Friday, 2 May 2014

Digitising Audio Visual Material


VHS and audio cassettes in the HIV/AIDS collections are the focus of this week’s blog by our project conservator, Emily:

In the HIV/AIDS collections there are 32 VHS and 46 audio cassette tapes. These cassettes are known as magnetic media as the tape used to carry the information is made from a thin layer capable of recording a magnetic signal which is supported by a thicker film backing. Although these were only formed during the 80s and 90s, they are already showing signs of deterioration. As the materials used to form the cassette ages, the magnetic signal is lost, resulting in a loss of audio and visual quality. This can occur just two years after recording and it is estimated that VHS and audio cassettes have a lifespan of just 30 years. The deterioration of magnetic media cannot be stopped. However, correct storage and handling can slow down the rate of deterioration and reduce the risk of damage due to physical factors.
Screen shot of GD22/12/24, an advert for the National AIDS Helpline. Shows loss of visual quality.
 
Unlike printed documents, magnetic media only stores the information. So to be able to access the data, not only does the object itself need to be conserved, but also the viewing equipment that reads the format. Therefore the information recorded on media devices can also be lost due to obsolescence of the media technology. It is becoming increasingly difficult to view VHS and audio cassettes and often impossible to view other formats. For example, we have been unable to access an 8 inch floppy disc in the collection due to lack of equipment. To overcome this problem, media objects can be digitised to transfer the data to a modern format. We recently sent a selection of VHS and audio cassettes consisting of a range of programmes and adverts aimed at different groups of people to be digitised. The information stored on the cassettes was transferred to an uncompressed format which avoids loss of quality and has now been returned to us on an external hard drive. Access copies were also made in a compressed format for ease of viewing. Here is a short example of one of the digitised items from the "Take Care Campaign":

video
GD22/12/30a RSA Advertising. "Take Care" and "Use a Rubber"

Although this stops the data being lost completely, it does not solve the problem. Modern formats of media storage are also subject to the same risks as older media storage systems. The materials used to make the current storage will degrade over time and the equipment used to view the media will also become outdated as technology advances. It is recommended that digitised items be transferred to new formats every five years, making the preservation of digital material an ongoing and potentially costly process. However, audio visual material provides a unique perspective of the past, so it is essential to carry out these tasks to avoid losing the unique information stored on the cassettes.

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