6.4.1.1 Once the action has been taken to convert the audio content to a suitable digital storage format for storage on a digital storage system, as defined earlier in this document, there is still a requirement to manage the ongoing preservation of the content. Section 6.3 Archival Storage includes a description of the issues surrounding management of the byte stream, i.e. ensuring that the digitally encoded data retains its logical structure through management of the storage technology.
6.4.1.2 There is, however, another aspect to the preservation of digital information, and that is ensuring that it is still possible to access the content encoded in those files. OAIS calls this function “preservation planning”, and describes it as “the services and functions for monitoring the environmentà and providing recommendations to ensure that the information storedà remains accessible to the Designated User Community over the long term, even if the original computing environment becomes obsolete” (OAIS 2002:4.2).
6.4.1.3 Preservation planning is the process of knowing the technical issues in the repository, identifying the future preservation direction (pathways), and determining when a preservation action, such as format migration, will need to be made.
6.4.2.1 When a file format becomes obsolete and is at risk of becoming inaccessible due to the unavailability of appropriate software to access the content, there are basically two approaches that can be made; migration, or emulation. In migration the file is modified, or migrated to a new format, so that the content can be recognised and accessed using the available software of the time. In emulation, the access or operating software is modified or designed so that it will open and play the obsolete audio file format on a new system which would not otherwise be able to open the content.
6.4.2.2 Our current understanding leads us to believe that for simple discrete files, such as uncompressed audio files, the most likely approach will be migration but this is not certain and all digital storage approaches and systems should be flexible enough to be responsive to the changing environment. Adequate preservation metadata as described in the PREMIS recommendations or the explicit file typing (including versioning) in BWF/AES31-2-2006 fields will support either approach, as will the standards being developed in AES-X098B which will be released by the Audio Engineering Society as AES57 “AES standard for audio metadata – audio object structures for preservation and restoration”. Harvard University is developing a toolkit which supports the population of the necessary fields which will be released in open source.
6.4.2.3 This aspect of digital preservation is the strongest argument for an absolute adherence to the standard format described. The large investment the audio and IT industries have made in the standard audio format (.wav) means that the requirement for professional software tools which will enable the continued access to content will help to ensure that the sound archive can manage access to their collections. Likewise, the large investment in a single format will also help support the continuance of that format for the longest period, as the industry will not change an entrenched format without significant benefits.
6.4.3.1 Though the wise choice of standard formats, and an observance of industry practices will delay the eventuality, the day will come where it will be necessary to undertake a preservation action of some type which will be needed to maintain access to the audio content stored. The issue for sound archivists concerned with their digital content will be determining when to undertake that step and what precisely to do.
6.4.3.2 A number of initiatives are being developed to help support this need. These include the Global Digital Format Registry (GDFR http://hul.harvard.edu/gdfr/), which exists to support “the effective use, interchange, and preservation of all digitally-encoded content.” Other services provide recommendations about suitable format, such as those provided by the Library of Congress (US) or The National Archives (UK).
6.4.3.3 The factors which will motivate a sound archivist to undertake some sort of preservation action will be the recognition that new software no longer supports the old format, and the industry as a whole moving to select a new format. Knowledge of the events that herald change comes from expert understanding of the technology, the industry and the market and sound archivists are well advised to take heed of the recommendations services such as those noted above.
6.4.3.4 Software and services under development, such as the Automatic Obsolescence Notification System (AONS), will provide advice to collection managers on when changes have occurred in the market requiring action (https://wiki.nla.gov.au/display/APSR/AONS+II+Documentation). The implementation of such services will occur in parallel with the development of the GDFR.