 Figure 1: Composition of a CD-R disc |
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A blank CD-R disc is divided into the areas shown in Figure 1.
Figure 1: Composition of a CD-R disc |
 Figure 2: Cross-section through a CD-R disc.
A cross-section through a CD-R disc is shown in Figure 2. The disc comprises four different layers. Transparent plastics material (the same as conventional CDs) is used as the substrate. Onto this a special greenish-tinged translucent layer is applied. The substrate has already been provided with a preformed track spiral into which the audio data will be written during recording. On top of the green recording layer is a reflective gold layer and a protective layer of plastic material. |
| 2.1. The additional CDR area of a CD-R disc. The additional CDR
area is divided into two areas: 1. The Program Memory Area (PMA) which contains, for example, the track numbers of the titles recorded with respective start and stop points. 2 The Program calibration Area (PCA) The CD recorder to calibrate the laser energy needed for recording on the disc via a trial recording. |
 Figure 3: Cross section through a blank CD-R
disc.2.2. Blank CD-R disc. Figure 3 shows the blank CD-R disc's cross section. Next to the centre hole is an area for the mechanical clamping of the disc in the player/recorder. Adjacent to this is the unrecorded area of the blank CD-R disc. |
 Figure 4: Cross section through a partially
recorded CDR disc. 2.3. Partially recorded CD-R disc. After the first recording the recording area is divided, giving a CD-R disc the cross-section shown in Figure 4. The "Lead-in", "program area" and "Lead-out" areas are present on every conventional prerecorded CD. For the partially recorded CD-R disc, the PCA and PMA areas are incorporated in front of the Lead-in. Track numbers with associated absolute start and stop times are stored in the PMA. |
| The possibility exists of making further recordings later. It would also
be possible to declare the disc as fully recorded. In which case, the definitive table of
contents (TOC) is written into the Lead-in and further recording is no longer possible. Parts of the program area (for example, faulty recordings) can be marked as invalid and these will be skipped over when the disc is subsequently played. |
 Figure 5: Cross section through a fully recorded CD-R
disc. 2.4. Fully recorded CD-R disc. Figure 5 shows the cross-section through a fully recorded CD-R disc.The fully recorded CD-R disc has a program area containing up to a maximum of 74 minutes playing time, a lead-in area with table of contents and a lead-out track. The areas specific to the CD recorder, the PCA and PMA, are still present but are simply not used by conventional CD players. When the lead-in area is provided with the table of contents, the CD recorder uses the information stored here and not the data from the PMA area. |
Identification of the end of the disc is stored in the Lead-out. The CD player stops playback of a disc on reaching this area.
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Page 4:Function Blocks of a CD Recorder: A/D D/A and other modules.