Noise reduction system for color television signal

Claim 1

A noise reducer for processing a received video signal comprising: detection means for detecting a difference between the received video signal and two-frame delayed signals of said received video signal and producing a two-frame difference signal; noise reduction means for deducting remaining noise from said two-frame difference signal and from the received signal in response to control signals and producing respective noise reduced signals; subtraction means for subtracting the noise reduced signal based on said two-frame difference signal from the noise reduced signal based on said received signal and producing a still video image signal having a noise component thereof suppressed; noise level detection means for detecting a noise level of an original video signal before transmission based on said two-frame difference signal; motion level detection means for detecting a motion condition of said received video signal; and control means for producing said control signals controlling the deducted ratio of said two-frame difference signal obtained by said detection means and the received video signal within said noise reduction means, said control signals being generated in accordance with said noise level of the original video signal detected by said noise level detection means and said motion condition detected by said motion level detector means; and wherein said noise level detection means includes an absolute value circuit receiving said two-frame difference signal and producing an output fed to a hold circuit for holding said output in response to a signal from said motion level detection means representing zero motion, the output of said hold circuit representing a detected average level of the noise component in the original signal and being fed to a nonlinear amplifier for amplifying the detected average level of the noise component in response to a signal representing a noise level of the system transmitting the received video signal and producing said signal generated in accordance with the detected noise level of the original signal fed to said control means.