JPH0342832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a scanning line interpolation device for improving image quality by interpolating scanning lines of a television video signal.
In particular, the present invention relates to a video adaptive scanning line interpolation device that changes the method of synthesizing interpolation signals in accordance with screen conditions.

2. Description of the Related Art A scanning line interpolation device is known that interpolates scanning lines of a television video signal to improve image quality.

As one of the scanning line interpolation devices, as shown in FIG. 6A, it includes an original video signal input terminal 1, an original video signal output terminal 2, and an interpolated video signal output terminal 3,
There is a so-called double writing device that outputs the same signal as the original video signal as an interpolated video signal.

Another scanning line interpolation device, as shown in FIG.
(horizontal) 1-scan line delay circuit 4 that delays the scan line;
Some devices include an adder circuit 5 and a 1/2 coefficient unit 6 and output an arithmetic average value between adjacent scanning lines as an interpolated video signal.

Furthermore, another scanning line interpolation device includes an original video signal input terminal 1, an original video signal output terminal 2, an interpolated video signal output terminal 3, and a 1-field delay circuit 7 that delays the original video signal by one field. There is a method that uses correlation to output a video signal one field before as an interpolated video signal.

Problems to be Solved by the Invention In the above-mentioned scanning line interpolation device using double writing, when a diagonal line appears in the screen as illustrated in FIG. 7A, interpolation is performed as shown in FIG. 7B. There is a problem in that step-like line segments are displayed in the subsequent screen, and the smoothness of the line segments is lost.

Furthermore, in a scanning line interpolation device that uses the arithmetic average value between adjacent scanning lines as an interpolated video signal, there is a problem that the contour in the vertical direction becomes blurred, as shown in FIG.

In addition, in a device that uses the video signal of one field before as an interpolated video signal, it is necessary to use an expensive large-capacity field.
Not only does this require memory, but there is also the problem that the image quality deteriorates when there is large movement on the screen and the correlation between fields is small.

A scanning line interpolation device of the present invention which solves the problems of the prior art described above creates controllable weighted interpolation signals from vertically adjacent original video signals on adjacent scanning lines. a correlation detection circuit that detects the degree of correlation between vertically and diagonally adjacent original video signals on adjacent scanning lines, and the higher the degree of correlation detected by this correlation detection circuit, the more the and a weighting control circuit that controls the weighting in a direction to equalize the weighting.

A scanning line interpolation device according to the second aspect of the present invention includes a synthesis circuit that creates a controllable weighted interpolation signal from original video signals that are vertically and diagonally adjacent on adjacent scanning lines; and a correlation detection circuit that detects the degree of correlation between original video signals adjacent in the direction.

Furthermore, this scanning line interpolation device is configured such that the greater the degree of correlation in the vertical direction detected by the correlation detection circuit, the greater the weighting in the vertical direction of the combining circuit than in the diagonal direction, and the direction in which the weighting is made equal between adjacent scanning lines. and weighting control for controlling the diagonal direction weighting of the synthesis circuit to be greater than the vertical direction and equalized between adjacent scanning lines as the degree of correlation in the diagonal direction detected by the correlation detection circuit increases. It is equipped with a circuit.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

Embodiment FIG. 1 is a block diagram showing the configuration of a scanning line interpolation device according to an embodiment of the present invention.

This scanning line interpolation device has an original video signal input terminal 1.
, an original video signal output terminal 2 , and an interpolated video signal output terminal 3 .

Moreover, this scanning line interpolation device converts the video signal into one
(Horizontal) 1-scan line delay circuit 1 that delays one scan line
1 pixel delay circuits 21, 22, 23, and 24 that delay 0 and the video signal by one pixel, and subtracters 31, 3
2 and 33.

Furthermore, this scanning line interpolation device includes an absolute value circuit 4
1, 42, and 43, a minimum value selection circuit 44, a coefficient generator 45, a synthesis circuit including coefficient units 46, 47, and an adder 48.

The original video signal supplied to the input terminal 1 is delayed by the time of one scanning line in the one scanning line delay circuit 10, and at the same time the subsequent scanning line H2 starts to be supplied to the one scanning line delay circuit 10, the previous scanning signal is delayed. It is output here as line H1. This preceding scanning line H1 is
The signal is further delayed by one pixel in the one-pixel delay circuits 23 and 24, and is supplied to one input terminal of the subtracter 33.

When realizing this scanning line interpolation device in a digital format, the one-scanning line delay circuit 10, one-pixel delay circuits 23, 24, etc. are composed of RAM, etc., and after the writing of the video signal is completed, one scanning line or one pixel is Reading starts after a minute.

On the other hand, the original video signal supplied to input terminal 1 is
1 pixel delay circuits 21 and 2 as the subsequent scanning line H2
2, the signal is delayed by one pixel time and is supplied to one input terminal of the subtracter 32. Subtractor 32
The preceding scanning line H1 output from the one-scanning line delay circuit 10 is supplied to the other input terminal of . Further, the subsequent scanning line H1 is supplied to the other input terminal of the subtracter 33. Furthermore, one pixel delay circuits 21 and 23 are connected to both input terminals of the subtracter 31, respectively.
output is supplied.

FIG. 2 is a conceptual diagram for explaining the operation of FIG. 1. In the figure, H1 and H2 are adjacent scanning lines in the original video signal, and I is a composite signal from the original video signals on these adjacent scanning lines. This is an interpolated scan line. Also, a,
b and c are adjacent pixels on the previous scanning line H1, d,
e and f are adjacent pixels on the subsequent scan line H2, and i is an interpolation pixel on the interpolation scan line I. The scanning lines H1, H2 and pixels a to f in FIG. 2 correspond to the video signals at the locations with the same reference numerals in FIG. 1.

The subtracter 31 outputs a difference output b-e between the video signal b on the preceding scanning line H1 and the video signal e on the succeeding scanning line H2 as a vertical difference signal between adjacent scanning lines. Further, from the subtracter 32, the video signal c on the preceding scanning line H1 and the subsequent scanning line H
The difference output c-d of the video signal d on 2 is output as a diagonal difference signal between adjacent scanning lines. Further, the subtracter 33 outputs a difference output a-f between the video signal a on the preceding scanning line H1 and the video signal f on the succeeding scanning line H2 as a diagonal difference signal between adjacent scanning lines. .

The absolute values of the difference outputs of the subtracters 31 to 33 are taken in the corresponding absolute value circuits 41 to 43, and are supplied to the minimum value selection circuit 44 as the absolute values lc-dl, lb-el, la-fl of the difference outputs. Ru. Each of the above absolute values indicates the degree of correlation between adjacent scanning lines in the diagonal direction and the vertical direction, and the smaller the corresponding absolute value, the greater the degree of correlation in the diagonal direction or the vertical direction.

When implementing this scanning line interpolation device in a digital format, the minimum value selection circuit 44 is composed of a combination circuit of a subtracter and a logic gate, and the minimum value selection circuit 44 is composed of a combination circuit of a subtracter and a logic gate.
Out of the absolute values of the three differential outputs supplied from 1 to 43, the smallest one, ie, the one with the largest correlation between adjacent scanning lines, is selected and supplied to the coefficient generator 45.

If this scanning line interpolation device is implemented in a digital format, the coefficient generator 45 is composed of a ROM or the like that stores the corresponding coefficient at the address of the minimum value.
A coefficient k having a size corresponding to the minimum value supplied from the minimum value selection circuit 44 is sent to the coefficient units 46 and 47 and the adder 4.
It is supplied to a synthesis circuit consisting of 8.

The coefficient multiplier 46 supplies a signal obtained by multiplying the video signal e on the subsequent scanning line H2 by k to one input terminal of the adder 48. Further, the coefficient multiplier 47 supplies a signal obtained by multiplying the video signal b on the previous scanning line H1 by (1-k) to the other input terminal of the adder 48.

The relationship between the minimum value supplied to the coefficient generator 45 and the coefficient k output from the coefficient generator 45 is the third
As illustrated in the figure, when the minimum value is 0, that is, when the correlation in the diagonal or vertical direction is 100%, k
=0.5. The coefficient k approaches 1 as the minimum value increases (correlation between adjacent scanning lines weakens), and becomes 1 in a range where the minimum value is somewhat large (range where there is no correlation between adjacent scanning lines).

Therefore, if the correlation in the diagonal or vertical direction is 100%, the video signal b on the preceding scanning line H1 and the video signal e on the video signal H2 on the succeeding scanning line H2
The interpolated video signal i, which is synthesized by equally weighting the signals, is output from the interpolated video signal output terminal 3.

Further, as the correlation in the diagonal direction or the vertical direction becomes smaller, the specific weight of the video signal e on the subsequent scanning line H2 increases. Furthermore, when there is almost no correlation between adjacent scanning lines, k=1, and only the video signal e on the subsequent scanning line H2 is supplied to the interpolation output terminal, and scanning line interpolation by so-called double writing is performed. Vertical contour blurring is avoided.

When the correlation between adjacent scanning lines disappears due to exchanging the coefficient units 46 and 47,
It is also possible to write twice using the video signal b on the preceding scanning line H1.

FIG. 4 is a block diagram showing the configuration of a scanning line interpolation device according to an embodiment of the second invention.

Components in FIG. 4 denoted by the same reference numerals as those in FIG. 2 are the same as the components already described in connection with FIG.

In the scanning line interpolation device shown in FIG. 4, switches 51 and 52 are added to the device shown in FIG. 2, and the minimum value selection circuit 44 controls switching of the switches 51 and 52 according to the selected minimum value. Functions are added.

That is, when the minimum value selection circuit 44 selects the absolute value 1b-e1 of the vertical difference signal outputted from the absolute value circuit 41 as the minimum value, it switches the switches 51 and 52 to the middle position in the figure. , the video signals e and b are processed by coefficient multipliers 46 and 47, respectively.
At the same time, a coefficient k corresponding to the degree of correlation between the video signals e and b is supplied to each coefficient unit 46 and 47. The minimum value and coefficient k in this coefficient generator 45
The relationship is almost the same as that shown in FIG. 3, and in the limit where the minimum value is 0, equal weighting is performed, and as the minimum value increases, weighting is gradually applied to one side.

Therefore, as illustrated in FIG. 5A, when a vertical line segment appears in the screen, the video signal b existing on this vertical line segment is
An interpolated signal i resulting from equal combination of and e is output from the interpolated signal output terminal 3.

Further, the minimum value selection circuit 44 is connected to the absolute value circuit 42.
The absolute value of the diagonal difference signal output from lc−
When dl is selected as the minimum value, switch 5
1 and 52 are switched to the upper position in the figure, the video signals d and c are supplied to the coefficient multipliers 46 and 47, respectively, and the coefficient k corresponding to the degree of correlation between the video signals d and c is supplied to each coefficient multiplier 46. and 47. Therefore, when a diagonal line slanting downward to the left appears on the screen, as illustrated in FIG. Signal i is interpolated signal output terminal 3
is output from.

Furthermore, the minimum value selection circuit 44 includes an absolute value circuit 43
The absolute value la− of the diagonal difference signal output from
When fl is selected as the minimum value, switch 5
1 and 52 are switched to the lower positions in the figure, the video signals f and a are supplied to the coefficient multipliers 46 and 47, respectively, and the coefficient k corresponding to the degree of correlation between the video signals a and f is supplied to each coefficient multiplier 46. and 47. Therefore, when a diagonal line rising to the right appears on the screen, as illustrated in FIG. Signal i is interpolated signal output terminal 3
is output from.

As is clear from FIG. 5, smooth diagonal lines and vertical line segments are displayed depending on the type of line segment appearing on the screen, that is, the video signal.

In addition, no matter which minimum value or selection is made,
When the value is large to some extent, that is, when the correlation in the diagonal or vertical direction is small to some extent, the output d, e, or f of the coefficient circuit 46 is directly outputted from the interpolation signal output terminal 3 as the interpolation signal i. , and the blurring of the vertical contour is effectively avoided.

As in the case of FIG. 2, by exchanging the coefficient units 46 and 47, instead of writing the video signal on the subsequent scanning line H2 twice,
The above video signal may be written twice.

In addition, in the scanning line interpolation device shown in FIG. 4, a continuously variable weighting circuit for vertical and diagonal video signals is installed in place of the switches 51 and 52.
It is also possible to adopt a configuration in which greater weighting is given in the direction of greater correlation.

Effects of the Invention As explained in detail above, the scanning line interpolation device of the present invention detects the degree of correlation between original video signals adjacent in the vertical direction and diagonal direction on adjacent scanning lines, and the higher the degree of correlation, the more the signal is synthesized. This is because it is configured to perform scanning line interpolation that adapts to the screen situation by equalizing the weighting of the circuit, or by controlling the weighting to be equalized between adjacent scanning lines while giving greater weighting in the direction of greater correlation. The effect of this is that it can effectively solve all of the problems that occur with conventional devices, such as loss of smoothness of diagonal lines, blurring of vertical contours, or deterioration of image quality due to lack of correlation between fields. is played.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.
2 and 3 are conceptual diagrams for explaining the operation of the present invention, FIG. 4 is a configuration block diagram of an embodiment of the second invention, and FIG. 5 is the scanning line interpolation device of FIG. 4. 6 is a block diagram of a conventional scanning line interpolation device, and FIG. 7 is a conceptual diagram illustrating problems of the conventional device shown in FIG. 1...Original video signal input terminal, 2...Original video signal output terminal, 3...Interpolation signal output terminal, 10...1
Scanning line delay circuit, 21 to 24... 1 pixel delay circuit, 31 to 33... Subtractor, 41 to 43... Absolute value circuit, 45... Coefficient generation circuit, 46, 47...
Coefficient unit, 48...adder, 51, 52...switch.

Claims (1)

[Scope of Claims] 1. A combining circuit that creates an interpolated signal by combining a pair of vertically adjacent original video signals on adjacent scanning lines in the same field under controllable weighting; a correlation detection circuit that detects the degree of correlation within each pair of three pairs of original video signals adjacent in the vertical and diagonal directions, and the degree of correlation in the vertical or diagonal direction detected by this correlation detection circuit increases. A video adaptive scanning line interpolation device comprising: a weighting control circuit that controls the weighting in a direction that equalizes the weighting of the combining circuit. 2. A combining circuit that creates an interpolation signal by combining three pairs of original video signals that are vertically and diagonally adjacent on adjacent scanning lines in the same field under controllable weighting; and a correlation detection circuit that detects the degree of correlation within each pair for three pairs of diagonally adjacent original video signals as the degree of correlation in the vertical direction and the degree of correlation in the diagonal direction; As the degree of correlation in the direction increases, the weighting in the vertical direction of the synthesis circuit is controlled to be greater than that in the diagonal direction and equalized between adjacent scanning lines, and the weighting in the diagonal direction detected by this correlation detection circuit is and a weighting control circuit that controls the weighting in a direction such that the greater the degree of correlation, the greater the weighting in the diagonal direction of the synthesis circuit than in the vertical direction, and the weighting is equalized between adjacent scanning lines. type scan line interpolator.