A receiver-compatible system for channel noise reduction

A method that reduces transmission channel noise in a receiver compatible manner is developed. In this method, the television signal is processed on a frame-by-frame basis, dividing each frame into low- and high-spatial-frequency components. The low-frequency component of each frame is subsampled, quantized, and transmitted digitally on a side channel. The high-frequency components is adaptively modulated and added back to a compressed version of the low-frequency component to produce a receiver-compatible signal to be transmitted on the normal analog channel. An advanced receiver can use the information in the digital side channel along with the receiver analog signal to produce a picture devoid of most channel degradations. A standard receiver can still receive an acceptable picture, although with slight contrast. It is shown how the parameters of the system can be adjusted to favor either compatibility with existing receivers or the noise reduction capabilities of advanced receivers.