This paper proposes a blind digital audio water- marking algorithm that utilizes the quantization index modulation (QIM) and the singular value decomposition (SVD) of stereo audio signals. Conventional SVD-based blind audio watermarking algorithms lack physical interpretation since the matrix construction method for the input matrix for SVD is heuristically defined. However, in the proposed approach, because the SVD is directly applied to the stereo input signals, the resulting decomposed elements convey a conceptually meaningful inter- pretation of the original audio signal. As the proposed approach effectively utilizes the ratio of singular values, the embedded watermark is highly imperceptible and robust against volumetric scaling attacks; most QIM-based watermarking schemes are weak to these types of attacks. Experimental results under well-known practical attacks, such as compressions, resampling, and various types of signal processing, confirm that the proposed algorithm performs well compared to conventional audio watermarking algorithms.

In this paper we present an efficient coding method for the upper band(4-7kHz) of wideband(0.5-7kHz) speech coding based on a band-split approach. Due to the impulselike characteristics in upper band signal, it is very difficult to efficiently quantize the signal at low bit-rate when we use transform coding techniques. We propose two temporal normalization techniques, direct temporal energy normalization and frequency domain linear prediction, to reduce the extremely noticeable artifacts. Simulation results show that the proposed algorithm successfully encodes the upper band signal, and the new split-band type wideband coder adopting the proposed technology provides better quality than 56 kbit/s ITU-T G.722 at the bitrate of 20 kbit/s.