  In this paper the approximation of the optimal compressor function using the
first-degree spline functions and quadratic spline functions is done.
Coefficients on which we form approximative spline functions are determined by
solving equation systems that are formed from treshold conditions. For Gaussian
source at the input of the quantizer, using the obtained approximate spline
functions a companding quantizer designing is done. On the basis of the
comparison with the SQNR of the optimal compandor it can be noticed that the
proposed companding quantizer based on approximate spline functions achieved
SQNR arbitrary close to that of the optimal compandor.
