53
9.1.3. Session-at-Once (SAO)
As a writing method that combines the advantages of the above-mentioned “Disc-at-
Once” and “Track-at-Once,” you can combine multiple tracks into one session and write
them, and then add additional data.
For example, this is the writing method used to create a CD EXTRA format CD. The audio
tracks will be recorded in the first session and the data will be recorded in the second.
9.1.4. Packet Writing
This mode is used when writing to a track of a disc using small blocks of data called
“packets,” in a manner similar to a floppy disk. This mode is useful when making small
incremental backups of data. You will need to use software which specifically supports
packet writing, such as Adaptec’s DirectCD.
Discs must be formatted before they can be used for packet writing. With CD-
RW, erased data can be overwritten until the disc is completely full. With CD-R,
the space used by the erased data cannot be reused and is “masked” so that it
is no longer visible. This can be done up to 100 times.
Lead-in
Lead-out
Lead-out
/Lead-in
Data
Audio
Audio
Audio
0
650MB
Track 1
Track 2
Track 3
Track 4
Session 1
Session 2
Example: CD EXTRA
1
2
3
4
5
6
7
8
.
.
.
.
.
.
.
.
.
.
.
.
Packet
Same as writing to floppy or hard disk
