JP3821672B2 - Video signal processor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a video signal processing apparatus for improving the image quality of a video signal, and more particularly to a video signal processing apparatus for improving the quality of a display video signal in a video display device such as a projector or a television.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a video display device, a technique for detecting an edge component of a video signal and sharpening the detected edge is known as a technique for improving the image quality of the video signal. This technique is called Luminance Transient Improvement (Luminance Transient Improvement) technique or Color Transient Improvement (Color Transient Improvement) technique (hereinafter referred to as LTI technique). FIG. 7 is a diagram illustrating a state in which the edge of the video signal is sharpened by the LTI technique. In FIG. 7, when the LTI technique is applied to a slowly changing video signal as shown by a broken line, the range of A and B is detected as an edge component, and as a result of sharpening the edge, as shown by a solid line A video signal is obtained.
[0003]
[Problems to be solved by the invention]
However, the LTI technique has a problem in that the effect of improving the image quality is limited as described below. In the LTI technology, the effect of improving the image quality appears only in the portion of the video signal detected as the edge component. Therefore, if the edge detection conditions are changed so that the effect of improving the image quality is insufficient and the effect is further extended to the high frequency range, the effect appears excessively in all lower frequency ranges. For this reason, when the video signal that should change smoothly changes in a staircase pattern and the video signal is displayed, the viewer receives an unnatural impression as if all objects were made up of flat surfaces. As described above, in the LTI technique, when the effect of improving the image quality is strengthened, there is a side effect that the video signal that should be smoothly changed changes in a stepped manner, and thus the effect of improving the image quality cannot be increased beyond a certain level. There is a problem.
[0004]
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a video signal processing apparatus that improves the image quality of a video signal by a novel method different from the LTI technology.
[0005]
[Means for Solving the Problems and Effects of the Invention]
A first invention is a video signal processing apparatus that performs correction processing on a changed portion of a video signal,
Correction value holding means for holding a correction value for the video signal;
Condition holding means for holding a condition for determining a pixel to be corrected in the video signal;
According to the conditions held in the condition holding means, the portion where the horizontal component of the video signal changes in a mountain shape and a valley shape is specified, and the pixels located at the peak and valley bottom are respectively designated as the peak pixel and the valley bottom pixel. Correction pixel detection means for detecting;
The video signal includes addition / subtraction means for adding the correction value held in the correction value holding means to the peak pixel and subtracting the correction value from the valley pixel.
[0006]
According to the first aspect of the invention, the peak pixel and valley bottom pixel are detected from the video signal, and the peak pixel is higher and the valley bottom pixel is corrected lower. Therefore, a sharp image that emphasizes the changed portion. A signal can be provided. In particular, as with the LTI technology, the video signal that should change smoothly changes in a staircase shape, and when the video signal is displayed, an unnatural impression is given to the viewer as if all things were composed of flat surfaces. Without giving it, it is possible to provide a high-quality video signal that is sharper than the LTI technology.
[0007]
In a second aspect based on the first aspect, the correction pixel detection means comprises:
Primary differential detection means for obtaining a primary differential signal of a video signal;
And a first-order differential processing means for detecting a peak pixel and a valley-bottom pixel based on the first-order differential signal obtained by the first-order differential detection means.
[0008]
According to the second invention as described above, it is possible to provide a sharp image signal in which a peak pixel and a valley pixel are obtained based on a first-order differential signal and a changed portion is emphasized.
[0009]
In a third aspect based on the second aspect, the correction pixel detecting means comprises:
Noise removal means for removing noise components from the primary differential signal obtained by the primary differential detection means;
The primary differential processing means is characterized by detecting a peak pixel and a valley bottom pixel based on the primary differential signal that has passed through the noise removing means.
[0010]
According to the third aspect, when noise is superimposed on the video signal, it is possible to prevent a problem in which a larger noise component than the original video signal is superimposed on the corrected video signal. Therefore, it is possible to stably provide a high-quality video signal with enhanced sharpness by performing a stable operation even on a video signal having a lot of noise components.
[0011]
In a fourth aspect based on the second aspect, the primary differential processing means determines the signal level of the primary differential signal obtained by the primary differential detection means at the i-th pixel (i is an integer) from the left of the screen. D _i (D _i-1 -D _i ) And (D _i -D _{i + 1} ) Is larger than the threshold value held in the condition holding means, and D _i If the absolute value of is smaller than the predetermined value, the i-th pixel is detected as the peak pixel, and (D _i -D _i-1 ) And (D _{i + 1} -D _i ) Are both greater than the threshold and D _i When the absolute value of is smaller than a predetermined value, the i-th pixel is detected as a valley pixel.
[0012]
According to the fourth aspect of the invention, it is possible to obtain a peak image pixel and a valley bottom pixel by determining the magnitude of the signal level of the first-order differential signal, and to provide a sharp video signal that emphasizes the changed portion. it can.
[0013]
In a fifth aspect based on the first aspect, the correction pixel detecting means sets the signal level of the video signal at the i-th pixel (i is an integer) from the left of the screen to P _i (P _i -P _i-1 ) And (P _i -P _{i + 1} ) Are larger than the threshold value held in the condition holding means, the i-th pixel is detected as a peak pixel, and (P _i - ₁ -P _i ) And (P _{i + 1} -P _i ) Are larger than the threshold value, the i-th pixel is detected as a valley pixel.
[0014]
According to the fifth aspect of the invention, it is possible to provide a sharp video signal that emphasizes the changed portion by determining the magnitude of the signal level of the video signal to obtain the peak pixel and the valley pixel.
[0015]
In a sixth aspect based on the first aspect, the apparatus further comprises condition control means for controlling the condition held in the condition holding means based on the input control signal.
[0016]
According to the sixth aspect of the invention, it is possible to freely set a range in which the effect of the image quality correction is set, and to provide a high-quality video signal with enhanced sharpness according to the taste of the viewer and the characteristics of the video signal can do.
[0017]
In a seventh aspect based on the first aspect, the correction value holding means holds the correction value for addition and the correction value for subtraction separately,
The addition / subtraction means adds the correction value for addition to the peak pixel, and subtracts the correction value for subtraction from the valley bottom pixel.
[0018]
According to the seventh aspect, by separately controlling the correction value for the peak pixel and the correction value for the valley pixel, it is possible to balance the correction effect between the peak pixel and the valley pixel. .
[0019]
In an eighth aspect based on the first aspect, the addition / subtraction means adjusts the correction value held in the correction value holding means in accordance with the level of the video signal, and adds / subtracts the adjusted correction value to / from the video signal. It is characterized by that.
[0020]
According to the eighth aspect of the invention, by automatically adjusting the correction value according to the signal level of the video signal, the strength of the effect of the image quality correction is automatically adjusted with higher accuracy, and the sharpness is further improved. It is possible to provide a high-quality video signal with increased feeling.
[0021]
In a ninth aspect based on the first aspect, the apparatus further comprises correction value control means for controlling the correction value held in the correction value holding means based on the input control signal.
[0022]
According to the ninth aspect of the invention, it is possible to freely set the strength of the effect of image quality correction, and to provide a high-quality video signal with enhanced sharpness according to the viewer's preference and the characteristics of the video signal can do.
[0023]
According to a tenth aspect, in the ninth aspect, the correction value control means controls the correction value held in the correction value holding means based on the amount of motion calculated from the video signal.
[0024]
According to such a tenth aspect, when the video signal is a moving image, the correction effect can be balanced between the still image and the moving image by increasing the correction value.
[0025]
In an eleventh aspect based on the first aspect, the apparatus further comprises a densifying means for increasing the number of horizontal pixels of the video signal,
The correction pixel detection unit and the addition / subtraction unit perform processing on the video signal that has passed through the densification unit.
[0026]
According to the eleventh aspect of the invention, by increasing the sampling frequency of the video signal by the densification means, the frequency band of the reproducible signal is increased without causing problems such as aliasing noise in the subsequent processing. Letting But it can.
[0027]
A twelfth aspect of the present invention is a video signal processing method for performing correction processing on a changed portion of a video signal,
A correction value holding step for holding a correction value for the video signal;
A condition holding step for holding a condition for detecting a pixel to be corrected in the video signal;
According to the conditions held in the condition holding step, the part where the horizontal component of the video signal changes in a mountain shape and a valley shape is specified, and the pixels located at the peak and the bottom of the valley are designated as the peak pixel and the valley bottom pixel, respectively. A correction pixel detection step to detect;
The video signal includes an addition / subtraction step for adding the correction value held in the correction value holding step to the peak pixel and subtracting the correction value from the valley pixel.
[0028]
A thirteenth aspect of the present invention is a computer-readable recording medium that records a program for causing a computer to execute a video signal processing method for performing correction processing on a changed portion of the video signal.
A correction value holding step for holding a correction value for the video signal;
A condition holding step for holding a condition for detecting a pixel to be corrected in the video signal;
According to the conditions held in the condition holding step, the part where the horizontal component of the video signal changes in a mountain shape and a valley shape is specified, and the pixels located at the peak and the bottom of the valley are designated as the peak pixel and the valley bottom pixel, respectively. A correction pixel detection step to detect;
The video signal includes an addition / subtraction step for adding the correction value held in the correction value holding step to the peak pixel and subtracting the correction value from the valley pixel.
[0029]
According to such twelfth and thirteenth inventions, the peak pixel and valley pixel are detected from the video signal, and the peak pixel is corrected higher and the valley pixel is corrected lower. It is possible to provide a certain video signal. In particular, as with the LTI technology, the video signal that should change smoothly changes in a staircase shape, and when the video signal is displayed, an unnatural impression is given to the viewer as if all things were composed of flat surfaces. Without giving it, it is possible to provide a high-quality video signal that is sharper than the LTI technology.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a video signal processing apparatus according to the first embodiment of the present invention. The video signal processing apparatus shown in FIG. 1 includes a densification unit 1, a primary differential detection unit 2, a noise removal unit 3, a correction pixel determination condition control unit 4, a correction pixel determination condition storage unit 5, a correction pixel determination unit 6a, An addition / subtraction value control unit 7, an addition / subtraction value storage unit 8, and an addition / subtraction unit 9 are provided.
[0031]
The video signal processing apparatus shown in FIG. 1 generally operates as follows. The high density unit 1 increases the number of horizontal pixels of the input video signal 11 to obtain a high density video signal 12. The correction pixel determination condition storage unit 5 stores a threshold value 31 for determining a pixel to be corrected. The addition / subtraction value storage unit 8 stores a correction value 33 for addition and a correction value 34 for subtraction for addition / subtraction to the high-density video signal 12. The threshold value 31 is controlled by the correction pixel determination condition control unit 4, and the two correction values 33 and 34 are controlled by the addition / subtraction value control unit 7.
[0032]
The primary differential detection unit 2 generates a primary differential signal 13 of the high-density video signal 12. The noise removing unit 3 removes a noise component from the primary differential signal 13 generated by the primary differential detection unit 2. The correction pixel determination unit 6a determines the magnitude of the first differential signal 14 after noise removal using the threshold value 31, specifies a portion where the high-density video signal 12 changes in a mountain shape and a valley shape, A pixel located at the apex (hereinafter referred to as “mountain peak pixel”) and a pixel located at the bottom of the valley (hereinafter referred to as “valley bottom pixel”) are detected.
[0033]
The addition / subtraction unit 9 adds the correction value 33 for addition to the pixel detected as the peak pixel by the correction pixel determination unit 6a in the high-density video signal 12, and the correction pixel determination unit 6a detects the pixel as a valley bottom pixel. A correction value 34 for subtraction is subtracted from the pixel.
[0034]
Details of each component will be described below. An input video signal 11 is input to the densification unit 1. The input video signal 11 may be a video luminance signal or a video color difference signal, but is assumed to be a video luminance signal in this embodiment. The high density unit 1 applies a filtering process for increasing the number of horizontal pixels to the input video signal 11 and outputs a high density video signal 12. For example, the densification unit 1 converts an input video signal 11 that is an NTSC signal into a high-density video signal 12 that is a high-vision signal. In this way, by increasing the sampling frequency of the input video signal 11 by the densification unit 1, the frequency band of the reproducible signal is increased without causing problems such as aliasing noise in the subsequent processing. But it can.
[0035]
The primary differential detection unit 2 obtains the primary differential signal 13 of the high-density video signal 12 using the following formula (1), and outputs the result to the noise removal unit 3.
D _i = P _{i + 1} -P _i-1 ... (1)
However, in the above formula (1), P _i And D _i Are the signal levels of the high-density video signal 12 and the primary differential signal 13 at the i-th pixel from the left of the screen, respectively.
[0036]
The noise removing unit 3 removes a noise component included in the primary differential signal 13 using a so-called frame noise reduction method, and outputs the primary differential signal 14 after noise removal to the correction pixel determining unit 6a. More specifically, the noise removing unit 3 accumulates the first-order differential signal 13 for a plurality of frames, takes out pixels at the same position on the screen from each frame, and performs a filtering process in the time direction. Thereby, noise intermittently superimposed on each pixel can be removed. In a video signal processing apparatus that does not include the noise removal unit 3, when noise is superimposed on the input video signal 11, noise is also superimposed on the primary differential signal 13, and the determination in the correction pixel determination unit 6a is affected. A larger noise component than the input video signal 11 is superimposed on the output video signal 15. The noise removing unit 3 has a function of preventing such a problem.
[0037]
In order to reduce the circuit amount for data accumulation, the noise removal unit 3 ignores the lower-order bits of the primary differential signal 13 and performs noise removal only on the higher-order bits. Also good. For example, when the data width of the high-density video signal 12 is 10 bits, the noise removal unit 3 may ignore the lower 2 bits and perform noise removal only on the upper 8 bits.
[0038]
The corrected pixel determination unit 6 a receives the first-order differential signal 14 after noise removal and the threshold value 31 stored in the correction pixel determination condition storage unit 5. Based on these inputs, the correction pixel determination unit 6a detects a peak pixel and a valley pixel included in the high-density video signal 12, and outputs a correction pixel determination signal 32 indicating the position thereof.
[0039]
In addition to the high-density video signal 12, the addition / subtraction unit 9 receives a correction pixel determination signal 32, a correction value 33 for addition, and a correction value 34 for subtraction. The addition / subtraction unit 9 adds the correction value 33 for addition to the pixel in which the correction pixel determination signal 32 indicates the peak pixel in the high-density video signal 12, and the correction pixel determination signal 32 starts from the pixel in which the correction pixel determination signal 32 indicates the valley bottom pixel. Then, the correction value 34 for subtraction is subtracted.
[0040]
FIG. 2 is a flowchart showing the operation of the correction pixel determining unit 6a. The corrected pixel determination unit 6a performs the process shown in FIG. 2 on each pixel of the primary differential signal 14 after noise removal, and determines whether each pixel is located at the peak or the bottom of the valley.
[0041]
As shown in FIG. 2, the correction pixel determination unit 6a first determines the signal level of the primary differential signal of the pixel to be determined as D _i , The signal level of the primary differential signal of the pixel to the left of the pixel to be judged is D _i-1 , The signal level of the primary differential signal of the pixel to the right of the pixel to be determined is D _{i + 1} The threshold value 31 stored in the correction pixel determination condition storage unit 5 is T, and the second threshold value used in step S101 is Δ (step S100).
[0042]
Next, the correction pixel determining unit 6a _i Is sufficiently close to the value 0. Specifically, the correction pixel determination unit 6a _i Absolute value (| D _i |) And the second threshold value Δ are compared. If the former is smaller than the latter, the process proceeds to step S102; otherwise, the process proceeds to step S111 (step S101). In the present embodiment, it is assumed that the second threshold value Δ is stored in the correction pixel determination unit 6a. Instead, the second threshold value Δ is stored in the correction pixel determination condition storage unit 5 together with the threshold value T. It is good to be.
[0043]
Next, the correction pixel determination unit 6a performs D through the processing from step S102 to step S109. _i-1 , D _i , D _{i + 1} Determine the magnitude relationship. More specifically, the correction pixel determination unit 6a performs D _i-1 To D _i Is obtained (step S102). If the obtained difference X is larger than the threshold value T, the process proceeds to step S104. Otherwise, the process proceeds to step S106 (step S103).
[0044]
In the case of Yes in step S103, the correction pixel determination unit 6a _i To D _{i + 1} Is obtained (step S104). If the obtained difference X is larger than the threshold value T, the process proceeds to step S110. Otherwise, the process proceeds to step S111 (step S105).
[0045]
In the case of No in step S103, the correction pixel determination unit 6a _i To D _i-1 Is obtained (step S106). If the obtained difference X is larger than the threshold value T, the process proceeds to step S108. Otherwise, the process proceeds to step S111 (step S107).
[0046]
In the case of Yes in step S107, the correction pixel determination unit 6a determines that D _{i + 1} To D _i Is obtained (step S108). If the obtained difference X is larger than the threshold value T, the process proceeds to step S112. Otherwise, the process proceeds to step S111 (step S109).
[0047]
Thereafter, the correction pixel determination unit 6a determines that the target pixel is “peak of mountain” in step S110, “bottom of valley” in step S112, and “other” in step S111, and ends the process for that pixel. To do.
[0048]
FIG. 3 is a diagram showing how the video signal is corrected by the video signal processing apparatus according to the present embodiment. In FIG. 3, P _i And D _i Are the signal levels of the high-density video signal 12 and the primary differential signal 13 at the i-th pixel from the left of the screen, respectively.
[0049]
As shown in FIG. 3A, when the video signal reaches a maximum at the i-th pixel, _i-1 -D _i ) And (D _i -D _{i + 1} ) Is a relatively large value, and D _i Becomes a value close to 0. Therefore, (D _i-1 -D _i ) And (D _i -D _{i + 1} ) Are both greater than the threshold value T, and D _i Is smaller than the second threshold value Δ, the i-th pixel is detected as a peak pixel, and a correction value 33 for addition (value A shown in FIG. 3A) is detected in this pixel. Is added.
[0050]
Further, as shown in FIG. 3B, when the video signal is minimal at the i-th pixel, (D _i -D _i-1 ) And (D _{i + 1} -D _i ) Is a relatively large value, and D _i Becomes a value close to 0. Therefore, (D _i -D _i-1 ) And (D _{i + 1} -D _i ) Are both greater than the threshold value T, and D _i Is smaller than the second threshold value Δ, the i-th pixel is detected as a valley pixel, and a subtraction correction value 34 (value B shown in FIG. 3B) is detected from this pixel. Subtracted.
[0051]
In this way, by detecting the peak pixel and valley bottom pixel from the video signal and correcting the peak pixel higher and lower valley pixel lower, the change part of the video signal is emphasized and the sharpness of the video signal is increased. Can do.
[0052]
On the other hand, as shown in FIG. 3C, when the video signal changes from an increase to a constant in the pixel Pi, (D _i-1 -D _i ) Is a relatively large value, but (D _{i + 1} -D _i ) Is a value close to 0. Therefore, the correction pixel determination unit 6a determines that such a point is neither a peak pixel nor a valley pixel. Therefore, correction processing is not performed on such pixels.
[0053]
FIG. 4 is a diagram illustrating how correction pixels are detected by the video signal processing apparatus according to the present embodiment. For example, when the signal level of the horizontal component of the video signal changes as shown in FIG. 4, the video signal processing apparatus according to the present embodiment has a peak pixel indicated by a white circle and a valley bottom pixel indicated by a black circle. Are detected, and a predetermined addition / subtraction process is performed on these four pixels. On the other hand, this apparatus determines that all the pixels other than the pixels shown in FIG. 4 are “others”, and does not perform addition / subtraction processing on these pixels. In particular, this apparatus has a feature that correction processing is not performed on pixels whose signal level is constant on one side, such as a portion denoted by reference symbol P. Further, this apparatus has a feature that only one pixel is corrected for a portion where the signal level changes.
[0054]
In the flowchart shown in FIG. 2, the difference X of the primary differential signal is obtained in four steps (S102, S104, S106, and S108). _i Is sufficiently close to the value 0, D at each step _i May be regarded as a value of 0 to simplify the arithmetic processing. When this method is adopted, D _i-1 And (-D _{i + 1} ) Are both greater than the threshold value T, and D _i Is smaller than the second threshold value Δ, the i-th pixel is detected as a peak pixel. Also, (-D _i-1 ) And D _{i + 1} Are larger than the threshold value T, and D _i Is smaller than the second threshold value Δ, the i-th pixel is detected as a valley bottom pixel.
[0055]
Hereinafter, a method for setting the threshold value 31 and the two correction values 33 and 34 will be described. The threshold value 31 is stored in the corrected pixel determination condition storage unit 5. The correction pixel determination condition control unit 4 controls the threshold value 31 based on the first control signal 21. That is, the threshold value 31 is controlled based on the first control signal 21.
[0056]
As the first control signal 21, the characteristics of the input video signal 11 are given. For example, in the first control signal 21, whether the input video signal 11 is a component signal or a composite signal, or whether the input video signal 11 is in a 4: 2: 2 format or a 4: 4: 4 format. Indicates.
[0057]
The correction pixel determination condition control unit 4 controls the threshold value 31 based on the first control signal 21 as described above. As a result, the range in which the effect of the image quality correction reaches can be adjusted according to the characteristics of the input video signal 11 to perform the optimum image quality correction.
[0058]
On the other hand, the correction value 33 for addition and the correction value 34 for subtraction are stored in the addition / subtraction value storage unit 8. The addition / subtraction value controller 7 controls these two correction values 33 and 34 based on the second control signal 22. That is, the two correction values 33 and 34 are controlled based on the second control signal 22.
[0059]
As the second control signal 22, first, an image quality adjustment signal from a viewer is given. For example, when the video signal processing apparatus is configured to adjust sharpness (sharpness), an image quality adjustment signal from the viewer is input to the second control signal 22.
[0060]
As the second control signal 22, secondly, the amount of motion calculated from the input video signal 11 is given. When the same correction value is added to or subtracted from a still image and a moving image, the human eye recognizes that the correction for the moving image is less effective. Therefore, when the video signal is a moving image, it is possible to balance the correction effect between the still image and the moving image by increasing the two correction values 33 and 34.
[0061]
The addition / subtraction value control unit 7 controls the correction value 33 for addition and the correction value 34 for subtraction based on the second control signal 22. Thereby, the strength of the image quality correction can be adjusted according to the viewer's preference and the amount of motion calculated from the input video signal 11, and the optimum image quality correction can be performed.
[0062]
Note that the signals given as the first and second control signals 21 and 22 are not limited to those described above, and the threshold value 31 and the two correction values 33 are based on arbitrary control information that affects the image quality. , 34 can be controlled.
[0063]
The reason why the correction value 33 for addition and the correction value 34 for subtraction are stored separately is as follows. When the same correction value is added to or subtracted from the top pixel and the bottom pixel, the human eye recognizes that the correction for the top pixel is less effective. Accordingly, the correction value for the summit pixel (that is, the correction value for addition 33) and the correction value for the valley bottom pixel (that is, the correction value for subtraction 34) are stored separately, and the former is made larger than the latter, so that the summit The correction effect can be balanced between the pixel and the valley bottom pixel.
[0064]
As described above, according to the video signal processing device according to the present embodiment, the peak pixel and the valley pixel are detected from the video signal, and the peak pixel is corrected higher and the valley pixel is corrected lower. It is possible to provide a sharp video signal that emphasizes the above. In particular, as with the LTI technology, the video signal that should change smoothly changes in a staircase shape, and when the video signal is displayed, an unnatural impression is given to the viewer as if all things were composed of flat surfaces. Without giving it, it is possible to provide a high-quality video signal that is sharper than the LTI technology.
[0065]
Also, by increasing the sampling frequency of the video signal, the frequency band of the reproducible signal can be increased without causing problems such as aliasing in subsequent processing. But it can. Further, by removing noise from the video signal, it is possible to prevent the influence of noise superimposed on the video signal from reaching the corrected video signal. Therefore, it is possible to stably provide a high-quality video signal with enhanced sharpness by performing a stable operation even on a video signal having a lot of noise components. In addition, by controlling the threshold value and the correction value based on the control signal, the range of image quality correction effect and the strength of the image quality correction can be freely set, and the characteristics of the video signal, the viewer's preference and the video signal It is possible to provide a high-quality video signal with increased sharpness according to the amount of motion calculated from the above.
[0066]
(Second Embodiment)
FIG. 5 is a block diagram showing a configuration of a video signal processing apparatus according to the second embodiment of the present invention. The present embodiment is characterized in that a pixel to be corrected is determined based on an input video signal instead of a primary differential signal. Among the constituent elements of the present embodiment, the same constituent elements as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
[0067]
As in the first embodiment, the noise removal unit 3 performs noise removal using a frame noise reduction method. However, since the high-density video signal 12 is input to the noise removal unit 3, the high-density video signal 16 after noise removal is output from the noise removal unit 3.
[0068]
The corrected pixel determination unit 6b receives the high-density video signal 16 and the threshold value 31 after noise removal. Based on these inputs, the correction pixel determination unit 6b detects a peak pixel and a valley pixel included in the high-density video signal 12, and outputs a correction pixel determination signal 32 indicating the position thereof.
[0069]
FIG. 6 is a flowchart showing the operation of the correction pixel determination unit 6b. The correction pixel determination unit 6b performs the process shown in FIG. 6 for each pixel of the high-density video signal 16 after noise removal, and determines whether each pixel is located at the top of the mountain or the bottom of the valley.
[0070]
As shown in FIG. 6, the correction pixel determination unit 6b first sets the signal level of the high-density video signal of the pixel to be determined to P _i , The signal level of the high-density video signal of the pixel to the left of the pixel to be judged is P _i-1 , The signal level of the high-density video signal of the pixel to the right of the pixel to be judged is P _{i + 1} The threshold value 31 stored in the corrected pixel determination condition storage unit 5 is set to T (step S201).
[0071]
Next, the correction pixel determination unit 6b performs P through the processes from Step S202 to Step S209. _i-1 , P _i , P _{i + 1} Determine the magnitude relationship. More specifically, the correction pixel determination unit 6b _i To P _i-1 Is obtained (step S202). If the obtained difference X is greater than the threshold value T, the process proceeds to step S204. Otherwise, the process proceeds to step S206 (step S203).
[0072]
In the case of Yes in step S203, the correction pixel determination unit 6b _i To P _{i + 1} Is obtained (step S204). If the obtained difference X is larger than the threshold value T, the process proceeds to step S210. Otherwise, the process proceeds to step S211 (step S205).
[0073]
In the case of No in step S203, the correction pixel determination unit 6b _i-1 To P _i Is obtained (step S206). If the obtained difference X is larger than the threshold value T, the process proceeds to step S208. Otherwise, the process proceeds to step S211 (step S207).
[0074]
In the case of Yes in step S207, the correction pixel determination unit 6b _{i + 1} To P _i Is obtained (step S208). If the obtained difference X is larger than the threshold value T, the process proceeds to step S212. Otherwise, the process proceeds to step S211 (step S209).
[0075]
Thereafter, the correction pixel determination unit 6b determines that the target pixel is “peak of mountain” in step S210, “bottom of valley” in step S212, and “other” in step S211, and ends the process for that pixel. To do.
[0076]
As described above, the correction pixel determination unit 6b according to the present embodiment can also detect the peak pixel and the valley pixel included in the high-density video signal 12. Therefore, the video signal processing device according to the present embodiment has the same effects as the video signal processing device according to the first embodiment.
[0077]
In the first and second embodiments described above, the addition / subtraction unit 9 adds or subtracts the correction value 33 for addition or the correction value 34 for subtraction as it is. Instead, the addition / subtraction unit 9 adjusts these two correction values 33 and 34 according to the signal level of the high-density video signal 12 and adds / subtracts the adjusted correction value to / from the high-density video signal 12. Also good. For example, the addition / subtraction unit 9 increases the two correction values 33 and 34 when the signal level of the high-density video signal 12 is high, and decreases the two correction values 33 and 34 when the signal level of the high-density video signal 12 is low. The corrected correction value may be added to or subtracted from the high-density video signal 12.
[0078]
Alternatively, the signal level of the high-density video signal 12 is the maximum value P _max When the correction value 33 for addition is added, the sum is the maximum value P _max When the value exceeds the sum, the addition / subtraction unit 9 determines that the sum is the maximum value P. _max It is also possible to add the adjusted correction value 33 after adjustment to the high-density video signal 12 after the adjustment correction value 33 is adjusted to be small so as not to exceed. The signal level of the high-density video signal 12 is the minimum value P _min The same applies to cases close to. In this way, by automatically adjusting the correction value according to the signal level of the high-density video signal 12, the strength of the effect of the image quality correction is adjusted with higher accuracy, and the image quality is further enhanced with sharpness. A video signal can be provided.
[0079]
Further, in the flowcharts shown in FIGS. 2 and 6, the common threshold value T is used in the four determination steps, but different threshold values may be used in the four determination steps. Alternatively, a common first threshold value may be used in the two determination steps for determining the peak pixel, and a common second threshold value may be used in the two determination steps for determining the valley pixel. Good.
[0080]
In the above-described embodiment, the high density unit 1 and the noise removing unit 3 are provided in order to enhance the image quality improvement effect. However, these components may not be provided. Further, although the video luminance signal is corrected, the same usage may be applied to the video color difference signal. In this case, the threshold value 31, the correction value 33 for addition, and the correction value 34 for subtraction are images. Color difference Needless to say, a value suitable for the signal should be used.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a video signal processing apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing an operation of a correction pixel determining unit of the video signal processing apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating how a video signal is corrected by the video signal processing apparatus according to the first embodiment of the present invention;
FIG. 4 is a diagram illustrating a state in which pixels to be corrected are detected by the video signal processing apparatus according to the first embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration of a video signal processing apparatus according to a second embodiment of the present invention.
FIG. 6 is a flowchart showing an operation of a correction pixel determination unit of the video signal processing apparatus according to the second embodiment of the present invention.
FIG. 7 is a diagram illustrating a range of pixels to be corrected in a conventional edge enhancement technique.
[Explanation of symbols]
1 ... Densification part
2 ... Primary differential detector
3. Noise removal unit
4. Correction pixel determination condition control unit
5. Correction pixel determination condition storage unit
6a, 6b ... correction pixel determination unit
7: Addition / subtraction value controller
8. Addition / subtraction value storage unit
9 ... Addition / subtraction unit
11 ... Input video signal
12 ... High-density video signal
13 ... Primary differential signal
14: First derivative signal after noise removal
15 ... Output video signal
16: High-density video signal after noise removal
21, 22 ... Control signal
31 ... Threshold
32 ... Correction pixel determination signal
33 ... Correction value for addition
34 ... Correction value for subtraction

Claims (13)

A video signal processing apparatus that performs correction processing on a changed portion of a video signal,
Correction value holding means for holding a correction value for the video signal;
Condition holding means for holding a condition for determining a pixel to be corrected in the video signal;
According to the condition held in the condition holding means, the portion where the horizontal component of the video signal changes in a mountain shape and a valley shape is specified, and the pixels located at the peak and the bottom of the mountain are the peak pixel and the valley bottom, respectively. Correction pixel detection means for detecting as pixels;
An image signal processing apparatus comprising: an addition / subtraction unit that adds a correction value held in the correction value holding unit to the peak pixel and subtracts the correction value from the valley pixel. The correction pixel detection means includes
Primary differential detection means for obtaining a primary differential signal of the video signal;
2. The video signal processing according to claim 1, further comprising: a first-order differential processing unit that detects the peak pixel and the bottom pixel based on the first-order differential signal obtained by the first-order differential detection unit. apparatus. The correction pixel detection means includes
Noise removing means for removing a noise component from the primary differential signal obtained by the primary differential detection means;
The video signal processing apparatus according to claim 2, wherein the primary differential processing unit detects the peak pixel and the valley bottom pixel based on a primary differential signal that has passed through the noise removing unit. The first order differentiation processing means, in the pixel of the i-th from the left of the screen (i is an integer), the signal level of the primary differential signal which has been determined by the first derivative detection means when the D _i, (D _{i −1} −D _i ) and (D _i −D _{i + 1} ) are both larger than the threshold value held in the condition holding means and the absolute value of D _i is smaller than a predetermined value, The i-th pixel is detected as the peak pixel, and (D _i −D _i−1 ) and (D _{i + 1} −D _i ) are both larger than the threshold value, and the absolute value of D _i is The video signal processing apparatus according to claim 2, wherein, when smaller than a predetermined value, the i-th pixel is detected as the valley pixel. The corrected pixel detecting means, in the pixel of the i-th from the left of the screen (i is an integer), the signal level of the video signal is taken as _{P i, (P i -P i} -1) and (P _i - If both P _{i + 1} ) are larger than the threshold value held in the condition holding means, the i-th pixel is detected as the peak pixel, and (P _i − ₁ −P _i ) and (P _2. The video signal processing apparatus according to claim 1, wherein when both _{i + 1−} P _i ) are larger than the threshold value, the i-th pixel is detected as the valley pixel. The video signal processing apparatus according to claim 1, further comprising condition control means for controlling a condition held in the condition holding means based on an input control signal. The correction value holding means holds the correction value for addition and the correction value for subtraction separately,
2. The video signal processing apparatus according to claim 1, wherein the addition / subtraction unit adds the correction value for addition to the peak pixel and subtracts the correction value for subtraction from the valley pixel. . The addition / subtraction unit adjusts a correction value held in the correction value holding unit according to a level of the video signal, and adds / subtracts the adjusted correction value to / from the video signal. The video signal processing apparatus according to 1. The video signal processing apparatus according to claim 1, further comprising a correction value control unit that controls a correction value held in the correction value holding unit based on an input control signal. 10. The video signal processing apparatus according to claim 9, wherein the correction value control unit controls a correction value held in the correction value holding unit based on a motion amount calculated from the video signal. Further comprising a densification means for increasing the number of horizontal pixels of the video signal,
The video signal processing apparatus according to claim 1, wherein the correction pixel detection unit and the addition / subtraction unit perform processing on the video signal that has passed through the densification unit. A video signal processing method for performing correction processing on a changing portion of a video signal,
A correction value holding step for holding a correction value for the video signal;
A condition holding step for holding a condition for detecting a pixel to be corrected in the video signal;
In accordance with the conditions held in the condition holding step, the portion where the horizontal component of the video signal changes in a mountain shape and a valley shape is specified, and the pixels located at the top and bottom of the mountain are the top pixel and the bottom pixel, respectively. Correction pixel detection step to detect as,
A video signal processing method comprising: an addition / subtraction step of adding the correction value held in the correction value holding step to the peak pixel and subtracting the correction value from the valley bottom pixel for the video signal. A computer-readable recording medium recording a program for causing a computer to execute a video signal processing method for performing correction processing on a changed portion of a video signal,
A correction value holding step for holding a correction value for the video signal;
A condition holding step for holding a condition for detecting a pixel to be corrected in the video signal;
In accordance with the conditions held in the condition holding step, the portion where the horizontal component of the video signal changes in a mountain shape and a valley shape is specified, and the pixels located at the top and bottom of the mountain are the top pixel and the bottom pixel, respectively. Correction pixel detection step to detect as,
An addition / subtraction step for adding the correction value held in the correction value holding step to the peak pixel and subtracting the correction value from the valley pixel for the video signal is added to the computer. A computer-readable recording medium on which a program for execution is recorded.

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