Abstract: A method is provided for receiving and restoring data from an optical recording medium exhibiting strong asymmetry in the regenerated RF signal. The method provides digital partial response asymmetry compensation of a digital RF signal. The asymmetry of the digital RF signal is detected through the measurement of the envelopes of a short T pulse (xT pulse) and a long T pulse (yT pulse), where the T is the bit clock of the recovered bit stream. Through the evaluation of the xT upper and lower envelopes and the asymmetry factor, upper and lower thresholds are determined. Only the asymmetric parts of the digital RF signal are selected and compensated.

Abstract: The present invention relates to an adaptive Viterbi detector, and to an apparatus for reading from and/or writing to recording media using such adaptive Viterbi detector. It is an object of the invention to offer an alternative design for an adaptive Viterbi detector in order to improve the phase locking and the correct data restoring for an RF signal exhibiting a strong vertical asymmetry. This object is achieved by a Viterbi detector with adaptive reference levels for bit recovery from an input RF signal, in which the reference levels are adaptive to the incoming RF signal, with means for optimising the reference levels for every state transition based on the deviation between the input RF level and the corresponding reference level, which is determined by the current state with the largest likelihood.

Abstract: The present invention relates to a method for receiving and restoring data from an optical recording medium exhibiting strong asymmetry in the regenerated RF signal. According to the invention a method for digital partial response asymmetry compensation of a digital RF signal comprises the steps of: —detecting the asymmetry ? of the digital RF signal through the measurement of the envelopes of a short T pulse (xT pluse) and a long T pulse (yT pulse), T being the bit clock of the recovered bit stream, —determining upper and lower thresholds through the evaluation of the XT upper and lower envelopes and the asymmetry factor ?, and—selecting and compensating only the asymmetric parts of the digital RF signal.