Last updated: 2012-02-21
WebM global metadata is based on the Matroska tag specification. This document describes where the formats differ.
the Tags element SHOULD be placed at the end of the file to allow for trivial updates
TagName SHOULD appear before the tag data, i.e., TagString, TagBinary
a SimpleTag SHOULD NOT contain other SimpleTags
when concatenating multiple files new Segments should be used to avoid merging tags common to each file