[vorbis] Here we go again...

[David Balazic]

Uh , let me inject some facts into this thread. There are many,
many , many levels or error correction on an audio CD ( and even
more on data CD ). The Red Book should describe it pretty well,
but it is not available on-line for free. But there is ECMA 130,
which is supposedly the same as Yellow Book and should contain enough
information :

  Standard ECMA-130
  Data Interchange on Read-only 120 mm Optical Data Disks (CD-ROM) 

  2nd edition (June 1996) 

  available as PDF an PS at http://www.ecma.ch/ecma1/STAND/ECMA-130.HTM

I think it lacks info about the structure of the (sub)frames ( about the P,Q,R,
S,T,U,V,W channels , sync , parity info ). You can find that info on the web
though ( an exercise for the reader :-)

More links :
- Chip's CD Media Resource Center , http://www.chipchapin.com/CDMedia/index.php3
- just use google for Pete's sake !

Jonathon Fowler (jonof at dingoblue.net.au) wrote :

> Maybe I'm just forgetful but I was always under the impression that it 
> was the CD-R formats that wrote error correction data in the (2328-2048) 
> bytes at the end of each sector. I always thought the CD-audio format 
> never had error correction data and used the entire 2328-byte sectors 
> for audio data storage without error correction information, unless of 
> course I'm getting confused and really don't know the finer details of 
> the CD format as I thought I did. 
>
> Jonathon 
>
> craig duncan wrote: 
> 
> > Hongli Lai wrote: 
> > 
> >>On Monday 23 July 2001 14:38, you wrote: 
> >> 
> >>>On Sun, 22 Jul 2001, [Windows-1250] Jernej Simonèiè wrote: 
> >>>When standalone CD player (or your CD-ROM when playing through 
> >>>soundcard) encounters uncorrectable error on disc, it silences that 
> >>>part of audio, as it's less hearable that pop or click. However, when 
> >>>you digitally extract that same place, your ripper won't "turn the 
> >>>volume down" for the click, but will simply write it to disk. 
> >>> 
> >>> 
> >>Isn't it possible to detect read errors on disc, and then instead of 
> >>digitalizing the error, digitalize the correction? 
> >> 
> >> 
> > 
> > That'll be the s/w that defeats this particular scheme. Just a little ripper 
> > add-on. In regard to the question about pops & clicks vs. dropouts, the 
> > (above) implied answer is that you _don't_ experience a dropout because the 
> > CD format comprises a good deal of redunandancy in the form of extra error 
> > correction data. So they put errors on the disc but also the extra 
> > redundancy data to correct the errors. I can't believe anyone would think 
> > this would defeat the hacker community's ability to program a ripper that 
> > does exactly what Hongli wrote, though -- save the corrected data. 
> > 
> > craig 
> > 


-- 
David Balazic
--------------
"Be excellent to each other." - Bill & Ted
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