2. Primary and secondary information

Any archival document consists of multiple forms of information. Some may be considered primary information. This includes the obviously audible or visible time-based content, i.e., the sound or picture signals. Other forms of information may be considered secondary, where they play a contextual or supporting role to the primary information. For example this might include information about the contents (perhaps written on a physical carrier), information about the carrier itself, or for video, timecode embedded within the video stream.

Both primary and secondary information form part of an audiovisual document, whether carrier-based or file-based. The relative importance of the two will vary depending on the content, the type of carrier and the needs of users, both present and future. Secondary information, however, becomes a crucial factor in the authentication of primary information transferred from another carrier format, or as a potential source for other analyses or research. Secondary information may be present in file-based born digital content or in content on physical carriers. When file-based content is format-migrated, or when carrier-based content is transferred to file-based formats, care must be taken to retain the secondary information. A minimum combination of primary and secondary information is required to preserve a document’s essence sustainably, and it is the responsibility of the archive to define that combination of information explicitly, through careful analysis of actual and potential use as well as ethical, legal or other institutionally mandated considerations.


Any and all metadata may be considered secondary information, including machine-actionable data allowing specific functionality, such as DVD menus or video game functionality.

In discussing video, the terms ancillary and associated data are often used, to describe such things as timecode, captions, and any other information that is not strictly sound or picture.

Physical carriers can often be considered as significant cultural objects in their own right, for example mass-produced sound discs, and the scholarly and cultural value of commercial disc sleeves and labels should be borne in mind.

Researchers may find the secondary information held in video timecodes of special interest as they can provide clues to a television producer’s editing processes.

When digitising film, for reasons of authenticity it is important to digitise all information written or recorded on the film prior to and after the essential images, including the geometrics of the sprockets, either as part of the preservation copy, or at least in the metadata.