W3C Candidate Recommendation Ontology for Media Resources 1.0 (July 2011):

“The intent of this vocabulary is to bridge the different descriptions of media resources, and provide a core set of descriptive properties. This document defines a core set of metadata properties for media resources, along with their mappings to elements from a set of existing metadata formats.”

Mapped metadata standards: CableLabs 1.1, DIG35, Dublin Core, EBUCore, EXIF 2.2, ID3, IPTC NewsML-G2, LOM 2.1, Media RSS, MPEG-7, OGG, QuickTime, DMS-1, TTML, TV-Anytime, TXFeed, XMP, YouTube

Example XML for most standards can be viewed in the testsuite.

(Via Johannes Schmidt.)