Improved Characteristic Waveform Decomposition and Novel Bit Reduction Scheme for WI Coders

In this paper, we proposed an improved SEW/REW decomposition method with pitch-dependent phase generation and a noble VBR scheme for bit rate reduction in waveform interpolative coders. The proposed decomposition is performed in the magnitude domain to reduce spectral distortions. The phase of the characteristic waveforms is generated after classifying the signal into silence, unvoiced and voiced speech using the pitch value. The proposed VBR scheme is achieved by substituting white Gaussian noises with the excitation signal of silence and unvoiced speech and allocating bit rates variably. Experimental results show that our proposed algorithm achieves the improved speech quality while reducing the required bit rate compared to the conventional methods. Key-Words: Characteristic waveform decomposition, Excitation signal, Speech coders, Variable bit rates, Waveform interpolation