Date:         Wed, 24 Sep 2003 15:23:57 -0400
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         Samuel Brylawski <[log in to unmask]>
Subject:      Re: Optical Groove Digitization
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LC is a big place with room for differing opinions. James may be right
about 2-D, but maybe not, and many of us see several reasons to pursue
both 2-D and 3-D mapping. Two offices at the Library of Congress are
working actively with the Berkeley group to refine and improve 2-D as well
as 3-D.

Sam

On Wed, 24 Sep 2003, James L Wolf wrote:

>   Just wondering. Once the processing and storage capabilities for 3-D
> modeling of a groove arrive (10+ years?), wouldn't it also be possible
> to model a "perfect" stylus for that groove and create a result from
> their ideal virtual interaction? Would this be the best way to extract
> info from a groove?
>    From what I recall of the lecture at the Library by two guys from
> Berkeley who are working on something similar to the folks on the web
> page cited, creating a 3-D map of a groove doesn't require anything
> physical to be placed in the groove (if that's what you mean by a
> probe), just two linked "cameras" to plot the coordinates of each point
> of the groove. But it takes a hell of a long time. I think with current
> hardware and technology it takes a couple days to 3-D map a 2-minute
> cylinder, maybe more.
>    But 3-D is the only way to go. Jon Noring is absolutely right; 2-D
> is a waste of time. It only reads the edge(s) of the bottom of the
> grove, the results I've heard  (under relatively good listening
> conditions) were really poor, and vertical grooves are impossible, so
> there's no point in messing with it, except maybe for emergency
> preservation of broken laquers or something similar.
>
> James
>
>
> >>> [log in to unmask] 09/24/03 08:43AM >>>
> Dear All,
>     I agree, and must add another dimension to solving this problem -
> my
> twopennyworth! The only practical way to do a three-dimensional map of
> a
> groove (whether hill-and-dale, lateral, or stereo) is to use a test
> probe
> controlled by a digital device of some sort. However, there is no
> anti-aliassing filter for the data. Therefore the wanted sound is going
> to
> be corrupted by an enormous amount of aliassing, and ultrasonic
> components
> will become "folded down" into the audio spectrum.
>     The fundamental idea is a good one, but I'm afraid I cannot see how
> to
> get around this problem - *except* by playing the groove with a stylus
> and
> having an anti-aliassing filter *before* the result(s) are digitised.
> If
> anyone can think of how to conquer that, it *would* be a good idea!
> Peter Copeland
>
> -----Original Message-----
> From: Jon Noring [mailto:[log in to unmask]]
> Sent: 22 September 2003 22:46
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Optical Groove Digitization
>
>
> [Project Gramophone cc'd]
>
> Kurt Nauck wrote:
>
> > Have you seen this?
> >
> > http://www.eif.ch/visualaudio/
> >
> > Perhaps now the tinfoil playback problem has been solved!
> >
> > There is a description of this system in the July 2003 IASA Journal.
> > Fax: (425) 930-6862
>
> I've been intrigued for a long time with "optical" methods to preserve
> and to recover the "sound in the grooves." This work is definitely the
> next step in the right direction.
>
> My current thinking, however, for the most advanced playback of older
> recordings is to get a true, high resolution, 3-D characterization of
> the entire record. In essence, to create a very precise topographic
> "map" of the record. This way, the full information of the recording
> is preserved, and it may be possible, using a super-computer and the
> right algorithms, to do the highest possible quality "transfer" of the
> recording (interestingly, one may be able to precisely correct for
> complex warping of the records.)
>
> The problem with the current playback methods, such as a stylus
> running in the groove or the optical method noted in the article
> described above, is that they still "linearize" and mix information
> together, and once one does that, one loses a lot of information that
> otherwise will be useful for the best possible restoration.
>
> With the 3-D topographic approach, in principle one should be able to
> best ascertain what the original signal was based on full analysis of
> both walls of the groove, from the top of the record to the bottom of
> the groove. It may be possible to recover the original signal from
> some
> types of groove damage, and to minimize the effects of nicks and
> impurities in the record substrate (e.g., the abrasive particles
> records
> used to use to polish the steel playback needle -- these stick out
> like
> boulders in the groove path.)
>
> Of course, some challenges to this 3-D topographic approach are:
>
> 1) Huge amount of data: To get adequate 3-D resolution will require
>    sampling a *lot* of data -- I haven't figured it out yet, but we
>    are talking about many gigs at the minimum for a typical 10" 78rpm
>    disc. (But disk space nowadays is readily available.)
>
> 2) Coming up with the program and requisite algorithms to analyze the
>    data. It would not surprise me that it would take a super-computer
>    (such as a cluster of PC's) several hours to extract the optimized
>    signal from the grooves (if this is the case, then this project
>    could tap the huge reservoir of volunteer pc's out there, such as
>    what Project SETI uses.) Maybe I'm being overly pessimistic, and
>    that in the distant future this can be done quite fast and by the
>    "ordinary" restoration engineer.
>
> 3) And of course, how to actually scan for this data. There is no
>    doubt equipment/techniques that will do this, but it is unknown if
>    there is any "commercial" equipment that does this (there might
> be);
>    rather, it may still be in the province of advanced research at
>    places such as the National Labs, for example (I used to work as an
>    engineer at Lawrence Livermore Laboratory, and making high
> resolution
>    3-D "topographic" maps of surfaces is something that someone there
>    may have expertise in -- one of these days I plan to check if this
>    is so.)
>
>
> Just my $0.02 worth.
>
> Jon Noring
>
>
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             *********************************
Samuel S. Brylawski
Head, Recorded Sound Section
Motion Picture, Broadcasting and Recorded Sound Division
Library of Congress
Washington, D.C.  20540-4690
E-mail: [log in to unmask]
"Usual disclaimers apply"
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