LCAudioMD is an XML schema developed by the Library of Congress for recording the technical characteristics of audio digital objects. It serves a critical role in digital preservation workflows, capturing the codec, encoding, and signal information needed to ensure long-term accessibility of audio content. AudioMD is typically used as an extension schema within METS (Metadata Encoding and Transmission Standard) documents, complementing the descriptive and administrative metadata provided by other schemas.
Background
AudioMD was developed by the Library of Congress as part of a broader effort to create technical metadata schemas for different media types in digital preservation contexts. Recognizing that METS provided a container for packaging metadata but lacked domain-specific technical detail for audiovisual materials, LC created AudioMD alongside VideoMD in the mid-2000s. The two schemas share a homepage and are often discussed and used together. AudioMD draws on earlier work in audio preservation metadata, including concepts from the AES (Audio Engineering Society) standards for audio metadata.
Purpose & Scope
AudioMD captures the technical properties needed to understand, render, and preserve audio digital objects. It is intended for use by digital preservation systems, digital asset management platforms, and institutional repositories that hold audio content. The schema addresses both file-level technical characteristics and the physical properties of the audio signal.
Key Elements / Properties
| Element | Description |
|---|---|
compression |
Codec and compression scheme used |
dataRate |
Bit rate of the audio stream |
dataRateMode |
Fixed or variable bit rate |
samplingFrequency |
Samples per second (e.g., 44100 Hz) |
bitsPerSample |
Bit depth of each audio sample |
byteOrder |
Endianness of the audio data |
channels |
Number of audio channels |
duration |
Length of the audio content |
soundField |
Spatial configuration (mono, stereo, surround) |
Serializations & Technical Formats
AudioMD is defined as an XML Schema (XSD). Instances are XML documents, typically embedded within METS <techMD> or <digiprovMD> sections. The schema is available for download from the Library of Congress website.
Governance & Maintenance
AudioMD is maintained by the Library of Congress Network Development and MARC Standards Office. Updates are published on the LC standards website. As a relatively stable technical metadata schema, it undergoes infrequent revisions.
Notable Implementations
AudioMD is used within the Library of Congress's own digital preservation infrastructure. It is supported by digital preservation tools and frameworks that work with METS, including Archivematica and DSpace configurations for audiovisual materials. Cultural heritage institutions with significant audio collections use AudioMD for preservation metadata.
Related Standards
- VideoMD -- The companion schema for video technical metadata, sharing the same homepage and design philosophy.
- METS -- The Metadata Encoding and Transmission Standard, which serves as the primary container for AudioMD metadata.
- PREMIS -- The preservation metadata standard, which addresses broader preservation concerns alongside AudioMD's technical focus.
- AES-X098C -- The Audio Engineering Society's standard for audio object metadata, covering similar technical ground.