> According to Johan Vromans:
> > [...] They claim it makes CDs uncopyable, and that they
> > even cannot be played on computer CD-ROM drives.
>
> Can they be played on my regular CD player, e.g. my Philips CD 880 from
> 1986? If so, fine, otherwise, the product is flawed and I return it.
>
> Does anyone know such a beast or is there even a list of them on the
> internet? If borken CDs are around, this should be documented so that
> other consumers can take this into consideration...
Based on what I've read recently, this copy-protection scheme works by
deliberately introducing errors into the audio data - mangling the
data and the Reed-Solomon C1/C2 error correction bits. In theory, a
regular audio CD player will see this situation as an irrecoverable
read error, and will use its error concealment logic (waveform
interpolation, or brief muting) to make the error inaudible.
Many CD-ROM drives do not implement error concealment in their SCSI- or
IDE/ATAPI-bus data ripping interface. If an CD has an error which
cannot be corrected by the C1/C2 codes, the CD-ROM drive will
frequently return the un-corrected/mis-corrected data over the bus,
with no warning at all to the host software. I first ran into this
problem with the MKE (Panasonic) CD-ROM drives used in the 3DO
videogame system - we had to get MKE to add error concealment to the
bus interface in order to avoid occasional pops, bangs, and other
nastiness during play.
According to the claims in the press by the creators of this
technology (I believe it's a Macrovision thing but I'm not sure), the
CDs which are pre-flawed in this way are playable in all "normal" CD
players, but can't be ripped in CD-ROM drives.
Naturally, any PC which plays CDs by ripping the data and sending it
to the sound card via the PCM interface will have trouble playing
these discs. Older PCs, which use CD-ROM drives with on-board DACs
and error-concealment logic, and a separate analog cable to the mixer
input on the sound card, will probably play them OK.
I don't know to what degree some of the newer, more-sophisticated CD
players might have trouble with these discs. It's possible that some
car players, or portable players having anti-skip buffers, might also
find these discs less than fully digestible.
Several interesting questions come to mind:
- Are there CD-ROM drives which can already "rip" these discs
accurately, by implementing error concealment on the data sent over
the bus interface? I'd be interested to see how well Plextor
drives do, as these have an extremely good reputation for ripping
quality.
- Will CD-ROM drive vendors upgrade their firmware to add error
concealment, or start shipping new models which have it? If so,
will the music labels file criminal charges against the drive
manufacturers, claiming that such firmware violates the Digital
Millennium Copyright Act by creating a copy-protection
circumvention device?
- Will Philips and/or Sony declare that discs manufactured in this
way are violating the Red Book specifications, to the extent that
they can no longer use the "Compact Disc" logos on the disc and
packaging?
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