148 · Representative Documents: Format Policies
RUcore. Sound Objects
Audio/Video Standards Working Group: RU-CORE and NJDH Standards Analysis for Audio Objects
I. Beard, I. Bogus, N. Gonzaga, B. Nahory, R. Sandler 2 Last update: 8/9/2010
Recommended Standards for NJDH and RU-CORE Audio Sampling
• Minimum sampling rate: 44.1kHz 16-bit (CD Audio)
This is the minimum acceptable rate to ensure a good preservation master. Most Compact Discs (CDs)
are mastered at this rate. As such, all audio obtained from CDs will be archived at this rate.
Additionally, 44.1kHz is a suitable sampling rate for RU-Core partners when mastering recordings of
spoken-word speech (i.e. interviews, speeches, press conferences and lectures), that are not accompanied
by high-fidelity sound or music.
• Recommended Sampling rate: 96kHz, 24-bit audio
This is widely considered an ideal rate for high quality audio recordings, including DVD-Audio. For
most audio formats, this sampling rate is the maximum sampling rate that also supports Quad (Dolby
4.0) and Surround (5.1) audio. When repository content partners are making a first generation sample of
musical or high-fidelity recordings from an analog master, it is recommended that this sampling rate be
used whenever technically possible.
• High Level (Maximum) Sampling rate: 192kHz, 24-bit audio
This sampling rate is often touted by audiophiles as one of the best sampling rates to work with in the
editing of audio recordings and creating master samples. However, this format is generally not
supported in current mass-produced formats for Quad or Surround sound. As such, recordings sampled
at this rate should be limited to Mono or Stereo recordings. In general, this sampling rate, and higher
rates, are recommended if there is a reasonable justification for using such a high sampling rate, and it is
believed that the 96kHz rate will not be sufficient for accurate reproduction of the original sound.
Recommended File formats for preservation and presentation of audio objects
The following formats are recommended for the preservation and presentation of audio.
• For Preservation: Standard WAV or Broadcast WAV Format (BWF)
BWF is an extension of the popular WAV audio format. It was first specified by the European Broadcasting
Union in 1997, and updated in 2001. WAV records audio using Pulse Code Modulation (PCM), the industy
standard method for digitizing audio and is used in CDs and DVDs.
The stated purpose of these two file formats is the seamless exchange of digitized audio between different
computer platforms. BWF also specifies additional metadata, allowing audio processing elements to identify
themselves, document their activities, and permit synchronization with other recordings. This metadata is
stored as an extension chunk in an otherwise standard digital audio WAV file.
• No compression of archival master is recommended
As of this writing, the Audio and Video Standards Working Group recommends that no compression of the
preservation master occur. While there are some lossless compression formats available (e.g. Shorten and
FLAC), the open source formats that are currently available are not mature, nor do they have a large enough
user base to justify their use. Doing so may expose the repository to the risk of being unable to later
decompress and access these masters if at some point in the future, support and development for the chosen
compression scheme is abandoned. However, the working group does recommend that the issue of lossless
compression for archival masters be re-assessed at a later date, to determine whether an open standard is
more widely accepted, likely to be readily available and supported for the foreseeable future, and suits our