DVD drives are divided into those that can only read and those that can read and write. In the first case, we speak of DVD players, in the second of DVD writers. Due to the large number of DVD formats, there is a high degree of incompatibility among DVD drives, mainly among DVD writers.
DVD writers usually work slower in write mode than in read mode. In addition, the write speed is reduced considerably when rewriting. For this reason, several speed values are given in the specifications for DVD writers: The read speed, the write speed, and the rewrite speed. In addition, it should be noted that DVD writers write different DVD formats at different speeds and that some DVD drives can also play CDs.
DVD drives use a red light laser with a wavelength of 650 nm (635 nm) to scan the spiral track, which has much smaller spacing than the compact disc( CD), whose laser has a wavelength of 780 nm. They have error correction with Reed-Solomon code, which is particularly powerful and offers a very low error rate. The single speed data transfer rate of DVD drives is 11.08 MB/s, which is about 6 times that of CD drives. DVD recorders offer disk-at-once operation( DAO) and incremental writing in track-at-once operation as write methods.
Backward-compatible DVD drives, which can also read compact discs (CDs), operate with two laser systems, an infrared laser with a wavelength of 780 nm and a red laser with a wavelength of 650 nm.
DVD drives are used for data storage in personalcomputers and as mass storage in jukeboxes.