Efficient methods for high quality low bit rate wideband speech coding

This paper describes efficient encoding and decoding methods for achieving high quality wideband speech at low rates. CELP-based technologies have been successful in achieving high quality speech at low bit rates, however, new efficient techniques are needed to maintain high speech quality when the model is applied to wideband signals. This article discusses some techniques that improve the performance of the CELP model including efficient perceptual weighting and pitch codebook, and decoding techniques such as gain smoothing, periodicity enhancement, and high frequency generation. These techniques have been incorporated in the AMR-WB (adaptive multi-rate wideband) codec selected by 3GPP and ITU-T, where high quality wideband speech can be maintained at bit rates around 13 kbit/s.