A new, computationally efficient technique for calculation of the Line Spectrum Frequencies (LSF) that can be applied to any order of the LPC analysis is proposed in this paper. It is based on the Quotient-Difference (Q-D) root-finding algorithm that enables simultaneous solution for all the LSFs. It is an iterative procedure that offers the tradeoff between accuracy and complexity, what is especially important for the real-time applications. To improve the convergence, a nonlinear mapping of the LSFs is also proposed. For low accuracy applications, the method is even more effective then the fast converging Newton-Rapshon method, but is at the same time exceptionally simple, has a very regular structure and requires only basic mathematical operations.