A continuous modulated single sideband bandwidth extension
Bandwidth extension (BWE) is an important parametric technique applied by modern audio coders in order to achieve efficient data rate compression at low bitrates. The perceptual quality of BWE enhanced signals is, however, often hampered by artifacts caused by inharmonicity. We propose hence a bandwidth extension method that avoids inharmonicity, and, at the same time, avoids the costly transmission of additional control parameters for frequency shifts. Harmonicity of the decoded signal is ensured by calculation of the autocorrelation function of the magnitude spectrum. The proposed bandwidth extension method is implemented by single sideband modulation (SSM). Fitting nicely in the general scheme of well established spectral band replication (SBR), the new method has some potential to replace the SBR patching algorithm. Potentially, the SSM can additionally govern the subsequent spectral shaping. Listening test results demonstrate an advantage of the novel scheme compared to SBR as used in high efficiency advanced audio coding (HE-AAC).