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Selecting an Audio Digitisation System

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Summary

This document is a discussion of some of the primary audio digitisation systems available for digitising analogue audio media. This document is intended to be of use to staff engaged in the digitisation of analogue audio, whether dealing with only a few or a few hundred tapes.

Introduction

The transfer of analogue audio files to a digital format holds many benefits to institutions, including the preservation of resources and providing greater accessibility to others. As the methods of delivering the digital files to users are becoming more sophisticated and the technologies available for digitisation are also becoming more advanced, it is imperative to keep abreast of the developing climate and the needs of your users.

The process of digitisation requires scrupulous planning with careful attention to detail and it is important that every technical consideration is met for this process to be a success. This document presents a few of the available systems for digitising audio and their inherent features, and covers best practice for setting up an audio digitisation suite.

Analogue audio to Optical Disc (CD or DVD)

A simple and quick method of digitising is to play the audio directly to an optical disc recording device. The analogue playback device is directly connect to the recording machine which writes the audio to a disc in real-time. This method eliminates the used of a computer and audio interface as the A>D and D>A conversion is done internally within the recording machine. Although this primitive method may be appealing due to its speed and ease of use, there can be disadvantages involved for the long-term preservation of audio files.

Advantages

Can be carried out by a member of staff who is comparatively unfamiliar with the technology involved.
CD-audio and DVD-data discs are very common and non-proprietary formats (i.e. not supported by only a single manufacturer.
In newer machines data can be transferred to external hard drives once digitised for storage.
CD and DVD discs and authoring equipment are inexpensive.
High audio quality can be achieved when digitising to DVD discs (up to 192KHz 24-bit or DSD format).

Disadvantages

Some of the cheaper priced machines may not offer as accurate digitisation as other systems available.
Optical discs may suffer from condition problems which makes them unusable in the mid to long term.
In order to generate further copies a computer or external hard drive must be used or the tape replayed and recaptured.

These factors mean optical discs recorders are an excellent format for local delivery, but are not commonly used as a format for storage or preservation.

Analogue audio to hard disk recorder

Similar to the method described above, all-in-one units are available that digitise audio directly to a hard drive. These units provide a quick and easy solution where digitisation can be done and removable hard drives can be ejected and stored on the shelf straight away for preservation.

Advantages

Easy to use system allows a member of staff who is comparatively unfamiliar with the technology involved to operate the workflow.
Offers high quality capture settings.
Some units offer integration directly with a computer based system via Firewire if required.

Disadvantages

Limited or no metadata inputting/editing capabilities.
Limited or no editing, restoration or post-production features.

For digitisation this method presents a good quality alternative to using the computer based system, discussed further in this document. However, for projects wishing for more than just capture of audio, as any manipulation of files beyond basic capture will require a computer, herein lies an argument for choosing a computer based system over this approach.

Analogue audio to digital audio tape

A preferred choice some years ago, Digital Audio Tape (primarily ADAT and Sony's DAT formats) began to replace magnetic tape for recording new media and transferring older media from magnetic formats in the mid-1980's. At present digital audio tape formats are considered to be a vulnerable media carrier and now that playback equipment is obsolete, digitising to digital audio tape formats is not recommended.

Analogue audio to computer hard drive

This method of digitising uses a desktop (or even laptop) computer hard drive as direct storage of an audio signal fed through an audio interface; which converts the analogue signal to digital and passes the information to the computer. The computer requires dedicated software for capture and is capable of sophisticated editing and any post-production techniques if necessary. This method can range in price with some of the more expensive systems offering extremely high quality A>D conversion and audio manipulation and control.

Using a computer based system with a dedicated external analogue to digital converter is fast becoming standard digitisation practice within the archival community.

Advantages

Produces the highest quality audio conversion currently available.
Can process multiple audio tracks at once for time efficient digitising.
The price of computer components and systems is constantly falling as is the price of hard disk drives, which is currently inexpensive.
Offers the ability for advanced editing and post-production work, i.e. restoration of audio.
Reformatting of audio files is easily and quickly achieved with software.
Access available through software to utilise any metadata schema desirable.
Hard drives can be removed quickly and easily from the host computer and stored on shelves with little or no environmental control measures.
Hard drive technology is non-proprietary and subsequently ideal as one method of long-term storage.

Disadvantages

Equipment can be bulky, heavy and not ideal as a portable solution.
Not particularly suitable for non-technical people to learn, set-up, or administer, as a good understanding of IT and audio-visual systems is required.
Current hard drives contain a spinning disc; this technology is increasingly being replaced by solid state (flash drive) technology over the next few years. Solid state is likely to be more robust and even better suited to storing digital audio data. However, this is not necessarily a problem as files stored on currently available hard drives can easily be copied onto new solid state drives as they become affordable.

A typical analogue audio to computer hard drive system is looked at in detail in the JISC Digital Media document Equipping an Audio Digitisation System.

High-end automated audio digitisation systems

Some large-scale digitisation projects can have so much analogue media to be digitised that an automated system provides the best solution to ingest all the audio within the timescale of the project. This system takes full control, albeit to user defined settings, over the playback control of audiotape machines, capture, error checking, transcoding and producing metadata records. The more advanced systems can even perform automated restoration techniques on batches of files.

These complicated systems usually require a number of desktop computers over a local network and as a result are often out of the price range and considered too excessive for most digitisation projects.

Advantages

Largely automatic, needing little human input.
Extremely quick and efficient.
High quality digital audio and high quality metadata is automatically produced.

Disadvantages

Out of the price range of most institutions.
Exceptions still require human input which could prove to be inefficient in certain circumstances - such as when digitising a large amount of different analogue media types from different eras and in differing states or repair.
Often only a single system can be purchased due to cost. This means there is no backup in case of major malfunction.
Support for some systems is not available outside the US.

All of these automated systems work differently but each is essentially an analogue audio to computer hard drive system. As such, the process carried out is simply an automated version to that described in the previous section.

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