5. Safeguarding the information

a. By preservation of the carrier

Although the life of audiovisual carriers cannot be extended indefinitely, efforts must be made to preserve carriers in useable condition for as long as is feasible.

For carrier-based content, preservation of the carrier requires storage in an environment suited to the purpose, separating primary and secondary information sources where appropriate, and performing routine maintenance and cleaning as needed. Maintenance includes the regular checking of reference signals and frames, if available, on analogue carriers, and regular checking of the data integrity of digital carriers. In addition, the equipment used for handling and replay must meet the physical requirements of the carriers. Preservation includes minimising the use of original copies by making access copies available.

b. By subsequent copying of the information

Because the life expectancy of carriers and the availability of hardware are limited, the preservation of the document in the long term can only be achieved by copying the contents to new carriers/systems while this remains possible.

In the analogue domain, primary information suffers an increase in degradation each time it is copied. Only the digital domain offers the possibility, when done diligently, of lossless copying when refreshing or migrating recordings (see section 12). For the long-term preservation of primary information held on an analogue carrier it is necessary, therefore, to first transfer it to the digital domain.

Separating the primary information from the original carrier raises the question of future authentication of the sound and images. Future users may only have access to an audiovisual document in the form of a file-based copy; in this event, the importance of adequate secondary or contextual information increases. Secondary information held visually on tape boxes, disc sleeves or labels may be best captured and retained in associated image files, in which case this information should be documented and reproduced according to recognised archival standards for generating such content. Other types of secondary information such as descriptions of the original format may take the form of preservation metadata, and so should be recorded in a systematic manner, and be made accessible together with the primary information (see section 14). By this means, future users can be better assured of the authenticity of the document.