Data processing apparatus

A data processing apparatus operable to correct for distortion of a data signal into which a template signal has been introduced into at least first and second frequency bands of said data signal, each of the template signals introduced into said first and second frequency bands having a predetermined relationship with each other, said apparatus comprising:

• a detection processor operable to identify said distortion of said data signal in accordance with a relative frequency change between versions of said template signal recovered from said first and said second frequency bands of said data signal, wherein said detection processor is operable to generate parameter data representative of said identified distortion;
• and
• an inversion processor operable to receive said parameter data representative of said distortion according to transform of said data signal and to reverse said distortion of said data signal.

An image processing apparatus operable to receive image data representative of a distorted image and to reverse the distortion applied to said image, said image having template signals introduced into respective at least first and second frequency bands of said image, said image processing apparatus comprising:

• a detection processor operable to identify said distortion of said image in accordance with a relative frequency change between versions of said template signal recovered from said first and said second frequency bands of said image, wherein said detection processor is operable to generate parameter data representative of said identified distortion;
• wherein said parameter data is representative of parameters of a transform applied to said image, which transform is representative of the distortion applied to the image, and
• an inverse transform processor operable to invert the transform representative of the distortion in accordance with said parameters.

A data processing apparatus operable to combine at least first and second template signals into first and second frequency bands respectively of a data signal, said template signals having a predetermined relationship with one another and being combined in said first and second bands with the effect that distortion of said data signal produces a relative change in frequency between said first and said second template signals.

A method of processing data for detecting distortion of a data signal to which a template signal has been introduced into first and second frequency bands of said data signal, each of the template signals introduced to said first and second frequency bands having a predetermined relationship with each other, said method comprising (a) generating data representative of the frequency components of a first and a second of said different frequency bands of said signal, and (b) identifying said distortion of said data signal in accordance with a relative frequency change between said versions of said recovered template signal.