Efficient and robust frame-synchronized blind audio watermarking by featuring multilevel DWT and DCT

This paper presents a self-synchronizing blind audio watermarking method developed based on the distinctive features of multilevel discrete wavelet transform (MDWT) and discrete cosine transform (DCT). In the proposed design, the repetitive pattern hidden in the 11th approximation subband is used to control frame synchronization, and the wideband signal covering the first to ninth detail subbands is used to hide binary information. Tracing the zero-crossings across the extracted synchronous signal makes it possible to recalibrate frame positions and achieve synchronous watermarking on a rational dither modulation (RDM) framework. We also developed a windowed vector modulation (WVM) scheme suited for the time as well as DCT domain to enhance watermark imperceptivity. The proposed watermarking method currently achieves a payload capacity of 86 bits per second. The results of PEAQ testing confirm that the watermarked audio signal retains quality nearly indistinguishable from the original. Compared with two existing synchronized methods designed specifically to cope with playback speed modification, the proposed MDWT–DCT–RDM–WVM method demonstrates superior robustness to commonly encountered attacks. When encountering desynchronization attacks, such as cropping and resampling time-scale modification, the proposed technique is capable of retrieving the watermark bits with a high degree of accuracy.