JPH06153164A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To prevent deterioration in the resolution due to too much noise reduction of a low frequency replacement signal. CONSTITUTION:Noise of an input MUSE signal is eliminated by a noise reduction circuit 2 and the resulting signal is interpolated by an interpolation processing circuit 3 and a low frequency is replaced by a low frequency replacement circuit 5. Furthermore, part of the noise reduction signal is subject to control of noise reduction sensitivity in response to the motion quantity at a noise reduction control circuit 10, the result is subtracted from an output of the noise reduction circuit at a subtractor 12 and then a low frequency replacement signal is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit for decoding an offset-sampled video signal such as a MUSE signal.

[0002]

2. Description of the Related Art One of the methods for band-compressing and transmitting a high-definition signal is the MUSE method (see "MUSE-high-definition transmission method" published by the Institute of Electronics, Information and Communication Engineers).

In the MUSE system, due to the sampling characteristics, there is a region where the low frequency region (4 MHz or less) does not include temporal aliasing, that is, where each field is completely transmitted. Therefore, MUSE decoding is performed only on the high frequency side of that portion, and the transmitted signal can be used as it is for the low frequency portion. In this case, since the same movement as an image that has not been band-compressed is exhibited in a large area, even if there is a slight decoding error, the movement expression is not deteriorated.

Such low-frequency substitution is called "low-frequency sedge replacement". FIG. 2 shows a conventional video signal processing circuit having the low band shift changing function. 8-bit MU from input terminal 1
Noise is removed from the SE signal by the motion adaptive noise reduction circuit 2. The output of the noise reduction circuit is interpolated by the interpolating circuit 3 for the still image, and the field interpolation is performed for the moving image using the line memory. The signal subjected to the interpolation processing is further subjected to MUSE decoding processing such as sampling conversion in the signal processing circuit 4, and then supplied to the low frequency band substituting circuit 5. On the other hand, the input MUSE signal is delayed in the memory 6 by a delay amount (1 frame and several lines) in the interpolation processing circuit 3 and then supplied to a replacement signal forming circuit 7 including a low-pass filter. Then, the low band replacement signal is extracted and supplied to the low band replacement circuit 5. The low-frequency replacement circuit 5 replaces only the low-frequency part of the output of the signal processing circuit 4 with the low-frequency replacement signal and outputs it.

The circuit described above has a drawback in that an 8-bit memory 6 is required to match the two inputs of the low-frequency replacement circuit 5 and the replacement signal is not subjected to noise reduction.

Further, as a conventional example for solving the above-mentioned drawbacks, as shown in FIG. 3, a signal delayed by passing through a memory 31 in an interpolation processing circuit 3 composed of a memory 31 and an interpolation filter 32 (interpolation: Not used) to form the replacement signal. According to this method, no memory is required for time adjustment.

However, the above-mentioned method has a drawback that the resolution in the low frequency range is deteriorated when noise reduction having the same characteristics is applied to the low frequency band, which has a lower temporal correlation than the high frequency band.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks and provides a video signal processing circuit in which the capacity of the memory for time compensation is reduced and the resolution of the low frequency band is improved. .

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a noise reduction circuit for removing noise of a MUSE signal encoded by the MUSE method, an interpolation processing circuit for performing an interpolation process on the output of the noise reduction circuit, and the interpolation process. A video signal including a replacement signal forming circuit for forming a replacement signal by extracting a low-frequency component of the signal before performing, and a low-frequency replacement circuit for replacing the low-frequency component of the interpolation processing circuit output with the replacement signal. In the processing circuit, the noise reduction circuit output is used as the replacement signal, and a noise reduction control circuit for controlling the noise reduction sensitivity of the replacement signal according to the amount of movement of the image is provided.

[0010]

The present invention acts so that the noise reduction sensitivity of the low-frequency replacement signal is greatly reduced when the amount of image movement is large.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the circuit of this embodiment.
The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.
The noise reduction circuit 2 includes a subtracter 21 and a first coefficient unit 2
2, a well-known cyclic type composed of an adder 23 and a frame memory 24.
If the output is y, the frame memory output is x ′, and the coefficient of the first coefficient unit is K,

[0013]

[Equation 1]

[0014]

Here, the first coefficient multiplier output K (x'-x) is called a noise reduction signal, and noise reduction is realized by adding this signal to the input signal x.

Therefore, the larger the coefficient K, the greater the degree of noise reduction. And the coefficient K
Is controlled in the range of 0 to 1 according to the amount of movement from the movement detection circuit 8. That is, it is controlled so that it is close to 1 for an image with little movement close to a still image, and close to 0 for an image with large movement.

Further, the output of the noise reduction circuit 2 is supplied to the interpolation processing circuit 3, and passes through the memory 31 in the interpolation processing circuit 3 and is delayed as in FIG. 3 (not interpolated). To form the permutation signal.

On the other hand, the output of the first coefficient unit 22 is stored in the memory 9
In the interpolation processing circuit 3, a delay corresponding to the delay amount (1 frame and several lines) is applied, and then supplied to the noise reduction control circuit 10. The noise reduction control circuit comprises a second coefficient unit 101 controlled by the output of the motion detection circuit 8 and a switch 102 controlled by the output of the noise level detection circuit 11. The output of the noise reduction control circuit 10 is subtracted by the subtracter 12 from the output of the memory 31 of the interpolation processing circuit 3 and supplied to the replacement signal forming circuit 7. That is, the subtractor 12 has a function of lowering the noise reduction sensitivity by subtracting the noise reduction signal from the signal subjected to the noise reduction.

Next, the noise reduction control circuit 1
The operation of 0 will be described.

First, the second coefficient unit 101 multiplies the noise reduction signal by a coefficient according to the amount of motion. That is, when the amount of movement is small, the coefficient is close to 0, and when the amount of movement is large, the coefficient is close to 1.

If the noise level detected by the noise level detection circuit 11 is above a predetermined threshold value, the switch 102 is turned off, and if it is below the threshold value, the switch is turned on.

Therefore, when the noise level is high, the switch 102 is off, so that the low-frequency replacement signal is a signal subjected to noise reduction similarly to the MUSE-decoded signal processing circuit 4 output.

On the other hand, when the noise level is low, the switch 102 is turned on, and the noise reduction signal corresponding to the amount of motion is subtracted from the low frequency replacement signal, so that the noise reduction sensitivity of the low frequency replacement signal is lowered. This noise reduction sensitivity is controlled so as to decrease as the amount of movement increases.

If the input MUSE signal is 8 bits, the noise reduction signal is about 4 bits, so the memory 9 for time adjustment may be 4 bits.

[0025]

As described above, according to the present invention, when there is much noise, the replacement signal used for low-frequency replacement is sufficiently noise-reduced, and when there is little noise, replacement is performed according to the amount of motion. By lowering the noise reduction sensitivity of the signal, it is possible to prevent deterioration of resolution due to excessive noise reduction in the low frequency region, which has a lower temporal correlation than the high frequency region.

Since the memory for adjusting the time of the replacement signal only needs to delay the noise reduction signal, it requires only half the capacity of the system for delaying the video signal itself.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal processing circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a video signal processing circuit in a conventional example.

FIG. 3 is a block diagram of a video signal processing circuit in another conventional example.

[Explanation of symbols]

 2 noise reduction circuit 3 interpolation processing circuit 5 low-frequency replacement circuit 8 motion detection circuit 9 memory 10 noise reduction control circuit 101 second coefficient unit 11 noise level detection circuit

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[Procedure amendment]

[Submission date] September 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Such low-frequency substitution is called "low-frequency sedge replacement". FIG. 2 shows a conventional video signal processing circuit having the low band shift changing function. 8-bit MU from input terminal 1
The noise of the SE signal is removed by the noise reduction circuit 2. The output of the noise reduction circuit is interpolated by the interpolating circuit 3 for the still image, and the field interpolation is performed for the moving image using the line memory. The signal subjected to the interpolation processing is further subjected to MUSE decoding processing such as sampling conversion in the signal processing circuit 4, and then supplied to the low frequency band substituting circuit 5. Meanwhile, input MUSE
The signal is delayed in the memory 6 by a delay amount (several lines) in the interpolation processing circuit 3, and then supplied to a replacement signal forming circuit 7 including a low-pass filter. Is extracted and supplied to the low-frequency replacement circuit. The low-frequency replacement circuit 5 replaces only the low-frequency part of the output of the signal processing circuit 4 with the low-frequency replacement signal and outputs it.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

However, the above-mentioned method has a drawback in that when the noise reduction having the characteristics similar to those in the high range is applied to the part having low temporal correlation, that is, the moving part, the deterioration of the resolution becomes remarkable.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

On the other hand, the output of the first coefficient unit 22 is stored in the memory 9
In the interpolation processing circuit 3, a delay corresponding to the delay amount (several lines) is applied and then supplied to the noise reduction control circuit 10. This noise reduction control circuit is composed of a switch 102 controlled by the output of the motion detection circuit 8. The output of the noise reduction control circuit 10 is subtracted by the subtracter 12 from the output of the memory 31 of the interpolation processing circuit 3 and supplied to the replacement signal forming circuit 7. That is, the subtractor 12 has a function of lowering the noise reduction sensitivity by subtracting the noise reduction signal from the signal subjected to the noise reduction.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

[0025]

As described above, according to the present invention, when there is much noise, the replacement signal used for low-frequency replacement is sufficiently noise-reduced, and when there is little noise, replacement is performed according to the amount of motion. By reducing the noise reduction sensitivity of the signal, it is possible to prevent deterioration of resolution due to excessive low-frequency noise reduction in a portion having low temporal correlation, that is, a moving portion.

Claims (2)

[Claims] 1. M encoded by the MUSE method
A noise reduction circuit for removing noise of the USE signal, an interpolation processing circuit for performing an interpolation process on the output of the noise reduction circuit, and a replacement for extracting a low-frequency component of the signal before the interpolation process to form a replacement signal A signal forming circuit,
In a video signal processing circuit including a low-frequency replacement circuit that replaces a low-frequency component of the interpolation processing circuit output with the replacement signal, a noise reduction circuit output is used as the replacement signal, and noise reduction sensitivity of the replacement signal is improved. A video signal processing circuit provided with a noise reduction control circuit that controls according to the amount of movement of an image. 2. The video signal processing circuit according to claim 1, wherein when the noise level is equal to or higher than a predetermined value, the operation of the noise reduction control circuit is stopped.