MFDigital CD DVD Information Library
Thursday, June 10, 2004
Compact Disc Parameters
The main Compact Disc parameters are below.
Data includes -Parameter: Value, and Comments.

Diameter: 12 (or 8) cm, 8 cm CDs have not been successful
Thickness: 1.2 mm, Tolerance of +0.3, -0.1 mm
Width of pits: 0.5 microns
Length of pits: 0.8 to 3 microns, Depends on data stored
Depth of pits: 0.15 microns
Scan velocity: 1.3 m/s, Tolerance +/- 0.1 m/s
Track pitch: 1.6 microns, Tolerance +/- 0.1 microns
Laser wavelength: 770 to 830 nm, Typically 780 nm
Playing time: 74 mins 44 secs, Playing times can be longer
Number of tracks: 99 max, Can use indexes to subdivide tracks
Modulation: EFM, 8 to 14 bits plus 3 merging bits
Channel bit rate: 4.3218 Mb/s, Actual raw data rate

Compact Discs are 12 cm in diameter and 1.2 mm thick.   The pits containing the audio or other data are about 0.15 microns deep and 0.8 to 3 microns in length depending on the data stored.  This raw data is read at 4.32 Mb/s, but after demodulation (17 bits become 8) and error correction the data rate is 1.4 Mb/s.  The total length of the helical 'track' of pits is about 5,800 m.