Film sound preservation
Film sound is the synchronised audio component or soundtrack of a motion picture or television show. Although we have both optical and magnetic formats in our holdings, most are in a magnetic format.
Magnetic film has a polyester or acetate plastic base with a magnetic coating. It comes in 35mm, 17.5mm and 16mm gauges (widths) with perforations down one or both sides. These types of films are prone to chemical degradation – especially films with an acetate base which can suffer from 'vinegar syndrome'.
In the past, we copied analogue magnetic film sound material to a more stable film base. However, due to the format obsolescence and physical storage problems with these records, we now digitise the audio content.
As with all film preservation, there are the challenges of the use and ongoing maintenance of ageing and obsolete technology. There is no longer support for many of the tools and equipment used in the repair, cleaning and playback of film sound items. Servicing and spare parts for this equipment have become increasingly difficult to source.
Preserving our film sound holdings
The copying projects are determined by the tape content and format. We carefully examine film sound items before they are auditioned or copied. Preparation of the film prior to playback can include cleaning or repair to ensure the highest possible audio quality.
Analogue audio content is captured and preserved as Broadcast Wave Format (pdf, 238kB) (BWF) files in accordance with international audio preservation standards using a specialised digitisation workstation.
Once the files are created, checksums are generated. These mathematical fingerprints of the file 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.
Like motion picture image elements, original magnetic film sound items are prepared for long-term storage. We carefully wind the magnetic film recordings to preservation standard and store them in archival plastic canisters. These are stored in environmentally controlled conditions in our film vaults.