Double Density CD - Page 6

Disc Structure

There are three address expressions used in the DDCD system; the Block address contained in the sector header (Physical Sector Number), Subcode-Q channel (Subcode frame time number), and the address referred to the blocks of the Initiator system (LBA: Logical Block Address).

The address used by the Initiator system starts from 0 to the end of the recorded information on the disc. LBA 0 shall correspond with the sector header address of D300h and the Subcode-Q address of 0:12:00:16 (0 hour, 12 minutes, 00 second, 16 frame). Only the Data Area is generally addressable by using LBA. Subcode-Q areas are addressed in time based address.

The representation for a time based address is H:MM:SS:FF, where H = hours, MM = minutes, SS = seconds, and FF = frames. Hour field is 1 digit. MM:SS:FF are 2 digits respectively. When the time based address includes the hours field selection between LBA and H:MM:SS:FF is indicated by the appropriate TIME bit. One Hour is subdivided into 60 Minutes. One Minute is 60 Seconds. One Second is 75 frames.

Single Session Disc

A Session is a recorded sequence that includes a Lead-in Area, Program Area, and Lead-out Area. The Lead-in / Lead-out Area is a guard area at inner / outer part of the disc. The Lead-in Area also contains the table of contents (TOC) for Program Area. The Program Area is also known as the user area of the disc.

Multi-Session Disc

The multi-session allows a single disc to have several concatenated sessions. On a recorded disc, session may appear as shown in Figure 2. DDCD read only drives are not typically capable of reading through unrecorded areas on the medium. The DDCD read only drive needs EFM data in order to find and stay in the physical track. This is to ensure that a DDCD read only drive is capable of accessing all areas of a Program Area.

In order to assure readability with DDCD read only drives, the recording system shall always close the session before attempting interchange. Additional information is needed in order to locate all of the program areas. This is accomplished by using SubCode-Q Mode 5 in the Lead-in areas.