Contents:
- Normative References
- Informative References
- Scope
- ADC Performance Guideline (High Quality): Frequency Response
- Total Harmonic Distortion + Noise (THD+N)
- Dynamic Range (Signal to Noise)
- Cross-Talk
- Common-Mode Rejection Ratio (CMRR)
- Low Frequency Intermodulation Distortion (LF IMD)
- High Frequency Intermodulation Distortion (HF IMD)
- Amplitude Linearity
- Spurious Aharmonic Signals
- Alias Rejection
- Sync Input Jitter Susceptibility
- Jitter Transfer Gain
This document specifies a set of metrics and methods pertaining to the performance of the audio analog-to-digital converters (ADCs) used in preservation reformatting workflows. It is a product of FADGI’s AudioVisual Working Group and in particular the work of the primary consultant on the project, Chris Lacinak of AVPreserve. The introductory guide provides the background on how the metrics were determined.ADC performance is the central element within the larger topic of audio digitization system performance, which also includes the problem of interstitial errors (a topic still being studied by the working group) and consideration of the impact of other devices, cables, or interfaces that may be placed in the signal chain (outside the working group’s scope at this time). The metrics specified in the guideline pertain to the production of files using the highest quality ADC devices.
An important recommendation from a group representing top specialists in the field although they target archives with top professional staffing and equipment. However the authors admit that the metrics are quite stringent and that given “the range of types of archival organizations, some with strong resources and others in modest circumstances..as well as the variation in the categories of material to be reformatted..there might be circumstances in which relaxed levels of device performance would be acceptable.” Their intention to address these issues will be welcomed by smaller archives involved in audio digitization programs.