On Thu, 28 Jun 2001, Warwick wrote:

> >This is also how CD's work, ever wondered why they can be scratched lots
> >and still play quite happily ?
> >(off topic but still interesting :) )
>
> I am not so sure. I thought on a cd the interleaving was so that after the
> buffer has emptied, the next sector under the read head is next one
> required. If you do not interleave and have the data in consecutive sectors,
> as the buffer empties the next sector has just passed so you have to wait
> for the disk to do one whole revolution for it to come around again.
> Therefore the purpose of interleaving a cd is not for noise protection but
> for speed.
> By the nature of cd's, if you scratch them you are not going to scratch
> along sectors anyway - but across them. So the errors caused by scratches
> would be by nature "single bit(ish)" rather than continuous burst, wouldn't
> they?
> I wonder if Audio cd's have any CRC/parity involved at all. They seem very
> fragile. By comparison data cd's seem considerable more robust. From my
> personal experience anyway.
>
> cheers
> Warwick

sorry to ressurect an old topic, some may still find it interesting, the
following link..

http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/95x7.htm

explains it quite well, and even the less technical should be able to
follow his basic example of simple error correction by scrambling :)

--
Steve.
(who couldnt make sense of his own tech notes and so found them on the
net :) )
This message is part of the NZ ADSL mailing list.
see http://unixathome.org/adsl/ for archives, FAQ,
and various documents.
To unsubscribe: send mail to majordomo@unixathome.org
with "unsubscribe adsl" in the body of the message