An Efficient, Low-Complexity Audio Coder Delivering Multiple Levels of Quality for Interactive Applications

This paper proposes an efficient, low complexity audio coder based on the SPIHT (set partitioning in hierarchical trees) coding algorithm [5], which has achieved notable success in still image coding. A wavelet packet transform is used to decompose the audio signal into 29 frequency subbands corresponding roughly to the critical subbands of the human auditory system. A psychoacustic model ,which, for simplicity, is based on MPEG model I, is used to calculate the signal to mask ratio, and then calculate the bit rate allocation among subbands. We distinguish the subbands into two groups: the low frequency group which contains the first 17 subbands corresponding to 0-3.4 KHz, and the high frequency group which contains the remaining high frequency subbands. The SPIHT algorithm is used to encoder and decode the low frequency group and a reverse sorting process plus arithmetic coding algorithm is used to encode and decode the high frequency group. The experiment shows that this coder yields..

Scalable and perceptual audio compression

This thesis deals with scalable perceptual audio compression. Two scalable perceptual solutions as well as a scalable to lossless solution are proposed and investigated. One of the scalable perceptual solutions is built around sinusoidal modelling of the audio signal whilst the other is built on a transform coding paradigm. The scalable coders are shown to scale both in a waveform matching manner as well as a psychoacoustic manner. In order to measure the psychoacoustic scalability of the systems investigated in this thesis, the similarity between the original signal\u27s psychoacoustic parameters and that of the synthesized signal are compared. The psychoacoustic parameters used are loudness, sharpness, tonahty and roughness. This analysis technique is a novel method used in this thesis and it allows an insight into the perceptual distortion that has been introduced by any coder analyzed in this manner