On Sun 1 December 2002 23:42, Hanspeter Roth wrote: > Hello, > > what is the difference of an `audio-CD' compared to a `data-CD'? > Does it have something to do with the `restricted' attribute?
Not directly. The difference between a data and an audio CD is the way the bits are laid out on the disk. There are a whole lot of standards that specify exactly how the data should be written to the disk for it to be a legal audio CD, or data CD, or CD-I, or Video-CD, etc. These standards cater to different needs, for example the Red Book audio standard specifies that there should be extra data on the disk to recover from errors caused by scratches for example, and also exactly how this should be encoded. Video CD's need more capacity and it's not that bad if there's a couple of pixels that are bad now and then, so they don't have this error-detection and correction code. For data CDs it's absolutely imperative that every single bit is correct, so they have much more error correction code. Anyway, these standards are the coloured books. You may have heard of the Red Book standard, which describes the audio CD format; all the other formats have differently coloured books. The CDDA (Compact Disk Digital Audio) format was created by Philips, and they own the trademark on CDDA. Audio CDs that do not adhere to the Red Book standard are not Audio CDs at all, and may not carry the CDDA logo. The new "copy-protected" CDs the big record companies have been selling lately have defective error-correction codes or are formatted so that they seem to be a multi-session disk (amongs other things, different technogies exist). Normal CD players only understand standard Red Book CDs, and don't know anything about the other formats, so they just ignore the part that says "I'm a multi-session CD" and play it. CD-ROM drives are usually smarter, see the multi-session layout, and then get confused because the disk is not layed out as a multi-session disk. So you can't rip the CD (unless ofcourse you use a felt-tip pen to black out the part of the CD that causes the confusion, in which case it will work just fine again). The bad thing is that if you buy such a CD, you can't rip it and encode it as MP3s to use with your portable MP3 player, and you can't play it in your computer. Or, if the error correction codes have been tampered with, the disk will be of lower quality because real errors can no longer be corrected anymore. At any rate, because these CDs don't follow the standard, they are not CDDAs at all, and that's why J�rg referred to them as "coasters in CD shape". The Red Book CD format does not have any "restricted" attributes or anything, there is no kind of DRM built-in whatsoever, which is part of the reason why the format became so popular. I read a couple of reviews of the new download-DRMmed-music services the record companies are starting, and they really seem to be more trouble than they're worth, with you needing a Windows PC and special software and then it still only works now and then. I'll stick to buying (non-restricted) CDs for now, preferably from small labels... HTH, Lourens -- GPG public key: http://home.student.utwente.nl/l.e.veen/lourens.key -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
