KR100406961B1 - Noise reducting device and method for video signal - Google Patents

Abstract

Disclosed are an apparatus and a method for adaptively attenuating noise according to brightness of an input video signal. The noise reduction device of the video signal includes a brightness detector for detecting the brightness of an input video signal and a spatial noise attenuator for changing the attenuation of impulsive noise generated in the video signal according to the brightness of the video signal detected by the brightness detector. And a time axis noise attenuator for changing the amount of attenuation of white noise generated in the video signal according to the brightness of the image signal sensed by the brightness detector. Thus, the noise attenuation apparatus of the video signal can effectively attenuate not only the white Gaussian noise but also the impulsive noise of the video signal. In addition, the noise attenuation apparatus of the video signal can adaptively attenuate the noise according to the brightness of the input video signal.

Description

Noise reducting device and method for video signal

The present invention relates to a noise reduction device and method for a video signal, and more particularly, to a noise reduction device and a method for adaptively attenuating noise components included in a video signal to provide clearer image quality. .

A video signal output device that reproduces an input video signal. A CRT device that emits color pixels on a fluorescent panel by means of an RGB electron beam, and scatters a uniform array of liquid crystals in response to color image signals. LCD (Liquid Crystal Display) panel to adjust the color image is widely used.

Among them, CRT devices are mainly employed in color television transmitted by air or cable from broadcasting stations, while LCD panels are employed in projectors or projection televisions that project color images on relatively large screens. However, in the case of an image processing system employing an image output device constituted by a CRT device or an LCD panel, for example, a color television or a projection television, a noise component is mixed with the original broadcast video signal in a signal transmission system, or the signal of the color television is When an external noise component affects the processing system, wave-shaped noise or white Gaussian noise is displayed on an image signal displayed on the image output device, thereby deteriorating image quality. do. Therefore, it is necessary to provide a noise attenuation apparatus for attenuating noise components in the video signal processing system.

1 is a view showing a noise attenuation apparatus of a video signal according to the prior art. Referring to the drawings, the noise attenuation apparatus includes a low pass filter (LPF) 101, a first amplifier 103, a second amplifier 105, an inverter 107, a buffer 109, and a high pass filter (HPF) ( 111, a third amplifier 113, a subtractor 115, and a switching element 117.

The LPF 101 extracts only components of a predetermined band or less with respect to the input video signal. The components extracted by the LPF 101 are sent to the first amplifier 103. The first amplifier 103 receives an image signal extracted from the LPF 101. The first amplifier 103 amplifies the received video signal and transmits the amplified video signal to the second amplifier 105 and the inverter 107. The second amplifier 105 amplifies the received video signal again.

The inverter 107 inverts the video signal amplified by the first amplifier 103. The video signal inverted by the inverter 107 is transmitted to the buffer 109 for buffering. The image signal buffered by the buffer 109 is transmitted to the HPF 111, and the HPF 111 filters to remove noise components from the received image signal. The video signal filtered by the HPF 111 is transmitted to the third amplifier 113 and amplified.

The subtractor 115 receives an image signal amplified by the second amplifier 105 and the third amplifier 115 and amplifies the image signal by the third amplifier 115 from the image signal amplified by the second amplifier 105. The decoded video signal is subtracted to attenuate the noise component from the video signal component. For example, the switching device 117 is configured to respond to the operation of the video noise canceling button provided in the remote controller for the remote control of the color television according to the noise attenuation control signal CS applied from the controller (not shown). An output of the video signal component amplified by 105 or a component of the video signal whose noise component is attenuated by the subtractor 115 is selectively output. When the noise component is included in the video signal, the noise attenuation control signal CS is applied to the switching element 117 by the controller, whereby the switching element 117 is switched to the subtractor 115 side and connected.

However, in the noise attenuation apparatus according to the related art, only white Gaussian noise is considered and impulsive noise is not considered. Therefore, the noise component not filtered by the high pass filter 111 is output as it is and the The disadvantage is that effective attenuation is difficult. In addition, since the noise attenuation apparatus according to the related art does not consider the difference in partial brightness of the input video signal, the noise distributed in the dark portion is more than the noise distributed in the bright portion in the overall noise attenuation. It appears to be less attenuated.

The present invention was devised to solve the above problems, and effectively attenuates not only white Gaussian noise, but also impulsive noise, and noise attenuation that can adaptively attenuate noise according to the brightness of an input video signal. It is an object of the present invention to provide an apparatus and method.

1 is a view showing a noise attenuation apparatus of a video signal according to the prior art;

2 is a view schematically showing a noise attenuation apparatus of a video signal according to the present invention;

FIG. 3 is a diagram illustrating noise adaptively attenuated by the apparatus of FIG. 2, and FIG.

4 is a flowchart illustrating a noise attenuation method according to FIG. 2.

Explanation of symbols on the main parts of the drawings

201: brightness detection unit 210: spatial noise attenuation unit

211: average value calculation unit 213: mapping constant determination unit

215: Median filter 217: First noise attenuation output unit

230: time axis noise attenuation unit 231: motion vector detection unit

233: frame delay unit 235: second noise attenuation output unit

Noise reduction device for a video signal according to the present invention for achieving the above object, a brightness detector for detecting the brightness of the input video signal, the video signal according to the brightness of the video signal detected by the brightness detector A spatial noise attenuator for varying the amount of attenuation of impulsive noise generated in the < RTI ID = 0.0 > and < / RTI > do.

The spatial axis noise attenuator comprises: an average value calculator for calculating an average value of the brightness of the input video signal and the brightness of the surrounding video signal; and a mapping constant for determining a mapping constant based on the average value calculated by the average value calculator. A determining unit, a filtering unit which mediates the input image signal, and an outputting image signal of which the impulsive noise is attenuated based on the input image signal, the mapping constant, and the median filtered image signal; One noise attenuation output section is provided.

The first noise attenuation output unit outputs the video signal in which the impulsive noise is attenuated by the following equation.

NR Out Data = k × M + (1-k) × C

Here, NR Out Data is an image signal in which the impulsive noise is attenuated, k is the mapping constant, M is the median filtered video signal, and C is the video signal input.

The time axis noise attenuator comprises: a frame delay unit, a motion vector detection unit detecting a motion vector based on the repetitive signal in which the impulsive noise is attenuated, and an image signal delayed by the frame delay unit, and the impulsive noise is attenuated. And a second noise attenuation output unit configured to output a video signal of which the white noise is attenuated based on the video signal and the detected motion vector delayed by the frame delay unit. The frame delay unit delays a frame of the video signal output by the second noise attenuation output unit for a predetermined time.

Here, the second noise attenuation output unit outputs the video signal in which the white noise is attenuated by the following equation.

NR Out Data '= k' × A + (1-k ') × B

Here, NR Out Data 'is a video signal in which the white noise is attenuated, k' is the motion vector, A is the video signal in which the impulsive noise is attenuated, and B is the video delayed by the frame delay unit. It is a signal.

On the other hand, according to the noise attenuation apparatus of the video signal according to the invention, the step of detecting the brightness of the input video signal, according to the brightness of the video signal detected by the sensing step of the impulsive noise generated in the video signal A first attenuation amount changing step of changing the attenuation amount, and a second attenuation amount changing step of changing the attenuation amount of the white noise generated in the video signal according to the brightness of the image signal detected by the sensing step Attenuation method is provided.

Thus, the noise attenuation apparatus of the video signal can efficiently attenuate not only white Gaussian noise but also impulsive noise. In addition, the noise attenuation apparatus of the video signal can adaptively attenuate the noise according to the brightness of the input video signal.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a view schematically showing a noise attenuation apparatus of a video signal according to the present invention. Referring to the drawings, the noise attenuation apparatus of a video signal includes a brightness detector 201 for detecting the brightness of an input video signal, a spatial noise attenuator 210 for changing the attenuation amount of impulsive noise, and attenuation amount of white noise. And a time axis noise attenuation unit 230 for changing. Here, the spatial noise attenuation unit 210 includes an average value calculator 211, a mapping constant determiner 213, a median filter 215, and a first noise attenuation output unit 217. The time axis noise attenuator 230 includes a motion vector detector 231, a frame delay unit 233, and a second noise attenuation output unit 235.

The brightness detector 201 detects the brightness of the input image signal. Here, the video signal is input in units of frames, and the brightness sensor 201 detects brightness of each field with respect to the video signals input in units of frames.

The spatial noise attenuation unit 210 changes the attenuation amount of the impulsive noise generated in the image signal according to the brightness of the image signal sensed by the brightness sensing unit 201. That is, the spatial noise attenuation unit 210 adjusts the dark portion of the video signal so that the amount of attenuation by the median filter 215 is large, and reduces the amount of attenuation by the median filter 215 for the bright portion of the video signal. By adjusting, the amount of attenuation of the impulsive noise of the input video signal is changed.

The average value calculator 211 calculates an average value of the brightness of the input video signal and the brightness of the Youngshin signal around the input video signal. The mapping constant determiner 213 determines a mapping constant k that determines a relationship between the brightness of the input video signal and the brightness of the peripheral video signal based on the average value calculated by the average value calculator 211.

The median filter 215 filters the input image signal. Here, the median filter 215 is a nonlinear filter having an output having a medium size value among the input data when a predetermined data set is input. That is, the median filter 215 outputs (N + 2) / 2th size data when N + 1 data is input. Where N is even and represents the order of the filter. The median filter 215 may effectively remove the impulsive noise by replacing the value of the pixel in which the impulsive noise has occurred with the median of the peripheral values.

The first noise attenuation output unit 217 is configured to generate impulsive noise based on an input video signal, a mapping constant determined by the mapping constant determiner 213, and a video signal filtered by the median filter 215. Outputs a video signal of which the attenuation amount is adjusted. If this is expressed as an expression, it is as follows.

NR Out Data = k × M + (1-k) × C

Here, NR Out Data is a video signal in which the amount of attenuation of impulsive noise is adjusted by the first noise attenuation output unit 217, k is a mapping constant determined by the mapping constant determiner 213, and M is a median filter. The median filtered video signal by 215, and C is the input video signal.

3 is a diagram for explaining noise adaptively attenuated by the apparatus of FIG. Referring to the drawings, the impulsive noise is attenuated by the median filter 215 within a predetermined brightness (threshold point for the brightness of the input video signal: a) with respect to the brightness S of the input video signal. Between the points, the video signal inputted and the video signal outputted by the median filter 215 are crossfaded by the method of Equation 1 to change the attenuation amount of the impulsive noise. Since the section after b point is a section where noise is hard to see, the input image signal is output as it is.

The time axis noise attenuation unit 230 changes the amount of attenuation of the white noise generated in the image signal according to the brightness of the image signal detected by the brightness detecting unit 201. That is, the time axis noise attenuation unit 230 adjusts the delay amount by the frame delay unit 233 for the dark frame of the video signal less, and adjusts the delay amount by the frame delay unit 233 for the bright frame of the video signal. By large adjustment, the amount of attenuation of the white noise with respect to the entire frame of the input video signal is changed.

The motion vector detector 231 detects a motion vector based on an image signal in which impulsive noise is attenuated by the first noise attenuation output unit 217 and a video signal delayed by the frame delay unit 233.

The second noise attenuation output unit 235 is provided to an image signal whose impulsive noise is attenuated by the first noise attenuation output unit 217, an image signal delayed by the frame delay unit 233, and a motion vector detection unit 231. Based on the detected motion vector, a video signal whose attenuation amount of white noise is adjusted is output. If this is expressed as expression, it is as follows.

NR Out Data '= k' × A + (1-k ') × B

Here, NR Out Data 'is an image signal in which attenuation amount of white noise is adjusted by the second noise attenuation output unit 235, k' is a motion vector detected by the motion vector detector 231, and A is a first signal. The video signal whose attenuation amount of the impulsive noise is adjusted by the noise attenuation output unit 217, and B is the video signal delayed by the frame delay unit 233.

The frame delay unit 233 delays a frame of the video signal output by the second noise attenuation output unit 235 for a predetermined time.

4 is a flowchart illustrating a noise attenuation method according to FIG. 2. Referring to the figure, the brightness detecting unit 201 detects the brightness of the input image signal (S401). In addition, the brightness sensor 201 detects the brightness of the video signals around the input video signal. The brightness detected by the brightness sensor 201 is transmitted to the average value calculator 211. The average value calculator 211 receives the brightness signal detected by the brightness sensor 201 and calculates an average value of brightnesses of the input video signal and surrounding video signals (S403). The average value calculator 211 transmits the calculated average value to the mapping constant determiner 213. The mapping constant determiner 213 determines a mapping constant that determines a relationship between the input video signal and surrounding video signals based on the received average value.

The median filter 215 performs median filtering of the input image signal (S405). The median filter 215 outputs (N + 2) / 2th size data when N + 1 data is input. Where N is even and represents the order of the filter. The median filter 215 may effectively remove the impulsive noise by replacing the value of the pixel in which the impulsive noise has occurred with the median of the peripheral values.

The first noise attenuation output unit 217 receives an input video signal, a mapping constant, and a median filtered video signal, and attenuates the impulsive noise by cross fade based on each received signal. The adjusted video signal is output (S407). The video signal output by the first noise attenuation output unit 217 is transmitted to the time axis noise attenuation unit 230.

The motion vector detector 231 of the time axis noise attenuator 230 may generate a motion vector based on the image signal output by the first noise attenuation output unit 217 and the image signal delayed by the frame delay unit 233. It is detected (S409). The second noise attenuation output unit 235 is provided to an image signal whose impulsive noise is attenuated by the first noise attenuation output unit 217, an image signal delayed by the frame delay unit 233, and a motion vector detection unit 231. Receive the motion vector detected by. The second noise attenuation output unit 235 outputs an image signal in which the amount of attenuation of white noise is adjusted by cross fading based on each received signal (S411). Here, the frame delay unit 233 receives the video signal output by the second noise attenuation output unit 235, and delays the frame of the received video signal by a predetermined time and sends it.

Thus, the noise attenuation apparatus of the video signal can efficiently attenuate not only white Gaussian noise but also impulsive noise. In addition, the noise attenuation apparatus of the video signal can adaptively attenuate the noise according to the brightness of the input video signal.

According to the present invention, the noise attenuation apparatus of the video signal can adaptively attenuate the noise according to the brightness of the input video signal.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (10)

A brightness sensor detecting a brightness of an input video signal; A spatial noise attenuator for changing an attenuation amount of impulsive noise generated in the video signal according to the brightness of the video signal sensed by the brightness detector; And And a time axis noise attenuator for changing an attenuation amount of white noise generated in the video signal according to the brightness of the video signal sensed by the brightness detector. The method of claim 1, wherein the spatial noise damping unit, An average value calculator for calculating an average value of the brightness of the video signal and the brightness of the surrounding video signal; A mapping constant determining unit that determines a mapping constant based on the average value calculated by the average value calculating unit; A filtering unit which performs median filtering of the input image signal; And And a first noise attenuation output unit configured to output an image signal of which attenuation amount of the impulsive noise is adjusted based on the input image signal, the mapping constant, and the median filtered image signal. Signal noise attenuation device. The method of claim 2, The first noise attenuation output unit outputs the video signal in which the attenuation amount of the impulsive noise is adjusted by the following equation: NR Out Data = k × M + (1-k) × C Here, NR Out Data is an image signal of which the impulsive noise is attenuated, k is the mapping constant, M is the median filtered image signal, and C is the video signal to be input. The method of claim 3, wherein the time axis noise attenuation unit, Frame delay unit; A motion vector detector for detecting a motion vector based on the repetitive signal in which the impulsive noise is attenuated and the image signal delayed by the frame delay unit; And A second noise attenuation output unit configured to output an image signal of which the amount of attenuation of the white noise is adjusted based on the image signal in which the impulsive noise is attenuated, the image signal delayed by the frame delay unit, and the detected motion vector ;; And the frame delay unit delays a frame of the video signal output by the second noise attenuation output unit for a predetermined time. The method of claim 4, wherein The second noise attenuation output unit outputs the video signal of which the attenuation amount of the white noise is adjusted by the following equation: NR Out Data '= k' × A + (1-k ') × B Here, NR Out Data 'is a video signal in which the white noise is attenuated; k 'is the motion vector, A is the video signal in which the impulsive noise is attenuated, and B is the video signal delayed by the frame delay unit. Detecting brightness of an input video signal; A first attenuation amount changing step of changing an attenuation amount of impulsive noise generated in the video signal according to the brightness of the video signal sensed by the sensing step; And And a second attenuation amount changing step of varying attenuation amount of white noise generated in the video signal according to the brightness of the video signal detected by the sensing step. The method of claim 6, wherein the first attenuation change step, Calculating an average value of the brightness of the video signal and the brightness of the surrounding video signal; Determining a mapping constant based on the average value calculated by the average value calculating step; Median filtering the input image signal; And A first output step of outputting a video signal of which the amount of attenuation of the impulsive noise is adjusted based on the video signal input, the mapping constant, and the median filtered video signal; Noise attenuation method. The method of claim 7, wherein The first output step of the noise reduction method of the video signal, characterized in that for outputting the video signal in which the attenuation amount of the impulsive noise is adjusted by the following equation: NR Out Data = k × M + (1-k) × C Here, NR Out Data is an image signal of which the impulsive noise is attenuated, k is the mapping constant, M is the median filtered image signal, and C is the video signal to be input. The method of claim 8, wherein the second attenuation change step, Detecting a motion vector based on the repetitive signal with the impulsive noise attenuated and a video signal delayed by a frame delay unit; And A second output step of outputting a video signal of which the amount of attenuation of the white noise is adjusted based on the video signal attenuated by the impulsive noise, the video signal delayed by the frame delay unit, and the detected motion vector; Include, And the frame delay unit delays a frame of the video signal output by the second output step by a predetermined time. The method of claim 9, The second output step, the noise reduction method of the video signal, characterized in that for outputting the video signal in which the attenuation amount of the white noise is adjusted by the following equation: NR Out Data '= k' × A + (1-k ') × B Here, NR Out Data 'is a video signal in which the white noise is attenuated; k 'is the motion vector, A is the video signal in which the impulsive noise is attenuated, and B is the video signal delayed by the frame delay unit.