JPH11136542A - Noise reduction device control method and device - Google Patents

Abstract

(57) [Summary] [Problem] An S / S signal is applied to a video signal based on a signal source in which a pseudo scene change occurs, such as a movie film.
Provided is a control method of a noise reduction device capable of displaying a high-quality image without lowering an N ratio. SOLUTION: By a scene change judgment unit 2,
It is determined whether there is a scene change code due to a pseudo scene change in addition to a scene change code due to a video scene change in the signal source, and if there is no pseudo scene change, the scene change determination unit 2 With the output signal, the switch 13 is switched to the switching terminal t2 side by the control signal Fc from the driver 18, and the trailing of the afterimage by the noise reduction device 1 can be prevented. When a pseudo scene change exists, the switch is switched by the control signal Fc. 13 is held at the switching terminal t1, and it is possible to prevent the S / N ratio from deteriorating and the video quality from deteriorating due to the interruption of the noise reduction operation of the noise reduction device 1 at the time of a pseudo scene change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of a noise reduction device for controlling the operation of a noise reduction device for reducing noise of a video signal, and a device thereof.

[0002]

2. Description of the Related Art In a television receiver for transmitting a video signal and a video tape recorder for recording / reproducing, a video signal is obtained by utilizing a field correlation or a frame correlation of an image in order to obtain a high quality video signal. Is subjected to noise reduction processing. In this type of noise reduction processing, a difference between a video signal delayed by one frame or two frames and an input video signal is detected as noise, and the obtained detection signal is multiplied by a noise reduction coefficient and subtracted from the input video signal. Thus, a video signal with reduced noise is obtained.

[0003]

In the above-described conventional noise reduction method, a constant noise reduction is always applied to a video signal irrespective of a change in the video. Noise reduction adapted to the afterimage may not always be performed. In particular, it is known that when such a noise reduction process is performed, an afterimage is conspicuous as if a tail is left when a scene change occurs in a video signal, and the video becomes difficult to see.

In order to solve this problem, conventionally, as shown in FIG. 5, a switch 15 for switching between an output terminal t1 of the noise reduction device 1 and an output terminal t2 to which the video signal Fv is directly output is provided. A scene change code detection circuit 17 for detecting a scene change code in a muse signal corresponding to a video signal, and switches the terminal of the switch 15 from t1 to t2 every time the scene change code detection circuit 17 detects a scene change code; At the time of a scene change, the noise reduction operation was interrupted to suppress the occurrence of a trailing afterimage. According to this method, when a video tape photographed by a normal video camera is used as a signal source, it is possible to prevent the occurrence of a trailing afterimage at the time of a scene change.

However, when using a signal source obtained by converting a cinema film into a video tape of a VTR by a telecine apparatus, in order to prevent flicker in a cinema film shot 24 frames per second, The other process of darkening the image has been taken,
In addition to this processing, a pseudo-scene change occurs in addition to the actual scene change due to the processing of converting the frame number of the movie film into 60 frames per second on the television.

The scene change code in the muse signal includes a code corresponding to a pseudo scene change. A scene change code is detected by a scene change detection circuit 17 and a noise reduction operation is performed by a changeover switch 15. Is interrupted, the noise reduction operation is interrupted at the position of the pseudo scene change even though the video scene has not changed, so that the S / N ratio is instantaneously degraded and the video quality is degraded. feel.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described current situation of noise reduction in video signals, and has as its object to provide a video signal based on a signal source in which a pseudo scene change occurs, such as a movie film. In view of the above, an object of the present invention is to provide a control method of a noise reduction device capable of displaying a high quality video without lowering the S / N ratio, and a device therefor.

[0008]

In order to achieve the above object, the present invention relates to a method for controlling a noise reduction device, comprising the steps of: providing a delayed video signal obtained by delaying an input video signal by at least one frame; A noise signal is detected from the difference from the input video signal, and the noise signal is subtracted from the input video signal, thereby controlling the noise reduction device that performs the noise reduction process. When the scene change is detected, the execution of the noise reduction processing is prohibited.

[0009] Similarly, in order to achieve the above object, the present invention according to a control device of a noise reduction apparatus, comprises: a controller for detecting a difference between a delayed video signal obtained by delaying an input video signal by at least one frame and a current input video signal; Detect noise signal,
By subtracting the noise signal from the input video signal, the control device of the noise reduction device that controls the noise reduction device that performs the noise reduction process, detects the presence or absence of a scene change, when there is the scene change, The image processing apparatus further includes a prohibition unit that prohibits execution of the noise reduction processing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on one embodiment of a noise reduction device with reference to FIGS. FIG. 1 is a circuit diagram showing a configuration of the present embodiment, FIG. 2 is a time chart showing a signal source determining operation of the present embodiment,
FIG. 3 is a time chart showing a basic operation of noise reduction control according to the present embodiment, and FIG. 4 is an explanatory diagram of a scene change code generation for each signal source according to the present embodiment.

In this embodiment, as shown in FIG. 1, a noise reduction device 1 for performing a noise reduction operation is provided with 62 stages of D flip-flops 7 (1) to 7 (62), and a scene change code detection signal. A scene change determination unit 2 for determining a scene change based on a switch 1 for performing a switching operation between execution and interruption of a noise reduction operation
3 and a driver 18 for driving the switch 13. In the noise reduction device 1, the input terminal of the delay circuit 3, the plus input terminal of the adder 5, and the plus input terminal of the adder 6 are provided at the input terminal t3. The output terminal of the delay circuit 3 is connected to the negative input terminal of the adder 5. The output terminal of the adder 5 is connected to the minus input terminal of the adder 6 via the multiplication circuit 4, and the switching terminal t1 of the switch 13 is connected to the output terminal of the adder 6, and the switch 13 The input terminal t3 of the noise reduction device 1 is connected to the switching terminal t2.

The scene change determination unit 2 is provided with an input terminal t5 for inputting a scene change code detection signal Cs in the muse signal and an input terminal t6 for inputting a clock KLf in field units.
The input terminal t5 is connected to one input terminal of the AND circuit 11,
The input terminal t6 is connected to the D terminal of the first-stage D flip-flop 7 (1), and is connected to the D flip-flop 7 (1) of each stage.
C terminals of (1) to 7 (62) and D flip-flop 1
0 C terminal. The Q terminal of the first-stage D flip-flop 7 (1) is connected to the D terminal of the second-stage D flip-flop 7 (2), and the Q terminal of the second-stage D flip-flop 7 (2). Is connected to the D terminal of the third stage D flip-flop 7 (3), and similarly, the Q terminal of the 61st stage D flip-flop 7 (61) is connected to the 62nd stage D flip-flop 7 (62). ) D terminal. Then, the third stage D flip-flop 7 (3) to the 62nd stage D flip-flop 7 (62)
Are connected to the respective input terminals of the OR circuit 8, and the output terminal of the OR circuit 8 is connected to another input terminal of the AND circuit 11 via the inverting circuit.

Further, the output terminal of the AND circuit 11 is
One input terminal of the R circuit 12 and the D flip-flop 1
0, the Q terminal of the D flip-flop 10 is connected to the other input terminal of the OR circuit 12,
One input terminal of the driver 18 is connected to the output terminal of the D circuit 12, and the other input terminal of the driver 18 is supplied with a clock KLf in a unit of a field. Is "1", the logical value becomes 1 during the time 4tf corresponding to four fields, and if the logical value of the signal at the output terminal of the OR circuit 12 is "0", the logical value becomes "1". It is configured to output a control signal Fc that becomes 0 ”. The switch 13 is connected to a control signal F output from the driver 18.
If the logical value of c is "1", switching to the switching terminal t2 is performed for a time 4tf corresponding to four fields, and if the logical value of the control signal Fc is "0", switching to the switching terminal t1 is performed. It is configured to be.

Generally, as shown in Table 1, various kinds of control codes are set in the muse signal for the video signal Fv corresponding to each bit, and the motion signal including the scene change code is changed from 16 bits to 18 bits. Information is set.

[0015]

[Table 1]

The operation of the present embodiment having such a configuration will be described. In the present embodiment, when a video tape taken by a normal video camera is used as a signal source, as shown in FIG. Since the scene change code is detected, if the noise reduction operation is interrupted by this detection signal, it is possible to prevent the occurrence of a trailing image after the scene change. However, when using a signal source obtained by converting a cinema film into a video tape of a VTR by a telecine device, the cinema film is photographed 24 frames per second. In order to take the process of darkening the image and to convert the number of movie film frames into 60 frames per second on the television, scene A actually continues as shown in FIG. In spite of the fact that there is no change in the video, pseudo scene changes occur, and scene change codes are detected in response to these pseudo scene changes.

For this reason, in this embodiment, as shown in FIG. 2, a time T1 (approximately 1) corresponding to 60 fields is used.
In a state G1 in which a scene change code is detected at least once every second), it is determined that a pseudo scene change has occurred in a case where the signal source is a movie film or the like, and a predetermined scene corresponding to 60 fields or more is determined. In the state G2 in which no scene change code is detected at the time T2, it is determined that a video tape taken by a normal video camera is used as a signal source.

Here, the operation of the present embodiment will be described with reference to FIG. The video signal Fv input from the input terminal t3 of the noise reduction device 1 is input to the plus input terminal of the adder 5 and is also input to the delay circuit 3 to be delayed by 4 fields (2 frames) and output from the adder 5. The noise signal is input to the minus input terminal, and the adder 5 detects a noise signal based on the difference between the video signal Fv four fields before and the current video signal Fv. In this way, the noise signal detected by the adder 5 is input to the multiplying circuit 4 to obtain a corrected noise signal multiplied by a constant. In the adder 6, the corrected noise signal is converted from the current video signal Fv. The subtracted and noise-reduced video signal is output to the switching terminal t1. Further, a video signal Fv that is not reduced in noise is output from the input terminal t3 to the switching terminal t2.

On the other hand, the scene change code detection signal Cs input to the input terminal t5 of the scene change determination unit 2 is input to the D terminal of the first stage D flip-flop 7 (1), and the D flip-flop 7 (1) The clock KLf for each field is input to the C terminal of 1). By this clock KLf, the D flip-flop 7
The detection signal Cs output to the Q terminal of (1) is input to the D terminal of the second stage D flip-flop 7 (2), and each D flip-flop operates in the same manner. Therefore, the third stage D flip-flop 7 (3)
When the detection signal Cs is output to one of the Q terminals of the two-stage D flip-flop 7 (62) and the logical value of the signal at the Q terminal becomes “1”, the logical value of the signal at the output terminal of the OR circuit 8 becomes It becomes “1”.

Since the signal at the output terminal of the OR circuit 8 is inverted and input to the other input terminal of the AND circuit 11, the scene change code detection signal Cs input to one input terminal of the AND circuit 11 Is output from the AND circuit 11 when the detection signal Cs based on the pseudo scene change does not exist in the 60 fields from 3 fields before to 62 fields before, and the logic of the signal at the output terminal of the AND circuit 11 The value becomes "1". The output signal of the AND circuit 11 is input to one input terminal of the OR circuit 12 and the D terminal of the D flip-flop 10,
The logic value of the signal at the Q terminal of the flip-flop 10 becomes “1” according to the clock KLf.

Therefore, if the detection signal Cs based on the pseudo scene change does not exist between 60 fields before 3 fields and 62 fields before, the logical value of the signal at the output terminal of the OR circuit 12 is When the detection signal Cs based on the pseudo scene change exists even once in 60 fields from 3 fields before to 62 fields before, the signal at the output terminal of the OR circuit 12 becomes “1” corresponding to KLf. The logical value becomes “0” corresponding to the clock KLf.

For this reason, in the present embodiment, when the noise reduction operation is performed, the detection signal Cs based on the pseudo scene change does not exist in the 60 fields from 3 fields before to 62 fields before. FIG. 3 (a),
As shown in (c), when the detection signal Cs corresponding to the change of the image at tc is detected, the logical value of the control signal Fc output from the driver 18 becomes the logical value of FIG. As shown in the figure, the signal becomes "1" for a time 4tf corresponding to four frames, the switch 13 is switched to the switching terminal t2 side, and the noise reduction operation by the noise reduction device 1 is interrupted. Also, if the detection signal Cs based on the pseudo scene change exists between 60 fields before 3 fields and 62 fields before, the logical value of the control signal Fc output from the driver 18 becomes “0”, The noise reduction operation is continued while the switch 13 remains switched to the switching terminal t1 side.

As described above, according to the present embodiment, a video tape photographed by a normal video camera is used as a signal source, and a pseudo scene change other than a change in an actual image is performed. In a state where it is hardly detected as a scene change code, the switch 13 is turned on by the control signal Fc output from the driver 18 based on the output signal from the scene change determination unit 2 based on the scene change code detection signal Cs. By switching to the switching terminal t2 side, the noise reduction operation of the noise reduction device 1 is interrupted for a time corresponding to four frames, and it is possible to prevent the occurrence of a trailing afterimage at the time of a scene change. Even if a scene change occurs between 60 fields with such a signal source, it is a case where the original video is flickering, and the occurrence of some afterimage is not visually noticeable at all.

In this embodiment, the scene change determination unit 2 determines whether there is a scene change code based on a pseudo scene change in addition to a scene change code based on a scene change of an actual video. If a decision is made that a pseudo scene change is present in the case where, for example, a movie film is used as a signal source, the scene change decision unit 2
In response to the control signal Fc output from the driver 18, the switch 13 is kept at the switching terminal t1 side, and the noise reduction operation of the noise reduction device 1 is maintained. For this reason, when a movie film or the like having a scene change code due to a pseudo scene change is used, the noise reduction operation of the noise reduction device 1 is interrupted by the pseudo scene change, so that the S / N is reduced. The deterioration of the ratio and the deterioration of the image quality are prevented. In this case, the noise reduction operation of the noise reduction device 1 is continued during the actual scene change,
Even if some afterimages are present, the effect is small as the quality of the video is reduced every time a pseudo scene change occurs.

[0025]

According to the present invention, a noise signal is detected from a difference between a delayed video signal obtained by delaying an input video signal by at least one frame and a current input video signal, and the obtained noise signal is converted to an input video signal. The noise reduction process is performed by subtracting from the above, but the presence or absence of a scene change is detected. If there is a scene change, the execution of the noise reduction process is prohibited, so the detection time interval is shorter than the predetermined time interval. For example, by prohibiting a noise reduction operation in a pseudo scene change when a movie film is used as a signal source, it is possible to prevent a decrease in the S / N ratio.

When the input video signal is a MUSE signal, the noise reduction operation prohibition period is extended by one field, or a scene change code is transmitted based on a scene change code transmitted in response to the input video signal. Is detected, noise reduction processing is performed, and a similar effect can be obtained. Furthermore, the presence or absence of a scene change is detected at time intervals corresponding to 60 fields,
By prohibiting the noise reduction operation, a similar effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a time chart showing a signal source determining operation of the embodiment.

FIG. 3 is a time chart showing a basic operation of noise reduction control according to the embodiment.

FIG. 4 is an explanatory diagram of a scene change code generation for each signal source according to the embodiment.

FIG. 5 is an explanatory diagram showing control of a conventional noise reduction device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Noise reduction device, 2 ... Scene change determination unit, 3 ... Delay circuit, 4 ... Multiplier circuit, 5, 6 ... Adder, 7
(1) to 7 (62) D flip-flop, 8 OR circuit, 10 D flip-flop, 11 AND circuit, 1
2 ... OR circuit, 13 ... Switch.

Claims (5)

[Claims] 1. A noise signal is detected from a difference between a delayed video signal obtained by delaying an input video signal by at least one frame and a current input video signal, and the noise signal is subtracted from the input video signal. A method of controlling a noise reduction device that controls a noise reduction device that performs a noise reduction process, wherein the presence or absence of a scene change is detected, and the execution of the noise reduction process is prohibited when the scene change occurs. Control method of noise reduction device. 2. The control method according to claim 1, wherein when the input video signal is a MUSE signal, a period in which the execution of the noise reduction processing is prohibited is extended by one field. 3. The apparatus according to claim 1, wherein when the input video signal is a MUSE signal, the presence or absence of a scene change is detected based on a scene change code transmitted corresponding to the input video signal. Control method of noise reduction device. 4. A noise signal is detected from a difference between a delayed video signal obtained by delaying an input video signal by at least one frame and a current input video signal, and the noise signal is subtracted from the input video signal. A control device for a noise reduction device that controls a noise reduction device that performs a noise reduction process, the device having a prohibition unit that detects the presence or absence of a scene change and prohibits the execution of the noise reduction process when the scene change occurs. A control device for a noise reduction device, comprising: 5. The control device according to claim 4, wherein the prohibition unit detects the presence or absence of a scene change at a time interval corresponding to 60 fields and executes the prohibition operation.