Frequency domain postfiltering for multiband excited linear predictive coding of speech

A frequency domain postfilter for multiband excited linear predictive (MBELP) coders is proposed. It is based on the principle of multiplying the signal band magnitudes by the postfilter magnitudes obtained by sampling the postfilter response at the pitch harmonics. This approach offers two major advantages: first, the signal energies before and after postfiltering can be equalised by simply rescaling the signal band magnitudes; and secondly, the phase information will be retained owing to only the magnitude spectra being modified. A fast method is given for sampling the postfilter magnitude spectrum characterised by line spectral pair (LSP) parameters