Optical disc drive beam on a smaller spot size and to read smaller pits. DVD lens supports a different focus for CD or DVD media with same laser. With the newer Blu-ray disc drives, the laser only has to penetrate 0.1 mm of material. Thus the optical assembly would normally have to have an even greater focus range. In practice, the Blu-ray optical system is separate from the DVD/CD system. During the times of CD writer drives, they are often marked with three different speed ratings. In these cases, the first speed is for write-once (R) operations, the second speed for re-write (RW)
DVD-Audio DVD-Audio DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio uses most of the storage on the disc for high-quality audio and is not intended to be a video delivery format. DVD-Audio has much higher audio quality than most video DVDs containing concert films or music videos. The first discs entered the marketplace in 2000. DVD-Audio was in a format war with Super Audio CD (SACD), and along with consumers' tastes tending towards downloadable music, these factors meant that neither high-quality disc achieved considerable market penetration; DVD-Audio has been described as