This paper outlines a package synchronization scheme for blind speech watermarking in the discrete wavelet\ntransform (DWT) domain. Following two-level DWT decomposition, watermark bits and synchronization codes are\nembedded within selected frames in the second-level approximation and detail subbands, respectively. The\nembedded synchronization code is used for frame alignment and as a location indicator. Tagging voice active\nframes with sufficient intensity makes it possible to avoid ineffective watermarking during the silence segments\ncommonly associated with speech utterances. We introduce a novel method referred to as adaptive mean\nmodulation (AMM) to perform binary embedding of packaged information. The quantization steps used in mean\nmodulation are recursively derived from previous DWT coefficients. The proposed formulation allows for the direct\nassignment of embedding strength. Experiment results show that the proposed DWT-AMM is able to preserve\nspeech quality at a level comparable to that of two other DWT-based methods, which also operate at a payload\ncapacity of 200 bits per second. DWT-AMM exhibits superior robustness in terms of bit error rates, as long as the\nrecovery of adaptive quantization steps is secured.
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