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How does a CD recorder identify audio blank cd's

post #1 of 4
Thread Starter 
I have a CD recorder deck in my home system. I also burn CD's with my computer.

The CD recorder requires AUDIO blank CDR/s CDRW/s, and will not use computer blanks. How are they "marked"/identified?
How does the audio recorder know they are audio only cd's?

I just wondered, because I would like to erase audio cdrw's on my computer, and wonder if any writing on the computer will ruin the audio type cdrw's for use on the audio deck.
post #2 of 4
Each recording medium loses some of the available recording density to what is called "overhead." For example, when MiniDisc recorders record in LP2 mode, they only record at 132 kbps instead of half of 146 kbps because they need to tell non-LP-mode compatible players not to play any sound (as opposed to static noise).

I believe that overhead is also written onto the disc before use. So I would guess that an audio-only CDR would have some information at the beginning identifying itself as such to the CD recorder. As I understand it, this is done so that artists can be reimbursed for unlicensed copies of their music in consumer-level CD recorder decks. That's why you pay a tax on audio CDRs.
post #3 of 4
Thread Starter 
I am sure each disc is "marked" with overhead as to what type of disc it is.

But how?

Is it located as "standard" optical data in the center of the disc?
Someone told part of the tracks can "wobble", and the CD unit reads data from this "wobble". Sounds shakey to me.

What I need to know is

1) How is the information encoded or located on the CD.
2) Can you write or erase and AUDIO CDRW on a computer burner and still use it on an audio recorder for recording?
post #4 of 4
The blanks are the same as regular CDRs, when it comes to the material, and the extra $ is just to cover royalties paid to the record industry. The manufacturer pays a royalty to a studio consortium under the assumption that everything recorded to an audio CD-R is pirated material.

Some units have tricks that allow you to use normal blanks, but I'd say that in most cases it will require firmware alterations.
You can see it as something similar to mod-chipping DVD players to become multizone, for instance.

I have not used audio blanks, but I'd say almost for sure that the bit defining that it's not a regular blank is probably stored in the ATIP of the discs (A pre-written section of the disc that specifies disc characteristics, including the number of blocks on the disc, type of material, manufacturer, and perhaps more data). At least I'm not seeing anywhere else to put it.

So the answer is, no, you cannot change the ATIP, and if you erase RW media, the ATIP will always remain the same (and your stand-alone burner will still eat it happily).

ATIP btw comes from "Absolute Time In Pregroove", which is the main use. Pre-groove because it tells you how many blocks are in the groove that is already made in the CDR for your burner's laser to follow and burn. That's why your units tell you the exact size of a blank when you insert it.. they don't scan the whole CD... only read the value stored in the ATIP... unfortunately... other things can also be stored there.
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