JP5506377B2 - Image processing apparatus, image processing method, program, and display apparatus - Google Patents

Description

  The present invention relates to an image processing device, an image processing method, a program, and a display device.

  In recent years, for example, an image processing apparatus that can process an image signal encoded in units of blocks by dividing an image into small rectangular blocks such as an image signal according to MPEG-2 (ISO / IEC 13818) or JPEG. Is progressing.

  The image signal encoded in units of blocks as described above is subjected to data compression by assigning a code in units of blocks using a discrete cosine transform (hereinafter also referred to as “DCT”). For this reason, when an image signal encoded in units of blocks is displayed on the display screen, for example, noise such as block distortion (or block noise) or mosquito noise may occur, resulting in deterioration in image quality. There is.

  Under such circumstances, techniques for reducing noise that may occur when processing an image signal encoded in units of blocks have been developed. As a technique for reducing noise such as block distortion and mosquito noise that may occur when processing an image signal encoded in units of blocks, for example, Patent Document 1 may be cited.

JP-A-10-229546

  A conventional technique for reducing noise that may occur when processing an image signal encoded in block units (hereinafter referred to as “conventional technique”) is an image signal encoded in block units using a spatial filter. To reduce noise that may occur. Therefore, when the conventional technique is used, there is a possibility that, for example, block distortion and mosquito noise can be reduced.

  However, noise that can occur when processing an image signal encoded in units of blocks is not limited to block distortion or mosquito noise. For example, “block flicker” is an example of noise that may occur when an image signal encoded in units of blocks is processed. Here, “block flicker” is flicker recognized by a user viewing an image due to a relatively long period of fluctuation in the time axis direction in a block corresponding to the same region in the image indicated by the image signal. It can be regarded as a kind of noise. The “block flicker” will be described later.

  Since the conventional technique only performs filtering in the spatial direction, it is not possible to reduce noise that may be caused by fluctuations in the time axis direction such as the “block flicker”.

  In addition, as a method for reducing noise that may occur due to fluctuations in the time axis direction such as “block flicker”, for example, it is assumed to use a filter that performs filter processing in the time axis direction. If the image signal encoded in units of blocks is processed using a filter that performs filter processing in the time axis direction, noise that may be caused by fluctuations in the time axis direction such as “block flicker” is reduced. There is a possibility that

  Here, in order to reduce noise that may be caused by fluctuations in the time axis direction, such as the “block flicker”, it is necessary to use a filter having a certain level of strength. Therefore, when processing is performed in a predetermined processing unit such as a frame unit or a field unit, for example, an image signal that is a target of the previous processing (for example, an image signal corresponding to a frame immediately before the current frame processed immediately before) ) And the image signal to be processed this time (for example, the image signal corresponding to the current frame to be processed), and when there is a difference in the image indicated by the block, the time axis direction with respect to the pixel corresponding to the block When the above filtering process is performed, there is a possibility that the image quality is deteriorated by the filtering process.

  As a method for preventing the occurrence of a situation in which the image quality deteriorates as described above, for example, a motion is detected based on an image signal, and a time axis direction is selectively applied to a region where no motion is detected (still region). It is assumed that the filtering process is performed.

  However, since it is not always possible to accurately detect the motion, if a filter having such a strength as to reduce noise that may be caused by fluctuations in the time axis direction such as “block flicker” is applied to the image signal, There is a risk that the image quality will deteriorate. For this reason, even if the time-direction filter processing is selectively performed on a region where no motion is detected (still region) using the motion detection result, the filter cannot be strengthened sufficiently.

  Therefore, even if the conventional technique or a technique that combines motion detection and filtering in the time axis direction is used, noise caused by fluctuations in the time axis direction that may occur in the image signal encoded in units of blocks is reduced. It is not always possible to achieve high image quality.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce the noise caused by fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks and to improve image quality. It is an object of the present invention to provide a new and improved image processing apparatus, image processing method, program, and display apparatus capable of achieving the above.

  In order to achieve the above object, according to the first aspect of the present invention, an input image signal encoded in units of blocks and a control signal for each pixel that controls the output image signal to be output are input, A time axis filter for smoothing the input image signal in the time axis direction based on the control signal for each pixel and outputting the output image signal obtained by smoothing the input image signal, and information on the result of the time axis filter Or a memory for storing pixel information of a predetermined unit of the input image signal before the smoothing in the input image signal smoothed by the time axis filter as reference information, and the input image signal And a reference signal corresponding to the reference information most recently stored in the memory is input to each of the input image signal and a difference signal between the input image signal and the reference signal. DC determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel is DC, and the first pixel for each pixel based on the input image signal is determined. A detection unit that detects noise for each pixel based on a DC determination result, a second DC determination result for each pixel based on the difference signal, and an absolute value of a pixel value of the difference signal; An image processing apparatus is provided that includes a filter control unit that outputs the control signal for each pixel to the time axis filter based on a detection signal for each pixel indicating a noise detection result.

  With such a configuration, it is possible to reduce the noise caused by the fluctuation in the time axis direction that may occur in the image signal encoded in units of blocks and to improve the image quality.

  The detection unit performs the DC determination based on the input image signal, and outputs a first detection signal indicating the first DC determination result for each pixel, and the input image. An adder that subtracts the other signal from one signal of the signal and the reference signal and outputs the difference signal; performs the DC determination based on the difference signal output from the adder; and A second DC region detection unit that outputs a second detection signal indicating the DC determination result of each pixel, an absolute value of a pixel value in the difference signal output from the adder, and a predetermined threshold value for each pixel Based on the absolute difference determination unit that compares and outputs a third detection signal indicating the comparison result for each pixel, and the first detection signal, the second detection signal, and the third detection signal corresponding to each pixel. Display the detection signal. A determination unit that outputs each of the signals, wherein the determination unit indicates that the first detection signal and the second detection signal are direct current, and indicates that the third detection signal is smaller than the predetermined threshold value. In this case, a detection signal indicating that noise has been detected may be output.

  The filter control unit may output, as the control signal, a first control signal that defines a filter coefficient to be applied to the time axis filter based on the detection signal.

  The filter control unit may further output, as the control signal, a second control signal for limiting an output image signal output from the time axis filter based on the detection signal.

  A first signal separation unit that separates the input image signal into an AC component signal of the input image signal and a DC component signal of the input image signal; and the reference signal is an AC component of the reference signal. A signal that adds the second signal separation unit that separates the signal of the reference signal into the DC component signal of the reference signal, the AC component signal of the input image signal, and the output image signal output from the time axis filter A DC component signal of the input image signal and a DC component signal of the reference signal are input to the detection unit, and the DC filter of the input image signal is input to the time axis filter. A component signal may be input.

  In order to achieve the above object, according to a second aspect of the present invention, a time axis filter for smoothing an input image signal for each pixel in the time axis direction, and information on a result of the time axis filter Or an image processing apparatus comprising: a memory that stores, as reference information, pixel information of a predetermined unit of the input image signal before smoothing in the input image signal smoothed by the time axis filter An input image signal encoded in units of blocks, a difference signal between the input image signal and a reference signal corresponding to reference information most recently stored in the memory; In response to the input image signal, a direct current determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel is a direct current. Noise is detected for each pixel based on the first DC determination result for each pixel based on the second DC determination result for each pixel based on the difference signal and the absolute value of the pixel value of the difference signal. And a filter control step for inputting a control signal for each pixel for controlling an output image signal output from the time axis filter to the time axis filter based on a detection result of noise for each pixel in the detection step. And an image processing step of smoothing the input image signal in the time axis direction using a time axis filter to which the control signal is input in the filter control step.

  By using such a method, it is possible to reduce the noise caused by the fluctuation in the time axis direction that may occur in the image signal encoded in units of blocks and to improve the image quality.

  In order to achieve the above object, according to the third aspect of the present invention, a time axis filter for smoothing an input image signal for each pixel in the time axis direction, and information on the result of the time axis filter Or an image processing apparatus comprising: a memory that stores, as reference information, pixel information of a predetermined unit of the input image signal before smoothing in the input image signal smoothed by the time axis filter The input image signal encoded in block units, and the difference signal between the input image signal and the reference signal corresponding to the reference information most recently stored in the memory, A direct current determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel as a target pixel to be determined is a direct current, and each pixel is based on the input image signal. Detection step of detecting noise for each pixel based on the first DC determination result for each element, the second DC determination result for each pixel based on the difference signal, and the absolute value of the pixel value of the difference signal A filter control step for inputting a control signal for each pixel for controlling an output image signal output from the time axis filter to the time axis filter based on a detection result of noise for each pixel in the detection step; There is provided a program for causing a computer to execute an image processing step of smoothing the input image signal in the time axis direction using a time axis filter to which the control signal is input in the control step.

  By using such a program, it is possible to improve the image quality by reducing noise caused by fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks.

In order to achieve the above object, according to a fourth aspect of the present invention, an input image signal encoded in block units is input, the input image signal is smoothed in the time axis direction for each pixel, and An image processing unit that outputs an output image signal obtained by smoothing an input image signal; and an image display unit that displays an image on a display screen based on the output image signal output from the image processing unit. The processing unit receives the input image signal and a control signal for each pixel that controls the output image signal to be output, and smoothes the input image signal in the time axis direction based on the control signal for each pixel. A time axis filter that outputs an output image signal obtained by smoothing the input image signal, information on a result of the time axis filter, or an input image signal that has been smoothed by the time axis filter. A memory for storing pixel information of an input image signal in a predetermined unit before the smoothing as reference information, the input image signal, and a reference signal corresponding to the reference information most recently stored in the memory; And a predetermined number of pixels in the horizontal direction including the target pixel, where each pixel is a target pixel to be determined with respect to the input image signal and the difference signal between the input image signal and the reference signal. DC determination is performed to determine whether or not the pixel is DC, and a first DC determination result for each pixel based on the input image signal, and a second DC determination result for each pixel based on the difference signal, Based on the absolute value of the pixel value of the difference signal, a detection unit that detects noise for each pixel, and the control signal for each pixel based on a detection signal for each pixel that indicates a detection result of noise in the detection unit Display device and a filter controller for outputting to the time-axis filter is provided.

  With this configuration, noise caused by fluctuations in the time axis direction that can occur in image signals encoded in units of blocks is reduced to improve image quality, and images with reduced noise due to fluctuations in the time axis direction are displayed on the display screen. Can be made.

  According to the present invention, it is possible to reduce the noise caused by the fluctuation in the time axis direction that may occur in the image signal encoded in units of blocks, and to improve the image quality.

It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the noise by the fluctuation | variation of the time-axis direction made into the detection object by the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the DC determination process in the image processing apparatus which concerns on embodiment of this invention. It is a flowchart which shows an example of the direct current | flow determination process in the image processing apparatus which concerns on embodiment of this invention. It is a block diagram which shows an example of a structure of the image processing apparatus which concerns on embodiment of this invention. It is a block diagram which shows an example of a structure of the detection part with which the image processing apparatus which concerns on embodiment of this invention is provided. It is a block diagram which shows an example of a structure of the filter control part with which the image processing apparatus which concerns on embodiment of this invention, and a time-axis filter. It is a block diagram which shows the other example of a structure of the filter control part with which the image processing apparatus which concerns on embodiment of this invention is provided. It is explanatory drawing for demonstrating the process in the restriction | limiting process part of the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the other example of a structure of the image processing apparatus which concerns on embodiment of this invention. It is a block diagram which shows an example of a structure of the display apparatus which concerns on embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(Noise reduction approach according to embodiments of the present invention)
Before describing the configuration of an image processing apparatus according to an embodiment of the present invention (hereinafter sometimes referred to as “image processing apparatus 100”), first, a noise reduction approach in the image processing apparatus according to the embodiment of the present invention is described. Will be described.

  The image signal processing apparatus 100 is a variation in the time axis direction that can occur in an image signal encoded in units of blocks (hereinafter, simply referred to as “image signal”), such as “block flicker”. Detect noise due to and reduce the detected noise.

[An example of noise due to fluctuations in the time axis direction]
First, an example of noise due to variation in the time axis direction that is a detection target of the image processing apparatus 100 according to the embodiment of the present invention will be described. Each of FIG. 1 to FIG. 4B is an explanatory diagram for explaining an example of noise caused by fluctuations in the time axis direction that are detected by the image processing apparatus 100 according to the embodiment of the present invention. Here, each of FIGS. 1 to 4B shows an example of one block (block composed of 8 × 8 pixels) of an image signal quantized with 8 bits.

  FIG. 1 shows a block in an ideal state where there is no noise in the spatial direction in a region where the inclination of the image indicated by the image signal is gentle. 2A and 2B are examples of blocks showing the same image as the image shown in FIG. 1 in the image signal before being compressed using DCT or the like. FIG. 2A shows a block in frame N (N is an integer), and FIG. 2B shows a block corresponding to FIG. 2A in frame N + 1. 3A and 3B are examples of blocks showing the same image as the image shown in FIG. 1 in the image signal after compression using DCT or the like.

  In the ideal state as shown in FIG. 1, since there is no noise in the spatial direction, a gently sloping boundary is represented in the block. In the example of FIG. 1, the direct current (hereinafter sometimes referred to as “DC”) value that is the average value of the pixel values of the block shown in FIG. 1 is “8” when rounded to an integer.

  However, in reality, noise in a spatial direction having no correlation between frames is superimposed as shown in FIGS. 2A and 2B due to, for example, imaging noise generated during imaging. As described above, the noise in the spatial direction having no correlation between frames is superimposed, so that, for example, the DC value of the block of the N frame shown in FIG. May be “8”, while the DC value of the block of the N + 1 frame shown in FIG. 2B is “9”. For example, a DC fluctuation component due to the influence of an AGC (Auto Gain Control) amplifier may become noise in the spatial direction, and the DC value may take a value such as “10”, for example.

  In addition, when DCT is performed, particularly when the bit rate of the image signal is not sufficient, the alternating current (hereinafter sometimes referred to as “AC”) component of the DCT coefficient is almost deleted, and only the DC component remains. is there. When only a DC component remains by DCT as described above, the pixel values of the pixels in the block are all the same value.

  FIG. 3A shows a block in N frames in which the AC component is completely deleted when DCT is performed on the block shown in FIG. 2A, and FIG. 3B shows a DCT for the block shown in FIG. 2B. Shows the block in the N + 1 frame where the AC component has been completely removed.

  When the AC component is completely deleted when DCT is performed, the pixel values in the block are all the same as shown in FIGS. 3A and 3B. In addition, as shown in FIGS. 2A and 2B, when DCT is performed on a block in which noise in a spatial direction having no correlation between frames is superimposed, DCT is performed even after DCT is performed. As before, for example, the DC value of the block of the N frame shown in FIG. 3A is “8”, whereas the DC value of the block of the N + 1 frame shown in FIG. 3B is “9”. A difference occurs in the DC value in the frame.

  As described above, for example, when noise in a spatial direction with no correlation is superimposed between frames (when it is not an ideal state), even between blocks corresponding to the same region of the same image, between adjacent frames , There may be a difference in the DC value.

  Here, attention is focused on the difference value between the pixel value of frame N + 1 and the pixel value of frame N. 4A shows a difference value between the pixel value of the frame N + 1 shown in FIG. 2B and the pixel value of the frame N shown in FIG. 2A, that is, the difference between the pixel values in the block before DCT (before compression). . 4B shows the difference between the pixel value of the frame N + 1 shown in FIG. 3B and the pixel value of the frame N shown in FIG. 3A, that is, the difference between the pixel values in the block after DCT is performed (after compression). Show.

  When noise in the spatial direction with no correlation between frames is superimposed as shown in FIGS. 2A and 2B, blocks corresponding to the same region of the same image are used as shown in FIGS. 4A and 4B. However, a difference occurs between adjacent frames. That is, when there is a difference between adjacent frames as shown in FIGS. 4A and 4B, different images are displayed on the display screen. Here, as shown in FIG. 4A and FIG. 4B, a difference that occurs between adjacent frames in a block corresponding to the same region of the same image can be regarded as noise in the time axis direction.

  Here, the noise in the time axis direction as shown in FIG. 4A is fine noise in units of pixels in the block. Therefore, when the noise in the time axis direction is fine noise in units of pixels in the block as shown in FIG. 4A, even if the noise occurs, it is difficult for the user to recognize that the image quality has deteriorated.

  However, as shown in FIG. 4B, when noise in the time axis direction is generated in units of blocks by deleting the AC component, the noise is recognized by the user as “block flicker”. Therefore, when noise in the time axis direction is generated in units of blocks as shown in FIG. 4B, there is a risk that the user will recognize that the image quality has deteriorated.

  In addition, when the image displayed on the display screen is an image including an area with a gentle inclination or a flat area, the entire area of the area with a gentle inclination or the flat area is composed of a plurality of blocks. Then, noise in the time axis direction generated in units of blocks as shown in FIG. 4B can be generated independently between adjacent frames.

  Therefore, when the image displayed on the display screen is an image including a region with a gentle slope or a flat region, each block may flicker independently. If “block flicker” occurs independently in each block, the user will recognize that the image quality has deteriorated.

  In FIGS. 3A, 3B, and 4B, the case where the AC component of the DCT coefficient is completely deleted has been described as an example. However, even if some AC components remain, in each block, “block Flickering "may occur.

  Further, the noise in the time axis direction generated in units of blocks as described above is not limited to being generated in the luminance signal, but can also be generated in the color difference signal. When noise in the time axis direction generated in units of blocks as described above occurs in the color difference signal, block-shaped color noise is generated.

[Outline of noise reduction approach]
The image processing apparatus 100 according to the embodiment of the present invention detects the noise in the time axis direction generated in units of blocks as described above, and performs filter processing in the time axis direction based on the detection result, thereby performing block units. The image quality is improved by reducing noise caused by fluctuations in the time axis direction that may occur in the encoded image signal.

  More specifically, the image processing apparatus 100 includes a time axis filter that smoothes the image signal in the time axis direction for each pixel, and performs, for example, the following processes (1) to (3): Therefore, noise due to fluctuations in the time axis direction is reduced. Here, the following processes (1) to (3) can be regarded as processes according to an example of the image processing method according to the embodiment of the present invention.

(1) Detection Processing The image processing apparatus 100 receives an input image signal encoded in block units (hereinafter referred to as “input image signal”) and a reference signal corresponding to the reference information most recently stored in the memory. Based on the above, noise in the time axis direction is detected.

  Here, the reference information according to the embodiment of the present invention refers to pixel information of a frame or field before processing (pixel information of a predetermined processing unit) or time axis in an input image signal that has been processed in the past. It is the result of the filter. For example, when the time axis filter is configured by a non-recursive filter such as an FIR (Finite Impulse Response) filter, the image processing apparatus 100 performs predetermined processing before processing in an input image signal that has been processed in the past. Unit pixel information (that is, the past input image signal itself) is recorded in the memory as reference information. For example, when the time axis filter is configured by a cyclic filter such as an IIR (Infinite Impulse Response) filter, the image processing apparatus 100 records the result of the time axis filter in the memory as reference information.

  For example, every time filtering processing is performed in the time axis filter, the image processing apparatus 100 records pixel information of a predetermined processing unit processed in the past or a result of the time axis filter in a memory as reference information. Therefore, the “reference information stored most recently in the memory” used by the image processing apparatus 100 in the process (1) (detection process) is, for example, the image signal to be processed this time (for example, the current frame to be processed from now on) Is the reference information corresponding to the image signal to be processed (for example, the image signal corresponding to the immediately previous frame processed immediately before).

  Here, the image processing apparatus 100 updates the reference information stored in the memory with new reference information, for example, but is not limited thereto. For example, the image processing apparatus 100 can also store the reference information corresponding to each filter process performed in the time axis filter in the memory.

  Even if the reference information is recorded in the memory by any of the above methods, the information processing apparatus 100 uses the reference information stored most recently in the memory to perform the filtering process from now on using the time axis filter. The reference information corresponding to the input image signal one frame before (or, for example, one field before) the input image signal to be performed can be used for the detection process.

  More specifically, the image processing apparatus 100 detects noise in the time axis direction by performing, for example, the following processing (1-1) and processing (1-2).

(1-1) DC Determination Processing The image processing apparatus 100 performs DC determination on the input image signal and the difference signal corresponding to the difference between the input image signal and the reference signal. Here, the direct current determination according to the embodiment of the present invention refers to, for example, whether each pixel is a target pixel to be determined, and whether a predetermined number of pixels in the horizontal direction including the target pixel are DC in a piecewise manner. It means judging.

  As illustrated with reference to FIGS. 3A, 3B, and 4B, “block flicker” can be caused by, for example, deleting the AC component of the DCT coefficient. Therefore, the image processing apparatus 100 according to the embodiment of the present invention is included in the category determined to be DC by determining whether a predetermined number of pixels including the target pixel are DC in a segmental manner. A pixel is a pixel belonging to a block in which noise in the time axis direction may occur.

  FIG. 5 is an explanatory diagram for explaining an example of a DC determination process in the image processing apparatus 100 according to the embodiment of the present invention. Here, FIG. 5 illustrates an example in which the image processing apparatus 100 performs DC determination using seven horizontal pixels including the target pixel as one detection section. Note that the detection section set when the image processing apparatus 100 performs DC determination is not limited to the example shown in FIG. For example, the image processing apparatus 100 can set a plurality of pixels in the horizontal direction as detection intervals, such as eight detections in the horizontal direction as one detection interval.

  As shown in FIG. 5, the image processing apparatus 100 provides a direct current allowable range for determining direct current based on the pixel value of the target pixel, and the pixel values of each pixel in the detection section are all within the direct current allowable range. In this case, the pixel in the detection section is determined as a pixel belonging to a block in which noise in the time axis direction may occur.

  Here, the DC allowable range provided by the image processing apparatus 100 is defined in advance (for example, may be “0”), but is not limited thereto. For example, the image processing apparatus 100 can appropriately change the DC allowable range based on an operation signal according to a user operation transmitted from an operation device included in the image processing apparatus 100 or an external operation device such as a remote controller. .

[Specific example of DC judgment processing]
Hereinafter, the direct current determination processing in the image processing apparatus 100 according to the embodiment of the present invention will be described more specifically. FIG. 6 is a flowchart showing an example of a DC determination process in the image processing apparatus 100 according to the embodiment of the present invention. In the following description, it is assumed that the image processing apparatus 100 performs DC determination using an input image signal or a difference signal as a signal to be processed.

  The image processing apparatus 100 initializes a flag (S100). Here, the image processing apparatus 100 sets the flags corresponding to all the pixels to a state in which the flag is not determined to be direct current (for example, the flag is set to “0”).

  When the flag is initialized in step S100, the image processing apparatus 100 sets a target pixel and a detection section including the target pixel (S102).

  When the target pixel and the detection section are set in step S102, the image processing apparatus 100 performs DC determination on the detection section (S104). Then, the image processing apparatus 100 determines whether or not the set detection section is a direct current (S106). Here, for example, when all the pixels included in the detection section are within the DC allowable range, the image processing apparatus 100 determines that the detection section is DC.

  If it is not determined in step S106 that the detection section is direct current, the image processing apparatus 100 performs the process of step S110 described later without updating the flag corresponding to the pixel included in the detection section.

  If it is determined in step S106 that the detection section is DC, the image processing apparatus 100 sets a flag corresponding to the pixel included in the detection section to be DC (for example, sets the flag to “1”). (S108).

  If it is not determined in step S106 that the detection section is DC, or if the flag is updated in step S108, the image processing apparatus 100 determines whether there is a settable target pixel (S110). Here, the image processing apparatus 100 determines that there is no target pixel that can be set when, for example, the direct current determination is performed using all the pixels as the target pixel, but the present invention is not limited thereto.

  If it is determined in step S110 that there is a target pixel that can be set, the image processing apparatus 100 repeats the processing from step S102. If it is determined in step S110 that there is a target pixel that can be set, the image processing apparatus 100 ends the process.

  For example, the image processing apparatus 100 performs processing shown in FIG. 6 to selectively update the flag corresponding to each pixel to a state in which the flag is determined to be direct current. Therefore, the image processing apparatus 100 can uniquely specify a pixel belonging to a block in which noise in the time axis direction may be generated by using a flag corresponding to each pixel. That is, the flag corresponding to each pixel can be regarded as a direct current determination result for each pixel. Hereinafter, the direct current determination result for each pixel based on the input image signal is referred to as a “first direct current determination result”, and the direct current determination result for each pixel based on the difference signal is referred to as a “second direct current determination result”.

  Note that the DC determination result in the image processing apparatus 100 according to the embodiment of the present invention is not limited to being represented by the value of the flag. Needless to say, the DC determination processing in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the processing illustrated in FIG. 6.

(1-2) Detection Determination Processing When the above-described processing (1-1) (DC determination processing) is performed on each of the input image signal and the difference signal, the image processing apparatus 100 performs the first processing for each pixel. Noise is detected for each pixel based on the direct current determination result, the second direct current determination result for each pixel, and the absolute value of the pixel value of the difference signal.

  As described above, the first DC determination result for each pixel and the second DC determination result for each pixel indicate pixels belonging to a block in which noise in the time axis direction may be generated. Therefore, in a pixel, when both the first DC determination result and the second DC determination result indicate DC, the pixel has a time axis as shown in FIGS. 3A and 3B. There is a high possibility that the pixel belongs to a block in which direction noise may occur.

  However, for example, when the block A in the N frame and the block B at the position corresponding to the block A in the N + 1 frame show different images (for example, in the case of a moving image), for the block B in the N + 1 frame, If the filtering process in the time axis direction is performed, the image quality may be impaired.

  Therefore, the image processing apparatus 100 compares the absolute value of the pixel value of the difference signal with a predetermined threshold value for each pixel in order to prevent erroneous detection of a block in which noise in the time axis direction may occur. . Then, for example, when the absolute value of the pixel value of the difference signal is smaller than a predetermined threshold (or when it is equal to or lower than the predetermined threshold; the same applies hereinafter), the image processing apparatus 100 performs the first direct current. The detection result of the noise in the time axis direction using the determination result and the second DC determination result is valid.

  Here, the predetermined threshold is set in advance, for example, but is not limited thereto. For example, the image processing apparatus 100 may appropriately change the predetermined threshold based on an operation signal according to a user operation transmitted from an operation device provided in the image processing apparatus 100 or an external operation device such as a remote controller. it can.

  Note that the image processing apparatus 100 uses the first DC determination result and the second DC determination result for each pixel based on the comparison result between the absolute value of the pixel value of the difference signal and a predetermined threshold. By selectively determining whether or not the noise is generated, the detection result of the noise in the time axis direction can be made effective selectively, but is not limited to the above. For example, after detecting noise in the time axis direction using the first DC determination result and the second DC determination result, the image processing apparatus 100 calculates the absolute value of the pixel value of the difference signal and the predetermined threshold value. Based on the comparison result, the detection result of noise in the time axis direction can be selectively made effective.

  The image processing apparatus 100 may generate noise in the time axis direction, for example, by the process (1-1) (DC determination process) and the process (1-2) (detection determination process). Pixels belonging to the block can be detected. Note that the detection process in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the process (1-1) (DC determination process) and the process (1-2) (detection determination process). Needless to say.

(2) Filter control processing When a pixel belonging to a block in which noise in the time axis direction is likely to be generated is detected by the processing (detection processing) in (1) above, the image processing apparatus 100 performs the above (1). Based on the detection result of this process (detection process), a control signal for each pixel for controlling the image signal output from the time axis filter is input to the time axis filter. By causing the control signal to be input to the time axis filter, the image processing apparatus 100 controls an image signal output from the time axis filter (hereinafter referred to as “output image signal”).

  More specifically, the image processing apparatus 100 indicates that the detection result for each pixel in the process (1) (detection process) is a pixel belonging to a block in which noise in the time axis direction may occur. In the case shown, a control signal for reducing noise in the time axis direction is input to the time axis filter for each pixel.

  Here, as the control signal for reducing the noise in the time axis direction input to the time axis filter by the image processing apparatus 100 according to the embodiment of the present invention, for example, a filter coefficient applied to the time axis filter is defined. Control signals (hereinafter referred to as “first control signals”).

  Note that the control signal for reducing the noise in the time axis direction that is input to the time axis filter by the image processing apparatus 100 according to the embodiment of the present invention is not limited to the first control signal. For example, the image processing apparatus 100 can further input a control signal for limiting the output image signal output from the time axis filter (hereinafter referred to as “second control signal”) to the time axis filter.

  By causing the image processing apparatus 100 to input the second control signal to the time axis filter, the image processing apparatus 100 temporarily detects that the detection result for each pixel in the process (1) (detection process) is erroneously detected (more specifically, In this case, even if the pixel that does not belong to the block that may cause noise in the time axis direction is due to overdetection that is determined to belong to the block, the image quality that can be caused by the erroneous detection is The decrease can be suppressed.

  If the detection result for each pixel in the process (1) (detection process) does not indicate that the pixel belongs to a block that may generate noise in the time axis direction, the image processing apparatus 100. For example, a control signal indicating a predetermined filter coefficient or the like is input to the time axis filter for each pixel, but is not limited thereto. For example, when the image processing apparatus 100 has a function of detecting noise other than the noise in the time axis direction according to the embodiment of the present invention, the detection result of the function of detecting the other noise is included. It is also possible to input a control signal indicating a filter coefficient based on the time axis filter for each pixel.

(3) Image processing In the process (2) (filter control process), the image processing apparatus 100 smoothes the input image signal in the time axis direction using a time axis filter to which a control signal for each pixel is input. To do. Therefore, the image processing apparatus 100 can selectively reduce the noise in the time axis direction with respect to the pixels belonging to the block in which the noise in the time axis direction may occur, so that the image quality can be improved. it can.

  The image processing apparatus 100 performs, for example, the process (1) (detection process) to the process (3) (image process) as the process related to the noise reduction approach according to the embodiment of the present invention, thereby inputting the input image signal. Based on this, it is possible to detect noise due to fluctuations in the time axis direction and selectively reduce the noise. Therefore, the image processing apparatus 100 can achieve high image quality by reducing noise caused by fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks.

(Image processing apparatus 100 according to an embodiment of the present invention)
Next, the configuration of the image processing apparatus 100 capable of performing the processes (1) (detection process) to (3) (image process) according to the noise reduction approach according to the embodiment of the present invention described above. explain. Hereinafter, as an example of the configuration of the image processing apparatus 100 according to the embodiment of the present disclosure, a configuration in which the image processing apparatus 100 includes an IIR filter as a time axis filter will be mainly described as an example.

  FIG. 7 is a block diagram showing an example of the configuration of the image processing apparatus 100 according to the embodiment of the present invention. An input image signal Di is input to the image processing apparatus 100, and the image processing apparatus 100 outputs an output image signal Do.

  In the following description, it is assumed that the input image signal Di input to the image processing apparatus 100 is, for example, an N-bit digital signal. For example, the input image signal input to the image processing apparatus 100 may be transmitted from a broadcasting station and received by the image processing apparatus 100, but is not limited thereto. For example, an input image signal input to the image processing apparatus 100 may be transmitted from an external apparatus via a network such as a LAN (Local Area Network) and received by the image processing apparatus 100, or The image processing apparatus 100 may read a video file or an image file held in a storage unit (not shown) included in the image processing apparatus 100.

  Note that an input image signal input to the image processing apparatus 100 is, for example, an encoding processing unit (image processing unit) that performs processing such as DCT on an analog signal transmitted from a broadcasting station or the like and encodes the image signal in units of blocks. The image signal may be an image signal encoded in units of blocks in the apparatus 100 (not shown), or may be an image signal encoded in units of blocks in the external apparatus.

  The image processing apparatus 100 adds “0” of m bits (m is an integer of 0 or more) to the lower order of the N-bit input image signal Di, and extends the input image signal Di to N + m bits. Here, for example, the image processing apparatus 100 sets m = 0 when an FIR filter is used as a time axis filter, and m = k (k is a positive integer) when an IIR filter is used as a time axis filter. ). Here, the reason why the image processing apparatus 100 expands the input image signal Di to N + k bits when using the time axis filter is to increase the accuracy of the filter processing using the IIR filter.

  Needless to say, the image processing apparatus 100 according to the embodiment of the present invention can be configured not to expand the number of bits of the input image signal Di.

  Referring to FIG. 7, the image processing apparatus 100 includes a detection unit 102, a filter control unit 104, a time axis filter 106, a memory 108, and a memory control unit 110.

  The image processing apparatus 100 includes, for example, a control unit (not shown) configured by an MPU (Micro Processing Unit), various processing circuits, and the like that can control the entire image processing apparatus 100, and a control unit (not shown). ROM (Read Only Memory, not shown) in which control data such as programs used by the computer and calculation parameters are recorded, and RAM (Random Access) that temporarily stores programs executed by the control unit (not shown) Memory (not shown), a receiving unit (not shown) that receives an image signal transmitted from a broadcasting station, a storage unit (not shown) that can store video files, image files, and the like, which can be operated by the user You may provide the operation part (not shown), the communication part (not shown) for communicating with an external device (not shown), etc. The image processing apparatus 100 connects the above-described constituent elements by, for example, a bus as a data transmission path. The control unit (not shown) can also serve as, for example, the detection unit 102, the filter control unit 104, the time axis filter 106, and the memory control unit 110.

  Here, as the storage unit (not shown), for example, a magnetic recording medium such as a hard disk, an EEPROM (Electrically Erasable and Programmable Read Only Memory), a flash memory, a MRAM (Magnetoresistive Random Access) Non-volatile memory such as Memory (RAM), FeRAM (Ferroelectric Random Access Memory), PRAM (Phase change Random Access Memory), and the like, but is not limited thereto. Note that the image processing apparatus 100 can also include a storage unit (not shown) as the memory 108.

  Further, examples of the operation unit (not shown) include operation input devices such as a keyboard and a mouse, buttons, direction keys, and combinations thereof, but are not limited thereto.

  The image processing apparatus 100 and an external apparatus (not shown) include, for example, a USB (Universal Serial Bus) terminal, an IEEE 1394 standard terminal, a DVI (Digital Visual Interface) terminal, or an HDMI (High-Definition Multimedia Interface) terminal. It is also possible to make a physical connection via a wireless connection, or a wireless connection using WUSB (Wireless Universal Serial Bus), IEEE 802.11, or the like. Furthermore, the image processing apparatus 100 and an external apparatus (not shown) can be connected via a network, for example. Examples of the network include a wired network such as a LAN or a WAN (Wide Area Network), a wireless network such as a WLAN (Wireless Local Area Network) using MIMO (Multiple-Input Multiple-Output), or TCP / IP (Transmission Control). Examples include, but are not limited to, the Internet using a communication protocol such as Protocol / Internet Protocol. Therefore, the communication unit (not shown) has an interface corresponding to the connection form with the external device (not shown).

  The detection unit 102 plays the role of performing the process (1). More specifically, the detection unit 102 receives the input image signal Di and the reference signal Dp corresponding to the reference information read from the memory 108 by the memory control unit 110. For example, the detection unit 102 detects, as the detection result of the process (1), for each pixel, a detection signal Da indicating whether the pixel belongs to a block in which noise in the time axis direction may occur. This is transmitted to the filter control unit 104. Here, the detection signal Da corresponding to each pixel represents, for example, a detection result with 1 bit (for example, when it is “1”, it is a pixel belonging to a block that may generate noise in the time axis direction). Is not limited to the above.

[Configuration Example of Detection Unit 102]
FIG. 8 is a block diagram illustrating an example of the configuration of the detection unit 102 included in the image processing apparatus 100 according to the embodiment of the present invention. The detection unit 102 includes a first DC region detection unit 120, an adder 122, a second DC region detection unit 124, a difference absolute value determination unit 126, and a determination unit 128.

  The first DC region detection unit 120 performs the process (1-1) (DC determination process) based on the input image signal Di. Then, the first DC region detection unit 120 transmits the first detection signal Ddc1 for each pixel indicating the first DC determination result to the determination unit 128.

  The adder 122 generates a difference signal by subtracting the other signal from one signal of the input image signal Di and the reference signal Dp, and the difference signal is output from the second DC region detection unit 124 and the difference absolute value determination unit 126. Communicate to each. FIG. 8 shows a configuration in which the adder 122 generates a differential signal obtained by subtracting the reference signal Dp from the input image signal Di, but is not limited to the above.

  The second DC region detection unit 124 performs the above-described process (1-1) (DC determination process) based on the difference signal. Then, the second DC region detection unit 124 transmits the second detection signal Ddc2 for each pixel indicating the second DC determination result to the determination unit 128.

  The difference absolute value determination unit 126 serves to perform a part of the process (1-2) (detection determination process). More specifically, the difference absolute value determination unit 126 compares the absolute value of the pixel value of the difference signal with a predetermined threshold value for each pixel, and outputs a third detection signal Ddiff indicating the comparison result for each pixel.

  The determination unit 128 serves to perform a part of the process (1-2) (detection determination process). More specifically, the determination unit 128 determines that the first detection signal Ddc1 and the second detection signal Ddc2 are DC based on the first detection signal Ddc1, the second detection signal Ddc2, and the third detection signal Ddiff. When the third detection signal Ddiff is smaller than a predetermined threshold, a detection signal Da indicating that the pixel belongs to a block in which noise in the time axis direction may occur is output. In other cases, the determination unit 128 outputs a detection signal Da indicating that the pixel does not belong to a block in which noise in the time axis direction may occur.

  The detection unit 102 performs the process (1) (detection process) with the configuration illustrated in FIG. 8, for example, and transmits the detection signal Da to the filter control unit 104 for each pixel. Needless to say, the configuration of the detection unit 102 included in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the configuration illustrated in FIG. 8.

  With reference to FIG. 7 again, an example of the configuration of the image processing apparatus 100 according to the embodiment of the present invention will be described. The filter control unit 104 serves to perform the process (2) (filter control process). More specifically, the filter control unit 104 transmits a control signal to the time axis filter 106 for each pixel based on the detection signal Da for each pixel transmitted from the detection unit 102.

  Here, in FIG. 7, the filter control unit 104 selectively transmits the first control signal Dc to which the first control signal is selectively transmitted and the second control signal based on the detection signal Da. A configuration in which the second control signal Dl is selectively transmitted to the time axis filter 106 is shown.

  The time axis filter 106 serves to perform the process (3) (image processing). More specifically, the time axis filter 106 is controlled in filter processing based on the control signal transmitted from the filter control unit 104, and smoothes the input image signal Di in the time axis direction.

  The time axis filter 106 can also smooth the input image signal Di in the spatial direction by controlling the filter processing based on the control signal transmitted from the filter control unit 104.

[Configuration Example of Filter Control Unit 104 and Time Axis Filter 106]
FIG. 9 is a block diagram showing an example of the configuration of the filter control unit 104 and the time axis filter 106 included in the image processing apparatus 100 according to the embodiment of the present invention. Here, in FIG. 9, the memory control unit 110 is also shown.

  The filter control unit 104 includes a first filter control unit 130 that outputs a first control signal Dc, and a second filter control unit 132 that outputs a second control signal Dl.

  The first filter control unit 130 includes a selector SEL1 that selectively outputs one of the first control signal fc1 and the control signal fc2 as the first control signal Dc based on the detection signal Da. Here, the control signal fc2 is, for example, a control signal indicating a filter coefficient defined in advance, but is not limited thereto.

  More specifically, when the selector SEL1 indicates that the detection signal Da is a pixel belonging to a block that may generate noise in the time axis direction, the selector SEL1 uses the first control signal fc1 as the first control signal. Output as Dc. The selector SEL1 outputs the control signal fc2 as the first control signal Dc when indicating that the pixel does not belong to a block in which noise in the time axis direction may occur.

  The second filter control unit 132 includes a selector SEL2 that selectively outputs one of the second control signal func1 and the control signal func2 as the second control signal Dl based on the detection signal Da. Here, the control signal func2 is, for example, a control signal that places a restriction different from the second control signal func1 on the output image signal Do output from the time axis filter 106, but is not limited thereto. .

  For example, with the configuration shown in FIG. 9, the filter control unit 104 transmits the control signal to the time axis filter 106 for each pixel based on the detection signal Da for each pixel transmitted from the detection unit 102.

<Modification of Filter Control Unit 104>
The configuration of the filter control unit 104 according to the embodiment of the present invention is not limited to the configuration shown in FIG. FIG. 10 is a block diagram illustrating another example of the configuration of the filter control unit 104 included in the image processing apparatus 100 according to the embodiment of the present invention. Here, in FIG. 10, the time axis filter 106 and the memory control unit 110 having the same configuration as in FIG. 9 are shown together.

  Referring to FIG. 10, the filter control unit 104 according to the modification includes a region determination unit 140, a first filter control unit 142, and a second filter control unit 144.

  Based on the detection signal Da and the noise detection signals Da′1, Da′2,..., The region determination unit 140 includes a selector SEL3 included in the first filter control unit 142 and a selector SEL4 included in the second filter control unit 144. Are transmitted to the selectors SEL3 and SEL4. Here, the noise detection signals Da′1, Da′2,... Are a kind of detection signals transmitted from other detection units (not shown) for detecting other noises such as block distortion and mosquito noise. is there.

  The region determination unit 140 selects, for example, using a table in which a selection control signal to be output according to a combination of the transmitted detection signal Da and the noise detection signals Da′1, Da′2,. The control signal is output for each pixel, but is not limited thereto.

  The selector SEL3 configuring the first filter control unit 142 outputs one of the first control signal fc1, the control signals fc2_1, fc2_2,... As the first control signal Dc based on the transmitted selection control signal.

  Further, the selector SEL4 constituting the second filter control unit 144 outputs any one of the second control signal func1, the control signals func2_1, func2_2,... As the second control signal Dl based on the transmitted selection control signal. To do.

  Therefore, when the filter control unit 104 shown in FIG. 10 is provided, the image processing apparatus 100 can control the output image signal Do output from the more detailed time axis filter 106.

  The filter control unit 104 performs the process (2) (filter control process) with the configuration shown in FIGS. 9 and 10, for example, and transmits the control signal to the time axis filter 106. Needless to say, the configuration of the filter control unit 104 included in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the configurations illustrated in FIGS. 9 and 10.

  With reference to FIG. 9 again, an example of the configuration of the time axis filter 106 will be described. The filter 106 includes a filter unit 134, a restriction processing unit 136, and an adder 138.

  The filter unit 134 receives the input image signal Di and the first control signal Dc, and filters the input image signal Di. Then, the filter unit 134 transmits the filtered input image signal Di to the restriction processing unit 136 as a filter output signal Df.

  Here, the filter unit 134 is configured by, for example, an IIR filter. The filter unit 134 can also be configured with an FIR filter. When the filter unit 134 is configured by an FIR filter, the output image signal Do output from the adder 138 may not be input to the memory control unit 110. Further, when the filter unit 134 is configured by an FIR filter, the output of the filter unit 134 is, for example, the pixel information itself of the immediately preceding frame (or the immediately preceding field).

  The restriction processing unit 136 has the input image signal Di, the filter output signal Df transmitted from the filter unit 134, and the second control transmitted from the filter control unit 104 (more precisely, the second filter control unit 132). A signal Dl is input. Then, the restriction processing unit 136, based on the second control signal Dl and the difference signal for each pixel between the filter output signal Df and the input image signal Di, the restriction difference signal Dr corresponding to the second control signal Dl. Is output to the adder 138.

  FIG. 11 is an explanatory diagram for explaining processing in the restriction processing unit 136 of the image processing apparatus 100 according to the embodiment of the present invention. The second control signal Dl represents a function that defines the relationship between the differential signal Df-Di and the limited differential signal Dr as shown in FIG. 11, for example. The restriction processing unit 136 outputs a restriction difference signal Dr corresponding to the difference signal Df−Di in accordance with a function defined by the second control signal Dl.

  Needless to say, the limited difference signal Dr corresponding to the differential signal Df-Di output from the limit processing unit 136 is not limited to the example shown in FIG.

  With reference to FIG. 9 again, an example of the configuration of the time axis filter 106 will be described. The adder 138 receives the input image signal Di and the limit difference signal Dr transmitted from the limit processing unit 136, and adds the input image signal Di and the limit difference signal Dr. Then, the adder 138 outputs a signal obtained by adding the input image signal Di and the limited difference signal Dr as the output image signal Do.

  When the filter unit 134 is configured with an IIR filter, the output image signal Do output from the adder 138 is transmitted to the memory control unit 110, and the memory control unit 110 stores the memory 108 (not shown in FIG. 9). Recorded).

  For example, with the configuration shown in FIG. 9, the time axis filter unit 106 can perform the process (3) (image processing) and smooth the input image signal Di in the time axis direction. Needless to say, the configuration of the time axis filter unit 106 included in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the configuration illustrated in FIG. 9.

  With reference to FIG. 7 again, an example of the configuration of the image processing apparatus 100 according to the embodiment of the present invention will be described. The memory 108 stores reference information, and recording of the reference information into the memory 108 and reading of the reference information from the memory 108 are performed by the memory control unit 110.

  Here, examples of the memory 108 include non-volatile memories such as a flash memory and a PRAM, but are not limited thereto. For example, the memory 108 may be a volatile memory such as an SDRAM (Synchronous Dynamic Random Access Memory) or an SRAM (Static Random Access Memory). An example of the memory control unit 110 is a memory controller.

  The image processing apparatus 100 realizes the above-described processing (1) (detection processing) to (3) processing (image processing) according to the noise reduction approach of the embodiment of the present invention, for example, with the configuration illustrated in FIG. Can do. Therefore, the image processing apparatus 100 can achieve high image quality by reducing noise due to fluctuations in the time axis direction that can occur in an image signal encoded in units of blocks, for example, with the configuration shown in FIG.

[Modification of Image Processing Apparatus 100]
Note that the configuration of the image processing apparatus 100 according to the embodiment of the present invention is not limited to the configuration shown in FIG. FIG. 12 is an explanatory diagram showing another example of the configuration of the image processing apparatus 100 according to the embodiment of the present invention. Hereinafter, the image processing apparatus 100 according to the modified example illustrated in FIG. 12 is referred to as an “image processing apparatus 200”.

  The image processing apparatus 200 includes an AC / DC separation unit 202 (first signal separation unit), an AC / DC separation unit 204 (second signal separation unit), an addition unit 206, a detection unit 102, and a filter control unit 104. A time axis filter 106, a memory 108, and a memory control unit 110.

  The image processing apparatus 200 is similar to the image processing apparatus 100 shown in FIG. 7 in that a control unit (not shown), a ROM (not shown), a RAM (not shown), and a receiving unit (not shown). A storage unit (not shown), an operation unit (not shown), a communication unit (not shown), and the like may be provided.

  The AC / DC separation unit 202 separates the input image signal Di into an AC component of the input image signal Di and a DC component of the input image signal Di. Then, the AC / DC separation unit 202 transmits the AC component of the input image signal Di to the addition unit 206 and transmits the DC component of the input image signal Di to the detection unit 102.

  Here, the AC / DC separation unit 202 includes, for example, an ε-filter, but is not limited thereto.

  The AC / DC separation unit 204 separates the reference signal Dp into an AC component of the reference signal Dp and a DC component of the reference signal Dp. Then, the AC / DC separation unit 204 transmits the DC component of the reference signal Dp to the detection unit 102. Here, like the AC / DC separation unit 202, the AC / DC separation unit 204 can be configured by, for example, an ε-filter.

  The detection unit 102, the filter control unit 104, the time axis filter 106, the memory 108, and the memory control unit 110 are the filter control unit 104, the time axis filter 106, the memory 108, and the memory control included in the image processing apparatus 100 illustrated in FIG. Each unit 110 has the same configuration and function.

  Therefore, the image processing apparatus 200 is similar to the image processing apparatus 100 shown in FIG. 7, the process (1) (detection process) to the process (3) (image) related to the noise reduction approach of the embodiment of the present invention. Processing).

  The adder 206 outputs the AC component of the input image signal Di transmitted from the AC / DC separator 202 and the output image signal Do ′ processed from the DC component of the input image signal Di transmitted from the time axis filter 106. Is entered. Then, the adding unit 206 adds the AC component of the input image signal Di and the output image signal Do ′, and outputs the output image signal Do obtained by adding the AC component of the input image signal Di and the output image signal Do ′. To do. Here, the adding unit 206 is configured by an adder, for example.

  The image processing apparatus 200 realizes the processing (detection processing) from the above (1) to the processing (image processing) from (3) according to the noise reduction approach of the embodiment of the present invention, for example, by the configuration shown in FIG. Can do. Therefore, the image processing apparatus 200 can achieve high image quality by reducing noise due to fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks, for example, with the configuration shown in FIG.

  In addition, the image processing apparatus 200 performs the process (1) (detection process) to the process (3) (image process) using the input image signal Di and the Dc component of the reference signal Dp. That is, the image processing apparatus 200 performs the process (1) (detection process) on the DC component of the input image signal Di from which the AC component has been removed even if the AC component remains in each block. -The processing (image processing) of (3) above is performed.

  Therefore, the image processing apparatus 200 is not affected by the AC component even when the input image signal Di is an image signal having an area in which the AC component remains but the “block flicker” may occur. In addition, the processing according to the noise reduction approach of the embodiment of the present invention can be performed. Therefore, the image processing apparatus 200 can further improve the detection accuracy of noise in the time axis direction that is generated in units of blocks, as compared with the image processing apparatus 100 shown in FIG. 7, and can further improve the image quality.

  As described above, the image processing apparatus 100 according to the embodiment of the present invention is based on the input image signal by performing, for example, the process (1) (detection process) to the process (3) (image process). Thus, noise due to fluctuations in the time axis direction is detected, and the noise is selectively reduced. Here, the image processing apparatus 100, based on the first DC determination result for each pixel, the second DC determination result for each pixel, and the comparison result between the absolute value of the pixel value of the difference signal and a predetermined threshold value, Noise due to fluctuation in the time axis direction is detected for each pixel. Therefore, the image processing apparatus 100 can detect noise due to fluctuations in the time axis direction with higher accuracy than when using a technique that combines motion detection and filter processing in the time axis direction. Therefore, the image processing apparatus 100 can achieve high image quality by reducing noise caused by fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks.

  As described above, the image processing apparatus 100 has been described as an embodiment of the present invention. However, the embodiment of the present invention is not limited to such an embodiment. Embodiments of the present invention include, for example, a display device such as a CRT (Cathode Ray Tube display) display, an organic EL display (organic ElectroLuminescence display), and an LCD (Liquid Crystal Display), a PC (Personal Computer), a server ( Server), portable communication devices such as mobile phones, video playback devices, video recording / playback devices, and the like. The image processing apparatus 100 can also be realized as an IC (Integrated Circuit) chip in which the units shown in FIGS. 7 and 12 are integrated, for example. The application of the image processing apparatus 100 to a display device will be described later.

(Display device according to an embodiment of the present invention)
Next, a display device to which the image processing apparatus according to the embodiment of the present invention is applied will be described.

  FIG. 13 is a block diagram showing an example of the configuration of the display device 300 according to the embodiment of the present invention. 13 is an embodiment of the display device according to the embodiment of the present invention, and it is needless to say that the embodiment of the present invention is not limited to the configuration of FIG.

  Referring to FIG. 13, the display device 300 includes an image processing unit 302 and a video display unit 304.

  In addition, the display device 300 includes, for example, a control unit (not shown) configured by an MPU or the like that can control the entire display device 300, and control data such as a program and calculation parameters used by the control unit. ROM (not shown), a RAM (not shown) that primarily stores programs executed by the control unit, a storage unit capable of storing various data such as video files and image files, and display data for user interfaces (Not shown), an operation unit (not shown) that can be operated by the user, a receiving unit (not shown) that receives an image signal transmitted from a broadcasting station, and an external device (not shown). A communication unit (not shown) may be provided. The display device 300 connects the above-described constituent elements by, for example, a bus as a data transmission path.

  Here, examples of the storage unit (not shown) include a magnetic recording medium such as a hard disk, and a nonvolatile memory such as an EEPROM and a flash memory, but are not limited thereto. Further, examples of the operation unit (not shown) include operation input devices such as a keyboard and a mouse, buttons, direction keys, and combinations thereof, but are not limited thereto.

  Further, the display device 300 and an external device (not shown) may be physically connected via, for example, a USB terminal, a DVI terminal, or an HDMI terminal, or wirelessly using WUSB or the like. You can also connect with. Furthermore, the display device 300 and an external device (not shown) can be connected via a wired / wireless network, for example. Therefore, the communication unit (not shown) has an interface corresponding to the connection form with the external device (not shown).

  The image processing unit 302 has, for example, the same configuration as the image processing apparatus 100 according to the embodiment of the present invention illustrated in FIG. 7 and the image processing apparatus 200 according to the modification of the embodiment of the present invention illustrated in FIG. Can do. Therefore, the image processing unit 302 transmits, to the image display unit 304, an output image signal in which noise due to fluctuation in the time axis direction that may occur in the image signal encoded in units of blocks is reduced based on the input image signal Di. To do.

  The image display unit 304 displays an image (moving image / still image) on the display screen based on the output image signal transmitted from the image processing unit 302.

[Configuration Example of Image Display Unit 304]
The image display unit 304 includes a display unit 306, a row driving unit 308, a column driving unit 310, a power supply unit 312, and a display control unit 314.

  The display unit 306 serves as a display screen that displays an image represented by the image signal. The display unit 306 includes, for example, a plurality of pixels arranged in a matrix (matrix). For example, a display unit that displays an SD (Standard Definition) resolution image has at least 640 × 480 = 307200 (data lines × scanning lines) pixels, and the pixels are R, G, and B for color display. In the case of being composed of sub pixels, it has 640 × 480 × 3 = 921600 (data lines × scanning lines × number of subpixels). Similarly, for example, a display unit that displays an HD (High Definition) resolution image has 1920 × 1080 pixels, and has 1920 × 1080 × 3 sub-pixels for color display.

  In addition, the display unit 306 may include, for example, a pixel circuit (not shown) for controlling the amount of voltage / current applied to each pixel. The pixel circuit includes, for example, a switch element and a drive element for controlling the amount of current by an applied scanning signal and a voltage signal, and a capacitor for holding a voltage signal. The switch element and the drive element are composed of, for example, a thin film transistor.

  For example, the row driver 308 and the column driver 310 apply voltage signals to a plurality of pixels included in the display unit 306 to cause each pixel to emit light. Here, one of the row driving unit 308 and the column driving unit 310 applies a voltage signal (scanning signal) that determines ON / OFF of a pixel, and the other applies a voltage signal (image signal) corresponding to an image to be displayed. It can play the role of applying.

  Further, as a driving method of the row driving unit 308 and the column driving unit 310, for example, a dot-sequential driving scanning method in which light is emitted for each pixel arranged in the matrix form, and the pixels arranged in the matrix form for each column. Examples include a line sequential drive scanning method for emitting light, and a surface sequential drive scanning method for emitting light from all the pixels arranged in the matrix. The image display unit 304 of the display device 300 illustrated in FIG. 8 includes two drive units, a row drive unit 308 and a column drive unit 310, but the display device according to the embodiment of the present invention has one drive. Needless to say, it can be composed of parts.

  The power supply unit 312 supplies power to the row driving unit 308 and the column driving unit 310, and a voltage is applied to the row driving unit 308 and the column driving unit 310. In addition, the magnitude of the voltage that the power supply unit 312 applies to the row driving unit 308 and the column driving unit 310 varies according to the output image signal transmitted from the image processing unit 302.

  The display control unit 314 is configured by, for example, an MPU and the like, in accordance with an image signal (output image signal Do) transmitted from the image processing unit 302, one of the row driving unit 308 and the column driving unit 310 is turned on / off. A control signal for applying a voltage for determining OFF to the pixel is input, and an image signal is input to the other. The display control unit 314 can also control power supply to the row driving unit 308 and the column driving unit 310 by the power supply unit 312 in accordance with the output image signal transmitted from the image processing unit 302.

  The display device 300 according to the embodiment of the present invention has the configuration shown in FIG. 13, for example, to reduce noise due to fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks, and the noise is reduced. An image represented by the image signal can be displayed based on the image signal (output image signal). Needless to say, the configuration of the display device 300 according to the embodiment of the present invention is not limited to the configuration shown in FIG. 13.

  As described above, the display device 300 according to the embodiment of the present invention has the same function and configuration as the image processing device 100 according to the above-described embodiment of the present invention (or the image processing device 200 according to the modification). An image processing unit 302 is provided. Therefore, the display device 300 is encoded in units of blocks by performing the process (1) (detection process) to the process (3) (image process) according to the noise reduction approach of the embodiment of the present invention. It is possible to reduce noise caused by fluctuations in the time axis direction that may occur in the received image signal. Further, the display device 300 displays an image represented by an image signal (output image signal) in which noise due to fluctuations in the time axis direction is reduced on the display screen. Therefore, the display device 300 reduces the noise caused by the fluctuation in the time axis direction that may occur in the image signal encoded in units of blocks, thereby improving the image quality, and displays the image in which the noise due to the fluctuation in the time axis direction is reduced. It can be displayed on the screen.

  Further, although the display device 300 has been described as an embodiment of the present invention, the embodiment of the present invention is not limited to such a form. The embodiment of the present invention can be applied to, for example, a display device such as a CRT display, an organic EL display, and an LCD, a television receiver that receives a television broadcast, and the like. The embodiments of the present invention can be applied to various devices such as computers such as PCs and servers, and portable communication devices such as mobile phones.

(Program according to an embodiment of the present invention)
[Program for Image Processing Apparatus According to Embodiment of Present Invention]
By a program for causing a computer to function as an image processing apparatus according to an embodiment of the present invention, it is possible to reduce noise caused by fluctuations in a time direction that may occur in an image signal encoded in units of blocks and to improve image quality. it can.

[Program for Display Device According to Embodiment of Present Invention]
A program for causing a computer to function as an image processing unit of a display device according to an embodiment of the present invention reduces noise caused by fluctuations in the time direction that may occur in an image signal encoded in units of blocks, thereby improving image quality. Can be planned.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, FIG. 13 illustrates a configuration in which the image display unit 304 displays an image based on the output image signal transmitted from the image processing unit 302 on the display screen as the display device according to the embodiment of the present invention. However, the configuration of the display device according to the embodiment of the present invention is not limited to the configuration shown in FIG. For example, the display device according to the embodiment of the present invention performs other image processing on the output image signal transmitted from the image processing unit 302 between the image processing unit 302 and the image display unit 304 illustrated in FIG. A second image processing unit is provided, and the image display unit 304 can display an image based on the output image signal transmitted from the second image processing unit on the display screen. Here, as the second image processing unit, for example, an image processing unit having the same function and configuration as the image processing apparatus described in Japanese Unexamined Patent Application Publication No. 2009-124451 can be cited.

  Even with the above-described configuration, the display device according to the embodiment of the present invention includes the process (1) (detection process) to the process (3) (image process) according to the noise reduction approach of the embodiment of the present invention. ), An image based on an image signal in which noise due to fluctuations in the time axis direction is reduced can be displayed on the display screen. Therefore, the display device according to the embodiment of the present invention reduces noise due to fluctuations in the time axis direction that may occur in an image signal encoded in units of blocks, and is displayed on the display screen, even in the above configuration. The image quality can be improved.

  In the above description, it has been shown that a program (computer program) is provided for causing a computer to function as an image processing apparatus and a display apparatus according to the embodiment of the present invention. A storage medium storing the program can also be provided.

  The configuration described above shows an example of the embodiment of the present invention, and naturally belongs to the technical scope of the present invention.

100, 200 Image processing apparatus 102 Detection unit 102
104 filter control unit 106 time axis filter 108 memory 110 memory control unit 120 first DC region detection unit 122, 138 adder 124 second DC region detection unit 126 difference absolute value determination unit 128 determination unit 130, 142 first filter control unit 132, 144 Second filter control unit 134 Filter unit 136 Restriction processing unit 140 Area determination unit 202, 204 AC / DC separation unit 206 Addition unit 300 Display device 302 Image processing unit 304 Image display unit

Claims (8)

An input image signal encoded in units of blocks and a control signal for each pixel that controls the output image signal to be output are input, and the input image signal is smoothed in the time axis direction based on the control signal for each pixel. A time axis filter that outputs an output image signal obtained by smoothing the input image signal;
A memory for storing pixel information of a predetermined unit of the input image signal before the smoothing in the output image signal or the input image signal smoothed in the time axis filter as reference information;
The input image signal and a reference signal corresponding to the reference information most recently stored in the memory are input, and for each of the input image signal and a difference signal between the input image signal and the reference signal, A direct current determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel is a direct current, with the pixel being a target pixel to be determined, and a first pixel for each pixel based on the input image signal is determined. A detection unit that detects noise on a pixel-by-pixel basis based on a direct current determination result, a second direct current determination result for each pixel based on the difference signal, and an absolute value of a pixel value of the difference signal,
A filter control unit that outputs the control signal for each pixel to the time axis filter based on a detection signal for each pixel indicating a detection result of noise in the detection unit;
Bei to give a,
The detection unit indicates that the first DC determination result and the second DC determination result are DC, and a comparison result obtained by comparing an absolute value of a pixel value of the difference signal with a predetermined threshold is the predetermined value. An image processing apparatus that detects noise when the threshold value is smaller than the threshold value . The detector is
A first DC region detection unit that performs the DC determination based on the input image signal and outputs a first detection signal indicating the first DC determination result for each pixel;
An adder that subtracts the other signal from one signal of the input image signal and the reference signal and outputs the difference signal;
A second DC region detector that performs the DC determination based on the difference signal output from the adder and outputs a second detection signal indicating the second DC determination result for each pixel;
An absolute difference determination unit that compares the absolute value of the pixel value in the difference signal output from the adder with a predetermined threshold value for each pixel and outputs a third detection signal indicating the comparison result for each pixel;
A determination unit that outputs the detection signal for each pixel based on the first detection signal, the second detection signal, and the third detection signal corresponding to each pixel;
With
The determination unit indicates that the first detection signal and the second detection signal are direct current, and noise is detected when the third detection signal indicates that it is smaller than the predetermined threshold value. The image processing apparatus according to claim 1, wherein a detection signal indicating this is output. The said filter control part outputs the 1st control signal which prescribes | regulates the filter coefficient applied to the said time-axis filter as said control signal based on the said detection signal, The Claim 1 or Claim 2 characterized by the above-mentioned. the image processing apparatus according to.   The image processing apparatus according to claim 3, wherein the filter control unit further outputs, as the control signal, a second control signal that restricts an output image signal output from the time axis filter based on the detection signal. A first signal separation unit that separates the input image signal into an AC component signal of the input image signal and a DC component signal of the input image signal;
A second signal separation unit that separates the reference signal into an AC component signal of the reference signal and a DC component signal of the reference signal;
A signal adder that adds the AC component signal of the input image signal and the output image signal output from the time axis filter;
Further comprising
The detection unit receives a DC component signal of the input image signal and a DC component signal of the reference signal.
The image processing apparatus according to claim 1, wherein a DC component signal of the input image signal is input to the time axis filter. A time axis filter that smoothes an input image signal in the time axis direction for each pixel, and an output image signal that is information on the result of the time axis filter, or an input image that has been smoothed in the time axis filter An image processing method that can be used in an image processing apparatus including a memory that stores, as reference information, pixel information of an input image signal in a predetermined unit before the smoothing is performed in a signal,
A pixel of interest for which each pixel is to be determined with respect to an input image signal encoded in units of blocks and a difference signal between the input image signal and a reference signal corresponding to reference information most recently stored in the memory DC determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel is DC, and a first DC determination result for each pixel based on the input image signal and the difference signal A step of detecting noise for each pixel based on a second DC determination result for each pixel based on the absolute value of the pixel value of the difference signal;
Based on the detection result of noise for each pixel in the detection step, a filter control step for inputting a control signal for each pixel for controlling an output image signal output from the time axis filter to the time axis filter;
An image processing step of smoothing the input image signal in a time axis direction using a time axis filter to which the control signal is input in the filter control step;
I have a,
In the detection step, the first DC determination result and the second DC determination result indicate DC, and a comparison result obtained by comparing the absolute value of the pixel value of the difference signal with a predetermined threshold is the predetermined value. An image processing method , wherein noise is detected when the threshold value is smaller than the threshold value . A time axis filter that smoothes an input image signal in the time axis direction for each pixel, and an output image signal that is information on the result of the time axis filter, or an input image that has been smoothed in the time axis filter A program applicable to an image processing apparatus including a memory that stores, as reference information, pixel information of an input image signal of a predetermined unit before the smoothing in the signal,
A pixel of interest for which each pixel is to be determined with respect to an input image signal encoded in units of blocks and a difference signal between the input image signal and a reference signal corresponding to reference information most recently stored in the memory DC determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel is DC, and a first DC determination result for each pixel based on the input image signal and the difference signal A detection step of detecting noise for each pixel based on a second DC determination result for each pixel based on the absolute value of the pixel value of the difference signal;
A filter control step of inputting, to the time axis filter, a control signal for each pixel that controls an output image signal output from the time axis filter based on a detection result of noise for each pixel in the detection step;
An image processing step of smoothing the input image signal in the time axis direction using a time axis filter to which the control signal is input in the filter control step;
To the computer ,
In the detection step, the first DC determination result and the second DC determination result indicate DC, and a comparison result obtained by comparing the absolute value of the pixel value of the difference signal with a predetermined threshold is the predetermined value. A program in which noise is detected when it is smaller than a threshold value . An input image signal encoded in block units is input, the input image signal is smoothed in the time axis direction for each pixel, and an image processing unit that outputs an output image signal obtained by smoothing the input image signal;
An image display unit that displays an image on a display screen based on the output image signal output from the image processing unit;
With
The image processing unit
The input image signal and a control signal for each pixel that controls the output image signal to be output are input, the input image signal is smoothed in the time axis direction based on the control signal for each pixel, and the input image A time axis filter for outputting an output image signal obtained by smoothing the signal;
A memory for storing pixel information of a predetermined unit of the input image signal before the smoothing in the output image signal or the input image signal smoothed in the time axis filter as reference information;
The input image signal and a reference signal corresponding to the reference information most recently stored in the memory are input, and for each of the input image signal and a difference signal between the input image signal and the reference signal, A direct current determination is performed to determine whether or not a predetermined number of pixels in the horizontal direction including the target pixel is a direct current, with the pixel being a target pixel to be determined, and a first pixel for each pixel based on the input image signal is determined. A detection unit that detects noise on a pixel-by-pixel basis based on a direct current determination result, a second direct current determination result for each pixel based on the difference signal, and an absolute value of a pixel value of the difference signal,
A filter control unit that outputs the control signal for each pixel to the time axis filter based on a detection signal for each pixel indicating a detection result of noise in the detection unit;
Bei to give a,
The detection unit indicates that the first DC determination result and the second DC determination result are DC, and a comparison result obtained by comparing an absolute value of a pixel value of the difference signal with a predetermined threshold is the predetermined value. A display device , wherein noise is detected when the threshold value is smaller than the threshold value .

Images