Signal processing apparatus utilizing a partial response method, and signal processing method, information recording apparatus, and information reproduction apparatus therefore

A signal processing method in which a signal is processed using a partial response method, the method comprising:

• a signal processing step of performing an operation (1−D) on each bit of an input code, where D indicates a delay of one bit;
• and
• an equalizing step of equalizing a bit sequence processed by said signal processing step to a Nyquist characteristic.

An information reproduction apparatus in which an operation (1−D) is performed on an input bit sequence and said processed bit sequence is recorded onto a recording medium, the apparatus comprising:

• an equalizing unit which equalizes a signal reproduced from said recording medium to a Nyquist characteristic;
• and
• a maximum likelihood detection unit which detects a maximum likelihood bit sequence from the bit sequence equalized by said equalizing unit.