RE: Scanning Rolls (Stahnke Method)
By John Grant
Hello Wayne (and List Readers),
Thanks for your shared information (to Steve Harder) about your roll conversion methodology. To the extent you can do so without undue time involvement or revelation of "trade secrets", I hope you can provide answers to additional questions about your apparatus which suggest themselves:
1. What is the basic sensor technology you use to sense the holes in the rolls? The obvious/traditional choices are pneumatic (vacuum or pressure) and optical (visible/IR/laser). Mechanical feelers are probably unlikely although something electro-mechanical (akin to the Mills V-V reader but more precise) could be attractive.
> The scanner determines the location of each leading and trailing edge of
> each hole with very high accuracy, on the order of 0.1 mm.
2. By what means do you advance the paper, i.e., is it bulk drawn by the take-up spool or with a capstan/pinch roller arrangement? Assuming the former, what is the lateral speed of the paper and do you use different speeds for different conditions? Assuming the latter, do you use a continuous advance (of what velocity) or a step-wise advance (of what size and frequency?)
3. What is the "ordinate" of the data being recorded? If it is "time" then I would assume you are reading by the bulk-drawn method at a speed that is nominally the same as the intended tempo of the roll. If it is "distance" (along the length of the roll) I assume a step-wise paper movement of the 0.1mm resolution you mentioned.
4. Assuming step-wise paper advance (of whatever values), is the state of each (and every) sensor determined before the paper is advanced to the next step or are the sensors "scanned" asynchronously with respect to step timing?
5. Does your method capture and/or allow for the duplication of chain bridging? Ditto for other (mostly visual) aspects of the roll including lyrics, "pump" lines (and other printed directives), graphics (Duo-Art Audiographic, etc.)
6. What data format do the image files emulate (i.e., are they MIDI .MID files) and what hardware/software would be used to perceive the data? In the case of "expression" rolls, are the expression holes recorded simply as their X-Y positioning dictates and/or is there an attempt to convert the expression holes into meaningful intensity values (such as MIDI velocities in the case of MIDI data) to enable accurate dynamic playback on the hardware for which the files are designed? If such conversion is accomplished, are the algorithms available for sharing?
> If there are some Recordo rolls you have a particular interest in, send
> them to me and I will scan them for you. The resulting images are small
> (on the order of 50,000 bytes) and are easily transferred by attaching
> them as files to e-mail.
Guess that's enough for now, thanks for your help. -John Grant |
(Message sent Mon 4 Mar 1996, 07:43:50 GMT, from time zone GMT-0800.) |
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