Time domain television noise reduction system
First Claim
1. A noise reduction method for a baseband television signal received via a noise-introducing path, the method comprising the steps of:
- averaging the television signal over two or more frames to produce an averaged function of the incoming television signal in which recurrent stationary picture information in the television signal is substantially canceled and aperiodic picture information in the television signal, including noise, is averaged,processing the averaged function of the incoming television signal with a non-linear amplitude function to provide a noise reduction cancellation signal, the non-linear amplitude function having a transfer characteristic which is approximately constant from zero to a first predetermined amplitude value and which returns from the first predetermined amplitude value to approach zero at a second predetermined amplitude value, andsubtratively combining the noise reduction cancellation signal with the television signal to reduce noise therein.
4 Assignments
0 Petitions
Accused Products
Abstract
A noise reduction method for a baseband television picture signal, such as luminance or chrominance, received via a noise-introducing path comprises the steps of:
averaging the picture signal over a predetermined time interval related to frame rate of the picture signal, such as over a number of successive frames, to produce an averaged function of the picture signal wherein recurrent stationary picture elements the picture signal are cancelled, and wherein aperiodic events in the picture signal, including noise, are put out as an average,
passing the average through an amplitude function generator for putting out a non-linear function of the average, the non-linear function favoring low amplitude levels and disfavoring high amplitude levels in the picture signal, thereby to provide a noise reduction cancellation signal, and
combining the noise reduction cancellation signal with the picture signal, thereby to reduce the noise therein.
Apparatus for implementing the method, including time domaim comb filter apparatus for separating luminance and chrominance, is also described.
42 Citations
29 Claims
-
1. A noise reduction method for a baseband television signal received via a noise-introducing path, the method comprising the steps of:
-
averaging the television signal over two or more frames to produce an averaged function of the incoming television signal in which recurrent stationary picture information in the television signal is substantially canceled and aperiodic picture information in the television signal, including noise, is averaged, processing the averaged function of the incoming television signal with a non-linear amplitude function to provide a noise reduction cancellation signal, the non-linear amplitude function having a transfer characteristic which is approximately constant from zero to a first predetermined amplitude value and which returns from the first predetermined amplitude value to approach zero at a second predetermined amplitude value, and subtratively combining the noise reduction cancellation signal with the television signal to reduce noise therein. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
-
-
12. The noise reduction method set forth in claim 90 wherein for small overall noise levels in the television signal the first predetermined amplitude value is approximately 10 IRE units and the second predetermined amplitude value is approximately 30-40 IRE units and for large overall noise levels in the television signal the first predetermined amplitude value is approximately 20-30 IRE units and the second predetemiend amplitude value is approximately 50-60 IRE units.
-
13. A luminance component noise reducer for a quadrature modulated subcarrier color television signal including a separated luminance component signal and a separated chrominance component signal, the television signal being received via a noise-introducing path, comprising:
-
a luminance component signal input, a noise-reduced luminance signal output, frame delay means coupled to the input, averaging means coupled to the input and to the frame delay means for generating an average of luminance signal in which recurrent stationary picture information is cancelled and non-recurrent picture information, including noise, is averaged, amplitude function generator means for processing the average of luminance signal in accordance with a non-linear amplitude function transfer characteristic to provide a noise reduction cancellation signal, the non-linear amplitude function having a transfer characteristic which is approximately constant form zero to a first predetermined multitude value and which returns from the first predetermined amplitude value to approach zero at a second predetermined amplitude value, and combining means for substractively combining the luminance component signal obtained from the frame delay means with said noise reduction cancellation signal, whereby noise in said luminance component signal is reduced. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
-
-
21. A signal processor for a quadrature modulated subcarrier composite television signal receiver wherein the composite television signal applied to the receiver includes a luminance component and a chrominance component, the signal processor comprising
a time domain comb filter separator including: -
a V1 signal input for receiving the undelayed composite television signal, first frame delay means coupled to the V1 signal input and having a one-frame-delayed V2 output, second frame delay means coupled to the V2 output and having a two-frame-delayed V3 output, first amplifier means coupled to the V1 signal input for providing an output in the form of -1/4V1, second amplifier means coupled to the V2 output for providing an output in the form of +1/2V2, third amplifier means coupled to the V3 output for providing an output in the for of -1/4V3, and combiner means coupled for combining the -1/4V1, +1/2V2 and -1/4V3 outputs to provide a full bandwidth combed chrominance component signal; and the signal processor further comprising a luminance component noise reducer including; amplitude function generator means for processing the combed chrominance component signal in accordance with a non-linear amplitude function to provide a noise reduction cancellation signal, the non-linear function having a transfer characteristic which is approximately constant from zero to a first predetemined amplitude value and which returns from the first predetermined amplitude value to approach zero at a second predetermined amplitude value, first subtraction means for subtracting the noise reduction cancellation signal from the combed chrominance component signal to provide a chroma/noise cancellation signal, second subtraction means for subtracting the chroma/noise cancellation signal from the one-frame-delayed V2 output, thereby to provide a combed luminance component in which noise has been reduced. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
-
-
29. Noise reduction apparatus for a baseband television signal received via a noise-introducing path, comprising:
-
means for averaging the television signal over two or more frames to produce an averaged function of the incoming television signal in which recurrent stationary picture information in the television signal is substantially cancelled and aperiodic picture information in the television signal, including noise, is averaged, means for processing the averaged function of the incoming television signal with a non-linear amplitude function to provide a noise reduction cancellation signal, the non-linear amplitude function having a transfer characteristic which is approximately constant from zero to a first predetemiend amplitude value and which returns from the first predetermined amplitude value to approach zero at a second predetemiend amplitude value, and means for substractively combining the noise reduction cancellation signal with the television signal to reduce noise therein.
-
Specification