Digitisation of analogue audio and video recordings

The difference between analogue and digital audio and video

Analogue recording captures signals as physical variations on a medium, such as VCRs, tape or record players. Analogue devices read these signals by scanning the variations. For example, a record player creates sound by reading the grooves on a record.

Digital recordings use binary code (numbers). Devices like CD recorders or video cameras sample the signal at set intervals and convert it into digital information. A higher sampling rate gives better quality sound or video. Digital audio and video have key advantages over analogue recordings:

• computers can edit digital recordings to enhance and add effects, while analogue recordings can only play as they were originally captured
• digital files are non-linear, so they can be played or edited from any point
• digital recordings do not lose quality over time or with repeated use
• digital files can be compressed for efficient storage by identifying patterns in the data.

Why digitise?

All public offices have an obligation to retain accessibility to technology/equipment dependent records under s.14 of the State Records Act 1998. This applies to all State records, regardless of how long they are required to be kept. Digitisation may sometimes be required to guarantee continued authenticity.

Digitisation converts analogue recordings to digital format. Reasons to digitise include:

• devices to play analogue recordings, such as VCRs or record players, are no longer widely available
• analogue recordings become fragile and degrade over time or with repeated use threatening their accessibility
• digital recordings allow for enhancement, better indexing and faster search and retrieval
• digital files can be delivered online, making them more accessible
• new versions of recordings can be created for different uses.

Prioritising digitisation

Digitising analogue recordings can be expensive and time-consuming. Your organisation may, by necessity, need to take a risk based approach and establish priorities for digitisation. Priorities should include analogue recordings that:

• are masters and are used often, as frequent use degrades analogue recordings
• are already showing signs of wear and are at risk of being lost
• are required to be kept under your organisation’s retention and disposal authority, especially those marked as ‘State archives’.

Retention and disposal authorities will help you identify which recordings need to be kept for the long term.

Quick tips for digitisation

• Always use the best version of the analogue recording as the master.
• Digitise in the highest quality possible, without compression.
• Collect metadata throughout the process.
• Keep testing to ensure the essential characteristics are maintained.
• Create backups of the original and enhanced versions.
• Regularly monitor your digital files.

Digital audio and video file formats

When choosing file formats for digitised audio and video, consider:

• the purpose of the project
• the required quality of the audio or video
• how long the files need to be kept, as outlined in your retention and disposal authority.

For more information see Digital audio and video file formats.

Metadata

Metadata is structured information that describes records and makes them easier to find, access and manage. It also verifies the authenticity of files and helps with their long-term preservation.

Metadata for analogue recordings

Examples of metadata on analogue recordings include:

• record covers with information like the place of recording, speaker or event
• tape labels with production details, viewing restrictions, title and date.

Your organisation should identify the metadata needed for managing the files and supporting business needs.

Metadata for digitisation

When digitising recordings, it's important to collect specific metadata. This helps track the digitisation process and technical details about the old and new formats. Key metadata should include:

• the date of digitisation and the operator
• digital file recorder configuration settings
• digital file recorder identification; type, version, serial number
• details of the source tape and identifier
• source videotape reproducer identification; type, serial number etc
• master preservation file encoding details; codec type, versions etc
• transfer operator identification
• technical analysis of the video and audio signals
• a review date to remind you when the files need to be checked to monitor its condition and useability and if refreshment or replication is needed.

Ensure that the metadata is complete and accurate, and verify that automatic metadata capture is correct. If transferring the digitised recording as State archives, make sure the metadata follows the guidelines required by the Museums of History NSW.

Note: Establish high quality control and testing into the digitisation process to ensure that characteristics of the analogue recording are faithfully reproduced.

Disposal of analogue source records

Source records remaining after digitisation of analogue materials have been excluded from the General retention and disposal authority: source records that have been migrated. If you need assistance regarding the disposal of source records, contact State Records NSW.

Preservation of digital files

Digital files can become obsolete or degrade over time. It’s important to monitor the files regularly to make sure they stay usable. Preservation may involve refreshing or replicating files in newer formats. To protect the files:

• Digitise in high-quality, lossless formats.
• Store a copy in a different location for disaster recovery.
• Regularly check for file degradation or technological obsolescence.