Define ';constant angular velocity'; and explain how it applies how it applies to CD standards:?

Constant angular velocity of a rotating disk means that, given a stationary base reference line and a zero line on the disk, both extending from the center of rotation to the outside edge of the disk, the periodic change in angle between the two lines remains a constant. Such a disk will have constant angular velocity (CAV) if its rate of rotation or revolutions per minute (RPM) remains constant.





While it would be technically possible to have the linear velocity of the disk remain constant by gradually decreasing the speed of rotation as the player head moves across the disk (because the outer paths are longer than the inner ones), this would make things more complicated both for the recording and playback machines, and therefore more expensive.





The paths of information on a CD (or DVD) are analogous to the grooves on an LP recording. The recording and playback heads move across the disk (CD or LP) as it rotates. Actually, of course, there is only one spiral path or groove; on an LP, it goes from the outside edge toward the center; on a CD/DVD, it goes in the opposite direction. In deciding on the parameters for the LP and CD, engineers had to involve the amount of data to be recorded and the spacing required to record that data versus the size of the disk, the speed of rotation, the data capacity of the disk material, and the sensitivity of both the recording and playback heads.





The result of this engineering was set as the standard for recording audio LP's and CD's and, later, DVD's.