Soft-in soft-out decoder
A soft-in soft-out decoder is used by certain Error correcting codes to correct errors. The decoder takes corrupted data and calculates (based on the Parity bits) the most probable value for the data. Successive passes through the decoder gradually get closer to the original error free data. Soft refers to the fact that both the input and the output are probablistic. Soft-in Soft-out decoders are not guaranteed to produce the right result.