JP2007019796A - Image processing apparatus, method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate progressive images of high image quality when sequential scan conversion is performed. <P>SOLUTION: A gamma compensation part 13 performs gamma compensation, based on a gamma compensation value corresponding to a display device 30 with respect to image data of fields input before and after a present field, and a movement detection part 14 uses gamma-corrected image data to detect movements. Thus movements can be detected with respect to the same gamma-compensated image data as image data actually displayed on the display device, and unnecessary interpolation processing and the occurrence of combing noise due to missing movements can be prevented, and the image quality of progressive images is improved when sequential scan conversion is performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, an image processing method, and an image processing program, and more particularly to an image processing apparatus, an image processing method, and an image processing program for converting an interlaced television signal to a progressive scanning (progressive) method.

  In recent years, in high-quality liquid crystal televisions, PDP (plasma display panel) televisions, and the like, interlace television signals are converted (sequential scan conversion) into high-quality progressive methods by interpolation or the like.

  In the interlace method, one frame is formed by two fields. First, an image of the first field (hereinafter referred to as a top field) is displayed in 1/60 seconds using odd-numbered scanning lines, and then the second field using even-numbered scanning lines in 1/60 seconds. (Hereinafter referred to as the bottom field). When converting such an interlaced television signal to the progressive format, simply superimposing the image data of the preceding and following fields (still image processing), the resulting time difference between the fields results in a moving image like sports. On the other hand, horizontal stripes of comb-like noise called combing noise are generated in the frame image synthesized. In recent years, high-quality liquid crystal televisions and PDP televisions, which are becoming popular in place of CRT (Cathode Ray Tube) televisions, have a problem that the combing noise is noticeable.

  Therefore, in the conventional progressive scan conversion method, the motion of the input image is detected using a method using a motion vector or a method using a difference between frames, and a still image and a moving image are determined ( For example, see Patent Documents 1 and 2.) The pixels determined to have no motion are overlapped with the previous and subsequent fields, and the pixels determined to have motion have undergone an interpolation process to generate pixels.

FIG. 7 is a diagram showing a configuration of an image processing apparatus that performs conventional progressive scan conversion.
The conventional image processing apparatus 500 includes a progressive scan conversion unit 501, a gamma correction unit 502, a memory 503, a bus 504 for connecting them to each other, and a gamma correction value storage unit 505.

  The progressive scan conversion unit 501 inputs a YUV interlaced image from the television signal receiver (or video recorder) 510, performs motion detection and interpolation processing, and converts the image into a progressive image.

The gamma correction unit 502 performs RGB conversion on the YUV image data, performs gamma correction on the signals that are sequentially scan-converted based on the gamma correction values, and outputs the signals to the display device 520.
The memory 503 stores, in addition to the image data of the current field, the image data of the field input before and after the current field in order to detect motion by the sequential scanning conversion unit 501.

The gamma correction value storage unit 505 stores a gamma correction value set from the outside.
In such a conventional image processing apparatus 500, YUV interlaced image data input from the television signal receiver (or video recorder) 510 is sequentially input to the scan conversion unit 501. The sequential scanning conversion unit 501 detects a motion vector / motion amount based on a difference in luminance (Y component) between each pixel or region of the preceding and succeeding frame images, and the detected vector and motion amount exceed a threshold value. If it is, it is determined that it is moving, interpolation processing such as linear interpolation is performed, and a progressive image is generated. On the other hand, if it is determined that the image does not move, a progressive image is generated by superimposing pixels or regions in the preceding and following fields. The image data output from the progressive scan conversion unit 501 is input to the gamma correction unit 502 and is gamma corrected based on the gamma correction value.

Note that gamma correction is a process of changing the value of each gradation to a designated gamma correction value, and is performed to absorb differences in gradation characteristics that differ for each display device such as a liquid crystal panel or a PDP. In recent years, the gamma correction has become an indispensable function due to the widespread use of display devices that replace CRTs such as liquid crystal displays, PDPs, and organic EL (Electro Luminescence) displays.
JP-A-6-133280 JP-A-7-284071

  In a conventional image processing apparatus, motion detection at the time of progressive scan conversion is performed on an input signal. However, the image data actually displayed on the display device is a value after gamma correction. That is, in the conventional image processing apparatus, motion detection is performed on a signal different from the displayed image data. For this reason, there is a problem in that an image with no motion is determined as having motion, or an image with motion is determined as having no motion. As a result, there is a problem in that combing noise is generated due to unnecessary interpolation processing and motion detection leakage, resulting in deterioration of image quality.

The present invention has been made in view of these points, and an object of the present invention is to provide an image processing apparatus capable of generating a progressive image with good image quality at the time of progressive scan conversion.
Another object of the present invention is to provide an image processing method capable of generating a progressive image with good image quality at the time of progressive scan conversion.

  Another object of the present invention is to provide an image processing program capable of generating a progressive image with good image quality at the time of progressive scan conversion.

  In the present invention, in order to solve the above-mentioned problem, an image processing apparatus for converting a television signal of an interlaced scanning method into sequential scanning and performing gamma correction according to the display device and displaying an image on the display device is shown in FIG. As described above, the gamma correction unit 13 that performs gamma correction based on the gamma correction value corresponding to the display device 30 for the image data of the field input before and after the current field, and the gamma corrected image data An image processing apparatus 10 is provided that includes a motion detection unit 14 that performs motion detection using the motion detection unit 14.

  According to the above configuration, the gamma correction unit 13 performs gamma correction on the image data of the field input before and after the current field based on the gamma correction value corresponding to the display device 30 to detect motion. The unit 14 performs motion detection using the gamma-compensated image data.

  In the present invention, gamma correction is performed on the image data of the field input before and after the current field based on the gamma correction value corresponding to the display device, and motion detection is performed using the gamma corrected image data. Do. This enables motion detection to be performed on the same gamma-corrected image data as the actual image data displayed on the display device, thus preventing unnecessary interpolation processing and occurrence of combing noise due to motion detection leaks. In addition, the quality of the progressive image can be improved during the progressive scan conversion.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of an image processing apparatus according to an embodiment.
FIG. 2 is a diagram showing the flow of input data and output data of the image processing apparatus.

  The image processing apparatus 10 includes a memory 11, a bus 12, a gamma correction unit 13, a motion detection unit 14, an interpolation unit 15, selectors 16 and 17, an output-side gamma correction unit 18, and a gamma correction value storage unit 19. .

  The memory 11 stores interlaced image data input from a television signal receiver (or a video recorder or the like) 20. As shown in FIG. 2, the interlaced image data is image data of the top field (T0, T1, T2, T3,...) And the bottom field (B0, B1, B2,. Consists of. The memory 11 stores, in addition to the image data of the current field, image data of fields (hereinafter referred to as the preceding and following fields) input before and after the current field for motion detection described later.

The bus 12 transmits the image data from the television signal receiver 20 to the memory 11 and transmits the image data stored in the memory 11 to each unit.
The gamma correction unit 13 performs gamma correction on the image data in the preceding and following fields among the image data stored in the memory 11. When the image data input from the television signal receiver 20 is a YUV signal, the gamma correction unit 13 converts the image data into an RGB signal and then based on the gamma correction value stored in the gamma correction value storage unit 19. Perform gamma correction.

The motion detection unit 14 performs motion detection using the image data that has been gamma corrected by the gamma correction unit 13. Details of motion detection will be described later.
The interpolation unit 15 performs intra-frame interpolation, for example. Image data of a scanning line that needs to be interpolated (hereinafter referred to as a motion detection target line) is generated by performing interpolation processing such as linear interpolation for the input field.

  The selector 16 selects either the image data interpolated by the interpolation unit 15 or the image data of the previous field or the subsequent field stored in the memory 11 according to the determination result of the motion detection by the motion detection unit 14. Select and output.

  The selector 17 selects the output of the preceding selector 16 when the scanning line displayed on the display device 30 is a motion detection target line, and selects the image data of the current field as it is when the scanning line is not the detection target line. Output.

  The output-side gamma correction unit 18 performs gamma correction on the image data output from the selector 17 and outputs it to the display device 30. Here, when the image data input from the television signal receiver 20 is a YUV signal, it is converted into an RGB signal, and then gamma correction is performed based on the gamma correction value stored in the gamma correction value storage unit 19. Do. The gamma correction value to be used is the same as the value used in the gamma correction unit 13.

  The gamma correction value storage unit 19 stores gamma correction values set according to the display device 30 such as a PDP, a liquid crystal display, and an organic EL display. The gamma correction value can be arbitrarily set from the outside.

Hereinafter, an outline of image processing by the image processing apparatus 10 according to the present embodiment will be described. In the following, a case where the current field is the top field T1 in FIG. 2 will be described as an example.
When interlaced image data as shown in FIG. 2 is input from the television signal receiver 20 for each field, the image data is stored in the memory 11 for use in subsequent field processing. In addition, the image data of the current field is input to the interpolation unit 15 and, for example, intra-frame interpolation is performed. The input image data (YUV signal) of the top field T1 is linearly interpolated by the following equation, for example.

Y (x, y) = (a + b) / 2
U (x, y) = (c + d) / 2 (1)
V (x, y) = (e + f) / 2
In Equation (1), a is the luminance value of the bottom field B0, which is the previous field. b is the luminance value of the bottom field B1, which is the rear field. Further, c is a U component color difference in the bottom field B0, d is a U component color difference in the bottom field B1, e is a V component color difference in the bottom field B0, and f is a V component color difference in the bottom field B1.

  Image data of the bottom fields B0 and B1, which are the front and rear fields, is input to the gamma correction unit 13. When the input image data is a YUV signal, the image data is converted to RGB signal image data. The conversion is performed according to the following formula.

R = 1.64 (Y-16) +1.596 (V-128)
G = 1.64 (Y-16) -0.391 (U-128) -0.831 (V-128)
B = 1.64 (Y-16) +2.018 (U-128) (2)
Note that the conversion formula differs depending on the television standard, and in the formula (2), ITU-R BT. This is an example in the case of 601. Also, depending on the television standard, RGB signals may be input instead of YUV signals. In that case, RGB conversion is not performed.

  Next, the gamma correction unit 13 performs gamma correction on the RGB-converted signal (R, G, B) with reference to the gamma correction value stored in the gamma correction value storage unit 19. As the gamma correction value, a value of each gradation is set for each of the R, G, and B components. Examples of gamma correction values are shown in the table below.

  For example, if the signal (R, G, B) = (1, 1, 1) before compensation, the signal after compensation is (1, 2, 2) according to the above table. The gamma correction value can be changed for each type of display device 30.

  The result of gamma correction is input to the motion detection unit 14, and motion detection is performed. As a result of motion detection, when it is determined that there is motion, the selector 16 outputs the image data interpolated by the interpolation unit 15, and when it is determined that there is no motion, the selector 16 stores the bottom stored in the memory 11. The image data in the field B0 or B1 is selected and output.

  The selector 17 selects the output of the preceding selector 16 when the scanning line displayed on the display device 30 is a motion detection target line, and selects the image data of the current field as it is when the scanning line is not the motion detection target line. And output. The output of the selector 17 is input to the output side gamma correction unit 18. Then, the gamma correction unit 18 performs gamma correction on the image data output from the selector 17 and displays it as a progressive image of frames (F0, F1, F2, F3, F4, F5,...) As shown in FIG. Output to the device 30. If the image data input from the television signal receiver 20 is a YUV signal, the gamma correction unit 18 converts it into an RGB signal and then performs gamma correction.

  As described above, in the image processing apparatus 10 according to the present embodiment, the gamma correction unit 13 performs gamma correction on the image data of the preceding and following fields based on the gamma correction value corresponding to the display device 30, and moves The detection unit 14 performs motion detection on the result. Thereby, the image data whose motion is detected becomes the same as the image data actually displayed on the display device 30 (image data after gamma correction in the gamma correction unit 18).

  For this reason, it is determined that the image on the display device 30 is moving even though the image on the display device 30 is not moving due to the difference between the image data displayed as in the past and the image data whose motion is detected. It is possible to prevent the occurrence of combing noise due to interpolation processing or the determination that the movement is not performed despite the movement, and the image quality can be improved.

Details of the motion detection unit 14 of the image processing apparatus 10 according to the present embodiment will be described below.
FIG. 3 is a circuit block diagram illustrating a configuration of the motion detection unit.
The motion detection unit 14 according to the present embodiment includes a difference calculation circuit 140 for the ratio of RG, RB, and GB, a distance (difference) calculation circuit 150 between two pixels, and an OR circuit 160. .

  The difference calculation circuit 140 for the ratio of RG, RB, and GB is a pixel value of the preceding and following fields at the same position as the position on the motion detection target line in the current field (interpolation target position in the case of interpolation). Based on the above, the differences ΔRG, ΔRB, ΔGB between the preceding and succeeding fields of the ratios of the components R and G, R and B, and G and B of the RGB signal are calculated according to the following equation (3).

ΔRG = | R1 / G1-R0 / G0 |
ΔRB = | R1 / B1-R0 / B0 | (3)
ΔGB = | G1 / B1-G0 / B0 |
Here, (R0, B0, G0) is the pixel value of the previous field at the same position as the position on the motion detection target line in the current field, and (R1, B1, G1) is the motion in the current field. This is the pixel value of the subsequent field at the same position as the position on the detection target line. As described above, in the image processing apparatus 10 according to the present embodiment, the image data of the previous field and the subsequent field input to the motion detection unit 14 is data subjected to gamma correction.

The difference calculation circuit 140 for the ratio of R−G, R−B, and G−B that performs the above calculation can be realized with the following configuration.
FIG. 4 is a circuit block diagram of a difference calculation circuit for the ratio of RG, RB, and GB.

  The difference calculation circuit 140 for the ratio of R−G, R−B, and G−B includes division circuits 141a, 141b, 141c, 141d, 141e, and 141f for performing the calculation of Expression (3), and subtraction circuits 142a and 142b. 142c.

  Further, the comparison circuit 143a for comparing the calculation results of the expression (3) output from the subtraction circuits 142a, 142b, 142c, that is, ΔRG, ΔRB, ΔGB, respectively, with the thresholds rg_th, rb_th, gb_th set from the outside. , 143b, 143c. The threshold values rg_th, rb_th, and gb_th are stored in the threshold storage units 144a, 144b, and 144c, respectively.

  In such a difference calculation circuit 140 of the ratio of RG, RB, and GB, the division circuit 141a, 141b, 141c, 141d, 141e, 141f and the subtraction circuit 142a, 142b, 142c are used for the expression (3). Calculate Then, the comparison circuits 143a, 143b, and 143c compare the calculation results ΔRG, ΔRB, and ΔGB with the threshold values rg_th, rb_th, and gb_th, respectively. If the calculation results ΔRG, ΔRB, ΔGB are larger than the threshold values rg_th, rb_th, gb_th, the comparison circuits 143a, 143b, 143c output “1”.

  On the other hand, in FIG. 3, the inter-pixel distance (difference) calculation circuit 150 is at the same position as the position on the motion detection target line in the current field (interpolation target position in the case of interpolation) according to the following equation (4). In the RGB coordinate system, the pixel values (R0, B0, G0) of the previous field and the pixel values (R1, B1, G1) of the subsequent field at the same position on the motion detection target line in the current field The distance, that is, Δd which is the sum of the differences between the components is calculated.

Δd = | R1-R0 | + | G1-G0 | + | B1-B0 | (4)
The two-pixel distance (difference) calculation circuit 150 that performs the calculation as described above can be realized by the following configuration.

FIG. 5 is a circuit block diagram of a distance (difference) calculation circuit between two pixels.
The two-pixel distance (difference) calculation circuit 150 includes difference absolute value calculation circuits 151a, 151b, and 151c for calculating the equation (4), and an addition circuit 152.

  Furthermore, a comparison circuit 153 for comparing the calculation result of Expression (4) output from the adder circuit 152, that is, Δd with a threshold value d_th set from the outside is provided. The threshold d_th is stored in the threshold storage unit 154.

  In such a two-pixel distance (difference) calculation circuit 150, the difference absolute value calculation circuits 151a, 151b, and 151c and the addition circuit 152 calculate Expression (4). Then, the comparison circuit 153 compares the calculation result Δd with the threshold value d_th. If the calculation result Δd is larger than the threshold value d_th, the comparison circuit 153 outputs “1”.

  Also, the OR circuit 160 of FIG. 3 is a logical sum of three outputs of the difference calculation circuit 140 of the ratio of RG, RB, and GB and one output of the two-pixel distance (difference) calculation circuit 150. Is output as a motion determination result. One of the four outputs of the OR circuit 160 consisting of three outputs of the difference calculation circuit 140 of the ratio of RG, RB, and GB and one output of the two-pixel distance (difference) calculation circuit 150 is “1”. If "," output "1" and determine that there is movement. If all four inputs are “0”, “0” (no motion) is output.

The operation of the motion detection unit 14 is summarized below.
FIG. 6 is a flowchart for explaining the flow of motion detection processing by the motion detection unit.
Step S <b> 1: The motion detection unit 14 inputs image data of the front and rear fields after gamma correction from the gamma correction unit 13. For example, when the current field is the top field T1 in FIG. 2, the pixel values of the bottom fields B0 and B1 at the same position as the position on the motion detection target line in the top field T1 (interpolation target position in the case of interpolation). (R0, B0, G0) and (R1, B1, G1) are input.

Step S2a: R-G, R-B, G-B ratio difference calculation circuit 140 calculates R and G, R and B, and G and B ratio differences ΔRG, ΔRB, and ΔGB according to Equation (3). calculate.
Step S2b: In the distance (difference) calculation circuit 150 between two pixels, the pixel value (R0, B0, G0) of the previous field and the pixel value (R1, B1, G1) of the subsequent field according to the equation (4), Calculate the distance in the RGB coordinate system.

  Step S3: Calculation results ΔRG, ΔRB of the formulas (3) and (4) by the difference calculation circuit 140 and the two-pixel distance (difference) calculation circuit 150 of the ratio of RG, RB, GB. ΔGB and Δd are compared with threshold values rg_th, rb_th, gb_th, and d_th. When any of the calculation results ΔRG, ΔRB, ΔGB, and Δd exceeds the corresponding threshold values rg_th, rb_th, gb_th, and d_th, the OR circuit 160 determines that there is motion. If all of the calculation results ΔRG, ΔRB, ΔGB, and Δd are smaller than the corresponding threshold values rg_th, rb_th, gb_th, and d_th, the OR circuit 160 determines that there is no motion.

As described above, motion detection can be performed using gamma-compensated front and rear image data.
Note that the motion detection unit 14 described above is merely an example, and motion detection is performed using only the difference calculation circuit 140 of the ratio of RG, RB, and GB or only the distance (difference) calculation circuit 150 between two pixels. You may make it perform.

  Note that the processing content of the image processing apparatus 10 of the present embodiment can be realized by a computer. In that case, a program describing the processing contents of the functions that the image processing apparatus 10 should have is provided. By executing the program on a computer, the above processing functions are realized on the computer. The program describing the processing contents can be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include a magnetic recording device, an optical disk, a magneto-optical recording medium, and a semiconductor memory. Examples of the magnetic recording device include a hard disk device (HDD), a flexible disk (FD), and a magnetic tape. Examples of the optical disc include a DVD (Digital Versatile Disc), a DVD-RAM (Random Access Memory), a CD-ROM (Read Only Memory), and a CD-R (Recordable) / RW (ReWritable). Magneto-optical recording media include MO (Magneto-Optical disk).

  When distributing the program, for example, portable recording media such as a DVD and a CD-ROM on which the program is recorded are sold. It is also possible to store the program in a storage device of a server computer and transfer the program from the server computer to another computer via a network.

  The computer that executes the program stores, for example, the program recorded on the portable recording medium or the program transferred from the server computer in its own storage device. Then, the computer reads the program from its own storage device and executes processing according to the program. The computer can also read the program directly from the portable recording medium and execute processing according to the program. In addition, each time the program is transferred from the server computer, the computer can sequentially execute processing according to the received program.

  As mentioned above, although this invention was demonstrated based on the Example, this invention is not limited above, A various deformation | transformation is possible within the range as described in a claim.

It is a figure which shows the structure of the image processing apparatus of embodiment. It is a figure which shows the flow of the input data and output data of an image processing apparatus. It is a circuit block diagram which shows the structure of a motion detection part. It is a circuit block diagram of the difference calculation circuit of the ratio of RG, RB, GB. It is a circuit block diagram of a distance (difference) calculation circuit between two pixels. It is a flowchart explaining the flow of the motion detection process by a motion detection part. It is a figure which shows the structure of the image processing apparatus which performs the conventional progressive scanning conversion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image processing apparatus 11 Memory 12 Bus 13, 18 Gamma correction part 14 Motion detection part 15 Interpolation part 16, 17 Selector 19 Gamma correction value storage part 20 Television signal receiver (or video recorder)
30 display devices

Claims (5)

In an image processing apparatus that converts a television signal of an interlaced scanning method into sequential scanning, performs gamma correction according to a display device, and displays an image on the display device.
A gamma correction unit that performs gamma correction based on a gamma correction value according to the display device for image data of a field input before and after the current field;
A motion detector that performs motion detection using the image data that has been gamma-corrected;
An image processing apparatus comprising:   The motion detection unit is configured to calculate R and G, R and B, and G and B of RGB signals based on the pixel values of the fields input before and after the same position as the motion detection target position in the current field. The image processing apparatus according to claim 1, wherein a difference between fields input before and after the ratio of values is calculated, and it is determined that there is motion when the difference is greater than a predetermined threshold.   The motion detection unit is configured to perform RGB of the pixel values between the fields input before and after the front and back based on the pixel values of the fields input before and after the same position as the motion detection target position in the current field. The image processing apparatus according to claim 1, wherein a distance in a coordinate system is calculated, and it is determined that there is a motion when the distance is greater than a predetermined threshold. In the image processing method for converting the television signal of the interlaced scanning method into sequential scanning, performing gamma correction according to the display device, and displaying the image on the display device,
Gamma correction is performed based on the gamma correction value corresponding to the display device for the image data of the field input before and after the current field,
An image processing method, wherein motion detection is performed using the gamma-corrected image data. In an image processing program for converting a television signal of an interlaced scanning method into sequential scanning, performing gamma correction according to a display device, and causing a computer to function to display an image on the display device,
Gamma correction means for performing gamma correction on the basis of the gamma correction value corresponding to the display device for the image data of the field input before and after the current field,
Motion detection means for performing motion detection using the image data corrected for gamma,
An image processing program that functions as an image processing program.

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