Guidelines: Analog-to-digital converters (ADCs): high-level performance metrics and measurement
Audio-Visual Working Group

Performance guideline and methods of measurement

This activity analyzed two interrelated questions. First, what level of performance is required when digitizing analog sound recordings for preservation? Second, how can the multiple aspects of performance be measured to determine if a given ADC passes or fails?

The development of the guideline and recommended methods depended upon valuable prior work. For the pass-fail metrics, the starting point was Guidelines on the Production and Preservation of Digital Audio Objects (TC-04, Second Edition, 2009; International Association of Sound and Audiovisual Archives). For methods, starting point was AES standard method for digital audio engineering — Measurement of digital audio equipment (AES17-1998, r2009; Audio Engineering Society) and other standards cited in the guideline.

Benefits of ADC performance measurement

As the Working Group carried out this activity, it identified three benefits to performance testing. The first had been anticipated while the second and third emerged from field tests carried out in three federal audio-preservation facilities:

• Benefit 1. Did it pass? How did your ADC perform against the guideline recommendations? For high-level outcomes, the metrics in this guideline and its methods for measurement offer the best possible confirmation of performance.
• Benefit 2. Crosscheck system setup. Equipment and systems may have been incorrectly installed and operators may not be fully attentive. The formality of running the test spotlights problems and motivates corrective action.
• Benefit 3. Ongoing monitoring of ADC performance. Running a test and retaining a report provides a benchmark: run the test again a few weeks later and compare. If something has changed, this finding will motivate further checking and correction if needed.

High-level performance guideline, explanatory reports, and other resources

• Audio Analog-to-Digital Converter Performance Specification and Test Method: Guideline (High Level Performance) v.1.1 (PDF, 550 KB). Approved by Working Group, July 2016.

The twelve pass-fail metrics recommended in this guideline are for the highest level of ADC performance and their measurement requires relatively expensive equipment (typically on the order of $20,000) and advanced engineering skills. This topic is discussed in detail in two related documents listed below. The third link provides access to the device-specific scripts FADGI employed for its field testing:

• Audio Analog-to-Digital Converter Performance Specification and Test Method: Introduction. August 20, 2012.
• ADC Performance Testing: Report on Project Development During 2015. Includes comparisons of the v.1.0 (2012) and v.1.1 (2016) guidelines. February 16, 2016.
• Device-specific scripts used in the 2015 FADGI field tests. Appendix to report cited in preceding bullet. February 11, 2016.

Access to earlier versions of the guideline and planning documents is provided on the archived ADC documents page.

Working Groups

Still Image Working Group
This group is involved in a cooperative effort to develop common digitization guidelines for still image materials.

Audio-Visual Working Group
This group works collaboratively on common and sustainable technical guidelines, methods, and practices for digitized and born digital sound recordings and moving images.