Packet writing

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Optical disc authoring

Optical disc Optical disc image Optical disc drive Authoring software Recording technologies Recording modes Packet writing
Optical media types
Laserdisc Compact disc (CD): Red Book, 5.1 Music Disc, SACD, PhotoCD, CD-R, CD-ROM, CD-RW, Video CD, SVCD, CD+G, CD-Text, CD-ROM XA, CD-Extra, CD-i Bridge, CD-i MiniDisc DVD: DVD-R, DVD+R, DVD-R DL, DVD+R DL, DVD-RW, DVD+RW, DVD-RW DL, DVD+RW DL, DVD-RAM, DVD-D HD DVD: HD DVD-R, HD DVD-RW, HD DVD-RAM Blu-ray Disc (BD): BD-R, BD-RE UDO UMD Holographic data storage 3D optical data storage History of optical storage media
Standards
Rainbow Books File systems ISO 9660 Joliet Rock Ridge Amiga Rock Ridge extensions El Torito Apple ISO9660 Extensions Universal Disk Format Mount Rainier

Packet writing is an optical disc recording technology used to allow writeable CD and DVD media to be used in a similar manner to a floppy disk. Packet writing allows the user to access the contents of a CD-R or CD-RW disc directly through a mounted filesystem (Unix, Linux, Mac OS X) or drive letter (Windows). Without packet writing software, one would have to use regular CD mastering recording software to burn a whole disc.

Packet writing can be used both with once-writeable media such as CD-R, DVD+R and DVD-R, and also with rewriteable media such as CD-RW, DVD+RW and DVD-RW. Once-writeable media cannot however recover space once used; A deleted file does not free space on the disk, and a modified or overwritten file occupies additional space even if the file size has not increased. When the free space on a once-writeable disk is exhausted, no further update to the disk is possible.

Due to the characteristics of optical Rewriteable media (CD-RW, DVD-RW), the ability of data sectors to hold their contents wear out by changing them frequently (re-crystalized alloy de-crystalizes). To cope with this, a defect management is needed, replacing bad sectors with good sectors through internal re-mapping. While modern media (e.g. HD-DVD) provides this in the drive's hardware, CD-RW and DVD-RW require support in the operating system software for this. UDF, starting with revision 1.50, provides such support. Therefore, to use CD-RW or DVD-RW media as a rewritable volume, the UDF format should be used. While it could be possible to use any other volume format such as FAT on this kind of RW media, the missing defect management can quickly lead to data loss.

Several competing packet writing disk formats have been developed, notably those of Roxio Drag-To-Disc (formerly DirectCD), Nero AG InCD, and Sonic Solutions Drive Letter Access. Used standards include UDF 1.5 and Mount Rainier.