A low-complexity waveform interpolation coder

A recent independent survey found a 2.4 kbit/s waveform-interpolation (WI) algorithm to perform better than other state-of-the-art speech coders. However, this coder had a very high level of computational complexity. The introduction of various techniques, including a time-varying waveform sampling rate and a cubic B-spline waveform representation, has reduced the computational complexity by an order of magnitude. The new implementation allows full-duplex real-time operation on a single DSP device and on an average workstation (the latter using non-optimized compiled C source code). The new coder also contains a number of new features which improve the quality of the reconstructed speech signal