Monday, 2 August 2010

What is the difference between ISO 9660, Joliet and UDF?

CD-ROM File Systems

An ISO 9660 file system is a standard CD-ROM file system. Full ISO format requires all upper case characters or numbers, no spaces, very limited special characters, and no more than 30 characters in the name.

Joliet is the name of an extension to the ISO 9660 file system. Joliet format permits 64-character file names with lower-case alpha and other relaxed restrictions. It also relaxes the ISO requirement for directory nesting to no more than eight levels. It doesn't hurt to include the Joliet Directory if the names conform.

UDF is a hybrid filesystem that uses both UDF and ISO 9660. Also called a UDF bridge, it was commonly used until Microsoft incorporated support for UDF in its operating system. UDF permits 127 16-bit Unicode characters, or 254 8-bit Unicode characters. If any character in any name is not in the list of legal 8-bit Unicode characters, all names will be represented in 16-bit Unicode.

However Joliet is no longer needed since the ISO 9660 standard has been extended in 3 different levels:
Level 1: Filename cannot be longer than 8 chars , Filename extention cannot be longer than 3 chars.
Level 2: Filename can be up to 255 chars long.
Level 3: Same as level 2 but files can be written in multiple extents (-> Packet writing).

Normally a Mac can read both ISO 9660 and Joliet CDs.