A Study of Audio Watermarking Method Using Non-negative Matrix Factorization for a Duet of Different Instruments

Abstract

In this paper, we propose an audio watermarking method using non-negative matrix factorization (NMF) for a duet of different instruments. NMF is applied to host signal and the amplitude spectrogram is factorized into the basis matrix and the activation matrix. In the proposed method, the activation coefficients of each musical instrument can be obtained by NMF, and watermarks can be embedded into a specific instrument or multiple instruments. Onset and offset times are estimated from the activation matrix, and its duration is defined as one note. However, it is possibility that onset and offset times are changed due to embedding process, and watermarks cannot be extracted correctly unless note information is known. Therefore, in this paper, onset and offset times are estimated after smoothing activation coefficients, and errors of note estimation are reduced. From this, we want to extract watermarks even if note information is unknown.