Subject: [2-38] What's an ATIP?
(2002/12/11)
ATIP is an acronym for Absolute Time In Pregroove. All CD-R and CD-RW discs have a pre-cut spiral groove that wobbles slightly. The groove keeps the write head tracking properly, and the wobble (sinusoidal with a frequency of 22.05KHz) provides timing information to the recorder. The wobble is frequency-modulated with a +/-1KHz signal, which creates an absolute time clocking signal, known as the Absolute Time In Pregroove (ATIP).
In the lead-in area, which is at the start of the disc, the ATIP signal can be read to get some information about the disc. The only really useful bit of information is the number of blocks on the disc, which is determined by the length of the pre-formed groove.
The ATIP signal also holds some information about the disc's construction and manufacturer, but see section (2-33) for some comments about their usefulness.
http://www.orangeforum.or.jp/e/reference/index.htm used to have ATIP information, but the "Disc Identification Method" link is now password-protected.
Subject: [2-33] Who *really* made this CD-R blank?
(2000/09/03)
Many of the "big name" media manufacturers don't actually make their own media. Instead, they buy from other manufacturers and stamp their logo on the discs. Generally speaking, this isn't a bad thing, because the discs were certified good enough that the Big Brand was willing to put the company name behind the product.
If you have a picky recorder or player, though, it helps to be able to try several different pieces of media. If you buy several different brands, and they're all coming from the same manufacturer, chances are they'll all behave the same way, and your time and money will be wasted.
So... how do you tell who really made a piece of media? The short answer is: you don't.
It's tempting to believe that CD-R media identifier applications (e.g. section (6-2-9)) will give you the answer you need. Unfortunately, the data you get is unreliable at best. Charles Palmer, from cd-recordable.com, had this to say about the manufacturer identification:
"Two components that many users of these programs always take as gospel are Media Manufacturer and Dye Data. These two readings are next to worthless.
The reason for this is that many CD-R manufacturers (like CD- Recordable.com) purchase their stampers (the nickel die that all CD-R substrates are molded from) from 3rd party sources. These 3rd party sources (either other disc manufacturers, or mastering houses) encode the data that these 'Identification' programs read, at the time that the original glass master is encoded. The 'Manufacturer' information that is encoded is usually the name of the company that made the master. Since stampers made from that master will be sold to disc manufacturers the world over, all of discs that those manufacturers produce from those stampers will contain the same 'Manufacturer' information. Information which is obviously quite erroneous and irrelevant. Very seldom will the 'manufacturer' information encoded on a CD-R actually tell you anything other than who made the original master. [...]
The second piece of data (the dye type) is also dubious. Because most master/stamper configurations are designed to be matched to specific dye types (Phthalocyanine, Cyanine, Azo, Etc), the 'Dye' information that is encoded when the master is produced indicates the type of dye that the master was designed for. This of course, does not assure that the manufacturer that buys and uses this stamper will be using it with the dye that it has been designed for. It is quite possible that a stamper/dye combination is used by a CD-R manufacturer that contradicts the 'dye' information encoded on the master. Therefore that information becomes as potentially misleading as the 'Manufacturer' data discussed earlier."
The only reliable piece of information in the "ATIP" region is the disc length. See section (2-38) for further remarks.
