Voiced speech coding at very low bit rates based on forward-backward waveform prediction (FBWP)

The authors introduce a novel algorithm, called forward-backward waveform prediction (FBWP), for voiced speech coding at very low bit rates, that aims to produce high-quality speech with low complexity. This algorithm encodes and transmits partial representative waveforms (RWs) with which the complete voiced speech waveforms are reconstructed in the time domain. The RW can be encoded at 20-30 ms intervals, considering the special initial conditions of short- and long-terms. The basic idea of the FBWP method is essentially consistent with that of the PWI algorithm, which is capable of reproducing high-quality voiced speech. The FBWP algorithm does not require two synchronous prototype waveforms decomposed into sinusoidal components; thus it is very fast while the high-quality speech can be obtained at a bit rate of about 3 kbit/s. Like the PWI method, the proposed algorithm is easily combined with other linear-prediction-based speech codes using a noise-like excitation to reproduce unvoiced speech.<>