Systems and methods relating generally to data processing, and more particularly to adjusting gain parameters in relation to data processing.

A soft output detector is programmed with a first set of parameters. Soft information is generated according to the first set of parameters, including likelihood information that spans a maximum likelihood range. Error correction decoding is performed on the soft information generated according to the first set of parameters. In the event decoding is unsuccessful, the soft output detector is programmed with a second set of parameters, soft information according is generated to the second set of parameters (including likelihood information that is scaled down from the maximum likelihood range), and error correction decoding is performed on the soft information generated according to the second set of parameters.

In one embodiment, a method includes writing data to a storage medium, via a write channel, by applying a partial reverse concatenated modulation code to the data prior to storing encoded data to the storage medium. The applying the partial reverse concatenated modulation code to the data includes application of a C2 encoding scheme to the data to produce C2-encoded data prior to application of one or more modulation encoding schemes to the C2-encoded data to produce modulated data, followed by application of a C1 encoding scheme to the modulated data subsequent to the application of the one or more modulation encoding schemes to produce the encoded data.

In one embodiment, a data storage system includes a write channel for writing data to a storage medium, the write channel configured to utilize a partial reverse concatenated modulation code. The write channel includes logic adapted for encoding data sets using a C2 encoding scheme, logic adapted for adding a header to each subunit of the data sets, logic adapted for encoding the headers of the data sets with a first modulation encoding scheme, logic adapted for encoding data portions of the data sets with a second modulation encoding scheme, logic adapted for encoding portions of the one or more C2-encoded data sets using a C1 encoding scheme, logic adapted for combining the C1-encoded portions with the modulation-encoded headers of the C2-encoded data sets using a multiplexer, and logic adapted for writing the one or more combined C1 - and C2-encoded data sets to data tracks.

An adaptation technique for decoding low-density parity-check (LDPC) codes for hard disk drive (HDDs) systems is disclosed. The method includes tuning the normalization factor for LDPC decoding for each data zone and read head during the test stage of manufacturing. The LDPC decoder can be either a sum-product algorithm (SPA) decoder or a Min-Sum decoder. The channel detector can be any soft-output detector, such as a soft-output Viterbit detector (SOVA), a BCJR detector, a pattern-dependent noise-predictive (PDNP) detector, or a bi-directional pattern-dependent noise-predictive (BiPDNP) detector. The adaptation technique can optimize the LDPC decoding performance for each data zone and read head, thereby relaxing the acceptance criteria for hard disk drive read/write heads and disk media, enabling acceptance and use of a much broader range of head and media for hard disk drives.