Method and apparatus for reducing the word length of a digital input signal and method and apparatus for recovering a digital input signal

Method according to one of the proceeding claims, in which the amplitude of the noise signal (Na) is at least equal to a predetermined noise value.

Method according to one of the proceeding claims, in which noise shaping techniques are applied to obtain the noise signal (Na).

Method according to one of the proceeding claims, in which the reduced word length signal (Me), the non-linear device parameters (NLDp) and/or the noise parameters (Np) are recorded on a recording medium (13).

Method according to one of the proceeding claims, comprising the further step of providing a difference signal, the difference signal being equal to the intermediate signal (Di) minus the reduced word length signal (Me).

Signal processing apparatus, comprising a pseudo-random noise generator (12) for generating a noise signal (Na) being defined by noise parameters (Np), an addition element (11) connected to the noise generator (12) for adding the noise signal (Na) to an digital input signal (Mi) to provide an intermediate signal (Di), and a first quantising element (10) connected to the addition element (11) for transforming the intermediate signal (Di) having a word length of n bits into a reduced word length signal (Me) having a word length of m bits, n being larger than or equal to m, characterised in that

• the quantizing element (10) has a non-linear transfer function, the non-linear transfer function being defined by non-linear device parameters (NLDp).