A MDCT-based click noise reduction method for MPEG-4 AAC codec

A MDCT-based click noise reduction approach used for MPEG-4 AAC codec is proposed in this paper. This noise reduction technique can be embedded in MPEG-4 AAC codec as a function module of audio restoration. The proposed method contains two parts: click noise detection and click noise removal. The click noise detection is further divided in two steps. Firstly, the window type for MDCT is decided by perceptual entropy (PE). Secondly, the spectral entropy (SE) of clean audio signal and noisy signal can be calculated and the position of clicks noise can be determined using minimum error Bayesian decision. A MAD-based soft-thresholding criterion is adopted for click noise removal. In addition, the spectral smoothing is employed in the adjacent frames. The test results indicate that the proposed algorithm can improve the audio quality and provide a comparable performance with conventional click noise method.