1. A method for encoding speech comprising: processing an input speech signal using an encoder, resulting in a compressed encoder representation of the input speech signal, if a speech recognizer identifies a corresponding dictionary speech element, which approximates the input speech signal, determining a compressed recognizer representation of the corresponding dictionary speech element, calculating one or more differences between the compressed encoder representation and the compressed recognizer representation, compiling compressed speech information that includes representations of the one or more differences; and the method further comprising, if the speech recognizer does not identify a corresponding dictionary speech element, compiling the compressed speech information to include the compressed encoder representation of the input speech signal, and not to include the one or more differences.
2. The method of claim 1 , wherein processing the input speech signal includes using an analysis-by-synthesis encoder to determine an encoder representation of a formant filter for the input speech signal, and the method further includes: processing the input speech signal using a speech recognizer, which determines a recognizer representation of a formant filter for the corresponding dictionary speech element; and calculating the one or more differences includes calculating a set of formant filter parameter differences between the encoder representation of the formant filter and the recognizer representation of the formant filter.