Universal Subtitle Format

Universal Subtitle Format (USF) was an ambitious project to create a clean, documented, powerful and easy to use subtitle file format. It is based on XML for some the following reasons: flexibility, unicode support, a hierarchical system, and ease of administration.

USF subtitles are usually used in Matroska Containers.

The format has come under a lot of criticism, especially from the fansub community, because compared to the format it aims to replace, Advanced Substation Alpha (which is based on comma-separated values), it is more verbose and far harder for software to read, write and manipulate. It is also much harder to edit "by hand" in text editors such as notepad. For these reasons, as well as the lack of a generic cross-platform parsing/rasterizing library and mature editing programs that natively support it, have made the format unsuccessful in being used.

No known media player software implements more than basic support for this format. VSFilter and the VLC media player (starting with the upcoming 0.9.0 release) are able to extract the subtitle text, timing information and very restricted formatting.