Magnetic tape preservation
Magnetic tape is used for a variety of analogue or digital audio and video formats. Included are domestic and professional formats ranging from the compact cassette to digital betacam. The tapes can be held on an open reel or contained within a cassette. All feature a plastic base with a coating that can record a magnetic signal.
Magnetic tapes are prone to physical damage and chemical deterioration, as well as being subject to format obsolescence. Additionally, the preservation of magnetic tape-based formats faces the challenge of using tools and equipment for repair, cleaning and playback that manufacturers no longer support. Consequently, sourcing spare parts and servicing this equipment have become increasingly difficult.
In the past, magnetic tape preservation involved copying from the original audio or video carrier to another tape format. Now, we digitise all magnetic tapes to data files using specialised digitisation workstations.
Preserving our magnetic tape holdings
We inspect tapes for correct tension, dust or mould, physical damage and apparent chemical deterioration. Treatment may involve replacing broken cassette shells, mechanical or hand cleaning of the video tape, re-attaching leaders and splices, or other processes.
We copy the tape recordings to a digital file using dedicated digital workstations. During this process, the signal levels are monitored and adjustments are made to ensure the best possible replication of the original content.
Audio tapes are preserved as Broadcast Wave Format (pdf, 238kB) (BWF) files in accordance with international audio preservation standards.
We digitise video tapes to lossless, compressed video files.
Once we create the audio or video files, checksums are generated. These are mathematical fingerprints of the files, which allow us to verify the integrity of any file copying or movement. Metadata, such as title, date of production and copying history, is added to the preservation files. The Archives' databases are updated to include information about the digital copies and the changed status of original records.
The original tapes are repackaged and taken to long-term storage. The digital file copies are then stored on our preservation server.