JPH06152938A - Video interpolation device - Google Patents

Abstract

PURPOSE:To magnify pictures without losing much of the high frequency components of source pictures by comparing the absolute value of the difference of video signals between two picture elements with a certain threshold value and switching an interpolation coefficient to be inputted to a multiplier based on a result. CONSTITUTION:The difference of the video signals mutually in front and behind inside a scanning line is obtained by an adder 8. Since a coefficient to be inputted to the multiplier 10 is switched by the size at the difference, the difference of the input/output of a delay device 2 is calculated by the adder 9, is passed through an absolute value conversion circuit 12 so as to obtain the absolute value and is inputted to a coefficient switching circuit 13. Further, a straight line interpolation coefficient 14 and a polygonal interpolation coefficient 15 are inputted and the sizes of a reference threshold value 16 and signals passed through the absolute value conversion circuit 12 is compared and thus, the suitable coefficient is selected. In order not to lose much of the high frequency components of the source pictures, the straight line interpolation coefficient is used when the absolute value of the difference of the video signal is equal to or less than the reference threshold value 16 and the polygonal interpolation coefficient is used when the absolute value of the difference of the video signal is larger than the reference threshold value 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is suitable for application to an image enlarging device for enlarging an image to a specified magnification. As a result, it can be applied to products that require enlargement of moving images and still images such as multi-vision systems and copiers.

[0002]

2. Description of the Related Art Generally, linear interpolation is well known as an image interpolation technique for an image enlarging device. The image magnifying device here does not magnify the image optically, but magnifies the image by digital signal processing. Therefore, a memory such as a frame memory or a field memory is indispensable as the image storage means. Further, with the video interpolating device used in the present invention, it is necessary to interpolate data other than the original image when enlarging the image by the image enlarging device. However, such interpolating data other than the original image is obtained. Shall mean.

The above-mentioned linear interpolation requires that the same pixel of the original image must be read from the memory 25 times when a certain image is magnified 5 times vertically and horizontally, which results in a mosaic image. ,Not good.

Therefore, considering the horizontal direction of a specific scanning line, the signal enlarged by the pixel of the original image being output five times in succession as shown in FIG. The linear interpolation is to interpolate automatically. This can be confirmed by the fact that the mosaic-like screen becomes a smooth screen due to enlargement on the CRT screen.

However, in the linear interpolation, the high frequency component of the original image is lost, so that there is a problem that the image becomes unclear, and in order to improve it, there is also a method called polygonal line interpolation for performing the interpolation as shown by 41 in FIG. .

FIG. 6 shows an example of a linear interpolation circuit.
This is a circuit for performing horizontal interpolation shown in FIG.
7 is also an example of a linear interpolation circuit, but in order to eliminate the multiplier used in FIG. 6, the multiplier is replaced with a ROM.

[0007]

However, the simple linear interpolation circuit has a problem in that the high frequency components of the input image are lost and the image becomes a little sharply focused image with unclear image boundaries.

In view of the above-described drawbacks, the present invention, when performing data interpolation of an input image, compares the absolute value of the difference value of video signals between two pixels to be interpolated with a certain threshold value to obtain a straight line. The present invention intends to realize a video interpolating device in which a high-frequency component having a clear boundary is not significantly attenuated by selecting either interpolation or other interpolation.

Further, if the video interpolation circuit performs the luminance signal and the color difference signal, there is a problem that the hardware scale becomes large and the cost becomes high. This is a very costly problem because a multi-vision system requires a large number of image enlarging devices.

[0010]

A first video interpolating device of the present invention, when performing data interpolation of an input image, performs two types of interpolation according to an absolute value of a difference value of video signals between two pixels to be interpolated. By switching to either one of the coefficients, the image is enlarged without losing the high frequency components of the original image.

In the second video interpolating apparatus of the present invention, when the data of the input image is interpolated, the high frequency component of the original image is not lost so much in advance by the absolute value of the difference value of the video signals between the two pixels to be interpolated. The present invention intends to realize an image interpolating device in which a suitable ROM for a multiplier is prepared in advance so that a high-frequency component having a clear boundary is not attenuated so much.

[0012] This uses a ROM as a look-up table memory instead of a multiplier.

The third video interpolating device of the present invention interpolates only the luminance signal having a particularly large visual effect among the luminance signal and the color difference signal of the video signal, and does not interpolate the color difference signal. Is intended to be small and inexpensive.

[0014]

According to the first video interpolating device of the present invention, when the absolute value of the difference value of the video signals between two pixels to be interpolated is less than a certain threshold value, linear interpolation is performed, and the difference value is the threshold value. When it is larger, the image can be enlarged by performing polygonal line interpolation or non-linear interpolation without losing the high frequency component of the original image.

According to the second video interpolating device of the present invention, instead of using the above-mentioned multiplier, by using an appropriate multiplier ROM which does not lose high frequency components of the original image in advance, the original image of the original image can be obtained. The image can be enlarged without losing the high frequency component, and the hardware scale can be reduced and the cost can be reduced.

According to the third video interpolating device of the present invention, only the luminance signal is interpolated and the color difference signal is not interpolated, so that the hardware scale can be reduced and the cost can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a video interpolating device of the present invention will be described below with reference to FIG.
~ It demonstrates by FIG. First, FIG. 4 shows a block diagram of an image enlarging device including the image interpolating device of the present invention. In this way, vertical interpolation and horizontal interpolation are performed on the luminance signal and the color difference signal of the 8-bit digital signal output from the memory (the order may be horizontal interpolation first and then vertical interpolation depending on the memory configuration). ), D / A conversion, and encoding.

All of the first to third embodiments described here consider the horizontal interpolation on the screen, but the vertical interpolation can be processed in the same way.

(Embodiment 1) FIG. 1 is a diagram showing an interpolation circuit of a video interpolating apparatus according to a first embodiment of the present invention. First,
The input of digital data passes through the delay devices 1 and 2. However, since the digital data is continuous data several times for each magnification as described above, it is assumed that the digital data is latched with a different clock for each magnification and the input data itself to the delay device 1 matches the original original image data. .

The adder 8 takes the difference between the video signals before and after in one scanning line. Since the coefficient input to the multiplier 10 is switched according to the magnitude of this difference, the difference between the input and output of the delay device 2 is calculated by the adder 9, and the absolute value thereof is passed to the absolute value conversion circuit 12 to obtain the coefficient. It is input to the switching circuit 13. The linear interpolation coefficient 14 and the polygonal line interpolation coefficient 15 are input to the coefficient switching circuit 13, and the magnitude of the reference threshold value 16 and the signal passed through the absolute value conversion circuit 12 are compared to determine which of the above two types of coefficients is suitable. It is to select the coefficient.

From the viewpoint that the high frequency component of the original image is not lost so much, when the absolute value of the difference between the video signals is equal to or smaller than the reference threshold value 16, a linear interpolation coefficient is used, and the absolute value of the difference between the video signals is equal to the reference threshold value. If it is larger, the polygonal line interpolation coefficient is used.

The clocks of the delay units 5, 6, 7 and the signal processing after the delay units 5, 6, 7 are all performed by the delay units 1, 2, 3,
Use a system clock different from 4. This is because interpolation processing cannot be performed unless two types of clocks are used. The signal processing of FIG.

[0023]

[Equation 1]

It means that is executed by hardware. Here, X (n) and X (n + 1) are the magnitudes of the luminance signals of the original image shown in FIG. Further, α is a coefficient by which the difference value set for each magnification is multiplied. χ (m) is the interpolated output data, and the number of calculations changes depending on the magnification, so m is added to the subscript.

In order to realize an actual image enlarging device,
It is necessary to perform the above signal processing twice in the vertical direction and the horizontal direction. However, the configuration of FIG. 1 shows the interpolation in the horizontal direction. When performing the interpolation in the vertical direction, the delay device 1 is removed, and the luminance signal or the color difference signal of two pixels to be vertically interpolated is simultaneously added to the adder 8. Good to enter.

(Embodiment 2) FIG. 2 shows an interpolation circuit of a video interpolation apparatus according to a second embodiment of the present invention. The difference from FIG. 1 is that the multiplier is eliminated and a ROM is used instead. As a result, it can be seen that the hardware scale can be considerably reduced as compared with FIG.

The delay unit 17 is a sampling and latching flip-flop for obtaining pixel data of an original image from continuous data, and a clock input is obtained by appropriately dividing the system clock for each magnification. The clocks of the delay devices 18 and 19 and the circuits after the delay devices 18 and 19 are all operated by the system clock. This is because, in principle, data interpolation cannot be performed unless two clocks are used.

The ROM 23 determines in advance which of linear interpolation and polygonal line interpolation is to be selected according to the magnitude of the difference, and

[0029]

[Equation 2]

The data of (3) is written. As a result, the multiplier and coefficient switching circuit 13 and the circuits associated therewith which are necessary in FIG. 1 can be omitted. However, only a new addressing circuit 22 for the ROM is needed. As described above, it can be understood that the same signal processing as in FIG. 1 can be realized by the configuration of FIG. 2 by simplifying the hardware.

(Embodiment 3) FIG. 3 is a block diagram of an interpolation circuit of a video interpolation apparatus according to a third embodiment of the present invention.
The vertical interpolation 24 and the horizontal interpolation 25 are the interpolation circuits configured by the circuits described in the first and second embodiments. Figure 3
As shown in, the vertical interpolation and the horizontal interpolation are performed only on the luminance signal, and the interpolation processing is not performed on the color difference signal. As a result, not only the hardware can be simplified, but also the cost can be significantly reduced.

[0032]

The effects of each embodiment will be described. (1) According to the first video interpolating device of the present invention, the absolute value of the difference between the video signals between two pixels to be interpolated exceeds a certain threshold value. It is possible to enlarge the image without losing high frequency components of the original image by switching between two types of interpolation coefficients to be input to the multiplier based on the comparison result, which is larger or smaller. Become.

(2) According to the second video interpolating device of the present invention, the multiplier ROM is used instead of the multiplier described above, so that the image is enlarged without losing the high frequency component of the original image. In addition, the hardware scale can be reduced and the cost can be reduced.

(3) According to the third aspect of the present invention, by interpolating only the luminance signal having a large visual effect and not interpolating the color difference signal, the hardware scale can be reduced and the cost can be reduced. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an interpolation circuit of a video interpolation device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an interpolation circuit of a video interpolation device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an interpolation circuit of a video interpolation device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a video enlarging device including the video interpolating device of the present invention.

FIG. 5 is a diagram for explaining a linear interpolation method.

FIG. 6 is a diagram showing a linear interpolation circuit.

FIG. 7 is a diagram showing a linear interpolation circuit using a multiplier ROM.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Delay device 8 Adder 12 Absolute value conversion circuit 13 Coefficient switching circuit 14 Coefficient for linear interpolation 15 Coefficient for polygonal line interpolation 16 Reference threshold value 22 ROM addressing circuit 23 ROM 24 Vertical interpolation circuit 25 Horizontal interpolation circuit 26 D / A converter 29 Encoder 40 Linear interpolation method 41 Polygonal line interpolation method 46 Linear interpolation coefficient 49 Linear interpolation conversion ROM

Claims (5)

[Claims] 1. A video enlarging device for enlarging an original image to a certain magnification, wherein two lines before and after the original image are scanned within one scanning line.
When performing horizontal interpolation for interpolating between pixels and vertical interpolation for interpolating between two adjacent scanning lines of the original image, the magnitude of the absolute value of the difference between the luminance signal and the color difference signal between the two pixels to be interpolated is , When a value is larger than a certain threshold, interpolation is performed by inputting an interpolation coefficient having a high-pass characteristic that allows a high-frequency component to pass, and when the magnitude of the absolute value of the difference is below a certain threshold, a low-frequency component A video interpolating device, characterized in that interpolation is performed by inputting an interpolation coefficient having a low-pass characteristic for passing the signal to a multiplier. 2. An image enlarging device for enlarging an original image to a certain magnification, wherein two lines before and after one scanning line of the original image are arranged.
When performing horizontal interpolation for interpolating between pixels and vertical interpolation for interpolating between two adjacent scanning lines of the original image, there is an absolute value of a difference between a luminance signal and a color difference signal between two pixels to be interpolated. When it is larger than the threshold value, interpolation is performed by inputting an interpolation coefficient having a non-linear characteristic to the multiplier, and when the absolute value of the difference is less than or equal to a threshold value, an interpolation coefficient having a linear characteristic is input to the multiplier. A video interpolating device characterized by performing interpolation. 3. An image enlarging device for enlarging an original image to a certain magnification, wherein two lines before and after one scanning line of the original image are used.
When performing horizontal interpolation for interpolating between pixels and vertical interpolation for interpolating between two adjacent scanning lines of the original image, there is an absolute value of a difference between a luminance signal and a color difference signal between two pixels to be interpolated. When it is larger than the threshold value, interpolation is performed by inputting the polygonal line interpolation coefficient to the multiplier, and when the absolute value of the difference is less than or equal to a threshold value, interpolation is performed by inputting the linear interpolation coefficient to the multiplier. Video interpolator 4. A video enlarging device for enlarging an original image to a certain magnification, depending on the magnitude of the difference between the luminance signal and the color difference signal between two pixels for which the original image is to be interpolated, low pass, high pass, linear, non-linear, or Linear interpolation,
A video interpolating device, characterized in that a multiplier ROM taking into account polygonal line interpolation is created, and interpolation is performed using the ROM. 5. In a video enlarging device for enlarging an original image to a certain magnification, when interpolating between two pixels for which interpolation of the original image is desired, only the luminance signal is interpolated and the color difference signal is interpolated. A video interpolating device characterized in that the color difference signal of the original image is used without performing the above processing.