Re: arsclist media preservation and access project

[Jerome Hartke <jhartke@xxxxxxxxxxxx>]

Don Cox wrote:
> 
> On 19-Nov-02, Goran Finnberg wrote:
> 
> > As I do loadbacks from Red Book CDRs and doing reguarly bit for bit
> > verifications I can state that it will do that without no appearent
> > problem at all.
> >
> > I´ve done that reguarly since 9 years back and I´ve never seen a disk
> > that I´ve done that isn´t bit for bit identical with the original
> > soundfile on my Sonic Solutions hard disk.
> 
> If you are using a Plextor or similar drive, you may be getting back the
> exact bits, but the system doesn't guarantee it. If the Reed-Solomon
> correction can't restore the exact bits, a normal player will
> interpolate. A computer drive reading a WAV file will never interpolate.
> 
> 
> Regards
> --
> Don Cox

Virtually all CD drives apply C1 and C2 error correction to each frame.
Some use a "super-correction" chip that uses feed-forward techniques to
flag C1 burst errors, thereby enhancing C2 ECC capability. Most CD
drives will apply interpolation and/or blanking should severe errors
occur when playing CD-DA discs. This method relies on a forgiving ear
that ignores a few milliseconds of distortion or silence.

Additional Reed-Solomon Product Code error correction is applied at the
sector level when CD-ROM Mode 1 or CD-ROM XA Mode 2/Form 1 discs are
read. WAV files sould be recorded in such a format. Interpolation and/or
blanking is never applied to these formats because missing data cannot
be replaced.

Jerry

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