ISSN : 1796-203X
Volume : 2    Issue : 7    Date : September 2007

Computation of Immittance and Line Spectral Frequencies Based on Inter-frame Ordering
Vasyl Semenov
Page(s): 75-80
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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 computational 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