An accurate decorrelation method for parametric stereo coding

Decorrelator is a module to restore the specific correlation properties between stereo signals in parametric stereo audio decoder, which is vital to keep the spatial information of the stereo signals. Generally, the existing decorrelators are prone to have a comb-filter effect which results in an undesirable “metallic” sound and produce temporal smearing such as pre- and post-echoes artefacts. This paper presents an accurate decorrelation method based on solving the two decorrelation-related functions in complex-frequency domain. Using this method, a novel parametric stereo coding system is proposed. In this system, a modified discrete cosine transform and a modified discrete sine transform are used to transform stereo signals from time domain to complex-frequency domain for calculating the stereo parametric, and the Advanced Audio Coding module of MPEG-4 is chosen to perform the mono-channel coding and decoding process. The results of the subjective evaluation experiments show that the proposed system perform better than the HE-AAC system