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UBC Theses and Dissertations

Design of two psychoacoustic models for real time implementation of a wideband audio codec Koch, Anthony C.


Implementation of an audio codec (coder/decoder) is sought which meets a new standard proposed by the ISO/MPEG (International Standards Organization / Moving Pictures Experts Group) committee. The standard aims to encode wideband audio signals, achieving data compression by employing psychoacoustic modelling. By exploiting the properties of the human auditory system, psychoacoustic modelling shapes quantization noise spectrally to render it inaudible. This thesis provides the design of two new psychoacoustic models used to effect the real time implementation of the new ISO/MPEG audio codec on an existing hardware platform at MPR Teltech, a subsidiary of the British Columbia Telephone Co. The two new models are named: spreading function model and attenuation model. Both models overcome real time implementation problems of existing psychoacoustic models found in the literature by introducing new methods of calculating the global masking threshold and signal to mask ratios. Listening tests and simulation analyses show that while both models attain very high audio coding quality, the attenuation model is superior to the spreading function model, and is considered for implementation in the new ISO/MPEG codec on the existing hardware platform.

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