Bandwidth expansion of speech based on vector quantization

A progress on the traditional technique for high-band spectral envelope prediction based on codebook mapping is presented. A requantize method to train the codebook and a new refinement method based on VQ and voicing degree are also proposed. First, the narrow band speech is divided into three groups by voicing degree and energy, and in each group, the high-band spectral envelope is determined from the high-band code vector which is closest in shape to the spectral envelope of the frame of input narrowband speech under analysis. Second, the Gaussian white noise is adopted as the excitation signal to synthesis the high band signal. The method mentioned here is proved suitable for real time signal processing.