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Re: CDs, was DATs, Was Re: arsclist Duplicating casette tapes

Richard L. Hess wrote:
> At 09:43 AM 08/10/2002 -0700, Jerome Hartke wrote:
> >Our FAQs at http://www.mscience.com/faq.html point out the problems of
> >using BLER as a sole indicator of quality. Drill one 2 mm diameter hole
> >in the information area of a CD, making it unreadable in most drives.
> >BLER will increase slightly but will remain well within spec.
> Jerry, this raises an issue that I've heard mentioned but don't understand.
> When the AUDIO CD was introduced in whatever year at the AES, I recall SONY
> marketing people using electric drills to randomly drill 1/8 inch (~3mm)
> holes in CDs and showing how well they played.
> The "thing" that I've heard is that CD-ROM drives have one less layer of
> audio error CORRECTION than Audio CD players, but yet I've also heard that
> DATA is more robust than AUDIO.
> Informal experiments have borne this out. Perhaps I heard incorrectly and
> the process that is missing from CDROM drives (even when playing audio
> discs) is error CONCEALMENT.
> I would appreciate it if you could take some time and explain the layers of
> CORRECTION and (obviously CONCEALMENT for audio only) that are available on
> the CD and the DVD. I say the latter because people make claims that the
> error CORRECTION on the DVD is 10X better than the CD.
> Richard

CD-Audio had two levels of cross interleaved Reed Solomon error
correction in each 24 byte frame. CD-ROM Mode 1 adds a layer of Reed
Solomon product code at the 2K sector level, enhancing error correction.

DVD uses Reed Solomon product code in a 32K ECC block. It is more
powerful than CD-Audio, and comparable to CD-ROM Mode 1, but it
certainly is more efficient.

CD-Audio drives optionally use either interpolation or concealment
(blanking) when errors are uncorrectable. They would be used when audio
errors are severe, but also introduce some distortion.

See http://www.mscience.com/faq.html for additional information.

Media Sciences, Inc.

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