Ascii85

File Format
Name	Ascii85
Ontology	Electronic File Formats Transfer Encodings Ascii85

Ascii85, or Base85, is a binary-to-text encoding. It is similar in concept to Base64 and Uuencode. It is often used in PDF and PostScript files, and rarely anywhere else. One example among very few is the MkTags Matroska tag editor. There are several varieties of this encoding.

Identification

In PostScript, the "<~" delimiter marks the beginning of an ASCII base-85 string literal. The "~>" EOD marker is added by the ASCII85Encode filter when it is closed, hence it should be regarded as being part of the encoded data. Outside of PostScript, there is no official delimiter to mark the beginning of ASCII base-85 encoded data. In PDF, they solve it by putting the data (including the EOD marker) in a stream object, but that's a different story.

There is also a uuencoding-like format, delimited by lines that begin with "xbtoa Begin" and "xbtoa End".

Software

• ascii85.tgz
• btoa-5.2.tar.gz
• ASCII85-Tools, Perl command-line utilities - C version also available.
• MPPerl::Convert::ASCII85::XS, a Perl module with time-critical code written in C
• Ascii85 libraries are readily available for most popular programming languages.

Links

• Wikipedia article
• Online ASCII85 encoder
• Online ASCII85 decoder
• RFC 1924: A Compact Representation of IPv6 Addresses