Time and frequency domain noise shaping in speech coding

We present a general framework for the coding of signals with a time-varying short-term spectrum. The total quantization distortion is minimized by a dynamic bit allocation in time and in frequency. The resulting distortion is then white noise with fixed power. Such noise, however, is not optimal perceptually when coding speech signals. Spectral and temporal noise shaping are then used to minimize the perception of noise in frequency and in time. Initial experiments at 16 kb/s demonstrate the validity of shaping the noise in time as well as in frequency.