Editing Harmonic Vector Excitation Coding (section)

===Linear Predictive Coding===
HVXC uses [[Linear predictive coding]] (LPC) with block-wise adaptation every 20ms.<ref name="hvxc" /> The LPC parameters are transformed into [[Line spectral pairs|Line spectral pair]] (LSP) coefficients, which are jointly quantized.<ref name="hvxc" /> The LPC residual signal is classified as either [[voiced]] or [[unvoiced]]. In the case of voiced speech, the residual is coded in a parametric representation (operating as a [[vocoder]]), while in the case of unvoiced speech, the residual waveform is quantized (thus operating as a hybrid speech codec).