V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

PRML
       Partial Response - Maximum Likelihood (HDD, HD-DVD)


The Free On-line Dictionary of Computing (30 December 2018):

Partial Response Maximum Likelihood
PRML

    (PRML) A method for converting the weak analog
   signal from the head of a magnetic disk drive into a digital
   signal.  PRML attempts to correctly interpret even small
   changes in the analog signal, whereas peak detection relies
   on fixed thresholds.  Because PRML can correctly decode a
   weaker signal it allows higher density recording.

   For example, PRML would read the magnetic flux density pattern
   70, 60, 55, 60, 70 as binary "101", and the same for 45, 40,
   30, 40, 45.  A peak detector would decode everything above,
   say, 50 as high, and below 50 as low, so the first pattern
   would read "111" and the second as "000".

   (1996-12-27)