The total length of time that the image or audio signal lasts, expressed as a timecode.
Record the total duration for the content being described. For example, a title consisting of two videocassettes, each 60 minutes in duration would have a duration of two hours, or 02:00:00:000/1000.
A note on duration and extent for time-based media: For film, video, and audio, the duration of the content is recorded twice. Because the duration of the content, often expressed in minutes, pertains to the intellectual work itself (as opposed to a particular manifestation of it on videotape or in a digital file), it is recorded first in descriptive metadata, as "extent". (Information about a particular manifestation of the work is recorded in source or technical metadata.) In descriptive metadata, a film's extent might be described as "99 minute(s)."
Second, the duration of a particular manifestation is described in source or technical metadata as a timecode, in the "duration" element. For example, a title consisting of two videocassettes, each 60 minutes in duration, would have a duration of two hours, or 02:00:00:000/1000. (Do not confuse this timecode value with the actual timecode found on the physical piece; information about that timecode, such as type of timecode and how it is recorded on the media, is recorded in the "timeCode" element.)
The extent of the physical item, in terms of physical pieces, is recorded in the "extent" elements, in source metadata. For example, "2 videocassette(s)."
The actual length (linear measure) of the physical piece is recorded in the "length" element, in source metadata. For example, "232 ft."
For digital video and audio, the breakdown of content, in terms of segment start and stop times, is handled in the structure map.