Systems and methods for multi-pass alternate decoding

A method for data decoding, the method comprising:

• applying a data decode algorithm by a data decoder circuit to a decoder input to yield a first decoded output and an indication of at least one point of failure of the first decoded output;
• identifying at least a first symbol and a second symbol associated with the point of failure of the first decoded output;
• modifying at least one of the first symbol and the second symbol to yield a first modification;
• modifying the first decoded output to incorporate the first modification to yield a first modified decode output;
• applying the data decode algorithm to the decoder input guided by the first modified decode output to yield a second decoded output;
• identifying at least a third symbol and a fourth symbol associated with the point of failure of the second decoded output;
• modifying at least one of the third symbol and the fourth symbol to yield a second modification;
• and
• modifying the second decoded output to incorporate the first modification and the second modification to yield a second modified decode output.

A storage device, the storage device comprising:

• a storage medium;
• a head assembly disposed in relation to the storage medium and operable to provide a sensed signal corresponding to information on the storage medium;
• a read channel circuit including:
• an analog to digital converter circuit operable to sample an analog signal derived from the sensed signal to yield a series of digital samples;
• an equalizer circuit operable to equalize the digital samples to yield a data set;
• a data detector circuit operable to apply a data detection algorithm to the data set to yield a detected output;
• and
• a data decoding system including:
• a data decoder circuit operable to:
• apply a data decode algorithm to a decoder input to yield a first decoded output and an indication of at least one point of failure of the first decoded output, apply the data decode algorithm to the decoder input guided by a first modified decode output to yield a second decoded output and an indication of at least one point of failure of the second decoded output, and apply the data decode algorithm to the decoder input guided by a second modified decode output to yield a third decoded output and an indication of at least one point of failure of the third decoded output;
• a decode value modification circuit operable to:
• identify a first symbol of the first decoded output associated with the point of failure of the first decoded output, and to modify a subset of values associated with the identified first symbol to yield the first modified decode output;
• and
• identify a second symbol of the second decoded output associated with the point of failure of the second decoded output, and to modify a subset of values associated with the identified first symbol and the identified second symbol to yield the second modified decode output.