Wobble frequency

Optical discs with the exception of the DVD-RAM have their data encoded on a single spiral, or a groove, which covers the surface of the disc. In the case of recordable media, this spiral contains a slight sinusoidal deviation from a perfect spiral. The period of this sine curve corresponds to the wobble frequency. First of all, it is used as a synchronization source to achieve constant linear velocity while writing a disc. The frequencies quoted all assume that the disc is being written at the '1x' speed. The frequencies are appropriately higher for faster writing speeds.

CD-R and CD-RW discs, use a frequency modulated wobble of 140.6 kHz to encode some information, such as Absolute Time in Pregroove (ATIP) into the groove.[1]

DVD-R and DVD-RW have a constant wobble frequency of 140.6 kHz relying on data 'pits' beside the groove to convey information (Land pre-pit).[2]

DVD+R and DVD+RW have a constant wobble frequency of 817.4 kHz, but encodes its addressing information by periodically inverting the phase of the wobble signal (bi-phase modulation) to encode an exact address of the location on the spiral track (Address in Pregroove).[2] The practical upshot of this arrangement is that the recording drive can navigate to an exact location on the DVD+R(W) disc whereas it cannot do so with the DVD-R(W).

BD-R and BD-RE discs utilise Address in Pregrove.

HD DVD-R and HD DVD-RW uses the land pre-pit system of the common or garden DVD-R(W).

References

  1. ↑ "Recordable CD". Retrieved 24 April 2017.
  2. 1 2 "Why DVD+R(W) is superior to DVD-R(W) - Myce.com". Retrieved 24 April 2017.


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