Choosing a format or codec for digitising audio or video

Formats and codecs 

Audio and video files can come in a variety of file formats, such as mp3, mp4, .mov, etc. A codec is the method by which an audio or video bitstream is encoded or decoded. Audio or video files generally cannot play without the correct codec software to decode them.

More information can be found at Digitial audio and video files.

Prioritising recordings for digitisation

State Records NSW recommends prioritising the digitisation of analogue recordings that:

• Are master recordings used frequently: High use can degrade analogue recordings. Copies should not be made from masters.
• Are at risk due to wear and tear: Frequent use may already be causing damage.
• Have significant long-term value: Check the retention and disposal authority for recordings marked as “retain in agency” or “required as State archives.” These indicate ongoing importance to your organisation or the community.

Formats for short-term use

Recordings which are only needed for a short time or do not require high audio or video quality do not necessarily need high-quality storage media. Conversely, recordings requiring long-term retention and high-quality audio or video need to be stored accordingly. Choose a format and codec that suits the purposes for which the records are being retained, and the editing and playback capacity you can access. Processing power and storage availability should also guide your decision. 

Example: MP3 files are affordable, widely supported, and suitable for quick delivery (for example, online streaming). However, they use lossy compression, making them unsuitable for long-term preservation.

Example: Digital files do not degrade with frequent use, but physical media like CDs or DVDs can be scratched. 

Formats for long-term or archival use

If a recording needs to be kept long-term or at optimal quality, carefully select a format and codec:

1. Create a preservation master:
   • Use the highest possible quality to capture all details of the original recording.
   • Avoid copying to a format of lesser quality.
2. Create lower-quality copies for sharing or day-to-day use.
3. Use lossless codecs:
   • Only linear uncompressed codecs or mathematically reversible lossless codecs should be used for preservation.
   • Note that uncompressed files may require significant storage space and processing power.

Recommended formats for audio

• WAV or BWF: These are widely accepted for preservation and use lossless Linear Pulse Code Modulation (LPCM) codec. 
• FLAC: Stable, free and open-source with lossless compression. While suitable for preservation, FLAC may not be supported by the audio industry.

Considerations

• Ensure the chosen format is compatible with your editing and playback software.
• Save optimisation details separately from the preservation master.
• Lower-quality, compressed copies (for example, MP3) can be used for web delivery or other non-archival purposes.

Recommended formats for video

There is no consensus to date among the archival community for video preservation. Use these guidelines: 

1. Uncompressed or lossless codecs:
   • For small projects: Use MOV or AVI with uncompressed 8- or 10-bit encoding.
   • If storage capacity allows, use uncompressed encoding with an MXF wrapper.
2. Larger-scale projects:
   • Open and lossless formats like JPEG 2000 (with an MXF wrapper) are widely used.
3. Digitisation process:
   • Use an analogue-to-digital converter, such as a video capture card.
   • Your hardware and software may limit the formats available.

Key considerations

• Recordkeeping requirements: Proprietary systems generally use their own codecs, and systems should be well-researched prior to purchase to ensure that recordkeeping requirements will be satisfied. 
• Storage: High-quality formats require significant storage, especially for video.
• Software compatibility: Ensure chosen formats and codecs work with your editing tools.
• Compression: Use uncompressed or lossless methods for preservation masters. Compressed formats may be used for distribution if required.