Friday, May 10, 13:00 – 15:00 h, Room K2
W1 Perceptual Issues Related to Cascaded Audio Codecs

Chair: Thomas Sporer, Fraunhofer AEMT, Ilmenau, Germany
Panel:
John Couling, Dolby Laboratories Inc, UK
Jürgen Herre, Fraunhofer IIS, Erlangen, Germany
Martin Link, IRT, München, Germany
David Meares, BBC, UK

Summary
In analog times each processing step caused a reduction of the audio quality. For some time, digital processing seemed to solve the problem forever, at least as long as linear formats with high resolution were used in professional audio. Today several portions of the transmission chain include perceptual audio coding schemes. The raw material often comes from portable devices or the Internet and is encoded with MP3 or it is stored on MiniDisc using ATRAC. Some broadcasting archives use MUSICAM at high bit-rates and, finally, the emission networks employ MUSICAM (Europe), AC-3 (US) or AAC (Japan).
The mixture of different coding schemes at different bitrates makes transcoding and tandem coding a must. In each encoding step additional quantization noise occurs, possibly leading to serious impairments of the audio quality.
In this workshop typical usage scenarios are presented and discussed. Results from listening test conducted by ITU and EBU over the last years are summarized. Different solutions to reduce tandem artifacts are presented.
The panel includes broadcasters, manufacturers of audio coding schemes, and representatives of audio research laboratories.