US Patent 7290200 E

An E2PR4 Viterbi detector includes a recovery circuit and receives a signal that represents a sequence of values, the sequence having a potential state. The recovery circuit recovers the sequence from the signal by identifying a surviving path to the potential state and, after identifying the surviving path, adding a modified branch metric to the path metric of the surviving path to generate an updated path metric for the potential state. Updating the path metric of the surviving path after the surviving path is selected allows the E2PR4 Viterbi detector to be smaller and/or faster than an E2PR4 Viterbi detector that updates the path metric before selecting the surviving path.