Perceptual coding, distribution, and enhancement of audio

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The coding of audio is increasingly important for both storage and streaming of audio content. Taking accountof human hearing (psycho-acoustics) can be beneficial in reducing the bit rate needed to reproduce audiosignals with good quality. Only the frequency components that are audible need be coded. This project willexamine new methods that make even more efficient use of the bits when coding an audio signal, therebyallowing for greater reductions in the bit rate required to represent the signal. The coding will employ arepresentation of the audio signal using the "modulation spectrum". This representation dissects the audiosignal frequency-by-frequency to reveal the perceptually important fluctuations of the frequency components.This project also examines scalable and multiple description coding for audio streaming from, for instance, theInternet. This strategy uses a layered approach to coding. A base layer will allow usable quality, whileadditional layers give successively better renditions. In this way, a single audio stream can be used to serviceterminals with differing quality requirements. For instance, a hand-held wireless terminal might need only abasic quality, while a premium quality is appropriate for a home theatre setting. Multiple description codingprovides assurance of the quality delivered to the end user over error-prone media such as the Internet andwireless links.