Double Density CD - Page 8

DDCD Recordable and DDCD ReWritable Structure

An unrecorded DDCD-R or DDCD-RW disc does not have an EFM to find the physical track in the traditional way of DDCD read only drives. A blank DDCD-R or DDCD-RW has pre-groove and it has the built in wobble for the purpose of defining and finding the physical track. The wobble is a 22.05KHz signal modulated with digital information. The position within the pre-groove is contained in each pre-groove frame of 42 bits. This is known as an Absolute Time In Pre-groove (ATIP). The ATIP frame shall consist of 42 bits.

In the area that is expected to be the disc’s Lead-in Area, the additional information is interleaved between positional ATIP frames.

The additional information provided is:

- First possible start address for disc Lead-in (TOC)
- Last possible start address for disc Lead-out
- Special information about recording permissions
- Power and speed requirements for recording the medium
- DDCD-R vs. DDCD-RW medium

DDCD-R/RW discs have two additional areas prior to the first Lead-in; the Power Calibration Area (PCA), and the Program Memory Area (PMA). The Power Calibration Area (PCA) is present only in DDCD-R and DDCD-RW media for the purpose of write power calibration.

The PCA is divided into two areas: the test area and the count area. The test area is divided into 1000 calibration partitions. The count area is a counting area for use of the test recording. The Program Memory Area (PMA) is present only for DDCD-R and DDCD-RW media for the purpose of counting for the use of user data area on the medium. This information is contained only within the Subcode-Q channel of the PMA frames.