Method of video noise reduction using non-linear pre/de-emphasis

A method of pre-emphasizing a signal in a video signal transmission system and de-emphasizing the received signal, comprising the steps of:

• a) receiving the signal as an input;
• b) applying the input signal to a processing system comprising a plurality of parallel signal processing paths each comprising a non-linear phase filter and a non-linearity, the plurality of parallel signal processing paths including at least one pair of parallel signal processing paths in which the non-linear phase filters have substantially equal but opposite phase responses and substantially equal magnitude responses;
• c) said step of applying further comprising combining the outputs of the parallel signal processing paths to produce the de-emphasized signal, applying the input signal to a processing system in which the applied non-linearities are non-monotonic non-linearities, and wherein the parallel signal processing paths operate on different frequency bands;
• and
• wherein the input signal undergoes a non-linear dynamic range expansion which is phase linear.

Apparatus for pre-emphasising a signal, comprising:

• means for receiving an input signal;
• a system for processing the input signal, comprising a plurality of parallel signal processing paths each comprising a non-linear phase filter and a non-linearity and operating on a different frequency band, wherein the non-linear filters in the plurality of parallel signal processing paths have substantially equal but opposite phase responses and substantially equal magnitude responses;
• and means for combining the outputs of the plurality of parallel signal processing paths to produce a raw pre-emphasised signal, whereby the signal processing and combining steps produce a non-linear dynamic range compression of the input signal which is phase linear;
• and further comprising:
• pre-correction means comprising means for de-emphasising the raw pre-emphasised signal;
• means for subtracting the de-emphasised signal from the input signal to form an error signal;
• and
• means for combining the raw pre-emphasised signal with the error signal to produce a pre-emphasised signal with one degree of pre-correction.