This paper is to present a new high quality code-excited LPC (linear predictive coding) system. In this coder, the excitation comprises a set of compound pulses, and each compound pulse consists of a group of element pulses spaced uniformly at a lower rate. The compound pulse can be viewed as a subband of excitations sampled at a lower rate. Thus the excitation can be interpreted as the combination of a set of generalized subband signals. In the coder, the locations of the compound pulses and amplitudes of the element pulses are vector-quantized. We use two seperate codebooks: one for the locations of the compound pulses and the other for the amplitudes of the element pulses. Since the range of the locations and the number of the compound pulses are reduced according to pulse size, the location codebook is substantially reduced. After obtaining the pulse locations, the amplitudes are searched from the amplitude codebook. The coder is shown to have very good performance for the bit rate below 8kbps.
Bibliographic reference. Leung, S. H. / Lai, K. L. / Wong, O. Y. / Luk, A. (1991): "A new coded excitation model using multifrequency decomposition", In EUROSPEECH-1991, 245-248.