Pitch Synchronous LPC Analysis for Reduction of Coding Distortion caused by Misalignment between Synthesis Filter and its Residual

Several pre-processing algorithms modify the residual speech signal to facilitate efficient estimation of speech model parameters. This, however, can result in misalignment between the modified residual signal and the time-variant linear prediction (LP) filter used during the synthesis stage. The resulting misalignment may cause audible artifacts particularly at onsets when the frequency response of successive LP filters changes rapidly. We propose a new solution to control the LP filter gain at subframes. This technique is performed before and after time modification of speech and therefore is called preanalysis and post-processing. A pitch smoothing technique is used to illustrate the effect of the proposed technique