Those flags were added to the Matroska specification together with the already implemented hearing-impaired and visual-impaired flags. They allow specifying whether a track is a commentary track or in the original language without relying on the free-form track name, which makes consistent tagging and parsing by machines easier. Ref: https://github.com/ietf-wg-cellar/matroska-specification/pull/447 Ref: https://www.rfc-editor.org/rfc/rfc9559#name-original-flag Ref: https://www.rfc-editor.org/rfc/rfc9559#name-commentary-flag