10. Digital target formats and resolution

Digital coding schemes (formats) as well as digital resolution are the subject of further development. Notwithstanding these developments, it must be stressed that coding schemes used for preservation purposes must be openly defined and not proprietary to a limited number of manufacturers. Data (file) formats are superior to digital audio streams (R-DAT, CD-Audio) in terms of data security and their monitoring.

Digital formats have a limited resolution set by the defined and finite sampling frequency and digital word length. While for digitally originated signals the original resolution should comply with the digital preservation format, the choice for analogue originals will always be a compromise. In principle, high digital resolutions are desirable for the adequate representation of all the minute subtleties of original analogue signals.

Comment:
In recent years, storing audio in form of file formats has become the dominant practice and the .wav or BWF format has become a de-facto standard. This format is officially recommended by the Technical Committee (cf IASA-TC 04, 6.1.1.1 and 6.6.2.2).

Currently, A/D converters providing 192 kHz sampling rate and 24 bit amplitude resolution are standard. For analogue originals IASA recommends a minimum digital resolution of 48 kHz sampling rate at 24 bit word length. In heritage/memory institutions a resolution of 96 kHz / 24 bit has become widely adopted. Better transfers of the unintended parts of a sound document (cf paragraph 8) make the future removal of these artefacts by digital signal processing easier when making access copies. Speech recordings, because of the transient character of consonants, must be treated like music recordings.