Table of Contents

   Note: This page is a placeholder or work-in-progress. Content should not be referenced or treated as reliable.

The Table of Contents (TOC), also known as the lead-in, is the section of a CD before the audio data/program area. It contains each track's start time and control flags (pre-emphasis, copy permission, etc.) as well as the start time for the disc's lead-out section. Times are stored in minute-second-frame (M:S:F) format, counting up from the start of the disc's audio content.

The TOC is read by players/optical drives when the disc is first inserted, allowing display of the CD's track count and track and disc durations, as well as letting the player jump to the start of any specific track on the disc.

TOC information is encoded in the Q subcode blocks in the lead-in. These blocks are designated as Track 00. The data is repeated multiple times throughout the lead-in.

TOC/Program Area Mismatches

The control flags for each track also appear in the Q subcode blocks in the disc's program area (Tracks 01-99). It is therefore possible for a track's TOC control flags and program area control flags to disagree. Notably, there are a number of releases where the pre-emphasis flag is missing from the TOC but present in the program area. This does not affect playback in a standard CD player as players use the program area flag to control de-emphasis, but it can cause problems during DAE as most extraction tools -- including those, like iTunes, that automatically de-emphasize extracted audio -- rely on the PRE flag value in the ToC.

Similarly, it is possible for the track position information in the TOC to differ from the position information in the program area. Each frame on the disc is labeled with a track number, an index point number, its M:S:F position within the track, and its M:S:F position within the program area. It is therefore possible for the TOC to say that Track 02 starts at 02:10:44 but for the frame at 02:10:44 to be labeled as Track 01 Index 01.