Temporal normalization techniques for transform-type speech coding and application to split-band wideband coders

In this paper we present an efficient coding method for the upper band(4-7kHz) of wideband(0.5-7kHz) speech coding based on a band-split approach. Due to the impulselike characteristics in upper band signal, it is very difficult to efficiently quantize the signal at low bit-rate when we use transform coding techniques. We propose two temporal normalization techniques, direct temporal energy normalization and frequency domain linear prediction, to reduce the extremely noticeable artifacts. Simulation results show that the proposed algorithm successfully encodes the upper band signal, and the new split-band type wideband coder adopting the proposed technology provides better quality than 56 kbit/s ITU-T G.722 at the bitrate of 20 kbit/s.