16. One or more non-transitory computer storage media storing computer readable instructions that, when executed, perform a speech recognition method comprising: converting an analog signal corresponding to speech input received at a microphone into a digital signal corresponding to the received speech input; performing, using an initial recognizer, an initial speech recognition pass on a portion of the digital signal corresponding to an input speech utterance of the speech input to determine i) an initial recognition result corresponding to the input speech utterance, and ii) a reliability measure reflecting a per word reliability of the initial recognition result; performing, using a re-evaluation recognizer subsequent to completion of the initial speech recognition pass, a re-evaluation recognition pass on portions of the initial recognition result where the reliability measure is low to determine a re-evaluation recognition result corresponding to the re-evaluated portions of the input speech utterance; and determining a final recognition result based on the re-evaluation recognition result if any, and otherwise based on the initial recognition result; wherein the initial recognizer and the re-evaluation recognizer are complementary so as to make different recognition errors.
16. One or more non-transitory computer storage media storing computer readable instructions that, when executed, perform a speech recognition method comprising: converting an analog signal corresponding to speech input received at a microphone into a digital signal corresponding to the received speech input; performing, using an initial recognizer, an initial speech recognition pass on a portion of the digital signal corresponding to an input speech utterance of the speech input to determine i) an initial recognition result corresponding to the input speech utterance, and ii) a reliability measure reflecting a per word reliability of the initial recognition result; performing, using a re-evaluation recognizer subsequent to completion of the initial speech recognition pass, a re-evaluation recognition pass on portions of the initial recognition result where the reliability measure is low to determine a re-evaluation recognition result corresponding to the re-evaluated portions of the input speech utterance; and determining a final recognition result based on the re-evaluation recognition result if any, and otherwise based on the initial recognition result; wherein the initial recognizer and the re-evaluation recognizer are complementary so as to make different recognition errors. 20. The computer storage media of claim 16 , wherein the initial recognizer and the re-evaluation recognizer use one of different complementary acoustic models or different complementary language models.