Guidelines: Audio Digitization System Performance
Audio-Visual Working Group
Performance of audio digitization systems: overview. The Working Group has been exploring the issues pertaining to the performance testing of audio digitization systems. This activity responds to recommendation 2.4 of the National Recording Preservation Plan and is also intended to parallel efforts by the Still Image Working Group to develop metrics and methods for the performance testing of still image scanners and cameras. For audio digitization, two aspects have been under study: (a) the performance of analog-to-digital converters (ADCs) and (b) the problem of interstitial errors, i.e., accidental loss or transformations of audio samples within the digitizing system before the data stream is written to file. This activity is supported by the Working Group's expert consultant Chris Lacinak of Audiovisual Preservation Solutions.
Performance Guideline for ADCs: Approved and Draft Versions
This guideline pertains to the metrics and measurement methods for ADCs. Its starting point for metrics is Guidelines on the Production and Preservation of Digital Audio Objects (TC-04, Second Edition, 2009; International Association of Sound and Audiovisual Archives). For methods, its starting point is 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.
The pass-fail specifications recommended in this guideline are for the highest level of ADC performance. The rationale and implementation details for testing against this standard are presented in two related documents: Audio Analog-to-Digital Converter Performance Specification and Test Method: Introduction, August 20, 2012 and ADC Performance Testing: Report on Project Development During 2015.
As noted in the 2015 report, testing ADCs against the high quality standard requires relatively expensive equipment and advanced engineering skills. For this reason, the Working Group is also exploring specifications for moderate and minimum levels of performance, with lower equipment costs and requiring more modest engineering skills.
Analog-to-Digital Converter Performance Specification and Testing, v. 1.1 (PDF, 550 KB)
**NEW** Posted for public comment, February 17, 2016. Comments requested by May 30, 2016.
Analog-to-Digital Converter Performance Specification and Testing, v. 1.0 (PDF, 240 KB)
Approved by working group, August 20, 2012.
Analog-to-Digital Converter Performance Specification and Testing (PDF, 217 KB)
Earlier version. Drafted in February 2012 and reformatted June 19, 2012.
Performance Guideline for ADCs: Related Documents
ADC Performance Testing: Report on Project Development During 2015 (PDF 4.6 MB). Detailed technical report that includes comparisons of the 2016 and 2012 guidelines, a discussion (and proposed guideline) for lower-cost testing of performance at lower levels of quality, and a sketch of actions planned for the next round of work. Appendix to the report. Instructions and device scripts used in 2015 testing (zip file, 1 MB).
Audio Analog-to-Digital Converter Performance Specification and Test Method: Introduction, August 20, 2012. (PDF, 621 KB) Archived for reference: The earlier version drafted in February 2012 and reformatted June 19, 2012. (PDF, 506 KB)
Summaries of comments received on the guideline and introduction as of June 21, 2012 (PDF, 84 KB) and July 12, 2012 (PDF, 119 KB). These comments were considered when the August 20, 2012, version of the guideline was drafted.
Analog-to-Digital Converter Performance Specification and Testing, the original version of the combined explanatory report and recommended guideline dated February 24, 2012. (PDF, 499 KB).
Performance Impairments Caused by Interstitial Errors: Field Test Report
Interstitial errors consist of lost or altered samples within the recorded file, resulting in the loss of content and integrity. These errors--often very momentary--result from a failure in the chain of digital data, i.e., in the handoff from the ADC to the digital audio workstation (DAW), and in the DAW's writing of the file to a storage medium. The first item linked below, titled Study Report, describes a 2012 field test carried out in three federal audio facilities, designed to identify occurrences of interstitial errors in the course of actual work. The second item, titled Appendixes and completed in 2012, provides background information as well as re-presenting sections from the consultant's initial 2011 report.
Interstitial Error Study, Volume I. The Study Report. Presented to the Working Group April 8, 2013. (PDF, 3.6 MB).
Interstitial Error Study, Volume II. Appendixes. Presented to the Working Group September 11, 2012. (PDF, 1.9 MB).
Last Updated: 02/17/2016