[sdiy] OT: Scratchy CDs

[ChristianH]

Hai again,

I did some spec digging, and now it's getting a bit clearer.
There are several levels of CD error correction. 

There is the low level parity check (well, actually it's two parity
checks in a row) in each frame, which contains 6 stereo samples. It takes
588 channel bits (pit/land bits) to code those 6 samples (192 payload
bits) - that's quite a ratio...

Then there are blocks aka sectors.
- On a red book audio CD these blocks are completely used by audio data
(2352 data bytes, containing 1/75 sec of audio data, plus sub-channel
data), without any further ECC.
- On a CD-ROM those 2352 data bytes are divided into 2048 user data
bytes and 288 high level ECC bytes (plus some sync and header stuff).

So, it's good to know, that burning audio as WAV or AIFF should benefit
>from additional CD-ROM error correction safety. That should be able to
cope with those small scale errors I had seen with some audio CDs.

And for the question, whether ripping an audio track does error
correction - I think it's safe to assume that low level correction does take
place, but high level correction can't be used - it's simply not present
on an audio CD.

Christian



On Thu, 25 Sep 2003 15:55:14 +0200 Ingo Debus wrote:

> 
> Am Dienstag, 23.09.03 um 17:56 Uhr schrieb john mahoney:
> 
> >
> >>> The error correction process for an audio CD ...
> >>
> >> Does this error correction also work when a track is "ripped" (or
> >> however it's called) via a CD-ROM drive in a computer? ...
> >
> > Eerror correction is part of the Red Book spec for audio CDs. So yes, 
> > it is
> > there on writeable CDs, too. The usual burn errors are not due to a 
> > simple
> > lack of error correction code.
> >
> 
> I didn't mean burn errors. I was talking about errors that occur when a 
> track is read from an audio CD (not necessarily a CD-R) onto a 
> computer's hard disk.
> 
> Ingo