JP2006270220A - Video signal processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional video signal processing apparatus that medium and low frequency edge components existing in a flat part other than high frequency edge components are damaged resulting in that a displayed image is entirely blurred. <P>SOLUTION: A high frequency edge vicinity decision section 7 receives high frequency edge components outputted from two-dimensional high pass filters 2-1, 2-2, 2-3, 2-4, and 2-5 and delayed high frequency edge components from D flip-flops 3-1 to 6-5 as input signals, carries out high frequency edge vicinity decision for vertical 5 pixels and horizontal 5 pixels in total 25 pixels of the extracted high frequency edge components, and controls the selective operation of a signal selection section 9 by means of the high frequency edge vicinity decision in response to a result of the decision. The signal selection section outputs a signal after mosquito noise reduction processing applied to only the video signal in the vicinity of the high frequency edge components in the light of a phenomenon wherein the mosquito noise is produced only in the vicinity of the high frequency edges, or selects and outputs the original video signal not subjected to the mosquito noise reduction processing in other cases. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a video signal processing apparatus, and more particularly to a video signal processing apparatus that reduces mosquito noise that occurs during encoding and decoding in a system that compresses and transmits a digital video signal.

  When compressing a video signal into a digital image, a method is known in which a plurality of pixels adjacent in the horizontal and vertical directions of the video signal are regarded as one rectangular block, and compression encoding is performed in units of the rectangular block. A digital image signal that has been compression-encoded by such a compression-encoding method is subjected to decoding on a rectangular block basis on the receiving side after passing through a recording medium or a transmission path, so that the original video signal becomes Restored.

  In such a compression encoding and decoding method, when the compression rate is increased when it is desired to suppress the information amount of the video signal transmitted on the recording medium or the transmission path, ringing appears in the vicinity of the edge of the video signal. Mosquito noise is mixed in the video signal. This ring king occurs only in the rectangular block when an edge having a strong high frequency component exists in the rectangular block. It is known that mosquito noise is noise that appears to clutter around edges especially when there is a strong edge in a flat image such as around display characters.

  Various reduction devices for reducing the mosquito noise have been proposed (see, for example, Patent Document 1). In the conventional video signal processing apparatus described in Patent Document 1, since mosquito noise is generated around the edge, the video signal is divided into a high frequency edge portion and other flat portions, and the region determined to be a flat portion is By performing mosquito noise reduction processing that replaces a signal containing an AC component, the mosquito noise is reduced without impairing the high-frequency edge component.

Japanese Patent Laid-Open No. 9-130791

  However, in the above-described conventional video signal processing apparatus, the high frequency edge component is not impaired, but the middle and low frequency edge components existing in the flat portion other than the high frequency edge component are impaired, and as a result, displayed. There is a problem that the image is totally blurred.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a video signal processing apparatus capable of reducing mosquito noise without impairing mid-low range edge components existing in flat portions other than high range edge components. And

  In order to achieve the above object, the present invention provides a high-frequency edge component extracting means for extracting a high-frequency edge component of a video signal and a high-frequency edge component output from the high-frequency edge component extracting means. And a mosquito noise reduction processing unit that receives a video signal and reduces mosquito noise according to the output of the discrimination means. In the video signal processing device, the determination unit is a unit of a region including a plurality of predetermined pixels of a video signal including a high-frequency edge component, and a plurality of pixels around the pixel of interest in the center of the region. A first determination result in which a value of a pixel of interest is equal to or less than a threshold value among pixels and a value of any one or more of a plurality of surrounding pixels is greater than a set threshold value; When the value of the pixel is larger than the threshold, or when the second determination result in which the values of a plurality of surrounding pixels are equal to or less than the threshold is output and the first determination result is input, the noise reduction processing unit When the reduced video signal is selected and the second determination result is input, the video signal has a selection unit that selects the video signal on the input side of the high frequency edge component extraction unit.

  In the present invention, noise reduction processing is not performed on a video signal of a high frequency edge component portion having a high frequency edge component larger than a threshold value and a video signal of a portion that is not a high frequency edge component portion equal to or lower than the threshold value, and a high value larger than the threshold value is obtained. Only the video signal in the vicinity of the high-frequency edge component is noise-reduced by the noise reduction processing unit, so the deterioration of the edge component of the high-frequency edge component portion and the deterioration of the mid-low frequency edge component of the flat portion without the high-frequency edge component. Can be prevented.

  According to the present invention, with a relatively simple circuit configuration, only the video signal in the vicinity of the high frequency edge component larger than the threshold value is subjected to noise reduction processing by the noise reduction processing unit, thereby degrading the edge component of the high frequency edge component portion. The mid-low range that exists in the flat part other than the high-frequency edge component can prevent the deterioration of the mid-low frequency edge component of the flat part without the high-frequency edge component, can reduce the mosquito noise without degradation of the image quality It is possible to eliminate the occurrence of the overall blur of the image due to the loss of the edge component.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a video signal processing apparatus according to the present invention. The present embodiment is configured to perform mosquito noise reduction processing only in the vicinity of the high-frequency edge, and is roughly divided into six line memories 1-1 to 1-6 and five two-dimensional high-pass filters 2-1 to 2. -5, four D-type flip-flops 3-i, 4-i, 5-i, 6-i cascaded on the output side of the two-dimensional high-pass filter 2-i (i is 1 to 5), It is comprised from the area | region edge vicinity determination part 7, the mosquito noise reduction process part 8, and the signal selection part 9 by high area | region edge vicinity determination.

  The two-dimensional high-pass filters 2-1 to 2-5 have the same configuration, for example, the configuration shown in FIG. In the figure, A, B and C are input video signals each having a time difference by one line period, the input video signal B is delayed by one line period with respect to the input video signal A, and the input video signal C is The input video signal B is delayed by one line period (thus, the input video signal A is two line periods).

  The first filter unit 21 and the second filter unit 22 include a multiplier indicated by a triangular mark, a D-type flip-flop indicated by D for delaying a unit time (one pixel transmission period), and an adder. ing. The multiplication coefficient of the multiplier is indicated by a number beside the multiplier. The input video signals A and C are first signals given a predetermined frequency characteristic by the first filter unit 21 which is a digital filter, and the input video signals A, B and C are second filters which are digital filters. The second signal is provided with a predetermined frequency characteristic by the filter unit 22. These first and second signals are added by an adder 23 and extracted as a video signal to which a high-pass filtering characteristic is given. That is, the adder 23 extracts and outputs the most delayed high-frequency component of the input video signal C.

  Returning to FIG. 1, the operation of the present embodiment will be described. The input video signal is supplied to the first stage line memory 1-1 of the circuit unit including the line memories 1-1 to 1-6 cascaded in six stages, and is delayed for one line period, while the two-dimensional high-pass filter 2 -1. The two-dimensional high-pass filter 2-1 includes an input video signal of the line memory 1-1, an output video signal delayed by one line period, and a video signal delayed by one line for a total of two lines by the line memory 1-2. Based on the above, the high-pass filtering characteristic is added to extract the high-frequency edge component of the input video signal and supply it to the high-frequency edge neighborhood determining unit 7, 1, 4-1, 5-1, and 6-1, and delayed by one pixel period, and then supplied to the high-frequency edge vicinity determination unit 7. Therefore, the high-frequency edge vicinity determination unit 7 receives the high-frequency edge component of 5 pixels on one line of the video signal output from the line memory 1-2.

  Similarly, the two-dimensional high-pass filters 2-2, 2-3, 2-4, and 2-5 are each one line period input from three adjacent line memories among the line memories 1-1 to 1-6. Three different types of video signals are received as input signals, and high frequency edge components of the input video signals are extracted based on these video signals and supplied to the high frequency edge neighborhood determining unit 7, while four-stage cascade-connected D This is supplied to the type flip-flops 3-j, 4-j, 5-j and 6-j (j is 2 to 5), and is supplied to the high frequency edge vicinity determination unit 7 after being delayed by one pixel period. Therefore, the two-dimensional high-pass filter 2-j and the D-type flip-flops 3-j, 4-j, 5-j, and 6-j are more (j− than the output high-frequency edge component of the two-dimensional high-pass filter 2-1. 1) The high-frequency edge component of 5 pixels on the previous line is input.

  The high-frequency edge vicinity determining unit 7 includes high-frequency edge components output from the two-dimensional high-pass filters 2-1, 2-2, 2-3, 2-4, and 2-5, and D-type flip-flops 3-1 to 3-1. 6-5 each output delay high frequency edge component is received as an input signal, the high frequency edge component of the extracted high frequency edge component vertical 5 pixels, horizontal 5 pixels, a total of 25 pixels is determined, according to the determination result The selection operation of the signal selection unit 9 based on the high-frequency edge vicinity determination is controlled.

  On the other hand, the mosquito noise reduction processing unit 8 receives the delayed video signal output from the line memory 1-3 as an input signal, and performs known mosquito noise reduction processing on the delayed video signal. As this mosquito noise reduction processing unit 8, for example, a video signal processing device previously disclosed by the present applicant in Japanese Patent Laid-Open No. 2000-278557 can be used.

  The video signal processing apparatus proposed by the present applicant is set to be larger than the central rank among the signal levels of the reference pixels made up of a plurality of peripheral pixels centered on the central pixel in the input video signal. The upper limit detector for detecting the signal level of the pixel of the upper limit rank, the lower limit detector for detecting the signal level of the pixel of the lower limit rank set lower than the center rank, and the upper limit detection of the signal level of the center pixel. Amplitude limiting means for limiting and outputting the amplitude between the detector and the lower limit detector, and when the center pixel is isolated from the surrounding reference pixels and the level is small or large, the rank is set to the lower limit value or the upper limit value. In this configuration, a video signal with reduced noise is obtained by replacement and flattening.

  The signal selection unit 9 based on the determination of the vicinity of the high frequency edge receives the image signal after the noise reduction (reduction) processing output from the mosquito noise reduction processing unit 8 is input to the terminal 9a and is output from the line memory 1-3. A video signal of a line with pixels is input to a terminal 9b, and one of the input signals of these terminals 9a and 9b is selected and output based on a switch signal output from the high frequency edge vicinity determining unit 7.

  Here, the high-frequency edge vicinity determination unit 7 provides a threshold value for the high-frequency edge component, and the target pixel 11 out of a total of 25 pixels including five vertical pixels and five horizontal pixels centering on the target pixel 11 in FIG. Is equal to or lower than the threshold value and one or more of the 24 surrounding pixels other than the target pixel 11 has a high frequency edge component larger than the threshold value, the high frequency edge component is in the vicinity of the target pixel 11. 1 is controlled, and the signal selection unit 9 based on the high-frequency edge vicinity determination in FIG. 1 is controlled to select the signal after the mosquito noise reduction process input to the terminal 9a.

  On the other hand, when it is determined that there are no high-frequency edge components larger than the threshold value in the 24 pixels around the pixel of interest 11, the signal selection unit 9 is controlled by the high-frequency edge neighborhood determination, and the two-dimensional high-pass input to the terminal 9b The original video signal before passing through the filters 2-1 to 2-5 is selected. If the target pixel 11 itself is a high frequency edge component larger than the threshold, the signal selection unit 9 based on the high frequency edge vicinity determination is controlled to select the original video signal input to the terminal 9b.

  Thus, according to the present embodiment, in consideration of the phenomenon that mosquito noise occurs only in the vicinity of the high frequency edge, the pixel of interest 11 has the high frequency edge component I in the display image shown in FIG. When the pixel is in the vicinity of the high-frequency edge component in the vicinity position II, since one or more of the peripheral 24 pixels includes pixels of the high-frequency edge component that is larger than the threshold value of the high-frequency edge component portion I, Outputs a signal after mosquito noise reduction processing.

  Further, when the target pixel 11 is a portion other than the vicinity of the high frequency edge component, that is, the pixel of the high frequency edge component portion I in FIG. 4, or all the 24 pixels around the target pixel 11 are equal to or lower than the threshold value. In the case of the portion III pixel in which no band edge component exists, in this embodiment, the mosquito noise reduction (reduction) process input to the terminal 9b of the signal selection unit 9 by the high band edge neighborhood determination is not performed. Select and output the original video signal.

  Thus, according to the present embodiment, by performing noise reduction (reduction) processing only in the vicinity of the high frequency edge component, the deterioration of the edge component of the high frequency edge component portion and the flat portion without the high frequency edge component are performed. It is possible to prevent deterioration of the middle and low frequency edge components, and to reduce mosquito noise without deterioration of image quality.

  Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing a second embodiment of the video signal processing apparatus according to the present invention. In the figure, the same components as those in FIG. In the second embodiment shown in FIG. 5, in addition to the configuration of the first embodiment, in the vicinity of the high frequency edge component, rank 1 to rank n (n is an arbitrary value) depending on the distance from the high frequency edge. The strength of mosquito noise reduction processing can be varied for each rank.

  As shown in FIG. 5, the present embodiment includes six line memories 1-1 to 1-6, five two-dimensional high-pass filters 2-1 to 2-5, and two-dimensional high-pass filter 2-i (i 1 to 5) four D-type flip-flops 3-i, 4-i, 5-i, 6-i cascaded on the output side, a high-frequency edge neighborhood distance determination unit 12, and a mosquito noise reduction process It comprises an amplitude setting unit 13 and a mosquito noise reduction processing unit 14.

  Next, the operation of the present embodiment will be described. The high-frequency edge neighborhood distance determination unit 12 includes high-frequency edge components output from the two-dimensional high-pass filters 2-1, 2-2, 2-3, 2-4, and 2-5, and a D-type flip-flop 3-1. Each of the output delay high-frequency edge components of ˜6-5 is received as an input signal, and the neighborhood distance determination of the high-frequency edge components of the extracted high-frequency edge components of 5 pixels in the vertical direction and 5 pixels in the horizontal direction is made.

  That is, the high-frequency edge neighborhood distance determination unit 12 sets a threshold value for the high-frequency edge component, assigns ranks 1 to 2 for the 24 pixels around the target pixel 11 as shown in FIG. It is determined whether there is a high-frequency edge component larger than the threshold value. If there is a high-frequency edge component that is larger than the threshold, the number of ranks is input to the mosquito noise reduction processing amplitude setting unit 13 in FIG.

  Further, when there are high frequency edge components larger than the threshold value in a plurality of ranks, the high frequency edge vicinity distance determination unit 12 determines the priority order of the ranks, and sets the number of ranks with higher priority levels as the mosquito noise reduction processing amplitude setting. Input to the unit 13. In this embodiment, the priority is set to 1 → 2 in descending order. In addition, with regard to the surrounding 24 pixels, when there is no high-frequency edge component larger than the threshold value in any rank, or when the target pixel 11 is a high-frequency edge component larger than the threshold value, information that is out of rank is determined as mosquito noise reduction processing. Input to the amplitude setting unit 13.

  The mosquito noise reduction processing amplitude setting unit 13 inputs the amplitude limit setting value for each rank to the mosquito noise reduction processing unit 14 based on the inputted number information of ranks. The mosquito noise reduction processing unit 14 receives the delayed video signal output from the line memory 1-3 as an input signal, and with respect to the delayed video signal, the amplitude for each rank input from the mosquito noise reduction processing amplitude setting unit 13. A known mosquito noise reduction process having a strength corresponding to the limit set value is performed.

  For example, when the number of ranks is “1”, the amplitude limit is set to be narrow, thereby strengthening the mosquito noise reduction (reduction) process for the input video signal, and when the number of ranks is “2”, the amplitude limit is widened. By setting, the mosquito noise reduction (reduction) process for the input video signal is weakened, and when it is out of rank, the mosquito noise reduction (reduction) process is not performed. As this mosquito noise reduction processing amplitude setting unit 13, for example, a video signal processing device previously disclosed by the present applicant in Japanese Patent Laid-Open No. 2000-278557 can be used.

  Thus, in the present embodiment, in consideration of the phenomenon that mosquito noise is generated only in the vicinity of the high frequency edge, the target pixel 11 in FIG. 6 has the high frequency edge component I in the display image shown in FIG. When the pixel is in the vicinity of the high frequency edge component vicinity portion VI in the vicinity, the mosquito noise is reduced for each rank 1 to rank n (n is an arbitrary number) assigned according to the distance from the high frequency edge component portion I ( (Reduction) The strength of processing can be made variable.

  That is, according to the present embodiment, the pixel of interest of the high frequency edge component vicinity portion VI in the vicinity of the high frequency edge component portion I in the display image shown in FIG. The stronger the mosquito noise reduction (reduction) processing strength, the lower the distance, the weaker the mosquito noise reduction (reduction) processing strength. Reduction) No discomfort due to processing.

  In the present embodiment, the vicinity of the high frequency edge where the mosquito noise reduction processing indicated by VI in FIG. 7 is performed, and the high frequency edge component where the mosquito noise reduction (reduction) processing indicated by VII is not performed are shown in FIG. The boundary with the non-existing portion looks like a more natural image, and mosquito noise can be reduced without deterioration in image quality.

1 is a block diagram of a first embodiment of a video signal processing device of the present invention. FIG. It is a block diagram of an example of a two-dimensional high pass filter. FIG. 2 is a pixel arrangement diagram for explaining the operation of FIG. 1. It is a figure which shows an example of the display image for operation | movement description of FIG. It is a block diagram of 2nd Embodiment of the video signal processing apparatus of this invention. FIG. 6 is a pixel arrangement diagram for explaining the operation of FIG. 5. It is a figure which shows an example of the display image for operation | movement description of FIG.

Explanation of symbols

1-1 to 1-6 Line memories 2-1 to 2-5 Two-dimensional high-pass filters 3-1 to 3-5, 4-1 to 4-5, 5-1 to 5-5, 6-1 to 6-6 5 D-type flip-flop 7 High-frequency edge neighborhood determination unit 8 Mosquito noise reduction processing unit 9 Signal selection unit based on high-frequency edge neighborhood determination 11 Target pixel 12 High-frequency edge neighborhood distance determination unit 13 Mosquito noise reduction processing amplitude setting unit 14 Mosquito noise Mitigation processor

Claims (1)

A high frequency edge component extracting means for inputting a video signal and extracting a high frequency edge component of the video signal;
Discriminating means for detecting that the high frequency edge component output from the high frequency edge component extraction means causes mosquito noise and outputting a detection result;
A video signal processing apparatus comprising: a mosquito noise reduction processing unit which is supplied with the video signal and reduces the mosquito noise in accordance with an output of the discrimination means;
The discriminating unit is a unit of an area composed of a plurality of predetermined pixels of the video signal composed of the high frequency edge component, and the attention pixel of the attention pixel at the center of the area and a plurality of pixels around the attention pixel. A first determination result in which a pixel value is less than or equal to a threshold value and a value of any one or more of the peripheral pixels is greater than a set threshold value; and the value of the target pixel is Outputting a second determination result when the value of the plurality of surrounding pixels is less than or equal to the threshold when the threshold is greater than the threshold;
When the first determination result is input, the video signal subjected to noise reduction processing by the noise reduction processing unit is selected, and when the second determination result is input, the high frequency edge component extraction unit A video signal processing apparatus comprising selection means for selecting a video signal on the input side.

Images