A new bandwidth scalable wideband speech/audio coder

In this paper, we present a new bandwidth-scalable coder for wide band speech and audio signals. The proposed coder splits 8 kHz signal bandwidth into two narrow bands, and different coding schemes are applied to each band. The lower-band speech is coded with ITU-T G.729 Annex E, and the higher-band signal is compressed using a new algorithm based on the gammatone filter band with an invertible auditory model. Due to the split-band architecture and completely independent coding schemes for each band, the output speech of the decoder can be selected to be a narrowband or wideband coding according to the channel conditions. Subjective tests showed that, for wideband speech and audio signals, the proposed coder at 18 kbit/s produces superior quality to ITU-T 24 kbit/s G.722.1 with the shorter algorithmic delay.