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CD Replication: Physical Characteristics & Tech Info 3

The following text is an edited extract from original article at http://en.wikipedia.org/wiki/Compact_Disc

Frame

For the Red Book stereo audio CD, the time format is commonly measured in minutes, seconds and frames (mm:ss:ff), where one frame corresponds to one sector, or 1/75th of a second of stereo sound. Note that in this context, the term frame is erroneously applied in editing applications and does not denote the physical frame described above. In editing and extracting, the frame is the smallest addressable time interval for an audio CD, meaning that track start and end positions can only be defined in 1/75 second steps.

Logical structure

The largest entity on a CD is called a track. A CD can contain up to 99 tracks (including a data track for mixed mode discs). Each track can in turn have up to 100 indexes, though players which handle this feature are rarely found outside of pro audio, particularly radio broadcasting. The vast majority of songs are recorded under index 1, with the pre-gap being index 0. Sometimes hidden tracks are placed at the end of the last track of the disc, often using index 2 or 3. This is also the case with some discs offering "101 sound effects", with 100 and 101 being index 2 and 3 on track 99. The index, if used, is occasionally put on the track listing as a decimal part of the track number, such as 99.2 or 99.3. (Information Society's Hack was one of very few CD releases to do this, following a release with an equally-obscure CD+G feature.) The track and index structure of the CD carried forward to the DVD as title and chapter, respectively.

Manufacturing tolerances

Current manufacturing processes allow an audio CD to contain up to 80 minutes (variable from one replication plant to another) without requiring the content creator to sign a waiver. Thus, in current practice, maximum CD playing time has crept higher by reducing minimum engineering tolerances, while still maintaining acceptable standards of reliability.

 

Replicat Mar-2020: The red book standard for CD Audio production sets the maximum length of audio at 74 minutes and 30 seconds. This is the recommended maximum length for reliable playback on all standard CD players. Overlength surcharges can apply over this length due to the likelihood of the factory making several stampers to get one to pass readability tests. Contrary to the original wiki article above (written in 2005) it may also be necessary to receive a waiver, as some CD players may struggle to play overlength discs reliably.