(en cours de traduction) 

In typical digital broadcast operations several different codecs can be cascaded. Repeated compression and decompression using different codecs at different bitrates can severely impact overall audio quality experienced by the listeners at home or on the move. How good do MPEG Layer 2, MP3, ATRAC, AAC, Windows Media and other audio codecs perform in such cascades?  

An audio codecs demonstration device    

EBU Project Group B/AIM (Audio in Multimedia), chaired by Gerhard Stoll (IRT), attempted to answer  this  question. As part of the EBU study, 36 different cascades were tested by several EBU laboratories (BBC, IRT NRK, and TVP) using both objective and  subjective  evaluation methodologies. The results and conclusions are now available as Tech 3309.  

This document is a must to download if you care about audio quality in digital broadcast chains such as DVB, DAB and DRM! More information on B/AIM can be found here (Members only). 

NOTE: A summary of this study is given in the article entitled "Cascaded audio coding" by David Marston (BBC) and Andrew Mason (BBC). It is published the EBU Technical Review No. 304 (October 2005). 

fdj/nc