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Absolute Time in Pregroove

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Absolute Time In Pregroove (ATIP) is a method of storing information on an optical medium, used on CD-R and other writable discs. ATIP information is only readable on CD Burners, as normal drives don't need the information stored on it.

Usage

ATIP is used as a method of putting data on an optical medium, specifically:

  • Manufacturer
  • Writable/Rewritable
  • Dye type
  • Spiral length in blocks
  • Rated speed
  • Audio

Function

Every writable disc has three layers:

  • lacquer (plastic) - top layer
  • metal - middle layer
  • polycarbonate plastic - bottom layer

The polycarbonate layer has a spiral groove that is pressed into it by a stamper, which the laser tracks as it is writing. This spiral has a "wobble" introduced into it, which allows the laser to reference where it is on the disc. This wobble is further modulated with what is known as ATIP.

Importance

These features are rather important to the function as it lets the drive know if it is writable. If the disc is re-writable, and the ATIP is damaged, it will not be able to write more than once. Also, it lets the drive know what is the maximum write speed available for the disc, and how much space (in blocks) the disc holds.

See also

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