Incremental Write

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Unlike 'at once' recording, incremental writing (or packet writing) is a recording method which allows data tracks to be divided up into small chunks called packets (typically 64 Kb - 1 Mb in size). Each packet can then be written separately to the disc, with interruptions if necessary. Each packet uses an additional amount of disc space as overhead in addition to its required amount of space. This overhead is typically 15% of the size of the packet itself.

Between the writing of packets, there are virtually no data rate constraints. This means that writing can be interrupted for an unlimited amount of time, which reduces the risk of buffer underruns when writing large amounts of data to CD/DVD.

Incremental write modes can be used in different ways:

1. On the logical level, fixed packet writing can be combined with UDF which is ideally suited for incremental writing, or it can be combined with another file system such as ISO 9660 or even a combination of both.

2. On the physical level, the Orange Book standard offers the option to use either a fixed or variable packet size. The advantage of a fixed packet is that they eliminate the risk of buffer underruns. Variable packet writing, in which packets differ with the size of the files to be written, offers more backwards compatibility. Fixed packet writing can also be used in combination with multi-session writing.

IMPORTANT: A special driver may be required to read incrementally written discs. Some CD-ROM readers on the market cannot read incrementally written discs.

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