Residual-excited linear prediction
Residual-excited linear prediction is an obsolete speech coding algorithm. It was originally proposed in the 1970s and can be seen as an ancestor of code-excited linear prediction. Unlike CELP however, RELP directly transmits the residual signal. To achieve lower rates, that residual signal is usually down-sampled. The algorithm is hardly used anymore in audio transmission.
It is still used in some text-to-speech voices, such as the diphone databases found in the Festival and Flite speech synthesizers.
