A Systemic Approach to the Preservation of Audio Documents: Methodology and Software Tools

Table 7

Metadata associated to the audio files in the descriptive sheet of a preservation copy. Items marked with a star (*) are not obtained with JHove: the name of the file is given by the user, and the duration of the file is calculated with PSKit PreservationPanel (class MetadatiAudio, private method durataTraccia(File f) that returns a String with the duration in the format HH:MM:SS).

Metadata	Description
Name*	Name of the audio file contained in the preservation copy including the extension, and without any leading directory components.
Duration*	Duration of the audio file in the format HH:MM:SS.
Size	Size of the audio file in a human readable format, for example 874 MB or 1.2 GB.
Extension	Extension of the audio file, for example, wav.
Format (MIME type)	The standard recognized name for the format of the audio object.
Encoding	The encoding scheme used when audio digitization occurred for the described audio object. The majority of digital audio recordings will have a value of “PCM”.
Profile	String obtained with the combination of the values Format and Audio Format extracted from the header of the audio file. For example, PCMWAVEFORMAT. See the WAVE file format specifications for details.
Number of tracks	Tracks are here intended as channels; therefore a monorecording will have 1 track. This definition has been adopted to resolve the ambiguity of terminology between “track” (here intended as autonomous audio file, e.g., a CD has 14 tracks) and “channel” (typical values would be 1, 2, 4, and 8). Note that the metadata “Signal type” (mono, stereo, …) is not listed in this table because it is a qualitative evaluation of the operator and it cannot be extracted automatically—nevertheless it is included in the descriptive sheet in the section that describes the physical original. In the authors’ experience, “number of tracks,” “number of channels,” and “signal type” are the minimum combination of metadata to describe any type of recording format with no ambiguity whatsoever.
Bitdepth	The number of bits per sample for the audio content of the described audio object. This element describes the actual number of bits of the sample, whereas Word Size describes the number of bytes used to contain the sample.
Sample rate	The sample rate of the audio data for the described audio object.
Byte order	The order in which a sequence of bytes are stored in computer memory. Used to indicate whether the file is in little-endian or big-endian order.
First sample offset	The byte offset of the start of the data chunk which actually contains the waveform data with respect to the beginning of the file.
Compression	Name of the algorithm for data compression applied to the audio file, if any. For preservation copies, it should always be “none.”
Checksum MD5	A string indicating the checksum signature of the audio object. For example, 8847e21949079bfd4bf0c2bc26ba074a
Checksum CRC32	A string indicating the checksum signature of the audio object. For example, 422f2901
Checksum SHA-1	A string indicating the checksum signature of the audio object. For example, 10a000e21a4c99479b15b852fcb3467b51c08cf5