Friday, February 28, 2014

Mere Adequacy is Never Adequate

There are five fundamentals of high-quality digital sound archiving and preservation for analog source material: accuracy, appropriateness, adequacy, consistency, and explicitness.

Previously we examined accuracy (with regard to the source).Today we tackle the next two fundamentals, appropriateness and adequacy (with regard to your processes).

[Image Credit: Sarah Tehan, Aporia, 2013.]

The process of sound archiving and preservation is like scholarly editing. Just as the scholarly edition's basic task is to present a reliable text, the sound preservationist's basic task is to present a reliable digital record of an analog source. In both pursuits, decisions have to be made concerning (re-)construction and representation of the original material to achieve reliability.

Reliability in digital construction and representation of analog sound is a direct result of:
  1. Appropriateness: the extent to which a particular process (step) advances accurate sound representation, and the extent which the listener is satisfied with the sound produced.
  2. Adequacy: the extent to which a particular process (step) can be shown to be as good as necessary for its purpose or requirement.
The appropriateness and adequacy of the major function groups in the audio archiving and restoration pipeline can be characterized as follows:
  • Digital Recording
    Appropriate: Critical first step in the archiving process
    Adequate: 48 KHz minimum sampling rate; 24-bit minimum encoding depth
  • Audio Import/Export
    Appropriate: Advances sound data through the processing pipeline
    Adequate: No information lost in transfer
  • Format Conversion
    Appropriate: Ultimate sound output in format desired by listener or required by tools
    Adequate: No information lost in conversion; minimal information loss in compression
  • Automated Clean/Repair
    Appropriate: Algorithmic processing of common audio artifacts
    Adequate: No artifacts introduced 
  • Manual Clean/Repair
    Appropriate: Processing of artifacts unique to a given recording
    Adequate: Minimal audio loss; clipping eliminated; no artifacts introduced
  • Track Isolation
    Appropriate: Facilitates playback of individual songs/chapters/passages, etc.
    Adequate: Envelope of silence before and after track
  • Volume Normalization
    Appropriate: Addresses volume differences on playlists incorporating multiple titles
    Adequate: Target sound level -0.1 dB for all titles
  • Metadata Editing
    Appropriate: Captures relevant information about the original recording
    Adequate: Accurate, and without typographical errors

Another way of characterizing appropriateness and adequacy is that every step in your process must be necessary and your process as a whole must be sufficient. For a step to be necessary, eliminating that step would produce a less-reliable result. A process is sufficient if it is not a failure for having omitted other steps. All magic formulas for success break down on one or both of these criteria. Don't let it happen to you.

             Vinyl-to-Digital Restoration #65            

Artist: Miles Davis
Title: Porgy and Bess
Genre: Jazz
Year: 1958

To quote Dan Epstein: "Take George Gershwin's Porgy & Bess, add Miles Davis and arranger Gil Evans, and what do you get? A classic jazz album that--despite the fact that the material has been rendered almost overly familiar due to countless interpretations--still sounds remarkably fresh four decades after its initial release. Miles' soft yet piercing trumpet style is perfectly suited [TGD: appropriate] to Gershwin's melancholy melodies, Evans' musical direction of his 18-piece orchestra is impeccable [TGD: adequate], and their version of 'Summertime' may well be the finest ever waxed."

© 2014 Thomas G. Dennehy. All rights reserved.