Wave Field Synthesis vs. Higher Order Ambisonics; Audio Codec Improvement

Fri, 11/05/2010 - 10:30am - 12:00pm
CCRMA Seminar Room
Event Type: 
DSP Seminar
Speaker: Jens Ahrens from Deutsche Telekom at the TU Berlin
Time: Friday Nov. 5, 10:30AM-11:30AM
Title:  Analytical Methods of Sound Field Synthesis
Wave Field Synthesis (WFS) and Near-field Compensated Higher Order Ambisonics (NFC-HOA) constitute the two best known methods for sound field synthesis. Due to the different formulations, a comparison of the two approaches has only been possible with certain limitations. This talk presents a unified analytical framework based on fundamental integral equations covering both WFS and NFC-HOA. The relationships of the two approaches are pointed out and emphasis is put on the properties of the synthesized sound fields with respect to spatial aliasing. The latter constitutes an unavoidable artefact in practical implementations.
Speaker: Colin Raffel
Time: Friday Nov. 5, 11:30AM-noon
Title: Using Noise Substitution for Backwards-Compatible Audio Codec Improvement
A method for representing error in perceptual audio coding as filtered noise is presented. Various techniques are compared for analyzing and re-synthesizing the noise representation. A focus is placed on improving the perceived audio quality with minimal data overhead. In particular, it is demonstrated that per-critical-band energy levels are sufficient to provide an increase in quality. Methods for including the coded error data in an audio file in a backwards-compatible manner are also discussed. The MP3 codec is treated as a case study, and an implementation of this method is presented. 
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