xorrecord: Standards
2 MMC, Session, Track, Media types
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*MMC* is a standard out of the SCSI family which defines the interaction
between computers and optical drives. Since more than a decade all CD,
DVD, or BD recorders obey this standard regardless by what bus cabling
they are attached to the computer. libburn relies on this standard
compliance and on the capability of the operating system to perform SCSI
transactions over the particular bus cabling.
A *Session* is a data region on an optical disc which usually gets
written in a single sweep. It contains at least one *Track* which is a
contiguous string of readable blocks. 'xorrecord' produces a single
session with a single data track which consists of blocks with 2048
bytes each. It chooses the write mode automatically according to media
type, medium state, and option -multi.
On CD media there are other track types, like audio, and particular
write modes like TAO and SAO. CD and DVD- media can put more than one
track into a session. Some of these features can be addressed by
program *cdrskin*.
MMC describes several recordable *media types* which roughly form two
families.
*Sequentially recordable media* are CD-R, CD-RW, DVD-R, DVD-R DL,
DVD-RW, DVD+R, DVD+R DL, BD-R. Except DVD-R DL they can store more than
one session if there is still unwritten space and if the previous
session was written with option *-multi*. CD-RW and DVD-RW can be
blanked in order to be re-usable from scratch.
*Overwritable media* are DVD-RAM, DVD+RW, formatted DVD-RW, BD-RE. They
offer a single session with a single track for random access writing.
There is no need to blank overwritable media before re-use.
DVD-RW media are sold in sequentially recordable state but can be
formatted once to become overwritable. See options
*blank=format_overwrite* and *blank=deformat*.
If ISO 9660 filesystems are to be stored on overwritable media, then it
is possible to emulate multiple sessions, by using option
*-grow_overwriteable_iso*. In this case, the need for blanking before
re-use is emulated too.
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