ISO 9660 Volume
All DVDs also have an ISO 9660 volume. This volume only supports filenames with
single-byte ASCII characters. The ISO 9660 volume must conform to the “26.3” specification,
similar to the “8.3” specification mentioned earlier (26 characters maximum followed by
a 3-character extension; the only allowed characters are uppercase letters, numbers, and
the underscore). In addition, folders cannot have extensions in their names. Filenames
are automatically truncated and invalid characters replaced with an underscore. Filenames
using double-byte characters exclusively are renamed as FILE_1, FILE_2, and so on.