Test Media - Page 5

Philips SBC-444A

- Purpose

This disc has built-in defects that can be used for checking error rates. In addition to providing known errors, it tests the player under maximum stress. The purpose of this disc is adjustment / checking of the CD player. Note that the disc is not within specification concerning local defects. The defects found on the disc are interruptions of the information layer, black dots at out-read area, and simulated fingerprint.

Disc SBC 444A provides two kinds of defects: Missing information, and black spots. The tracks with missing information should provide fairly repeatable results since these errors are encoded into the data. The sections with Black Spots have the information in tact, but obscured by the black spots. In this case, not only is there information lost, but the servomechanisms are stressed. For example, when the readout beam encounters the black spot, focus, track following, and clock recovery servo signals disappear. After the beam has passed the black spot and the signal is restored, the pickup is out of focus, off track, and the bit clock is at the wrong frequency. This causes many additional errors to be generated in an unpredictable way.