Recording on a CDRW Disc

This material is from fact sheets developed by Philips
Copyright © 1997 Phillips Electronics N.V.  All rights reserved
EUonline use by permission

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• Blank CDRW discs feature a "phase-change" layer for recording, which changes from a non-crystalline (amorphous) state to a crystalline state under the influence of the laser beam. Because these changes are reversible, these discs can be erased and reused.
• After recording it is possible to erase the last track to correct recording mistakes
• This procedure can be repeated
• After recording it is possible to erase the complete disc for re-use
• CDRW discs can be played on CD-players prepared for Rewritable Discs after finalizing (CDRW discs have a lower reflectivity than pre-recorded and CDR discs)
• After finalizing the CDRW disc can be erased completely for reuse.

The CDR / CDRW disc

The Recording Process

CDR: Laser power  6-12 mW during writing pits. Deformation of the recording layer are creating the pits. This process is irreversible. CDRW: Laser power 8-14 mW during writing pits. Recording layer changes from a non-chrystalline (amorphous) to a chrystalline state. These states are reversible by overwriting. For reference: CD playback laser power is 0.5 mW

The three recording states of a recordable disc

Areas on a recordable disc

Power Calibration Area (PCA)
For optimium Power Calibration (OPC) to optimize the laser recording power with the recordable disc in use.
For this, a test recording is made on the disc in the test area after inserting the disc; the number of test recordings (maximum 99) is administrated in the count area.

Program Memory Area (PMA)
This is a preliminary Table of Contents
The PMA is updated after every recording

Lead-in area
Area where the final Table of Contents (TOC) is recorded during Finalization of the disc

Recorded Area
The recorded music (speech, etc.) tracks

Lead-Out Area
Area where the and marking is recorded during Finalization of the disc

Note: PCA and PMA area on the disc can not be read by normal CD-players

The Pre-Groove on a recordable disc

• Blank CDRW discs feature a pre-formatted groove.
• This Pre-Groove is used to guide the laser during recording.
• For motor servo control the pre-groove feature a wobble frequency of 22.5 kHz.

The Pre-Groove  also contains Disc Information

• Absolute Time In Pre-Groove (ATIP)
• Maximum recording time on the disc
• The Recommended Recording Power on the disc
• The type of disc (professional/consumer)