Kate is a free codec for text based data, which can also carry images.
It is typically used to create overlays on a video.

libkate, a codec for Kate streams, is required to build this plugin:
http://libkate.googlecode.com/

libtiger, a rendering library for Kate streams, is optional:
http://libtiger.googlecode.com/

The Kate plugin contains various elements to manipulate Kate streams:

 - katedec: decodes Kate streams to text and SPU images
 - kateenc: encodes Kate streams from text and SPU images
 - kateparse: parses Kate streams
 - katetag: allows changing metadata in Kate streams
 - tiger: decodes and renders Kate streams using libtiger (needs libtiger)

More information about Kate can be found at:
http://wiki.xiph.org/index.php/OggKate