Adaptive selection of lag-window shape for linear predictive analysis in the 3GPP EVS codec

Lag windowing has long been used for the autocorrelation method of linear predictive (LP) analysis to prevent possible instability of the synthesis filter with the obtained coefficients. We have investigated the lag-window shape in terms of the trade-offs between stability and the coding efficiency. On the basis of these investigations, we have devised an adaptive selection scheme in which the window shape selected depends on the periodicity of the signal. This scheme has proven to be effective for LP analysis to enhance the coding efficiency in both time and frequency domains in general. This scheme has thus been included in the speech and audio coding schemes of the newly established 3GPP EVS codec standard.