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Low complexity predictive vector quantization of LSF parameters

The paper presents a low complexity method for line spectrum frequencies (LSF) coding based on predictive vector quantization (PVQ) with switched-adaptive prediction. Complexity reduction is achieved in two ways. Vector quantization (VQ) is simplified by increasing the number of switched matrices. Secondly, the technique for reduction of the number of nonzero elements in switched matrices is applied to simplify the prediction. The structures of such sparse matrices as well as the optimal values of their nonzero elements are determined to maximize the closed-loop prediction gain of the coder. Designed coders are compared to the baseline coders with full prediction matrices as well as to coders incorporating diagonal matrices. The trade-off between complexity and quality of the proposed coders has been analyzed as a function of various coder parameters, verifying the effectiveness of the proposed approach.