[78-L] Removal of 78 surface noise

[DAVID BURNHAM]

Jeff Lichtman wrote:

Figuring out what part of the groove corresponds to the original 
cutting stylus is worse than non-trivial. Really, if the groove shape 
deviates from the shape of the cutting stylus, how is one to figure 
out where the groove is supposed to be? Knowing the shape isn't 
enough - you need to be able to figure out the lateral displacement.

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If I understand what you're saying here, the lateral displacement is the property which contains the recorded signal.  The process I described will locate the groove, or more accurately the cutting stylus' position when the recording was made.  The sequence of scans will indicate the lateral displacement of the groove.

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Here's a reduction ad absurdum argument. Suppose you have a record 
that is completely wiped out - the original signal has been worn from 
the grooves, so all that's left is noise. It seems obvious that no 
playback system could figure out the original signal - that 
information is gone. It doesn't help to know what the groove shape 
should be because the groove is worn so badly that the groove path 
could be literally *anything* (within the range of the recording 
medium). I maintain that, in the system you're proposing, the 
difference between a completely worn record and one that's only 
slightly worn is one of degree, not kind. Knowing what the groove 
shape should be doesn't necessarily tell you what the signal is, 
because every bit of wear removes some information that may not be 
deducible from the remaining groove.

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To start off with, a record that is completely wiped out is not a record at all.   I'm not going to repeat everything I've written already, but as I emphasized in a previous posting, each scan contains no signal information whatsoever, the only thing which is accomplished by a single scan is that the position of the cutting stylus is established for that instant by any portions of the groove wall which correspond to the reference cutting style shape.