JPS63316977A - Cyclical type noise reduction device - Google Patents

Abstract

PURPOSE:To realize noise reduction provided with respective advantage of both systems, by forming a delay output video signal by mixing a frame delay output video signal and a field delay output video signal with an appropriate ratio corresponding to the size of a field differential signal. CONSTITUTION:A cyclical type noise reduction device 11 mixes the frame delay output video signal receiving the delay of a frame period by line delay circuits 15-16 with the field delay output video signal receiving the delay of a field period falsely by the delay circuits 15 and 17 with the appropriate ratio corresponding to the size of the field differential signal by coefficient circuits 21 and 20, and forms the delay output video signal. In such a way, the generation of flicker is suppressed by giving priority on field cyclical type noise reduction when the field differential signal is larger, and deterioration in resolution at vertical edge part is suppressed by giving the priority on frame cyclical type noise reduction when the field differential signal is smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application] The present invention relates to a cyclic noise reduction device that reduces noise by using the correlation between intermediate images.

[Prior art 1] Among noise reduction devices that reduce noise by using field correlation or frame correlation of video signals, an image memory is used as a delay stage and the noise reduction target is circulated to equivalently reduce noise in multiple images. A cyclic noise reduction device that can achieve the same effect as using a memory has the advantage of being cheaper to manufacture than a non-cyclic noise reduction device.

The conventional cyclic noise reduction device 1 shown in FIG. , the output video signal obtained from the subtracter 4 is input to the subtracter 3 through a delay device 5 which delays the output video signal by 262 line periods or 263 line periods by alternating η for each field.Therefore, After passing through the subtracter 3 and the coefficient 42, the human video signal is multiplied by (+-K) by being subtracted from the original signal in the subtracter 4, and on the other hand, the output of the subtracter 4 is delayed in the delay device 5. The delayed output video signal thus obtained is multiplied by passing through the subtracter 3, the coefficient unit 2, and the subtracter '54.In this case, the difference signal between the manual video signal and the delayed output video signal obtained from the subtracter 3 is A moving image has a high level, and for a moving image, the larger the coefficient K is set in an attempt to increase the sound reduction effect, the larger the afterimage time constant becomes.

]Problem to be Solved by the Invention 1 The conventional cyclic noise reduction device using the field correlation described above cannot be used to reduce images having diagonal edges that cross the scanning line diagonally, as shown in FIG. 5(A), for example. , the low-frequency cyclic noise has the opposite effect, and false signals are generated at the diagonal edge portions. As a result, as shown in the same figure (r The problem was that the waveform turned into a rough staircase waveform, giving an unnatural impression.This was caused by the mixing of the even and odd field signals due to the low frequency cyclic noise in the part with no line correlation, resulting in false signals. This is an unavoidable and essential phenomenon for the field correlation type cyclic noise reduction device 1, which alternately switches the delay period in the delay unit 5 into a 262-line period and a 263-line period in the vertical scanning period. It was considered defective.

On the other hand, a cyclic noise reduction device using frame correlation that does not generate false signals in the diagonally shaded portion, such as using field correlation, has been proposed, but this one is a cyclic noise reduction device that uses field correlation! Since the afterimage time constant is human compared to , afterimages are more likely to occur in images with rapid movement, and noise reduction using frame correlation does not have a low-frequency effect on frame frequency noise components. For example, +I of a 2-head magnetic recording 111 production device that records while switching heads for each field or generates 1ff.
When the G raw output is supplied, there are problems such as the inability to remove flicker components of the frame period.

[Means for Solving the Problems J This invention solves the above problems, and adds a delayed output video signal obtained by delaying the video signal corresponding to the image unit to the human-powered video signal, thereby producing a signal with reduced noise. A cyclic noise reduction device that obtains an output video signal, which outputs a frame-delayed output video signal delayed by a frame period and a field-delayed output video signal delayed by a field period, as appropriate depending on the magnitude of the field difference signal. The present invention is characterized in that it is configured by providing a delay device that mixes the signals at a ratio and forms the delayed output video signal.

"Operation" This invention mixes a frame-delayed output video signal delayed by a frame period and a field-delayed output video signal delayed by a field period in an appropriate ratio depending on the magnitude of the field difference signal. This forms a delayed output video signal, and performs noise reduction that combines the eight advantages of the frame cyclic noise reduction method and the field cyclic noise reduction method.

[Embodiment 1] Hereinafter, an embodiment of the present invention will be explained with reference to FIGS. 1 to 3. FIG. 1 shows an embodiment of the cyclic noise reduction device of the present invention. The circuit configuration diagrams, FIGS. 2 and 3, are individual/output characteristic diagrams of the coefficient unit and coefficient control circuit shown in FIG. 1.

In Fig. 1, the cyclic noise low-band device II is a combination of a field cyclic noise reduction method and a frame cyclic noise reduction method, and performs subtraction to subtract the delayed output video part S) from the human video signal. Two devices, 12 and 13, are prepared for the field cyclic loop and the frame cyclic loop. Further, the delay device 14 used for delaying the output video signal has a configuration in which 262 line delay circuits 15 and 16 are connected in series with a double line delay circuit +7 in between, and these three delay circuits 15 and 17 and 16 are used to delay the frame. A delay is made. Also, by adding the output of the 262-line delay circuit 15 and the output of the 1-line delay circuit 17 at the addition "Z+18" and multiplying by 1/2 at the coefficient circuit 19, a pseudo field delay due to line interpolation is performed. The subtracters 12 and 13 use the outputs of the coefficient circuit 19 and the 262-line delay circuit 16 as subtraction inputs, respectively, and the outputs of each subtractor 12 and 13 are inputted into coefficients complementary to each other. The coefficient is multiplied by the coefficient circuits 20 and 21 having
By adding the field delayed output video signal and the frame delayed output video signal at an appropriate ratio, a delayed output video signal is formed. Note that the output of the adder 22 is used as the summation input of the subtracter 4.

Further, the delay device 14 connects the absolute value circuit 2 to the subtraction 'a I 2.
3 is connected, and the absolute value circuit 23 determines the magnitude of the field correlation, and the absolute value circuit 25 is also connected to the subtracter 24 that takes the difference between the human power and the output of the line delay circuit 17. The configuration is such that the magnitude of the line correlation is determined by the following. These absolute value circuits 23
．． 25, the field difference signal ΔF or line difference signal Δ1. The configuration is such that l-K is complementary to the coefficient of the coefficient circuit 20.21 each time it is supplied to the coefficient unit 26 and the coefficient control circuit 27.

The coefficient unit 26 uses the output ΔF of the absolute value detection circuit 23 as human power, and outputs Δ! of the absolute value detection circuit 23! , and the relationship between the output ΔL and the coefficient is a downward sloping characteristic as shown in FIG. The coefficient control circuit 27 inputs ΔF into the output of the coefficient unit 26 and complementarily switches 1-K to the coefficient of the coefficient circuit 20.21 according to the value, and its output characteristics are as follows. As shown in FIG. For this reason, the cyclic noise reduction device 1
As for the basic operation of No. 1, when the field difference signal ΔF detected by the absolute value circuit 23 is human, the coefficient control circuit 2
By setting the coefficient K to be large and the coefficient 1-K to be small by 4, priority is given to field cyclic noise reduction, and the +M generation of the two-head magnetic recording 11. Suppress the occurrence of flicker on the output. Conversely, the field difference signal Δ detected by the absolute value circuit 23
When F is small, the coefficient control circuit 25 makes the coefficient K small and the coefficient 1-K large, giving priority to low frame cyclic noise ^λ and suppressing resolution deterioration at the direct edge portion.
I can do 4” things.

Note that the larger the line difference signal ΔL, which is the output of the absolute value circuit 25, the smaller the coefficient of the coefficient multiplier 26 becomes.
ΔF in the field difference signal is correspondingly reduced, and the occurrence of afterimages at vertical edge portions can be suppressed more effectively.

In this way, the cyclic noise reduction device 11 receives the frame delayed output video signal delayed by the frame period by the line delay circuit +5.17.16 and the delay circuit 15.17.
The field-delayed output video signal which has been pseudo-delayed by the field period is mixed by the coefficient circuits 21 and 20 whose coefficients are complementary switched and the adder 22 at an appropriate ratio depending on the magnitude of the field difference signal. However, since it is configured to form a delayed output video signal, it is possible to perform noise reduction that combines the advantages of the frame cyclic noise reduction method and the field cyclic noise reduction method. In this case, by prioritizing field cyclic noise reduction, it is possible to effectively suppress the occurrence of flicker on the 11 raw output of a two-head magnetic recording/reproducing device, which is a problem with the frame cyclic noise reduction method. Conversely, when the field difference signal is small, it is possible to prioritize frame cyclic noise reduction and suppress resolution deterioration in the forward eno portion.

Furthermore, since the field difference signal ΔF supplied to the coefficient control circuit 27 is limited based on the line difference signal ΔL, resolution deterioration at the forward edge portion where there is a step between lines can be effectively prevented. ■I can do L.

[Effects of the Invention] As described in 1-1 above, the present invention allows a frame-delayed output video signal delayed by 11 frame periods and a field-delayed output video signal delayed by a field period to be output based on the magnitude of the field difference signal. Since the configuration is such that a delayed output video signal is formed by mixing at an appropriate ratio according to the If the difference signal is like a person, Hurray! By prioritizing field cyclic noise reduction, it is possible to effectively suppress the occurrence of flicker on the 111 raw output of a two-head magnetic recording device, which is a problem with the cyclic noise reduction method, and vice versa. When the field difference signal is small, priority is given to frame cyclic noise reduction, and excellent effects such as being able to suppress resolution deterioration at vertical edge portions can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the cyclic noise reduction device of the present invention, FIGS. 2.3 are individual/output characteristic diagrams of the coefficient unit and coefficient control circuit shown in FIG. 1, FIG. 4 is a circuit configuration diagram showing an example of a conventional cyclic noise reduction device, and FIG. 5 is a diagram showing an image for explaining the problems of the conventional cyclic noise reduction device shown in FIG. 4. It is. 11. 1-cycle noise reduction device, 14. ．． ．． delay device, 20
．． 2+, , coefficient circuit, 22. ,,adder,23. ,,
Absolute value circuit, 27. ,,Coefficient control circuit.

Claims (1)

[Claims] A cyclic noise reduction device that obtains an output video signal with reduced noise by adding a delayed output video signal obtained by applying a delay corresponding to an image unit to an input video signal, the frame delay output being delayed by a frame period. Cyclic noise reduction comprising a delay device that mixes a video signal and a field delayed output video signal delayed by a field period in an appropriate ratio depending on the magnitude of the field difference signal to form the delayed output video signal. Device.