Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1999-07-15
2002-06-04
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06400762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video signal processing circuit and a video signal processing method having a function of reducing noise of a video signal on the basis of a result of motion detection for an image.
2. Description of the Prior Art
In order to improve the S/N (signal-to-noise ratio) of a video signal, Japanese Laid-Open Patent No. 2-184176 (1990), for example, proposes a noise reduction circuit. This noise reduction circuit reduces noise by an inter-frame operation or an inter-line operation of a video signal in response to presence/absence of motion in an image. Thus, the S/N of the video signal can be improved in response to the type of the image.
Further improvement of the S/N is awaited for satisfying the recent requirement for higher picture quality. However, a video signal processing circuit must be miniaturized and reduced in cost, and hence it is unpreferable to complicate and increase the size of the noise reduction circuit for improving the S/N of a video signal.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a video signal processing circuit capable of further improving picture quality with a relatively simple structure.
Another object of the present invention is to provide a video signal processing method capable of further improving picture quality with a relatively simple structure.
A video signal processing circuit according to an aspect of the present invention comprises a detection circuit detecting presence/absence of motion in an image, a separation circuit separating a luminance signal and a chrominance signal from a composite video signal by an inter-frame operation or an intra-frame operation on the basis of the result of detection by the detection circuit, and a noise reduction circuit reducing noise of at least the luminance signal output from the separation circuit by an inter-frame operation or an intra-frame operation on the basis of the result of detection by the detection circuit.
In the video signal processing circuit, presence/absence of motion in the image is detected so that the luminance signal and the chrominance signal are separated from the composite video signal by an inter-frame operation or an intra-frame operation on the basis of the result of detection. At this time, noise of the composite video signal is reduced by an inter-frame operation. Further, noise of at least the luminance signal is reduced by an inter-frame operation or an intra-frame operation on the basis of the result of detection of motion in the image.
Thus, noise of the composite video signal is reduced and noise of at least the luminance signal is reduced in the separated luminance and chrominance signals, whereby the S/N of the video signal is further improved.
The detection circuit may include a motion detection circuit detecting presence/absence of motion in the image on the basis of the composite video signal, the separation circuit may separate the luminance signal and the chrominance signal from the composite video signal by an inter-frame operation or an intra-frame operation on the basis of an output signal of the motion detection circuit, and the noise reduction circuit may reduce noise of at least the luminance signal output from the separation circuit by an inter-frame operation or an intra-frame operation on the basis of the output signal of the motion detection circuit.
In this case, presence/absence of motion in the image is detected on the basis of the composite video signal, and the luminance signal and the chrominance signal are separated from the composite video signal by an inter-frame operation or an intra-frame operation on the basis of the result of detection. At this time, noise of the composite video signal is reduced by an inter-frame operation. Further, noise of at least the luminance signal is reduced by an inter-frame operation or an intra-frame operation on the basis of the result of detection of motion in the image.
Thus, noise of the composite video signal is reduced and noise of at least the luminance signal is reduced in the separated luminance and chrominance signals, whereby the S/N of the video signal is further improved.
Further, the motion detection circuit is provided in common for the separation circuit and the noise reduction circuit, whereby the circuit scale is not increased but the cost can be reduced.
Thus, the picture quality can be further improved with a simple structure.
The separation circuit may perform an intra-frame operation when the output signal of the motion detection circuit indicates presence of motion in the image and perform an inter-frame operation when the output signal of the motion detection circuit indicates absence of motion in the image, and the noise reduction circuit may perform an intra-frame operation or no operation when the output signal of the motion detection circuit indicates presence of motion in the image and may perform an inter-frame operation when the output signal of the motion detection circuit indicates absence of motion in the image.
In this case, the luminance signal and the chrominance signal are separated by an intra-frame operation when the image has motion, while the luminance signal and the chrominance signal are separated by an inter-frame operation when the image has no motion. Thus, high picture quality is obtained by an inter-frame operation as to a still picture.
Further, at least the luminance signal is subjected to an intra-frame operation or directly output with no operation in the separated luminance and chrominance signals when the image has motion, while at least the luminance signal is subjected to an inter-frame operation when the image has no motion. Thus, noise is reduced by an inter-frame operation as to a still picture.
Thus, the picture quality can be further improved in response to a motion picture and a still picture.
The video signal processing circuit may further comprise a first delay circuit delaying the composite video signal by one or more vertical scanning periods and a second delay circuit delaying at least the luminance signal output from the separation circuit by one or more vertical scanning periods, the motion detection circuit may detect presence/absence of motion in the image by operating the composite video signal and an output signal of the first delay circuit, the separation circuit may separate the luminance signal and the chrominance signal from the composite video signal by operating the composite video signal and the output signal of the first delay circuit, and the noise reduction circuit may reduce noise of at least the luminance signal output from the separation circuit by operating at least the luminance signal output from the separation circuit and an output signal of the second delay circuit.
In this case, the composite video signal is delayed by one or more vertical scanning periods and presence/absence of motion in the image is detected through the video signal and the delayed signal while the luminance signal and the chrominance signal are separated from the composite video signal by an inter-frame operation.
Further, at least the luminance signal is delayed by one or more vertical scanning periods, and noise of at least the luminance signal is reduced through at least the luminance signal and the delayed signal.
The motion detection circuit may calculate a differential value between the composite video signal and the output signal of the first delay circuit, for detecting presence/absence of motion in the image on the basis of the calculated differential value.
The motion detection circuit may determine that the image has motion when the calculated differential value is greater than a prescribed value, and determine that the image has no motion when the calculated differential value is not greater than the prescribed value.
The motion detection circuit may determine that the image has motion when the calculated differential value is greater than a first value, determine that the image has no motion when the calculated differential
Akin Gump Strauss Hauer & Feld L.L.P.
Kelley Chris
Matsushita Electric - Industrial Co., Ltd.
Wong Allen
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