JP2885442B2 - Scanning line converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention converts a high-definition television signal having a larger number of scanning lines and an aspect ratio than a standard television signal into a standard television signal. The present invention relates to a scanning line conversion device used in such a case.

(Prior art) MUSE as a new transmission system for high-definition television signals
(Multiple Sub-Nyquist Samping-Encording) method has been developed. However, in order to receive a signal of this system, since it is different from the conventional transmission system of the NTSC system, a separate receiver dedicated to the MUSE system is required. Currently, high-definition television receivers are expected to take some time to spread due to their high cost. Therefore, there is a demand for a device that receives a high-quality signal using a conventional NTSC receiver, converts the signal format, and views the received signal.

In order to obtain this system converter, a scanning line converter for converting 1125 scanning lines of a high-definition television signal into 525 scanning lines, which is the same as the NTSC signal, is required.

FIG. 3 is a diagram for explaining a method of converting 1125 scanning lines into 525 scanning lines. Fig. 3 (A)
Is the first field, FIG. 4B is the second field, the solid line is the input scanning line transmitted, and the broken line is the output scanning line after conversion. For example, scanning lines
The scanning line L5 is interpolated from L1, L2, and L3, and the scanning line L6 is interpolated from L2, L3, and L4. That is, new scanning lines are created at a rate of one in three.

In the second field, the scanning line L1 ′,
The scanning line L5 'is interpolated from L2', L3 ', and L2', L3 ', L
The scanning line L6 'is interpolated from 4'.

Here, new scanning lines obtained in the first field and the second field need to be obtained at the same position (vertical timing) in the vertical direction when compared between fields. Therefore, instead of simply adding the data of three scanning lines to 1/3, the scanning lines are multiplied by a predetermined coefficient in advance and added. For example, focusing on the scanning line L5, the signal at the position of the scanning line L5 has almost the same influence from L1 and L3, and has the strongest effect from L2. In the case of the scanning line L6, L3, L4
And the effect of L2 is the weakest.
Therefore, when adding each scanning line, it is necessary to create a scanning line L5 by multiplying by an appropriate coefficient and adding.

FIG. 4 shows an example of coefficients multiplied by data when one scanning line is created from three scanning lines. This example creates a new scan line at the top and bottom center,
1/4, 1/2, 1/4 for each scan line data a, b, c
And new scanning line data d is obtained. Such processing is filtering processing, and the vertical frequency characteristics of the output signal can be changed by changing the coefficient. Hereinafter, this coefficient is referred to as a filter coefficient.

As shown in FIG. 3, the scanning lines L2, L3, L4
Although L6 is interpolated, if the filter coefficients are symmetrical in the vertical direction when obtaining this scanning line, the resulting scanning line will be generated with contents adapted to the position of L3. However, it is necessary to adapt the content to the position of the scanning line L5. Therefore, when obtaining the scanning line L6, L2, L3, and L4 are subjected to filter processing (multiplied by a filter coefficient) and interpolated. . For example, (1/4) L2, (1/2) L3, (1/2) L4.

 FIG. 5 shows the scanning line conversion circuit described above.

The signal at the input terminal 11 is a 1H (one horizontal period) delay memory 14
And supplied to coefficient units 12 and 13. The output of the 1H delay memory 14 is supplied to a coefficient unit 15 and a 1H delay memory 19. The output of the 1H delay memory 19 is supplied to the adder 16 via the coefficient unit 20. The output of the coefficient unit 15 is also supplied to the adder 16.
The output of the adder 16 is supplied to the coefficient unit 17 and also to one input terminal of the selector 21. The output of the coefficient unit 17 is supplied to the adder 18. This adder 18 includes a coefficient unit
Twelve outputs are also supplied, and the added output is supplied to the other input terminal of the selector 21. In the figure, fractional characters shown adjacent to each coefficient unit are magnifications of each coefficient unit.

In the above circuit, a plurality of scanning line signals sequentially input from the input terminal 11 are synchronized on the output sides of the coefficient units 12, 13, 15, and 20. Moreover, the coefficients are multiplied by each coefficient unit. Now, assuming that the selector 21 selects the direct output of the adder 16 based on the control signal from the control terminal 22, a signal obtained by adding the outputs of the coefficient units 13, 15, and 20 is derived. Such a processing mode is formed when the scanning line L5 shown in FIG. 3 is obtained. Next, the selector 21
Derives the signal from the adder 18 when the scanning line L6 shown in FIG. 3 is obtained. This is L2, L3,
The signal at the position of L3 is once created by L4 (the output of the adder 16), and this is halved by the coefficient unit 17 while L4 is reduced to 1 by the coefficient unit 12.
/ 2 and add both. Thus, by switching the path through the coefficient unit, the vertical frequency characteristics can be changed.

FIG. 6 shows the relationship between the control signal supplied to the control terminal 22 of the selector 21 and the horizontal synchronizing signal. At the timing a, for example, the output of the adder 16 is selected, and the timing b
In, the output of the adder 18 is selected. At timing c, either may be used. This is because the converted output at the timing c is not used.

(Problems to be Solved by the Invention) According to the above-described conventional scanning line conversion circuit, there are the following problems. That is, when the scanning line L5 as shown in FIG. 3 is created, the signals of the three scanning lines are output from the coefficient units 13 and
Passing 15, 20. However, when creating the scanning line L6, the signals of the three scanning lines are output from the coefficient units 13, 15, 20 respectively.
, And is added by the adder 16 and further passes through the coefficient unit 17, while the scanning line L 4 has passed through the coefficient unit 12 once. Therefore, the converted scan lines L5 and L6 differ in the number of times they pass through the coefficient unit until they are created. Therefore, the vertical frequency characteristics of the circuits from which the scanning lines L5 and L6 are obtained cannot be regarded as the same. This is a case where the upper and lower scanning lines are compared in the same field. Become.

As described above, when a screen is formed using scanning line signals having different conversion characteristics, there is a problem that flicker or the like occurs.

FIG. 7 shows the filter coefficient for the center scanning line.
The vertical filter characteristics FV1 when 1/2 and 1/4 for the upper and lower scanning lines are shown. This corresponds to the characteristic when obtaining the scanning line L5 in FIG. But scan line L6
Is obtained by asymmetrically weighting in the vertical direction, so that the vertical filter characteristic becomes like the vertical filter characteristic FV2. As described above, if the vertical filter characteristics for obtaining the converted scanning line are different, flicker or the like is caused as described above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanning line conversion device which can make the vertical filter characteristics at the time of conversion the same for each scanning line when sequentially creating new scanning lines after conversion.

[Configuration of the Invention] (Means for Solving the Problems) A scanning line conversion apparatus according to the present invention comprises: a delay unit for synchronizing N (N is a natural number of 3 or more) input scanning line signals;
Of the N input scanning line signals output from the delay means, the coefficient for the central input scanning line signal is made larger than the coefficient for the other input scanning line signals, and the coefficient for the central input scanning line signal is increased and decreased around the central input scanning line signal. Auxiliary signal generation means for setting the coefficients for the input scanning line signals arranged in the direction so as to be symmetric, multiplying the input scanning line signal by the corresponding coefficient by a coefficient, and generating an auxiliary signal by adding and outputting, Signal switching means for alternately selecting and deriving one of upper and lower input scanning line signals adjacent to the central input scanning line signal from N input scanning line signals output from the delay means, and an output of the signal switching means A scanning line signal generating means for generating a new scanning line signal by weighting and adding the output of the previous auxiliary signal generating means and the output of the previous auxiliary signal generating means at a ratio corresponding to the position of the scanning line to be newly generated. It is intended to Bei.

The signal switching means of the scanning line conversion device according to the present invention selects the input scanning line signal sandwiching the position of the scanning line signal to be newly generated by the scanning line signal generation means with respect to the auxiliary signal. It is characterized in that it is derived.

(Operation) According to the above-mentioned means, all the output scanning line signals are created by using the same number of coefficient units, that is, passing through the vertical filters having the same characteristics. Output characteristics do not change between fields.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The digital video signal is supplied to the input terminal 31 and supplied to the 1H delay memory 33 having a delay time of one horizontal period, the coefficient unit 33, and to one terminal of the selector 39.

The output of the 1H delay memory 33 is further input to the 1H delay memory 37 and to the coefficient unit 34. 1H delay memory
The output of 37 is input to a coefficient unit 38 and a selector
It is supplied to the other input terminal of 39. Blocks surrounded by broken lines are used for synchronizing three scanning line signals sequentially input to the input terminal 31. And of the synchronized signals,
The two signals are supplied to the selector 39.

The outputs of the coefficient units 32, 34, and 38 are input to the adder 35 and are combined. In the figure, the fraction characters next to the coefficient units 32, 34, and 38 indicate the magnification of each coefficient unit. Outputs of the adder 35 and the selector 39 are input to coefficient units 36 and 40, respectively.
The outputs of the coefficient units 36 and 40 are added in an adder 41 and output to an output terminal 42.

Here, when the control signal synchronized with the horizontal synchronization signal is supplied to the terminal 43, the selector 39 selects and derives one of the inputs.

The above circuit converts the number of scanning lines and forms a vertical filter. Here, the operation will be described with reference to FIG.

Now, using the scanning lines L1, L2, and L3 in FIG.
Consider the case of creating L5. Assuming that the interval between the scanning lines is 1, in the case of this embodiment, the position of the scanning line L5 is set to a position shifted by 1/4 from the position of the center scanning line L2. First, 1H delay memories 33, 37, coefficient units 32, 34, 3
8. A signal corresponding to the position of the scanning line L2 (hereinafter, such a signal is referred to as an auxiliary signal) is generated by the circuit of the adder 35. If a signal is created at a position (scanning line L5) shifted upward by 1/4 from this position, a coefficient of 1/4 is added to the scanning line L1.
, The output (auxiliary signal) of the adder 35 is multiplied by a coefficient of 3/4, and then the two are added to obtain a signal at a position corresponding to the scanning line L5. Therefore, in this case, the selector 39 is controlled to select the scanning line L1 (the output of the 1H delay memory 37).

Next, a case where the scanning line L6 is created using the scanning lines L2, L3, and L4 will be considered. The scanning line L6 is set at a position shifted by 1/4 downward from the center scanning line L3. In this case, a signal (auxiliary signal) at a position corresponding to the scanning line L3 is obtained from the adder 35 first. To create a scanning line L6 using this auxiliary signal and a signal of another scanning line, multiply the auxiliary signal from the adder 35 by 3/4 and multiply the signal of the scanning line L4 from the terminal 31 by 1/4. Multiply and combine the two.

As described above, the selector 39 is switched according to the position of the scanning line by the control signal, and the operation timing is the same as that described in FIG.

Looking at the interpolation signal creation path of the above scanning line conversion device,
The number of coefficient units used when generating signals for the scanning lines L5 and L6 does not change. And selector 39,
Signal of input terminal 31 that does not pass through coefficient unit, or 1H delay memory
By simply selecting one of the 37 output signals, a signal above the scanning line L2 (scanning line L5) and a signal below the scanning line L3 (scanning line L
6) Can be created. Therefore, when the signals of the scanning lines L5 and L6 are generated, the vertical filter characteristics of the circuit do not change as in the related art.

This is the same when the scanning line is converted in the second field. However, the signal of the scanning line L5 'generated at the same position as the scanning line L5 is generated at a position shifted by 1/4 below the scanning line L2'. Also, the signal of the scanning line L6 'generated at the same position as the scanning line L6 is generated at a position shifted by 1/4 below the scanning line L4'.

According to the above-described embodiment, the vertical filter characteristic becomes like the characteristic FV3 shown in FIG. 7, and a characteristic close to the ideal characteristic FV1 can be obtained.

As described above, in this embodiment, first, a plurality of input scanning line signals are synchronized to generate an auxiliary signal (output of the adder 35) corresponding to a vertically symmetrical position, and this auxiliary signal has a constant coefficient K1. Multiply. On the other hand, a plurality of signals can be selected from the synchronized signals by the selector 39, and the selected signal is multiplied by a constant coefficient K2. Where the coefficients K1 and K2
Are set so that the sum is 1, and whether the new scanning line signal to be created is shifted upward or downward is left to the selecting operation of the selector 39. . By doing so, the vertical filter characteristics can be made the same in the course of creating all the scanning line signals, and it is possible to prevent the occurrence of factors such as flicker as in the related art.

In the above embodiment, a new interpolated scanning line signal is created using three scanning lines. However, the number of scanning lines to be used is not limited to this, and the conversion rate of the number of scanning lines is used. Is selected according to

[Effects of the Invention] As described above, according to the present invention, when new scanning lines are sequentially created, the vertical filter characteristics at the time of conversion can be made the same for each scanning line.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an explanatory view of a scanning line for explaining the operation of the apparatus of FIG. 1, and FIG. 3 is a circuit diagram of a conventional scanning line conversion processing apparatus. FIG. 4 is an explanatory diagram of a scanning line for explaining the operation, FIG. 4 is an explanatory diagram showing the principle of conversion of a scanning line, FIG. 5 is a circuit diagram showing a conventional scanning line converter, and FIG. 7 is a diagram showing an example of the vertical filter characteristics of the scanning line conversion device. 31 ... Input terminal, 32, 34, 38, 36, 40 ... Coefficient unit, 33,
37 ... 1H delay memory, 35, 41 ... Adder, 39 ... Selector.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-299377 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 7/01

Claims (2)

(57) [Claims] 1. A delay means for synchronizing N (N is a natural number of 3 or more) input scanning line signals, and a central input scanning line among N input scanning line signals output from the delay means. The coefficients for the signals are set larger than the coefficients for the other input scanning line signals, and the coefficients for the input scanning line signals arranged vertically in the center with respect to the central input scanning line signal are set to be symmetrical. An auxiliary signal generating means for generating an auxiliary signal by multiplying the input scanning line signal by a coefficient and adding and outputting the result; and an N input scanning line signal output from the delay means adjacent to the central input scanning line signal. Signal switching means for alternately selecting and deriving one of the upper and lower input scanning line signals, and the output of the signal switching means and the output of the preceding auxiliary signal generating means according to the position of the scanning line to be newly generated. Was Scanning line converting apparatus being characterized in that; and a scanning line signal generating means for generating a new scan line signal by adding weighted in focus. 2. The method according to claim 1, wherein said signal switching means selects and derives an input scanning line signal sandwiching a position of a scanning line signal to be newly generated by said scanning line signal generating means with respect to said auxiliary signal. The scanning line conversion device according to claim 1.