A waveform interpolation speech coding algorithm at 2.4kbit/s based on wavelet transform was proposed

in which characteristic waveform decomposition and reconstruction is processed using biorthogonal wavelet filters.At the encoder

the alignment operation was removed and the amplitude spectrum is decomposed without phase spectrum.Because of the wavelet compression

only the amplitude spectrum of last layer is transmitted.At the decoder

different scale space is reconstructed separately and random or fixed phase was combined to the spectrum based on voice degree at the last.Additionally

based on the time-variable feature of speech

voiced degree flag of each subframe was introduced to indicate the spectrum selection and quantization.Subjective R-A/B listening tests indicated that the synthesis speech quality of the 2.4kbit/s WT-CWI coding algorithm is better than that of standard 2.4kbit/s MELP coder and FS1016 4.8kbit/s CELP coder and is better than traditional 3.8kbit/s CWI coder.