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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 'x1' 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.〔http://www.powerdatarecovery.com/cd-dvd-resources/recordable-cd.html〕 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).〔http://www.myce.com/article/Why-DVDRW-is-superior-to-DVD-RW-203/〕 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).〔http://www.myce.com/article/Why-DVDRW-is-superior-to-DVD-RW-203/〕 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== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wobble frequency」の詳細全文を読む スポンサード リンク
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