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* Some CD-R(W) and DVD-R(W)/DVD+R(W) recorders operate in ZCLV, CAA or CAV modes. The digital data on a CD begins at the center of the disc and proceeds toward the edge, which allows adaptation to the different sizes available. Standard CDs are available in two sizes.
The same disc types exist for 8 cm discs: ISO standards still regard these discs as Types A–D, while the DVD Book assigns them distinct disc types. DVD-14 has no analogous 8 cm type. The comparative data for 8 cm discs is provided further down.
The DVD and Blu-ray discs hold a higher capacity of data, so reading or writing those discs in the same 74-minute time-frame requires a higher data transfer rate. Drive speed can be limited intentionally to reduce noise from the drive or slow down ripping, such as the firmware component Riplock.
As of 2021, multiple consumer-oriented, optical-disk media formats are or were available: Compact Disc ("CD"): digital audio disc CD-R: write once read many (WORM) CD; CD-RW: rewriteable CD; DVD: digital video disc DVD-R: WORM DVD defined by the DVD Forum; DVD-RW: rewritable DVD defined by DVD Forum; DVD+R: WORM DVD defined by the DVD+RW Alliance
CD-ROM drives are rated with a speed factor relative to music CDs. If a CD-ROM is read at the same rotational speed as an audio CD, the data transfer rate is 150 Kbyte/s, commonly called "1×" (with constant linear velocity, short "CLV"). At this data rate, the track moves along under the laser spot at about 1.2 m/s.
The results of the power tests are stored in a Recording Management Area (RMA), which can hold up to 7,088 calibrations (in DVD-R). The disc can not be written to after the RMA becomes full, although it may be emptied in RW discs. CD-R, CD-RW, DVD-R, DVD+R, DVD-R DL, DVD+R DL, DVD+RW and DVD-R all have a PCA.
Warner Bros., which used to release movies in both formats prior to June 1, 2007, often used the same encode (with VC-1 codec) for both Blu-ray Disc and HD DVD, with identical results. In contrast, Paramount used different encodings: initially MPEG-2 for early Blu-ray Disc releases, VC-1 for early HD DVD releases, and eventually AVC for both ...
Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines through the disc to be detected on the other side. Optical discs can store analog information (e.g. Laserdisc), digital information (e.g. DVD), or store both on the same disc (e.g. CD Video).