On Wed, 02 Apr 2008 15:42:23 +0800, Steve Underwood <steveu@dis.org>
wrote:
>Randy Yates wrote:
>> Hi Folks,
>>
>> I can't remember if I've asked this here in the past (I don't think so),
>> but a recurring problem I have is being able to recover the music from
>> an old audio CD that's become quite scratched. I'm aware of algorithms
>> such as cdparanoia (for linux) that attempt to reread problem areas and
>> reconstruct (interpolate - please no "definition" comments) bad data,
>> but in many cases the results are not satisfying and I believe a
>> simpler, "physical" approach such as simply cleaning up the CD surface
>> would have much better results.
>>
>> Sooo, does anyone have knowledge of good CD polishing kits or machines?
>> I'm not talking about a light scratch or two, but dozens (hundreds?)
>> of relatively severe, yet still on the surface, scratches.
>
>A lot of old CDs fail through corrosion, and I don't think there's much
>you can do about that. I live in a very humid climate, and a lot of my
>old CDs have failed in this way. I'd love to recover their contents.
>
>Obviously a very dirty CD needs cleaning, but what most people ignore
>about scratches is the diffraction grating effect of the very fine
>scratching which results from typical rubbing with a dry cleaning cloth.
>I've heard of immersion systems being used to effectively fill these
>scratches with a liquid of comparable refractive index. However, that
>isn't easy for most of us to try. Something more solid which fills the
>scratches, and won't be thrown off like a centrifuge, seems a reasonable
>goal. I don't know what would do the trick, though. Might some kind of
>clear wax polish work?
>
>Steve
There's a phenomenon called "CD rot" that has to do with poor
manufacturing processes used in the early days of CDs. That may be
what you're experiencing, but I think since then they should all be
pretty much hermetic and immune to environmental corrosion effects.
Dealing with scratches due to handling is certainly going to be a
common problem, though.
But, hey, the bloggers are telling us that music is going to all be
free here in just a little bit.
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
Reply by Ken Prager●April 2, 20082008-04-02
In article <m3prt8x5tf.fsf@ieee.org>, Randy Yates <yates@ieee.org>
wrote:
> Hi Folks,
>
> I can't remember if I've asked this here in the past (I don't think so),
> but a recurring problem I have is being able to recover the music from
> an old audio CD that's become quite scratched. I'm aware of algorithms
> such as cdparanoia (for linux) that attempt to reread problem areas and
> reconstruct (interpolate - please no "definition" comments) bad data,
> but in many cases the results are not satisfying and I believe a
> simpler, "physical" approach such as simply cleaning up the CD surface
> would have much better results.
>
> Sooo, does anyone have knowledge of good CD polishing kits or machines?
> I'm not talking about a light scratch or two, but dozens (hundreds?)
> of relatively severe, yet still on the surface, scratches.
> Hi Folks,
>
> I can't remember if I've asked this here in the past (I don't think so),
> but a recurring problem I have is being able to recover the music from
> an old audio CD that's become quite scratched. I'm aware of algorithms
> such as cdparanoia (for linux) that attempt to reread problem areas and
> reconstruct (interpolate - please no "definition" comments) bad data,
> but in many cases the results are not satisfying and I believe a
> simpler, "physical" approach such as simply cleaning up the CD surface
> would have much better results.
>
> Sooo, does anyone have knowledge of good CD polishing kits or machines?
> I'm not talking about a light scratch or two, but dozens (hundreds?)
> of relatively severe, yet still on the surface, scratches.
A lot of old CDs fail through corrosion, and I don't think there's much
you can do about that. I live in a very humid climate, and a lot of my
old CDs have failed in this way. I'd love to recover their contents.
Obviously a very dirty CD needs cleaning, but what most people ignore
about scratches is the diffraction grating effect of the very fine
scratching which results from typical rubbing with a dry cleaning cloth.
I've heard of immersion systems being used to effectively fill these
scratches with a liquid of comparable refractive index. However, that
isn't easy for most of us to try. Something more solid which fills the
scratches, and won't be thrown off like a centrifuge, seems a reasonable
goal. I don't know what would do the trick, though. Might some kind of
clear wax polish work?
Steve
Reply by Tim Wescott●April 2, 20082008-04-02
On Wed, 02 Apr 2008 00:02:20 -0400, Randy Yates wrote:
> Hi Folks,
>
> I can't remember if I've asked this here in the past (I don't think so),
> but a recurring problem I have is being able to recover the music from
> an old audio CD that's become quite scratched. I'm aware of algorithms
> such as cdparanoia (for linux) that attempt to reread problem areas and
> reconstruct (interpolate - please no "definition" comments) bad data,
> but in many cases the results are not satisfying and I believe a
> simpler, "physical" approach such as simply cleaning up the CD surface
> would have much better results.
>
> Sooo, does anyone have knowledge of good CD polishing kits or machines?
> I'm not talking about a light scratch or two, but dozens (hundreds?) of
> relatively severe, yet still on the surface, scratches.
I wonder if waxing may not be more effective, at least as a palliative
that would last long enough to get the data off the thing. The notion
being that if you polish down deep enough to get rid of the scratches,
you may well polish off some of the metal; on the other hand if you fill
the scratches with wax and polish _that_, you may be able to read data
that would otherwise be corrupted without further damaging the disk.
--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com
Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Reply by Randy Yates●April 2, 20082008-04-02
Hi Folks,
I can't remember if I've asked this here in the past (I don't think so),
but a recurring problem I have is being able to recover the music from
an old audio CD that's become quite scratched. I'm aware of algorithms
such as cdparanoia (for linux) that attempt to reread problem areas and
reconstruct (interpolate - please no "definition" comments) bad data,
but in many cases the results are not satisfying and I believe a
simpler, "physical" approach such as simply cleaning up the CD surface
would have much better results.
Sooo, does anyone have knowledge of good CD polishing kits or machines?
I'm not talking about a light scratch or two, but dozens (hundreds?)
of relatively severe, yet still on the surface, scratches.
--
% Randy Yates % "With time with what you've learned,
%% Fuquay-Varina, NC % they'll kiss the ground you walk
%%% 919-577-9882 % upon."
%%%% <yates@ieee.org> % '21st Century Man', *Time*, ELO
http://www.digitalsignallabs.com