1. A speech codec comprising: a classifier configured to process parameters that identify a transition region between at least two portions of a speech signal, at least one of the portions of the speech signal being a voiced portion; and a periodic smoothing circuit configured to smooth the transition region represented by at least one of a weighted representation of the speech signal, a residual signal, and a speech signal using at least one of an interpolated pitch lag and a constant pitch lag, the interpolated pitch lag being derived from a pitch track corresponding to the voiced portion of the speech signal.