Meta-Data-in-Ogg

The following are not valid VorbisI files!

These files were generated by losslessly merging the XML stream with an existing (and widely useable) Ogg-Vorbis file. They are intended for use in testing players aiming to provide forward compatibility by ignoring unknown stream types. One known artefact is a subtle periodic clicking; links to the originals are provided if you want to listen to the performances as the artists intended them. It's recommended that you use your browser's save as method (usually right click on the links) to save the '.oga' files.

If you can play the files you still won't see anything special (other than some good music). Alongside the main audio stream the files contain XML streams which can provide extra information (meta-data) on the stream contexts. This data, although here rather limited, can be far more comprehensive than the Vorbis comment headers, or the similar ID3 tags found on other audio formats. The XML data can extend to cover anything you would find in a cover booklet; for movies (using Ogg-Theora) it could contain cast lists. The same technique could carry SMIL information.

If you're so inclined you can view the start of the file with a hex editor and see the plain text of the XML packed into the Ogg stream. If you're really keen you could use the libogg API to pull out the XML packets and reassemble them into a single document. The RDF is hand generated, and while it validates it may contain mistakes. Two different examples are provided so chained playback can be tested.

Bach, Chorale: Nun freut euch lieben Christen

Busoni transcription performed by Debbie Hu from the Pandora Records Archive, both the original and the Ogg-Vorbis-XML file are provided under the terms of the EFF OAL.

• The original Bach-Busoni_Nun_freut_euch_3.ogg
• The Ogg-Vorbis-XML version Bach-Busoni_Nun_freut_euch_3.rdf.oga
• The XML/RDF description as a separate document
• With the XML page repeated after every fifth Vorbis page (useful for testing seeking): Bach-Busoni_Nun_freut_euch_3.multi.oga. (This is not a suggested way to add meta data, just a way of testing how players handle seeking in the presence of an unknown stream.)
• Evil Test Case, with the XML page repeated after every fifth Vorbis page and the stream ending on a meta data page (breaks simpler track-length strategies): Bach-Busoni_Nun_freut_euch_3.end.oga. (again, not a suggested format for meta data)

(Note: the metadata was changed on 2006-01-19 to credit Debbie Hu as a creator rather than a contributor. The BWV should really be included. Neither of these have any bearing on use as a test file. A newer metadata (Dublin Core) schema not used here would allow more precise crediting of roles.)

Disharmonic, On The Moon

Chilled trip-hop track from Czech DJ Disharmonic taken from ccMixter, both the original and the Ogg-Vorbis-XML file are provided under the terms of the Creative Commons Attribution 2.5 license.

• The original On The Moon (Trip Hop mix)
• The XML/RDF description as a separate document
• With the XML page repeated after every fifth Vorbis page (useful for testing seeking): disharmonic_-_On_The_Moon_(Trip_Hop_mix).multi.oga.
• Evil Test Case, with the XML page repeated after every fifth Vorbis page and the stream ending on a meta data page disharmonic_-_On_The_Moon_(Trip_Hop_mix).end.oga.

Content copyright Ian Malone 2005, except for the logos on the front page and where otherwise noted. Stylesheets and code cribbed from various sources on the web, see links section for a few.