Computation of Immittance and Line Spectral Frequencies Based on Inter-frame Ordering Property
Vasyl Yu. Semenov · Journal of Computers · 2007
Abstract — Line spectral frequencies (LSF) and immittance spectral frequencies (ISF) are widely used in modern speech codecs based on autoregressive model. This paper addresses LSF and ISF calculation problems. The investigation of LSF/ISF placement on adjacent quasi-stationary frames is performed. It is shown that in majority of cases the inter-frame ordering property takes place. On this basis a new approach to LSF/ISF calculation is proposed. It is shown that LSF/ISF localization task is mainly reduced to verification of inter-frame ordering property. The compu-tational expenses are reduced in 3.4 times in comparison with widely used Kabal’s method. Besides, the maximum number of operations is lower than the minimum expenses of accelerated Kabal’s method. The method is implemented on fixed-point DSP and showed stable performance. Index Terms — speech coding, autoregressive model, line spectral frequencies, rootfinding procedures, inter-frame ordering, immittance spectral frequencies I.