State Records recommends that priorities for digitisation should include analogue recordings that:
- are masters and are used very frequently (as analogue recordings can become degraded by use. Generally copies should not be made from masters)
- are already being degraded by high use and therefore in danger
- have the disposal action as ‘retain in agency’ or ‘required as State archives’ in the organisation’s current retention and disposal authority (as these indicate the recordings that have significant ongoing interest to the organisation or the community).
Frequent use will not degrade digital materials (unless CDs or DVDs become scratched and damaged). Even if the file is a corporate record, if the digitised copy only needs to be kept for a very short period of time, or if high audio quality is unnecessary, your organisation should use the format and codec which is most suitable for the aims of the project and the editing software to be used. The processing power and storage space you have available may also impact on your decision.
Example: many of the MPEG file formats (e.g. mp3) which are standard definition, affordable and widely available may be used if the recordings are only required in the short term and fast delivery (e.g. over the web) is the goal. However, they use lossy compression and are not considered to be of sufficient quality for preservation.
Long term or archival, or where quality is paramount
If the audio or video file:
- will require long term or archival retention or
- needs to be of optimal quality
the format and codec needs to be chosen very carefully. A preservation ‘master’ should be made using a suitable format of as high a quality as possible, then duplicating copies and reference copies can be made at a quality fit for purpose.
Digitising to a higher quality format (e.g. copying from VHS to Motion JPEG) will not increase the quality of the original analogue recording. However, the original recording should never be copied to a format of lesser quality when the aim is to create a preservation master. The aim should be to preserve as much quality of content as possible from the original recording. A lossless copy of uncompressed format will capture all of the original quality if the encoding to digital is optimal.
Only linear uncompressed codecs or mathematically reversible lossless codecs should be considered for preservation.  No compression is ideal, but the files may take up considerable storage space (particularly video files). Your organisation will also need the processing power to be able to open and view the files and do error checking etc.
Widely recognised and accepted formats for preservation purposes for audio are WAV or BWF as these are uncompressed and generally use the lossless Linear Pulse Code Modulation (LPCM) codec. 
FLAC is a suitable format for digital preservation as it is stable, free and open source and employs lossless compression. The National Archives of Australia converts a number of other audio files (including WAV) to FLAC during the process of normalisation for storage in their digital archive. If considering this format for business use, however, it is important to note that it is not widely supported by the audio industry.
Note: Certain file formats may not be compatible with some audio software. You should also ensure compatibility with the software you intend to use for editing or optimising the file.
If the image is to be optimised, lossless methods should be used and information regarding the optimisation should be saved with the audio file separately from the preservation master. Other copies of the recording could use compression if necessary for delivery e.g. over the Internet.
For more information and issues to consider when choosing an audio file format see the JISC Infokit Digital File Formats.
There is no consensus to date among the archival community as to which file format or codec should be used for the digitisation of analogue video which is required to be preserved in the long term or as archives. Therefore, State Records cannot make specific recommendations regarding what particular creation formats should be used.
Analogue video material is imported into a digital video format on a desktop computer by using an analogue-to-digital converter such as a video capture card. If digitisation is being done this way, the choice of capture formats may be limited by the small number of formats any given hardware capture card or software application can support. JISC recommend for mid-range desktop systems the losslessly compressed Blackmagic (proprietary) codec in an AVI or MOV wrapper or the losslessly compressed AJA (proprietary) codec in a MOV wrapper, which are widely used. The National Film and Sound Archive suggest an uncompressed encoding in an MXF wrapper for small scale projects of this nature if the storage capacity is available. If not, MOV or AVI can be used with an uncompressed 8 or 10 bit encoding. These may be converted to an open format later.
Several larger scale archival projects underway favour the open and lossless JPEG 2000 codec, e.g. with an MXF wrapper.
 National Film and Sound Archive (NFSA), Digital Media Preservation: Video [unpublished]
 National Archives of Australia, Xena Preservation Software, Supported formats, available at: http://xena.sourceforge.net/help.php?page=normformats.html
 MOV is likely to be the better choice of the two as it is more widely adopted and has more metadata capability. Its proprietary nature is of concern, however. If this is unaffordable the NFSA recommend, at the very least, well documented high-bit rate MPEG2 or DV encoding in the knowledge that there almost certainly will be a loss of quality.
Published January 2009