JPS5832823B2 - TV show - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for vertical signal interpolation of television video signals.

2. Description of the Related Art When displaying images such as still images on television or stop motion, there are cases where one field of video signals is repeated to form one frame of pseudo video signals for display.

Particularly regarding stop motion, when displaying regular frame signals based on the subject's movement, field flicker occurs due to time changes in the images of two adjacent fields, which is often inconvenient for stop motion displays; It is necessary to create a pseudo one frame signal from the signal.

In this case, the pseudo-formed frame signal (hereinafter referred to as pseudo-frame signal) has exactly the same content as the two field signals that form it, so when displaying an image by interlacing, it is scanned in the vertical direction of the screen. This causes the image to fluctuate up and down at the frame period by the distance between the lines, causing apparent line flicker.

Line flicker is particularly noticeable in areas with sharp contours in the image that are nearly parallel to the scanning line.

Furthermore, this line flicker phenomenon is observed not only in the case of the above-mentioned pseudo frame signal, but also in the horizontal contours of purely electronically formed character signals, pattern signals, and graphic signals in ordinary frame signals.

This is because the signal generation method for character signals and the like uses a method equivalent to the pseudo frame signal.

An object of the present invention is to provide a signal interpolation method for effectively reducing the line flicker phenomenon when forming this pseudo frame signal.

A detailed explanation will be given below with reference to the drawings.

FIG. 1a is a diagram illustrating the display of a pseudo frame signal without signal interpolation.

The horizontal axis represents the vertical direction of the screen, and the vertical axis represents the brightness of the screen.

The white circles represent the cross-sections of the scanning lines of the first field and the black circles represent the cross-sections of the scanning lines of the second field, which are spatially interlaced and displayed along the horizontal axis of the figure, that is, the vertical direction of the screen.

Here, the signal brightness is white for ease of explanation and understanding.
It is assumed that black is a binary value, and a transition between white and black is performed during one line.

This substantially corresponds to the display of the character signal and the like.

Now, the pseudo frame signal is displayed in the first field like a dotted line connecting white circles in FIG. 1a, and in the second field like a dotted line connecting black circles.

As can be seen from the figure, line flicker does not occur in areas where there is no change in brightness in the vertical direction of the screen, that is, in the horizontal direction of the figure, but line flicker occurs in the frame period at the transition points from black to white and from white to black. Occur.

The flicker intensity has a value corresponding to the difference in brightness level between the two fields at the transition point.

Conventionally, as a countermeasure against line flicker, line correlation has been used to reduce the spatial frequency response in the vertical direction, thereby reducing line flicker.

An example of this is a signal interpolation method that takes a simple arithmetic average of video signals of adjacent lines.

This is a method of taking the arithmetic mean of the video signal er of the r-th line and the video signal er-1 of the (r'-+)th line delayed by one line to obtain the video signal of the r-th line. .

In other words, if the arithmetic averaged video signal is el, then becomes.

The result of calculating equation (1) on the signal in Figure 1a is
It is shown in the figure.

As can be seen from the figure, the response in the vertical direction has decreased to -, but the flicker strength has also decreased to -.

However, when visually observing an image, signal interpolation using this method alone is not sufficient as a countermeasure against line flicker.

Generally, flicker can be reduced to - by signal interpolation using the arithmetic average of N line signals, but the vertical response also drops to -, which causes image quality deterioration that is different from flicker. In reality, anything other than N=2 is not practical.

The present invention aims to obtain more effective line flicker improvement results by correcting the signal shown in FIG. 1, which is the result of signal interpolation using equation (1), by signal processing using another method.

The correction method will be explained below.

Let ler be the difference signal between 81- and er~1.

An appropriate constant k is set here, and an operation is performed on the difference signal 1er in equation (2), and Ael in equation (4) is used as a correction signal.

At this time, if the sign of the value of k is set to be inverted for each field, Ael in equation (4) becomes a signal as shown in FIG. 1C.

As is clear from the figure, in Ael, the polarity of the difference signal is reversed for each field at the white/black transition portion.

In this figure, the value of k is set to the first field 1 Set to m- in the second field and set it to 2 in the second field. It shows what is happening.

The correction signal Jeφ of equation (4) obtained in this way is expressed as (1)
The interpolated signal eI is obtained by adding it to the arithmetic mean signal eζ of the equation.

This is shown in equation (6).

Adding e' in Figure 1 and J er' in Figure 1C (6
) is shown in Figure 1d.

As is clear from comparing d in Figure 1, 01' in equation (1) is interpolated complementary to each field by correction using Ael in equation (4), and line flicker is significantly improved. It can be seen that

As mentioned above, the signal example in Figure 1 is for the case where the brightness change in the vertical direction is the sharpest, that is, the transition between white and black occurs at one line interval. Figure 2 shows the slow →ri.

This is signal 1 in Figure 1. This is an example of the negative case of the transfer response.

Symbols a, b, c, d in Figure 2 correspond to those in Figure 1,
■ The value of is 1±- as in FIG.

As is clear from FIG. 2d, an extremely good interpolation signal can be obtained.

Next, the electric circuit that performs the signal processing of equations (1) to (6) described above will be explained.

FIG. 3 is a system diagram of an embodiment of an electric circuit that performs signal interpolation processing according to the present invention.

1 is a pseudo frame signal input, and the video signal of the r-th line is er.

2 is a 1-line delay circuit, and the output of 2 provides the (r-1th line video signal er1).

er and er H are addition circuit 3 and subtraction circuit 4
is added to the sum signal 5 and er
-er-1 becomes the difference signal 6.

The difference signal 6 is applied to the level selection circuit 8 through a low-pass filter in order to compensate for S/N deterioration caused by the subtraction operation.

The operation of the level selection circuit 8 will be described later.

The difference signal leaving the level selection circuit 8 enters a polarity inversion circuit comprising a switch 9 and an inversion amplifier 10.

The switch 9 is driven by a field switch 12 with a field switching signal 11, and a difference signal whose polarity is inverted for each field is obtained at the output of the switch 9.

This polarity inversion operation is for inverting the sign of the above-mentioned constant for each field.

In the example of FIG. 3, switch 9 is on the lower side in the first field.
It is set to the upper side in the second field.

The polarity-inverted difference signal is converted to a constant 1 by the variable resistance attenuator 13.
It is given an attenuation of kl and is added to the sum signal 5 in the adding circuit 14, and is attenuated to - by the resistance attenuator 15, resulting in an interpolated signal output 16 shown in equation (6).

Here, the level selection circuit 8 shown in FIG. 3 will be explained.

As is clear from the comparison between Figures 1 and 2, the more gradual the response at the transition point between white and black, the less noticeable line flicker becomes. In a small portion of the difference signal Aer in , correction by J er in equation (4) is not necessarily necessary.

Also, the small part of J er in equation 2) of the subtraction operation is S
/N is bad (, A Only noise remains in the part where er==O.

Therefore, if the difference signal is processed only by the linear circuit and added as a correction signal, the deterioration of the S/H will be noticeable in portions where the response of the screen is slow.

Considering these points, by the level selection circuit 8, (2)
Of the difference signal Aer in the equation, only a large portion above a certain level is allowed to pass, and a portion below a certain level is blocked.

This situation is shown in FIG. Figure 4a shows the level selection circuit 8.
FIG. 4 is the input of the difference signal J er to the output.

In the input to Jer in FIG. 4a, the minute level portion within the threshold level shown by the upper and lower dotted lines is cut together with noise, resulting in an output of zero, resulting in the waveform shown in FIG. 4.

These signal processes can prevent S/N deterioration in portions where the response is slow.

This threshold level may be made variable,
Ultimately, it is desirable to set the value of k together with the visual evaluation of the image.

Although the signal processing method according to the present invention has been described above with reference to FIGS. 3 and 4, any circuit may be used as long as it can obtain the interpolated signal peak shown in equation (6).

In particular, for signals such as character signals that are given as binary white and black values, the one-line delay circuit 2 shown in FIG. 3 can be constructed inexpensively using digital arithmetic elements without using an expensive analog delay circuit. A signal processing system for character signals etc. is configured inside the generator itself (
As a result, a character signal with good cost efficiency and no line flicker can be obtained.

Although the above description has been made regarding black and white luminance signals, it is unnecessary to explain that composite color signals can also be processed by YC separation.

Further, although the signal processing has been explained in terms of analog signals, signal processing can also be performed on digital PCM signals by digital calculation.

[Brief explanation of drawings]

FIG. 1 is an example of a signal waveform diagram showing the television video signal interpolation method according to the present invention, FIG. 2 is another example of the signal waveform diagram shown in the waveform diagram, and FIG. FIG. 4, which is a system diagram of one embodiment of the circuit, is a waveform diagram illustrating processing of a correction signal. In FIG. 3, 1 is a pseudo frame signal, 2 is a 1-line delay circuit, 3 is an addition circuit, 4 is a subtraction circuit, 7 is a low-pass filter, 8 is a level selection circuit, 9 is a switch, 10 is an inverting amplifier, 11 is a field switching signal, 12 is a field switching device, 13 is a variable attenuator, 14 is an addition circuit, 15
is a resistive attenuator.

Claims (1)

[Scope of Claims] 1. In a pseudo frame signal that pseudo-configures one frame video signal by repeating the video signal of one field of a television video signal, the video signal er of the rth line of one field and Delayed by 1 line (r-1
)-th video signal, set a constant 1<1 to 1, perform an operation by inverting the sign of the constant for each field, and use the operation result e: as the r-th line video signal. A television video signal interpolation method characterized by: