CD Audio and Data

[emeline-rec]

Ok, This is something that has confused me for a while.

Say we burn a audio CD-r at high speed then it is susceptible to a high error count. Also if we rip audio fast as a burst copy then lots of errors can happen. either way the audio is no longer exactly the same as the wav/aif we burned.

However we can copy data to and from a CD-r as fast as we like with no data loss. I believe this is the reason a DDP file would be favored by a manufacturing plant to an orange book CD-r.

So my question is whats the difference? surely digital data is just binary be it cd audio or a wav file on a CD-r so why are more errors created when dealing with cd audio as opposed to data files?

Thank you,

Ian

[Riccardo]

Error correction is different in Yellow Book (data CD-ROM) hence the reliability.

http://en.wikipedia.org/wiki/Rainbow_Books

[jamesp]

Originally Posted by emeline-rec

Say we burn a audio CD-r at high speed then it is susceptible to a high error count. Also if we rip audio fast as a burst copy then lots of errors can happen. either way the audio is no longer exactly the same as the wav/aif we burned.

All the errors in this process can be corrected - if you are doing things properly then the ripped files will be identical to the source files, no matter what speed you are working at. The only difference between audio and data CD's is that there is one less layer of error correction for audio CD's and some CD drives (and most software) don't handle audio errors properly.

Cheers

James.

[emeline-rec]

Originally Posted by Riccardo

Error correction is different in Yellow Book (data CD-ROM) hence the reliability.

http://en.wikipedia.org/wiki/Rainbow_Books

doesn't orange book deal with data as well as audio? this is quite confusing. from what i've read it seems any burnable cd comes under orange book. so does the data side of orange book have better error correction than the cd-da

ian

[Riccardo]

Yes it does....
"The recorded CD-R disc is “Red Book or Yellow Book compatible” so it can play back on conventional CD players. The CD-R format gives the possibility for both Audio (CD-DA) and Data (CD-ROM) recording. "

http://www.licensing.philips.com/information/cd/rec/

[Cojo]

Hi.

I've always been thinking of this as audio CD is a live data stream and because of this only have a limited amount of time to do error correction while data CD has all the time in the world and can repeat a section over and over again until it gets it right.

/Cojo

[dkatz42]

Originally Posted by Cojo

I've always been thinking of this as audio CD is a live data stream and because of this only have a limited amount of time to do error correction while data CD has all the time in the world and can repeat a section over and over again until it gets it right.

It's a holdover from the state of the art in technology when the format was defined (almost 30 years ago!) Good error correction requires several things--additional storage capacity (to hold the redundant data that makes error correction possible), sufficient RAM to do read-ahead (since the error correction takes time, and you don't want the audio to stop), and enough digital processing thrust to pull it all off.

All of this was rather difficult back in the bad old days, but can be done with a nickel's worth of sand today.

[emeline-rec]

thanks for your replys, thats clarified things a bit for me,

[jlsgear]

I'm a bit confused here ...

Isn't a file just a file ... audio or data? I'd thing the burning s/w wouldn't know the difference and wouldn't care ... but I must be missing something ....

imho It would differ if you were burning audio from a live source in real time ... hence the error correction s/w would have timing constraints ... but here we are talking about a resident WAV file ... and as such I can't see how the error rates could be different ...

jls

[jamesp]

Originally Posted by jlsgear

Isn't a file just a file ... audio or data? I'd thing the burning s/w wouldn't know the difference and wouldn't care ... but I must be missing something ....

Audio CD's and data CD's are very different. Audio CD's have a single long stream of data on them and no file structure. Data CD's have a similar long stream of data but also have an additional layer of error correction and a file structure which reduces the capacity of the disc. Have you ever wondered why a disc that holds 80 minutes of audio (800MB) will only handle 700MB of data? That 100MB is used up by the extra layer of error correction.

The error correction on audio CD's is fairly formidable as they stand with two levels of correction but the data CD adds a third layer. Most of the problems with audio errors when extracting CD's aren't down to the lack of error correction - they are more down to the poor audio error flagging on many CD drives and the lack of support for these flags in the extraction software. It seems strange, with the popularity of mp3 players and the widespread disc extraction going on, that more attention hasn't been paid to this but there are still many drives that cannot extract audio properly.

Cheers

James.