Old songs with a new sound
Saving the music
Countless speech and music recordings the world over are archived on magnetic tape. However, these tapes age over time. In order to salvage valuable assets, it is essential to digitize these recordings and in the process to assure that the digital copy is perfect.
Overview
This was the motivation for MediaServices GmbH (near Salzburg) to develop the AudioInspector™, a software product for efficient audio digitization and quality control. To enable the combination of interdisciplinary knowledge, the system has been continuously developed since 2006 by a work group including SCCH, programmers of MediaServices, Uni Software Plus GmbH and two departments at the University of Linz: Knowledge-Based Mathematical Systems (Prof. Klement) and Electric Measurement Technology (Prof. Zagar).
Challenge
Even the task of data collection is challenging: up to four tape decks can be controlled independently and deliver four audio signals that must be digitized and analyzed in parallel. This analysis encompasses more than twenty individual tests. On the one hand, technical parameters (measurements from signal processing and psychoacoustics) are computed. On the other hand, specialized detectors search for audible artifacts for which there had been few mathematical methods. Each potential error is evaluated in its context: recordings that were copied from a 78 rpm record from sixty years ago must be evaluated differently from studio tapings; voice recordings differently from classical music. It is important to merge this multitude of individual evaluations; this is where the strength of machine learning comes to bear. MediaServices assembled a collection of various, evaluated tape recordings. This evaluation, the human expert knowledge, can then be reproduced on the computer: This enables automatic compilation of an error profile from which the overall evaluation of the quality of the recording can be derived.
Solution
CEO Paul Leitner explains: "The AudioInspector™ combines all this behind a complex yet easy-to-use interface. While a sound technician once had to listen to each recording completely, he or she can now focus on the check of the locations classified as poor by the AudioInspector™. This enables efficient digitization and control even for large archives."