JP2009088829A - Three-dimensional noise reduction device and video signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-dimensional noise reduction device for reducing an after image even though performing three-dimensional noise reduction, and a video signal processor. <P>SOLUTION: The three-dimensional noise reduction device is provided with a video memory for storing videos, a three-dimensional noise reduction part for reducing noise on the basis of a time axis, and a control part for operating the three-dimensional noise reduction part, wherein the three-dimensional noise reduction device does not continuously perform three-dimensional noise reduction but intermittently perform the three-dimensional noise reduction by turning off it at predetermined time intervals. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a three-dimensional noise reduction device and a video signal processing device, and more particularly to a three-dimensional noise reduction device and a video signal processing device with reduced afterimages.

  When outputting an image to a television or the like, image quality improvement processing such as noise reduction and Y / C separation is performed. Noise reduction and Y / C separation include one-dimensional, two-dimensional, and three-dimensional processes, and processes having different dimensions may be used in combination. In addition, although the three-dimensional noise reduction and the three-dimensional Y / C separation bring about a great image quality improvement effect, if both are used together, the video memory to be consumed becomes large, so only one of the noise reduction and the Y / C separation is used. In some cases, one of them is performed exclusively.

  One-dimensional noise reduction uses the relationship in the horizontal direction (left and right) of one frame, and two-dimensional noise reduction uses the relationship in the vertical direction (up and down) in addition to the one-dimensional noise reduction. In the reduction and the two-dimensional noise reduction, the time axis is not compared. 3D noise reduction, which has the highest noise reduction effect, reduces the noise by averaging the previous and current frames by adding a time axis to the relationship between the horizontal direction (left and right) and vertical direction (up and down). It is processing to do.

  In the three-dimensional Y / C separation, when the composite video signal (CVBS) obtained by combining the luminance signal (Y signal) and the color signal (C signal) is separated into the luminance signal and the color signal, the interval between the previous and next frames is reduced. Compare the signals of the lines at the same position. For this reason, the luminance signal and the color signal can be separated with high accuracy, and the cross color generated in the case of one-dimensional Y / C separation or two-dimensional Y / C separation (occurred in a fine image such as an oblique line). Color noise) and dot interference (mesh-like noise generated in the color outline) can be reduced. The one-dimensional Y / C separation simply separates the luminance signal and the color signal according to the frequency, and the two-dimensional Y / C separation uses the line correlation of the scanning line to obtain the luminance signal and the color signal. It is separated.

  As described above, in the video signal processing apparatus, various image quality improvement processes are performed. Especially, when the reception state is bad and noise of the input video signal itself is large according to the three-dimensional noise reduction, That is, even when 3D Y / C separation or 2D noise reduction cannot provide a sufficient image quality improvement effect, the image quality can be improved by reducing the roughness of the video.

On the other hand, when three-dimensional noise reduction is performed, an afterimage may occur because feedback processing such as averaging the previous frame stored in the video memory and the current frame is performed.
For example, it is assumed that the image quality is improved by three-dimensional noise reduction when the image changes from a still image to a still image. In this case, if the previous frame and the current frame are simply averaged by three-dimensional noise reduction, the current frame is 1/2 of the previous frame image and 1/4 of the previous frame image. An afterimage occurs. In particular, if an afterimage is generated between a still image and a still image, the image tends to be difficult for the viewer to see.

  Under such circumstances, in Japanese Patent Laid-Open No. 2004-228867, when video signal processing for reducing noise is performed by processing in the time direction using a frame unit memory for a video signal, that is, when three-dimensional noise reduction is performed, There has been proposed a video signal processing method in which the residual of the video signal is reduced by stopping the noise reduction process in a predetermined period after the input signal is switched.

  In Patent Document 2, a video signal provided with a noise reduction means for performing noise reduction of an input video signal by utilizing the correlation of patterns between frames or fields of the input video signal, and a horizontal noise canceller for performing noise cancellation. In the processing circuit, when the input signal is a still image, a video signal processing circuit has been proposed in which the operation of the horizontal noise canceller is turned off or noise cancellation is weakened.

  Patent Document 3 proposes a noise reduction circuit that includes a noise reduction unit for a video signal and a level detection unit for a video signal, and controls the noise reduction capability of the noise reduction unit according to the detection result of the signal level. In this noise reduction circuit, the noise reduction processing is not performed when the luminance signal or the color signal is higher than a predetermined value. Further, when the Y signal or C signal is lower than a predetermined value, the motion signal from the motion detection circuit is referred to. Is determined to be a predetermined level.

Japanese Patent Laid-Open No. 7-162807 Japanese Patent Laid-Open No. 11-69202 JP-A-1-122273

  However, in the video signal processing method described in Patent Document 1, the noise signal processing is stopped after switching a plurality of input signals, and the noise signal processing is stopped before switching the plurality of input signals. Not in. For this reason, afterimages are likely to remain after noise signal processing, that is, feedback processing that causes a delay in time. In other words, even if the processing of the noise signal is stopped after switching the input signal, the video signal before switching, that is, an afterimage is likely to remain.

  In the video signal processing circuit described in Patent Document 2, the determination between a still image and a moving image is detected by a motion detection circuit, and the operation of the horizontal noise canceller is turned off after the moving image becomes a still image, or the noise canceller is applied. Is weakening. For this reason, the video before becoming a still image tends to remain. In addition, the afterimage between the still image and the still image is not reduced, and the afterimage tends to remain between the still image and the still image.

  In the noise reduction circuit described in Patent Document 3, the noise reduction processing is controlled based on the level of the luminance signal and the color signal, that is, the video signal itself, and when the level of the video signal, that is, the luminance signal and the color signal is large. This means that no noise reduction processing is performed by the noise reduction circuit. Even when the level of the video signal is low and it is determined as a still part, control is performed by setting the coefficient in the noise reduction processing to, for example, 0.5 based on the motion detection circuit, and a large afterimage is generated. Will do.

  In view of such circumstances, the present invention reduces the afterimage even when performing 3D noise reduction and a 3D noise reduction device and a video signal processing device that reduce the afterimage, especially between a still image and a still image. An object of the present invention is to provide a three-dimensional noise reduction device and a video signal processing device.

In order to achieve the above object, the present invention takes the following technical means.
The three-dimensional noise reduction device according to the present invention includes a video memory that stores video, a three-dimensional noise reduction unit that reduces noise based on a time axis, and a control unit that operates the three-dimensional noise reduction unit. In the three-dimensional noise reduction apparatus, three-dimensional noise reduction is performed intermittently.

  In three-dimensional noise reduction, noise reduction is performed based on a time axis. For example, since noise reduction is performed by taking a simple addition average of the image signal of the previous frame and the current frame, the previous frame stored in the video memory affects the current frame. In this case, if the video does not move, the noise reduction effect is enhanced. However, when the video moves, especially when the video changes from a still image to a still image, a past frame adversely affects the current frame, and thus an afterimage occurs.

  Therefore, when the three-dimensional noise reduction is intermittently performed and the three-dimensional noise reduction is temporarily turned off, the image of the previous frame is temporarily deleted and only the image of the current frame is displayed. That is, the image of the previous frame does not adversely affect the current image, the afterimage is reduced, and the image quality is improved.

  The three-dimensional noise reduction process is not necessarily a simple average of the previous frame and the current frame, but in the three-dimensional noise reduction, noise reduction is performed based on the time axis by applying feedback. Therefore, the video of the past frame affects the current frame. For this reason, afterimages are reduced and image quality is improved by intermittently performing three-dimensional noise reduction.

  In the three-dimensional noise reduction apparatus according to the present invention, it is preferable that the OFF time of the three-dimensional noise reduction that is intermittently performed is a time during which one still image is displayed.

In the three-dimensional noise reduction device, noise reduction is performed based on the time axis, so that the minimum OFF time can be set by setting the OFF time to the time for displaying one frame (one still image). it can.
If the minimum OFF time is set, the ON time, that is, the time during which the three-dimensional noise reduction is functioning can be lengthened, so that the noise reduction effect is enhanced and the image quality is improved.

  For example, in the NTSC system, since the frame rate is 30 fps, if the OFF time of 3D noise reduction is 1/30 seconds, the minimum OFF time can be completed, and the ON time of 3D noise reduction is lengthened. Therefore, three-dimensional noise reduction can be used effectively.

  The ON time corresponds to the input video and is preferably several hundred ms or more and several seconds or less. For example, when the afterimage is relatively large, the afterimage reduction effect can be increased by setting the ON time to 100 ms. If the afterimage is relatively small, the noise reduction effect by three-dimensional noise reduction can be enhanced by setting the ON time to 5 seconds.

  In the video signal processing apparatus according to the present invention, a tuner that converts an RF signal into an IF signal, an AGC amplifier that receives an IF signal from the tuner, a demodulator that receives an output signal of the AGC amplifier, A signal processing unit to which an output signal of the demodulator is input, a video memory for storing video, a three-dimensional noise reduction unit for reducing noise based on a time axis, and a control unit for operating the three-dimensional noise reduction unit A video signal processing apparatus comprising: a three-dimensional noise reduction device having an output signal of a signal processing unit and a video processing block to which an output signal of the three-dimensional noise reduction device is input. Is done intermittently.

For example, when the voltage level of the RF signal input from the antenna to the video signal processing device is low and the voltage is greatly amplified through an AGC amplifier to obtain a desired voltage, that is, when the noise component of the input video signal is large Even so, an afterimage generated by the three-dimensional noise reduction can be reduced while performing the three-dimensional noise reduction. For this reason, the image quality output from the video signal processing apparatus image to, for example, a liquid crystal display is improved.
In other words, in a video signal processing apparatus in which 3D noise reduction is intermittently performed and 3D noise reduction is temporarily turned OFF, the image of the previous frame is temporarily deleted and only the image of the current frame is displayed. Therefore, the afterimage is reduced and the image quality is improved.

  In the video signal processing apparatus according to the present invention, it is preferable that the OFF time of the three-dimensional noise reduction performed intermittently is a time for displaying one still image.

  By setting the OFF time of the 3D noise reduction device used for the video signal processing device to the time that one frame (one still image) is displayed, the OFF time of the 1D 3D noise reduction is sufficient. And a minimum OFF time. If the minimum OFF time is set, the ON time, that is, the time during which the three-dimensional noise reduction is functioning can be lengthened, so that the noise reduction effect is enhanced and the image quality is improved.

  According to the present invention, even if three-dimensional noise reduction is performed, a three-dimensional noise reduction device and a video signal processing device with reduced afterimages, particularly a three-dimensional image that reduces afterimages even between a still image and a still image. A noise reduction device and a video signal processing device can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of a video signal processing apparatus according to an embodiment of the present invention.
The video signal processing device 50 is used in a television, and receives an RF (Radio Frequency) signal (radio frequency signal) from an antenna 9. The input RF signal is selected by the tuner 1 and then converted into an IF (Intermediate Frequency) signal (intermediate frequency signal).

  The IF signal is converted into a constant voltage by an AGC (Automatic Gain Control) amplifier 2 (automatic gain control amplifier). In other words, the magnitude of the receivable radio waves varies depending on the geographical conditions and the voltage depending on the weather and the passage of the aircraft even in the same place. The radio wave having various voltages is converted into a constant voltage by passing through the AGC amplifier 2. Even if the IF signal has a constant voltage, it receives a low-intensity radio wave if the reception condition is poor, and converts the IF signal voltage to a constant voltage based on the received radio wave. Therefore, it contains a lot of noise components.

  Further, in the case of the NTSC system, the output of the AGC amplifier 2 is demodulated into a composite video signal (CVBS) by the demodulator 3 to become a baseband analog signal. The composite video signal is converted from the analog signal by the signal processing unit 4. Converted to a digital signal. Therefore, in the NTSC system, the signal processing unit 4 is an A / D converter. In digital broadcasting, the signal processing unit 4 separates the video signal from the signal in which the video signal and the audio signal are integrated.

  The output of the signal processing unit 4 is input to the three-dimensional noise reduction device 10. The three-dimensional noise reduction device 10 includes a three-dimensional noise reduction unit 5 that performs three-dimensional noise reduction, a control unit 7 that operates the three-dimensional noise reduction unit 5, and a video memory 8 that stores video. The three-dimensional noise reduction unit 5 includes a three-dimensional noise reduction arithmetic circuit.

  The video processing block 6 processes the output signal of the three-dimensional noise reduction unit 5, that is, the three-dimensional noise reduction device 10, into a displayable video. When the video signal processing device 50 is used for a liquid crystal television, that is, when a liquid crystal display is connected to the output side of the video processing block 6, the video processing block 6 is composed of a scaler or the like.

  The control unit 7 uses a CPU (Central Processing Unit) and has a built-in timer. Based on the time measured by the timer, a signal for switching ON and OFF of the three-dimensional noise reduction at a predetermined interval is output to the three-dimensional noise reduction unit 5. The video memory 8 is provided for performing three-dimensional noise reduction for comparing time axes, and stores a temporally previous image, that is, a frame.

  The three-dimensional noise reduction is an effective noise reduction for reducing the noise generated when the radio wave condition is poor as described above, and takes the average of the previous frame and the current frame. This is a noise reduction that is effective when the same frame continues.

On the other hand, if 3D noise reduction is always performed, that is, continuously, 3D noise reduction outputs the current image based on the time axis. In other words, the past image becomes the current image. An afterimage occurs because of the influence.
However, if the three-dimensional noise reduction is switched ON and OFF, that is, the three-dimensional noise reduction is intermittently performed and the three-dimensional noise reduction OFF period is provided, the past image is displayed in the OFF period. Does not affect the image. For this reason, afterimages are reduced and image quality is improved by providing a predetermined OFF period for the three-dimensional noise reduction.

FIG. 2 is an explanatory diagram of switching of the three-dimensional noise reduction according to the embodiment of the present invention.
FIG. 2A is a diagram illustrating an image signal input to the video signal processing device 50, and FIG. 2B is a diagram illustrating an ON period and an OFF period of the three-dimensional noise reduction according to the conventional example. is there.
Assume that an image signal as shown in FIG. 2A is input, and at time T1, the image signal is switched from a LOW level to a HIGH level, for example, from white to black.

  In this case, as shown in FIG. 2B, assuming that the three-dimensional noise reduction is performed continuously, that is, in a state in which the three-dimensional noise reduction is always on, a black afterimage is generated at time T1 in the above case. From time to time T3 (time τ) remains. The afterimage remains because, as described above, three-dimensional noise reduction is a simple addition average of the previous frame and the current frame, and the image of the previous frame remains.

  Thereafter, it is assumed that the image signal is switched from HIGH level to LOW level, for example, from white to black. Even in this case, as shown in FIG. 2B, if the three-dimensional noise reduction is continuously performed, in the above-described case, a white afterimage is generated during the period from time T4 to time T6 ( Time τ) remains.

FIG. 2C is a diagram showing an ON period and an OFF period of the three-dimensional noise reduction according to the embodiment of the present invention.
When the three-dimensional noise reduction is turned off at time T2, the afterimage is suppressed as shown in FIG. In this case, by performing the three-dimensional noise reduction intermittently, the afterimage period becomes Ta, which is shorter than the afterimage generation time τ when the three-dimensional noise reduction is continuously performed.

  Similarly, when the three-dimensional noise reduction is turned off at time T5, the afterimage is suppressed as shown in FIG. In this case, by performing the three-dimensional noise reduction intermittently, the afterimage period becomes Tb, which is shorter than the afterimage generation time τ when the three-dimensional noise reduction is continuously performed.

  The ON period and OFF period of the three-dimensional noise reduction performed intermittently are a predetermined interval. That is, the ON period of the three-dimensional noise reduction is several hundred ms or more and a few seconds or less, and the OFF period may be at least one frame period. For example, since the frame rate of the NTSC system is 30 fps (frame per second), the OFF period is at least 1/30 sec.

  As described above, when the three-dimensional noise reduction is intermittently performed by turning off at a predetermined time interval, the image of the previous frame does not remain in the OFF period, and thus the afterimage is reduced. That is, the image of the previous frame does not affect the image of the current frame, and the image of the current frame is output as it is, so that the afterimage is reduced.

  In particular, when an image changes between a still image and a still image, the noise reduction effect due to three-dimensional noise reduction is reduced, and if three-dimensional noise reduction is continuously performed, the image becomes difficult to see due to the influence of afterimages. Although it is easy, afterimages are reduced by intermittently performing three-dimensional noise reduction and providing OFF periods at predetermined intervals.

FIG. 3 is a diagram showing an afterimage by three-dimensional noise reduction according to the embodiment of the present invention.
FIG. 3A shows an image signal input from the outside, and a circular image is input in the image display 1. In the image after the elapse of time, as shown in the image display 2, the image display 3, and the image display 4, there is no circular image and nothing is displayed. Therefore, the same output image as the image signal input from the outside shown in FIG. 3A must be displayed.

  FIG. 3B is a diagram (conventional example) showing an output image when three-dimensional noise reduction is continuously performed. In the image display 1 of FIG. 3B, a circular image is displayed. In the image display 2 of FIG. 3B, there is an afterimage. For example, when a simple addition average of the previous frame and the current frame is taken in the three-dimensional noise reduction, the current image from the previous image (frame) is taken. The effect on the image (frame) is 1/2. Similarly, in the image display 3 of FIG. 3B, the influence from the image display 1 shown in FIG. 3A is 1/4, and in the image display 4 of FIG. 3B, it is shown in FIG. The influence from the image display 1 is 1/8.

FIG. 3C is a diagram illustrating an output image when the three-dimensional noise reduction is intermittently performed.
In the example shown in FIG. 3C, the three-dimensional noise reduction is turned off immediately after the image display 1 is finished, and the three-dimensional noise reduction is turned on again immediately after the image display 2 is finished.
In the image display 1 of FIG. 3C, a circular image is displayed. In the image display 2 of FIG. 3C, since the three-dimensional noise reduction is turned off, the current image, that is, the image display 2 of FIG. 3A is displayed as it is, and is displayed correctly and no afterimage is generated.

  Thereafter, also in the image display 3 in FIG. 3C, since the previous frame is the image shown in the image display 2 in FIG. 3C, three-dimensional noise reduction is performed, and a simple addition average between the images is performed. Even afterimage does not occur, the image shown in the image display 3 of FIG. 3A is output as it is, and becomes a normal output image.

Similarly, also in the image display 4 in FIG. 3C, since the previous frame is the image shown in the image display 3 in FIG. 3C, three-dimensional noise reduction is performed, and a simple addition average between the images is performed. Even if the image is taken, no afterimage is generated, and the image shown in the image display 4 in FIG. 3A is output as it is and becomes a normal output image.
As described above, three-dimensional noise reduction is intermittently performed, and by providing predetermined OFF periods and ON periods, afterimages are reduced and image quality is improved.

  In the present invention, various embodiments other than those described above can be adopted. For example, in the above embodiment, the frame memory is used as the video memory 8 and three-dimensional noise reduction is performed in units of frames. However, a field obtained by dividing one frame into two fields of an odd field and an even field is a unit. 3D noise reduction may be performed using a field memory stored as.

In addition, if 3D noise reduction processing is performed based on the time axis,
Any 3D noise reduction process such as a frame recursive 3D noise reduction may be used. In addition, a motion guarantee circuit is provided, and switching between ON and OFF of the three-dimensional noise reduction process may be performed in a state where a moving image portion and a stationary portion are provided in one frame.
In addition, Y / C separation may be performed by any one of Y / C separation such as one-dimensional Y / C separation, two-dimensional Y / C separation, and three-dimensional Y / C separation.

Needless to say, the three-dimensional noise reduction device 10 can also be applied to an external video playback device such as a DVD playback device or a VTR. The output device connected to the output side of the video signal processing device 50 may be any output device such as a plasma display in addition to a liquid crystal display.
Further, as long as the noise reduction device 10 of the present invention is used, the video signal processing device 50 may be either for analog broadcasting or digital broadcasting.

It is a block diagram of a video signal processing device. It is switching explanatory drawing of the three-dimensional noise reduction concerning embodiment of this invention. It is a figure which shows the afterimage by three-dimensional noise reduction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tuner 2 AGC amplifier 3 Demodulator 4 Signal processing part 5 3D noise reduction part 6 Video processing block 7 Control part 8 Video memory 10 3D noise reduction apparatus 50 Video signal processing apparatus

Claims (4)

In a three-dimensional noise reduction apparatus comprising a video memory for storing video, a three-dimensional noise reduction unit that reduces noise based on a time axis, and a control unit that operates the three-dimensional noise reduction unit,
A three-dimensional noise reduction device characterized in that three-dimensional noise reduction is intermittently performed. The three-dimensional noise reduction device according to claim 1,
A three-dimensional noise reduction apparatus characterized in that an OFF time of intermittent three-dimensional noise reduction is set as a time for displaying one still image. A tuner that converts an RF signal into an IF signal;
An AGC amplifier to which an IF signal from the tuner is input;
A demodulator to which the output signal of the AGC amplifier is input;
A signal processing unit to which an output signal of the demodulator is input;
A video memory for storing video; a three-dimensional noise reduction unit for reducing noise based on a time axis; and a control unit for operating the three-dimensional noise reduction unit; and an output signal of the signal processing unit is input A three-dimensional noise reduction device;
A video signal processing device comprising a video processing block to which an output signal of the three-dimensional noise reduction device is input;
A video signal processing apparatus characterized in that three-dimensional noise reduction is intermittently performed. The video signal processing apparatus according to claim 3, wherein
A video signal processing apparatus characterized in that an OFF time of three-dimensional noise reduction that is intermittently performed is a time during which one still image is displayed.

Images