally skeptical that the frame grabber solution works for all rolls (we've been scanning Aeolean Residence Organ rolls which are around 178 holes wide) because of the limited horizontal resolution, but prices for NTSC (standard US TV) cameras and frame grabbers are dropping dramatically. Putting the frames back together can be "interesting. When Mike and I started our project we were using a 386/SX-25. Now P5-90's are available for same price and P5-133's or better are available if necessary. There's still the issue of paper-transport, which is non-trivial if you want to be sure an old roll doesn't get "eaten".
Please don't give up in your pursuit of digitized roll music!
Jody
P.S. I'd really like to hear from others who have done or thought about roll digitizing. There's an amazing amount of material out there to be digitized... |
(Message sent Mon 20 Nov 1995, 03:56:40 GMT, from time zone GMT-0800.) |
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