First, the parameter’s indices are extracted from the received bitstream. These indices are decoded to obtain the coder parameters corresponding to a 10 ms speech frame. These parameters are the LSP coefficients, the two fractional pitch delays, the two fixed-codebook vectors, and the two sets of adaptive and fixed-codebook gains. The LSP coefficients are interpolated and converted to LP filter coefficients for each subframe. Then, for each 5 ms subframe the following steps are done:

The excitation is constructed by adding the adaptive and fixed-codebook vectors scaled by their respective gains. The speech is reconstructed by filtering the excitation through the LP synthesis filter. The reconstructed speech signal is passed through a post-processing stage, which includes an adaptive postfilter based on long-term and short-term synthesis filter, followed by a high-pass filter and scaling operation.