JPH06315159A - Inter-field interpolation device - Google Patents

Abstract

PURPOSE:To provide an inter-field interpolation device improving unnaturalness in the rapid color boundary line in a vertical direction, regarding an inter-field interpolation device interpolating in the calculation between two fields, where line sequential color difference signals for which a band compression is performed by a field offset subsampling, are continuous. CONSTITUTION:The level difference of upper and lower sampled points where the color difference signals which are the same kind as the non-sampled point within a frame are adjacent is determined by a difference detection circuit 17 and a comparison circuit 18 and an optinum interpolation signal by the level difference is selected by a switching device 22. Thus, even when a rapid level change in a vertical direction is generated, the leakage in the vertical direction is reduced and the damage to an image can be suppressed to a minimum also after a line sequential decoding is performed, in paticular.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-field interpolation device for interpolating a line-sequential color difference signal band-compressed by field offset sub-sampling by calculation between two consecutive fields.

[0002]

2. Description of the Related Art In the MUSE system, color difference signals are transmitted in a line-sequential manner. That is, R for each scan line
The -Y and BY signals alternate. In the still image processing of the color difference signal in the MUSE decoder, the original color difference signal is restored by performing inter-frame interpolation, inter-field interpolation, line-sequential decoding and the like on the input signal.

An example of a conventional inter-field interpolation device for color difference signals is the device shown in FIG. In FIG. 7, 101 is an input terminal for inputting a signal in which two types of different color difference signals are line-sequentially subjected to offset sub-sampling between fields, 102 is a field memory for delaying the input signal by one field, and 103 is input to the input terminal 101. A switching signal is switched between the input signal and the output signal of the field memory 102 depending on the sampling point and non-sampling point of the input terminal, and 104 is an output terminal for outputting the color difference signal interpolated between fields.

The operation of the conventional inter-field interpolation device having the above-mentioned structure will be described below. When the input signal input to the input terminal 101 is a sampling point, the switch 103 outputs the sampling point of the input signal as it is, and when it is a non-sampling point, it is output from the field memory 102.
Output the signal before the field. Since the input signal has an inter-field offset, when the input signal is a non-sampling point, the signal one field before is a sampling point.

FIG. 8 shows two scan lines and one pixel arrangement for one frame.
It is shown dimensionally, the dotted line is the odd field scanning line, the solid line is the even field scanning line, the solid line circle is the pixel of the sample point, and the dotted line circle is the non-sample point and is interpolated. It represents a power pixel. That is, as shown in FIG. 8, in the conventional inter-field interpolation, interpolation is performed by directly fitting the sample points a and b of the previous field to the non-sample points X and Y. Hereinafter, the above-mentioned inter-field interpolation method is referred to as a simple inset type.

As another example of the inter-field interpolation device, FIG.
The structure shown in FIG. In FIG.
111 is an input terminal for inputting a signal in which two types of different color difference signals are line-sequentially subjected to offset sub-sampling between fields, 112 is a field memory for delaying the input signal by one field, and 113, 114 and 115 are two lines of the input signal. A line memory for delaying, a switcher 117, 1 for switching an input signal of the line memory 113 and an output signal of the line memory 114 by field alternation.
18 is a coefficient unit with a gain of 1/4 and 3/4,
Reference numeral 119 is an adder, 120 is a switcher for switching the output signal of the line memory 115 and the output signal of the adder 119 between sampling points and non-sampling points of the signal output from the line memory 115, and 121 is an inter-field interpolation. It is an output terminal that outputs the generated color difference signal.

The operation of the inter-field interpolation device having the above structure will be described below. Input terminal 111
The input signal input to the signal is divided into a field delayed by 1 field in the field memory 112 and a signal delayed by 2 lines in the line memory 115. Line memory 11
If the output signal of 5 is a sampling point, the signal of the sampling point of the output signal of the line memory 115 is output as it is by the switch 120, and if it is a non-sampling point, the field memory 112 is output.
The non-sample points are interpolated by outputting the subsequent calculation results of the sample points in the previous field.

The signal output from the field memory 112 is two line memories 113 and 114 connected in cascade.
Are input to each of the lines and delayed by two lines. Switch 1
Reference numeral 16 outputs the output signal of the line memory 114 when the output signal of the line memory 115 is an odd field, and outputs the input signal of the line memory 113 when the output signal is an even field. Of the signals output from the line memory 115, X is a non-sample point, A is a sample point output from the line memory 113, and B is a sample point output from the switch 116. The pixel arrangement of B is as shown in FIG.

FIG. 10 is a two-dimensional view showing a scanning line and a pixel arrangement of one frame, where a dotted line shows an odd field scanning line and a solid line shows an even field scanning line.
(A) shows the case where the non-sample points are in the even field, and (b) shows the case where the non-sample points are in the odd field. In either case, A and B are the upper and lower adjacent sample points of the color difference signal of the same type as the non-sample point X. Further, B is located 3 lines away from the non-sample point X. The signals A and B are multiplied by 3/4 and 1/4 in the coefficient multipliers 118 and 117, respectively, added by the adder 119, and become a signal for interpolating the non-sampling point X.

When the output signal of the line memory 115 is a sampling point, the switching unit 120 outputs the sampling point as it is, and when it is a non-sampling point, the output signal of the adder 119 is selected to output the output signal from the output terminal 121. Obtain the interpolated color difference signal. That is, the non-sampling point X is interpolated with a signal of 3 / 4A + 1 / 4B using the upper and lower color difference signals A and B of the same type that are adjacent in the frame and considering the spatial center of gravity of the pixel. Hereinafter, the above interfield interpolation method is referred to as a center-of-gravity consideration type.

[0011]

However, in the conventional configuration such as the above-mentioned simple insertion type inter-field interpolation apparatus, since the pixels of the adjacent fields are simply inserted, the vertical direction of the interpolation signal is increased. The borders of are jagged and unnatural.

On the other hand, in the inter-field interpolation of the center of gravity consideration,
Interpolation is performed using upper and lower sample points of the previous field that are adjacent to non-sample points, resulting in an image that is smoother in the vertical direction than the simple interpolation type. However, since the color difference signals are line-sequential, as shown in FIG. 10, one of the upper and lower sample points of the same type of color difference signal adjacent to the non-sample point in the previous field is 3 in the frame. The line is far away. Therefore, when the level changes abruptly in the vertical direction, the calculation is performed using pixels that are separated by three lines from the non-sample point, so that extra information is leaked.

11 and 12 show an example in which the level changes from the maximum to the minimum in the vertical direction. FIGS. 11 and 12 are two-dimensional representations of scanning lines and pixel arrangements for one frame. Dotted lines are odd field scanning lines, solid lines are even field scanning lines, and (a) is an input signal. (B) shows the output of a simple insertion type inter-field interpolation device, and (c) shows the output signal of the center-of-gravity consideration type inter-field interpolation device.
Solid line circles are pixels at sample points, and dot line circles are pixels at interpolated non-sample points, and the pixel level is indicated by the darkness, that is, the narrow hatching interval. In both cases of FIG. 11 and FIG. 12, the center-of-gravity consideration type inter-field interpolation has a larger number of scanning lines affected by the inter-field interpolation than the simple insertion type inter-field interpolation. In addition, in the line-sequential decoding process, since scanning lines are created using these scanning lines, the range of the number of scanning lines affected by inter-field interpolation further expands vertically, and a sharp color boundary in the vertical direction is generated. The image is very unsightly. As described above, the conventional inter-field interpolation process produces an unnatural image in the vertical direction.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an inter-field interpolating device that improves the unnaturalness of abrupt color boundaries in the vertical direction.

[0015]

According to a first aspect of the invention, a color difference signal in which two types of different color difference signals are inter-field offset sub-sampled and line-sequentialized is input, and a non-sample point to be interpolated in a frame. Level difference determination means for determining the level difference between the scanning lines located above and below, and an interpolation signal for mixing the sampling points above and below the color difference signal of the same type as the non-sampling points in the frame from the input signal at an arbitrary ratio. When the result of the output means and the level determination means is smaller than the threshold value, the sampling point of the other field is output as the interpolation signal of the non-sampling point, and when it is larger, the output signal of the interpolation signal output means is output. And a second switching means for outputting the sampling point as it is when the input signal is a sampling point and outputting the output of the first switching means as an interpolation signal when the input signal is a non-sampling point. A configuration in which a changing means.

A second aspect of the present invention is to input a color difference signal in which two types of different color difference signals are line-sequentially subjected to inter-field offset sub-sampling, and the same type of color difference signal as a non-sample point to be interpolated in a frame. Peripheral pixel detecting means for outputting sample points located vertically and horizontally adjacent to each other, interpolation signal output means for obtaining signals for interpolating three types of non-sample points from the output of the peripheral pixel detecting means, and the interpolation An intermediate value selecting means for outputting an intermediate value of the signal output from the signal output means, and a sampling point as it is when the input signal is a sampling point, and an output of the intermediate value selecting means for a non-sampling point. This is a configuration including switching means for outputting as an interpolation signal.

[0017]

According to the first aspect of the present invention, since the optimum interpolation signal is selected according to the level difference between the upper and lower adjacent sampling points of the color difference signal of the same type as the non-sampling point in the frame, the first aspect of the present invention is sharp in the vertical direction. Even if a level change occurs, vertical leakage is small, and in particular, it is possible to minimize image distortion even after line-sequential decoding.

Further, the second invention has the above-mentioned structure.
In the frame, it is necessary to determine the level difference in the vertical direction by interpolating the non-sample points with the intermediate value of the three types of combinations of the upper, lower, left and right pixels of the same color difference signal as the non-sample points. The vertical unnaturalness can be improved without doing this.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an inter-field interpolation device according to the first embodiment of the present invention.

In FIG. 1, 11 is an input terminal for inputting a signal in which two types of different color difference signals are line-sequentially subjected to inter-field offset sub-sampling, 12 is a field memory for delaying the input signal by one field, 13, 1
4, 15 are line memories for delaying the input signal by 2 lines,
16 is an input signal of the line memory 13 and the line memory 14
A switching device for switching the output signal of the line memory 13 and the output signal of the switching device 1 by a field alternation.
A difference detection circuit that outputs the difference between the output signals of 6, a comparison circuit that outputs a magnitude relation between the difference detection circuit 17 and a threshold value that can be set arbitrarily, and 19 and 20 each have a gain of 1
/ 4, 3/4 coefficient unit, 21 is an adder, 22 is a switching unit which is a first switching means for switching the output signal of the adder 21 and the output signal of the line memory 13 by the output of the comparison circuit 18, Reference numeral 23 is a switch which is a second switching means for switching the output signal of the switch 22 and the output signal of the line memory 15 depending on whether the output of the line memory 15 is a sampling point or a non-sampling point, and 24 is interfield interpolation. It is an output terminal for outputting a signal.

The operation of the interfield interpolating apparatus of this embodiment having the above-described structure will be described below.
The input signal input to the input terminal 11 is delayed by one field in the field memory 12, and the line memory 1
5 is divided into two lines delayed. When the output signal of the line memory 15 is a sample point, the switch 23 outputs the signal of the sample point of the output signal of the line memory 15 as it is, and when it is a non-sample point, the field memory 12 is output.
The non-sample points are interpolated by outputting the subsequent calculation results of the sample points in the previous field.

The signal output from the field memory 12 is input to the two line memories 13 and 14 connected in cascade and delayed by two lines. The switch 16 outputs the output signal of the line memory 14 when the output signal of the line memory 15 is an odd field, and outputs the input signal of the line memory 13 when the output signal of the line memory 15 is an even field. Line memory 15
If the non-sample points among the signals output by the above are X, the sample points output from the line memory 13 are A, and the sample points output from the switch 16 are B, then X as seen in the frame,
The pixel arrangement of A and B is as shown in FIG.

FIG. 2 shows two scanning lines and one pixel arrangement for one frame.
It is shown dimensionally, and the dotted line represents the odd-field scanning line and the solid line represents the even-field scanning line. (A)
Shows the case where the non-sample point is in the even field, and (b) shows the case where the non-sample hand is in the odd field. In either case, A and B are the upper and lower adjacent sample points of the color difference signal of the same type as the non-sample point X. Further, B is located 3 lines away from the non-sample point X. The A and B signals are multiplied by 3/4 and 1/4 in the coefficient units 20 and 19, respectively, and added in the adder 21.

Further, the difference detection circuit 17 finds the level difference between the A and B signals, and the comparison circuit 18 checks the magnitude of the threshold value that can be arbitrarily set. When the level difference in the vertical direction is small, the image interpolated with the signal of 3 / 4A + 1 / 4B becomes smoother in the vertical direction than the image interpolated with the signal of A. Here, the interpolation by the signal of A is the simple fitting type of the conventional example, 3
The signals of / 4A + 1 / 4B correspond to the center-of-gravity consideration type in the conventional example.

Further, as shown in FIGS. 11 and 12, when the level difference in the vertical direction is large, B is distant from the non-sampling point X when interpolation is performed with a signal of 3 / 4A + 1 / 4B. The number of scanning lines affected by B becomes larger than that in the case of interpolation using only the signal of A. Therefore, the switch 22 is A,
If the difference of B is larger than the threshold value, the line memory 13
Output signal of A, that is, the signal of A is selected, and if it is smaller than the threshold value, the output signal of the adder 21, that is, 3/4 A
Select the + 1 / 4B signal. When the output signal of the line memory 15 is a sampling point in the switch 23, the sampling point is output as it is, and when the output signal of the line memory 15 is a non-sampling point, the output signal of the switch 22 is selected to interpolate between fields from the output terminal 24. Obtain a color difference signal.

As described above, according to this embodiment, by selecting the optimum interpolated signal of the non-sampling points according to the level difference in the vertical direction, even if a sudden level change occurs in the vertical direction, Leakage in the direction is small, and it is possible to minimize image distortion especially after line-sequential decoding.

In this embodiment, the level difference in the vertical direction is determined by the level difference between the upper and lower adjacent sample points of the same type as the non-sample points in the frame, but the level determination is limited to the configuration of this embodiment. is not. Further, although the level difference is determined using the color difference signal, the level difference may be determined including the corresponding luminance signal. Further, the gain of the coefficient unit may be any value.

The second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram of an inter-field interpolation device according to the second embodiment of the present invention.

In FIG. 3, 31 is an input terminal for inputting a signal in which inter-field offset sub-sampling is performed and two different types of color difference signals are line-sequentially input, 32 is a field memory for delaying the input signal by one field, 33, 3
Reference numerals 7 and 38 denote 1-pixel delay circuits that delay the input signal by 1 sampling point, 34, 35 and 36 denote line memories that delay the input signal by 2 lines, and 39 denotes an input signal of the 1-pixel delay circuit 37 and 1
A switcher that switches the output signal of the pixel delay circuit 38 by field alternation, a switcher 40 that switches the input signal of the line memory 34 and the output signal of the line memory 35 by field alternation, and 41 and 42 have gains of 1/4 and Three
/ 4 coefficient unit, 43 to 46 are coefficient units with a gain of 1/2,
47 to 49 are adders, 50 is an intermediate value selection circuit that outputs an intermediate value from three input signals, and 51 is a 1-pixel delay circuit 37.
Output signal of the intermediate value selection circuit 50 and the output signal of the intermediate value selection circuit 50 are switched by the output signal of the one-pixel delay circuit 37 depending on sampling points and non-sampling points, and 52 is an output terminal for outputting a signal inter-field interpolated. .

The operation of the interfield interpolating apparatus of this embodiment constructed as described above will be described below.
The input signal input to the input terminal 31 is the line memory 36.
Are delayed by two lines and those delayed by one field in the field memory 32. The signal delayed by two lines by the line memory 36 is delayed by one sampling point by each of the cascaded 1-pixel delay circuits 37 and 38.

The switch 39 outputs the output signal of the 1-pixel delay circuit 38 when the output signal of the line memory 36 is an odd field, and outputs the input signal of the 1-pixel delay circuit 37 when it is an even field. The output of the sampling point of the one-pixel delay circuit 37 is B, and the output of the sampling point of the switch 39 is C. The output signal of the field memory 32 is delayed by one sampling point by the one-pixel delay circuit 33. The output signal of the one-pixel delay circuit 33 is delayed by two lines by the two line memories 34 and 35 connected in cascade.

The switch 40 outputs the output signal of the line memory 35 when the output signal of the line memory 36 is an odd field, and outputs the input signal of the line memory 34 when it is an even field. The output of the sample point of the line memory 34 is A, and the output of the sample point of the switch 40 is D. If the non-sampling point of the signal output from the 1-pixel delay circuit 37 is X, the pixel arrangement of X, A, B, C, and D as seen in the frame is as shown in FIG.

FIG. 4 shows two scan lines and one pixel arrangement for one frame.
It is shown dimensionally, and the dotted line represents the odd-field scanning line and the solid line represents the even-field scanning line. (A)
Shows the case where the non-sample point is in the even field, and (b) shows the case where the non-sample hand is in the odd field. In any case, A, B, C and D are the adjacent upper, lower, left and right sample points of the color difference signal of the same type as X. The signals of A, B, C and D are set to 3 by the coefficient units 41 to 46 and the adders 47 to 49.
/ 4A + 1 / 4D, 1 / 2A + 1 / 2B, 1 / 2A + 1
Two types of signals of / 2C are obtained. The non-sample point X is interpolated using the intermediate value output from the intermediate value selection circuit 50 among these three types of signals.

5 and 6 show examples in which the level changes from the maximum to the minimum in the vertical direction. FIG. 5 and FIG. 6 show two-dimensionally the scanning lines and pixel arrangement of one frame. The dotted lines are odd field scanning lines, the solid lines are even field scanning lines, and (a) is the input signal. (B) shows the output result of inter-field interpolation according to the present embodiment. Solid line circles are pixels at sample points and dotted line circles are pixels at interpolated non-sample points, and the pixel level is shown by the darkness (that is, the hatching interval is narrow). In both cases, the vertical leakage is suppressed as compared with the conventional example.

As described above, according to this embodiment, since the interpolation is performed with the intermediate value obtained by using the sample points of the same kind of color difference signals above, below, left and right of the non-sample points in the frame, the conventional simple fitting Smooth interpolation can be performed compared to inter-field interpolation of the mold, and vertical leakage can be suppressed even when the vertical level changes suddenly. Furthermore, since the intermediate value processing is performed, it is not necessary to set a threshold value that serves as a criterion for determining the level difference in the vertical direction.

The combination of the calculation of the pixels around the non-sampling point is not limited to this embodiment, and may be any combination.

[0037]

As described above, according to the first aspect of the present invention, by selecting the optimum interpolation signal of the non-sampling point according to the level difference in the vertical direction, a rapid level change in the vertical direction can be achieved. Even if it occurs, there is little leakage in the vertical direction, and the distortion of the image can be minimized especially after line-sequential decoding, and its practical effect is great.

Further, according to the second aspect of the present invention, since interpolation is performed with an intermediate value obtained by using sample points of the same type of color difference signals above, below, left and right of the non-sample points in the frame, the conventional simple inset type is used. Smooth interpolation can be performed as compared with inter-field interpolation, and vertical leakage does not occur even in the case of a sudden vertical level change, and image distortion can be suppressed to a minimum especially after line-sequential decoding. Further, since the intermediate value processing is performed, it is not necessary to set a threshold value that serves as a criterion for determining the level difference, and the practical effect is large.

[Brief description of drawings]

FIG. 1 is a block diagram of an inter-field interpolation device according to a first embodiment of the present invention.

FIG. 2 is a pixel layout diagram of the embodiment.

FIG. 3 is a block diagram of an inter-field interpolation device according to a second embodiment of the present invention.

FIG. 4 is a pixel arrangement diagram of the embodiment.

FIG. 5 is a pixel arrangement diagram showing an example of output with respect to a sudden level difference in the vertical direction.

FIG. 6 is a pixel arrangement diagram showing another example of output with respect to a sudden level difference in the vertical direction.

FIG. 7 is a block diagram showing an example of a conventional inter-field interpolation device.

FIG. 8 is a diagram showing interpolation of a conventional inter-field interpolation device.

FIG. 9 is a block diagram showing another example of a conventional inter-field interpolation device.

FIG. 10 is a diagram showing the interpolation of a conventional inter-field interpolation device.

FIG. 11 is a pixel layout diagram showing an example of conventional output with respect to a sudden level difference in the vertical direction.

FIG. 12 is a pixel layout diagram showing another example of conventional output with respect to a sudden level difference in the vertical direction.

[Explanation of symbols]

 12 field memory 13, 14 line memory 16, 22, 23 switcher 17 difference detection circuit 18 comparison circuit 19, 20 coefficient unit 21, 47, 48, 49 adder 32 field memory 33, 37, 38 1 pixel delay circuit 34, 35, 36 Line memory 39, 40, 51 Switching device 41, 42, 43, 44, 45, 46 Coefficient device 50 Intermediate value selection circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenta Samukawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An inter-field offset sub-sampled color difference signal in which two different kinds of color difference signals are line-sequentially input, and the level difference of scanning lines located above and below a non-sample point to be interpolated in a frame is input. The level difference determination means for determining the magnitude, the interpolation signal output means for obtaining a signal for interpolating the non-sample points from the sampling points above and below the non-sample points in the frame from the input signal, and the result of the level determination means When it is smaller than the threshold value, the sampling point of the other field is output as the interpolation signal of the non-sampling point, and when it is larger, the first switching means for outputting the output signal of the interpolation signal output means, and the input signal is the sampling In the case of a point, the sampling point is output as it is, and in the case of a non-sampling point, a second switching means for outputting the output of the first switching means as an interpolation signal is provided. De between the interpolation apparatus. 2. The inter-field interpolation according to claim 1, wherein the interpolation signal output means mixes upper and lower sample points of the color difference signal of the same type as the non-sample points in the frame at an arbitrary ratio. apparatus. 3. An inter-field offset sub-sampled color difference signal in which two different kinds of color difference signals are line-sequentially input, and the color difference signals of the same kind as the non-sample points to be interpolated in the frame are positioned above, below, to the left and right. Output from the peripheral pixel detection means, interpolation signal output means for obtaining signals for interpolating three types of non-sample points from the output of the peripheral pixel detection means, and output from the interpolation signal output means. An intermediate value selecting means for outputting an intermediate value of the signal, and a switch for outputting the sampling point as it is when the input signal is a sampling point and outputting the output of the intermediate value selecting means as an interpolation signal when the input signal is a non-sampling point. An interfield interpolating device comprising means.