1. A non-transitory program storage device having stored thereon instructions to cause one or more processors to: receive a time based metadata track associated with a time based media track, the time based media track containing media data, the time based metadata track including a collection of tags, wherein each tag identifies one or more types of metadata in the time based metadata track; and index the time based metadata track as a non-time based description, the non-time based description including a set of identifiers, the set of identifiers including a first identifier and one or more additional identifiers each of which specify a unique combination, relative to all other identifiers in the set of identifiers, of one or more types of metadata in the time based metadata track, wherein the first identifier is associated with a first type of metadata during a first time interval of the time based metadata track, the first identifier specifying there is no metadata of the first type in the time based metadata track during the first time interval.