JPH0740733B2 - Signal converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image quality conversion of a color television signal, and more particularly to a signal conversion device suitable for use in a digital television receiver.

[Background of the Invention]

In recent years, the development of television receivers has progressed, and it has become possible to reproduce images with high image quality. Then, the technology has advanced more and more, and the research for replacing the video signal circuit of the current television receiver by the digital circuit has been advanced, and it has been realized. Along with this, various technologies have been devised for processing the television signals of the current system with higher image quality. Generally, the deterioration of the image quality of television signals of the current system is largely due to interlaced scanning, and (1) line flicker occurs near the boundary of horizontal stripes.

(2) Since the number of scanning lines per field is as small as 262.5, the higher the image quality, the more conspicuous the scanning line structure cannot be seen.

(3) In the current method, although the horizontal resolution has been improved due to the introduction of the comb filter, the vertical resolution has not been improved at all, so the overall resolution in the horizontal and vertical directions is Not improving.

There are problems such as.

Therefore, in order to solve the above problems and improve the image quality, line interpolation is performed using a line memory to double the number of scanning lines, and the current 2: 1 interlaced television signal is used. Is most effective when converted to a 1: 1 non-interlaced television signal. Here, a signal conversion device that performs such a conversion operation is referred to as a scanning line conversion circuit. Further, as the above-mentioned line interpolation method in the scanning line conversion circuit, there are the following two methods of iterative interpolation and average interpolation, and a publicly known example of the average interpolation method is, for example, JP-A-58-79378. To be

Now, a conventional scanning line conversion circuit will be described.

FIG. 2 is a block diagram showing a conventional scanning line conversion circuit.

In FIG. 2, 101 is an input terminal, 102 is a switch (S ₁ ), 103, 104 and 105 are line memories of 1H respectively, and 106
Switch (S ₂ ), 107 is an adder, 108 is a 1/2 attenuator, 109
Is a switch (S ₃ ), 110 is an output terminal, 111 is a line memory control circuit, and 112, 113 and 114 are R / W control signals, respectively.

Next, the operation of FIG. 2 will be described.

FIG. 3 is a timing chart for explaining the operation of FIG.

A luminance (Y) signal separated from the received NTSC television signal by Y / C separation is input to the input terminal 101 shown in FIG. The color (C) signal separated by Y / C separation is input to another similar scanning line conversion circuit in the form of a color difference signal, and the same operation is performed. Now, the line memories 103, 104 and 105 shown in FIG.
Assuming A, B, and C, the operation of each memory is performed at the timing shown in FIG. That is, for example, when the A line memory 103 is in the writing period (W), the other B line memory 104 and C line memory 105 are in the reading period (R). Since reading from each line memory is performed twice as fast as writing, reading is performed twice in the 1H period as shown in the figure. The R / W control of each line memory as described above is performed by the R / W control signals 112, 113, 11 output from the line memory control circuit 111.
It is carried out by 4 respectively.

Therefore, first, when the luminance signal is input to the input terminal 101, the switch (S ₁ ) 102 is connected to the three line memories 103, 104 and 105 every 1H period, and the input luminance signal is the line memory in the writing period (W). Written one after another.
In each line memory, when the writing is completed, the reading period (R) starts, and the reading is repeated four times every 1 / 2H cycle. The read signal is input to the switch (S ₂ ) 106, and the switching signal 115 from the line memory control circuit 111 outputs the data from each line memory at the timings shown in FIGS. The outputs 116 and 117 from the switch (S ₂ ) are added by the adder 107 and the 1/2 attenuator 108.
The averaged value is input to the switch (S ₃ ) 109. The switch (S ₃ ) 109 switches every 1 / 2H cycle, and the original signal and the averaged interpolation signal are alternately output to the output terminal 110 as shown in FIG. The converted signal is obtained. Further, by fixing the switch (S ₃ ) 109 to the upper side, the signal train 116 of FIG. 3 is output to the output terminal 110, so that a signal interpolated by repeating the scanning line twice can be obtained. It is possible.

Therefore, when a screen is configured by using the luminance signal output from the output terminal 110 and the color difference signal output in the same manner, it is possible to obtain an image by non-interlaced scanning.

By the way, when line interpolation is performed, the NT
Since the SC television signal is an interlaced scanning signal, looking at the position of one scanning line on the screen where line interpolation was performed, at that position the original scanning line was used. And the newly interpolated scan line will alternate for each field.

However, in the above-described conventional scanning line conversion circuit, since the information of the scanning line to be newly interpolated is not created in any relation with the information of the scanning line at the position in the previous field, In some cases, the image quality may be degraded rather than improved.
This will be described with reference to FIG.

FIG. 4 is an explanatory diagram showing a state of scanning line interpolation by a conventional technique.

In FIG. 4, l ₁ , l ₂ and l ₃ are scanning lines at specific positions respectively, and the state of the pixel when the field is changed from left to right by scanning in the direction perpendicular to the paper surface in the figure. Is shown. Solid line circles are actual pixels, and broken line circles are pixels newly created by scanning line interpolation (line interpolation). The above average interpolation method is shown in FIG.
To show the repeated interpolation method in FIG. (B), the scanning line l ₁ as a white scan lines, the scan lines l ₂ and l ₃ respectively and the scanning lines of black between the scanning lines l ₁ and l ₂ of It is assumed that the brightness has changed significantly.

In the case of FIG. 4 (a), the scanning line of the first field
l ₂ is the average of scan line l ₁ and scan line l ₃ , and is gray as shown in the figure. The same interpolation method is applied to the second field and the third field. In this case, scan line l ₁
Focusing on, the white and gray are alternately repeated for each field, and the line flicker is reduced. The same applies to the scanning line l ₃ . This method has the advantage that line flicker can be reduced by interpolating the intermediate color of gray compared to before interpolating the scan line, but on the contrary, gray blurs the vicinity of the border and deteriorates the vertical resolution more than before. There is a problem that it will end up.

Next, in the case of FIG. 4B, the scanning line l _{2 of} the first field
Is a white color obtained by repeatedly interpolating the scanning line l ₁ . Second
The scanning line l _{1 of the} field becomes white by repeatedly interpolating the previous scanning line (not shown), and the scanning line l ₃ becomes black by the repeated interpolation of the scanning line l ₂ . Scan line l of field 3
₂ becomes white like the first field. Focusing on the scanning line l ₂ , white and black are repeated for each field, and a line flicker of 30 Hz occurs.

As described above, the conventional scanning line conversion circuit has an advantage that the scanning line structure is hard to see, but the problems with respect to line flicker and vertical resolution have not been solved.

[Object of the Invention]

The object of the present invention is to solve the above-mentioned problems of the prior art,
It is an object of the present invention to provide a signal conversion device that can prevent the occurrence of line flicker and can improve the vertical resolution by performing scanning line conversion of a digital television receiver.

[Outline of Invention]

In the present invention, considering that the television signal has a correlation between fields, a field memory for newly storing the information of the previous field is added to the scanning line conversion circuit having the line memory configuration, and the information of the previous field is stored. It is characterized by preventing the occurrence of line flicker, improving the vertical resolution, and realizing high-quality signal conversion by using the determination of the scanning line interpolation in the current field and the scanning line interpolation. In addition, when the television signal is a color television signal, it is considered that the human visual characteristics are inferior to the luminance signal in the color difference signal and that the line flicker is mainly based on the luminance signal. Scanning line interpolation using a field memory may be performed for signals, and scanning line interpolation using a conventional line memory may be performed for color difference signals.

Example of Invention

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, 401 is an interpolation circuit, 402 is a switch (S ₄ ), 403 and 404 are field memories, 405 is a switch (S ₅ ), 406 is a field memory control circuit, and 407 and 4
Reference numeral 08 is a field memory control signal, 409 is a field memory output image signal, and the same reference numerals as in FIG.

Next, the operation of this embodiment will be described.

A luminance signal is input to the input terminal 101 shown in FIG. 1 as in the conventional example shown in FIG. Switch (S ₁ ) 102, line memories 103, 104, 105, switch (S ₂ )
The operations of 106 and the line memory control circuit 111 are the same as those of the conventional example shown in FIG. That is, when the luminance signal is input to the input terminal 101, the line memory operates as described above.

On the other hand, the field memories 403 and 404 are the switches (S ₄ ) 40
By 2, only one is selected alternately for each field, and the image for one field is written in each.

Then, after the image writing is completed, each field memory sequentially receives information of one scanning line (information for one line) twice at a speed twice as fast as the writing during the next one field period. Read out repeatedly. That is, for example, if the information of the scanning line l ₁ is read repeatedly twice in a certain 1H period, the information of the subsequent scanning line l ₂ is read repeatedly twice in the next 1H period.

Such field memories 403 and 404 are controlled by the field memory control signals 407 and 408 output from the field memory control circuit 406, and writing and reading are alternately repeated in each field memory. When one field memory is in the writing period, the other field memory is controlled to be in the reading period.

On the other hand, the switch (S ₅ ) 405 is switched for each field similarly to the field memory and is always connected to the field memory in the reading period.
That is, the switch (S ₅ ) 405 is always connected to a different field memory from the switch (S ₄ ) 402.

When the switch (S ₅ ) 405 is connected to the field memory in the reading period, the image information read from the field memory is sent to the interpolation circuit 401 via the switch (S ₅ ) 405. That is, from the switch (S ₅ ) 405, 1
Field-delayed image information 409 is output continuously,
It will be input to the interpolation circuit 401.

By the way, the field memories 403 and 404 require an enormous memory capacity when all signals for one field are stored, but since the information of the field memory is basically used for determination as described later, the memory capacity is reduced. However, it is sufficient to reduce the memory capacity by reducing the total number of pixels written to the field memory to 1/3 to 1/4 and reducing the precision of each pixel, so that the effect is not impaired.

Next, the operation of the interpolation circuit 401 will be described with reference to FIGS. 5 and 6.

FIG. 5 is a block diagram showing the configuration of the interpolation circuit 401 in FIG.

In FIG. 5, 501 is a front scanning line input terminal to which the aforementioned image information 116 is input, 502 is a rear scanning line input terminal to which the aforementioned image information 117 is input, and 503 is a front field scanning line input terminal. The image information 409 described above is input. Further, 504 is an intra-field scanning line comparator, 505 is an inter-field scanning line comparator, 506 is an encoder, 507 is a computing unit, 508 is a switch (S ₆ ), 509 is an output terminal, and is connected to the output terminal 110. ing.

FIG. 6 schematically shows the relationship between the screen of three consecutive fields of a television signal and the scanning line, and the solid line is the scanning line.

In FIG. 6, the broken line shown in the third field is the interpolation scanning line created by the interpolation circuit 401.

The operation of FIG. 5 will be described below, but before that, the time relationship between the image information 116, 117, and 409 will be described.

The image information 116 differs from the image information 117 as shown in FIG.
It is delayed for 1H period. Therefore, at a certain moment, if image information 117, for example, information of the scanning line Y as shown in FIG. 6 is inputted to the rear scanning line input terminal 502, at that moment, to the front scanning line input terminal 501. As the image information 116, the information of the scanning line X one line before the scanning line is input.

On the other hand, in the image information 409, as described above, the field memories 403 and 404 sequentially read the information of one scanning line two times at a time and read it at a speed twice as fast as the writing time. Is the same as the form of the information sequence of the image information 116 and 117. Furthermore, image information 409
Is the image information delayed by one field from the image information 116 and 117 as described above. Therefore, from these facts, the rear scanning line input terminal 50
If the information of the scanning line Y is input as the image information 117 to 2, the previous field scanning line input terminal is at that moment.
As the image information 409, the information of the scanning line Z of the immediately preceding field is input to 503.

Now, the operation of FIG. 5 will be described.

At a certain moment, as described above, the image information of the scanning line X in the third field shown in FIG.
When the image information of the scanning line Y is input to the rear scanning line input terminal 502 and the image information of the second field scanning line Z is input to the front field scanning line input terminal 503, the intra-field scanning line comparator 504 scans. The luminance difference between the line X and the scanning line Y is compared, and a signal 510 is output as the difference α between them. Similarly, the inter-field scanning line comparator 505 compares the luminance difference between the scanning line X and the scanning line Z and outputs a signal 511 as a difference β.

Next, the encoder 506 receives the signals 510 and 511,
From the magnitude relationship between the differences α and β described above, a determination is made for each pixel as described later, and a calculation switching signal 512 corresponding to the determination result is generated and sent to the calculator 507.

On the other hand, the image information 116, 117, 409 from the respective input terminals 501, 502, 503 are input to the computing unit 507, respectively, and therefore, at a certain moment described above, the image information of each of the scanning lines X, Y, Z is input. ing. The calculator 507 calculates the average of the scanning line X and the scanning line Y, and, in accordance with the sent operation switching signal 512, the information of the scanning line X or the scanning line Y is calculated for each pixel as described later. Information, the average information of the scanning lines X and Y, or the information of the scanning lines Z,
Is selected and output as interpolation scanning line information.

The interpolation scan line information created in this way is switched (S ₆ ) 50.
8, the information of the original scanning line is alternately switched, the number of scanning lines is doubled and converted into a signal, and the signal is output to the output terminal 509. The signal is output as the final output of the scanning line conversion circuit.
It is output to 110.

Next, the scanning line interpolation method will be described with reference to FIG.

FIG. 7 is an explanatory diagram showing the state of interpolation, focusing on an arbitrary pixel on the scanning lines X, Y, Z in FIG.

When the difference signals α and β are obtained from the arbitrary pixels Xp, Yp, and Zp of the scanning lines X, Y, and Z as described above, as an example of this possible combination, as shown in FIG. = Small, β = Small, (b)
α = large, β = small, (c) α = large, β = large, (d) α =
There are four possible cases of small and β = large.

First, in the case of (a) α = small and β = small, the correlation between the pixels Xp, Yp, and Zp is large, so the average of both pixels is interpolated between the pixel Xp and the pixel Yp. Next, in the case of (b) α = large and β = small, the correlation between the pixel Xp and the pixel Yp is small, and the correlation between the pixel Xp and the pixel Zp is large.
This indicates that the correlation between the fields of the pixel Xp and the pixel Zp is large, so that the pixel Xp is directly interpolated between the pixel Xp and the pixel Yp. Next, in the case of (c) α = large and β = large,
Although there is no correlation between pixel Xp and pixel Yp and between pixel Xp and pixel Zp, this indicates that there is a large correlation between pixel Yp and pixel Zp, so between pixel Xp and pixel Yp In the pixel
Interpolate Yp. Finally, in the case of (d) α = small and β = large, the correlation between the pixel Xp and the pixel Yp is large, and the correlation between the pixel Xp and the pixel Zp is small. Since this has a large intra-field correlation and a small inter-field correlation, the pixel Zp of the previous field is directly interpolated as an interpolation signal.

In this way, by repeating the interpolation for each pixel while correlating the intra-field and inter-field, it is possible to obtain a high-quality converted luminance signal having twice the number of scanning lines.

Next, the color difference signal will be described.

Considering that the visual characteristic of the color difference signal is inferior to that of the luminance signal as described above, the method of taking the average of the conventional example is sufficient as the interpolation method. As a result, the field memory for color difference signals can be deleted. In FIG. 2, when a color difference signal is input to the input terminal 101, scanning line interpolation by the line memory is performed as described above, and the output terminal 11
At 0, a color difference signal having twice the number of scanning lines is output.

As described above, by using the field memory, the image quality improvement signal conversion can be realized more economically.
Further, the present invention can also obtain the same effect on a television signal demodulated into an RGB signal.

〔The invention's effect〕

According to the present invention, a field memory having a medium capacity of an image is provided for storing the information of the previous field, and the information of the previous field is used for the determination of the scanning line interpolation in the current field and the scanning line interpolation. Flicker can be prevented and vertical resolution can be improved. Also, the television signal is separated into a luminance signal and a color difference signal,
By performing the scanning line interpolation using the field memory only for the luminance signal and performing the scanning line interpolation using the line memory for the color difference signal, it is possible to make the color television signal image quality improvement signal conversion device more economical. There is an effect that can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional signal converter for performing scanning line conversion, and FIG. 3 is a timing chart for explaining the operation of FIG. 4, FIG. 4 is an explanatory diagram showing a state of scanning line interpolation by a conventional technique, FIG. 5 is a block diagram showing a configuration of the interpolation circuit of FIG. 1, and FIG. 6 is a relation between a screen of three consecutive fields and scanning lines. FIG. 7 is a schematic diagram showing the above, and FIG. 7 is an explanatory diagram showing a state of scanning line interpolation according to the present invention. 101 …… input terminal, 102 …… switch (S ₁ ), 103,104,10
5 …… Line memory, 106 …… Switch (S ₂ ), 107 ……
Adder, 108 …… 1/2 attenuator, 109 …… Switch (S ₃ ), 1
10 ... Output terminal, 111 ... Line memory control circuit, 401 ...
… Interpolation circuit, 402 …… Switch (S ₄ ), 403,404 …… Field memory, 405 …… Switch (S ₅ ), 406 …… Field memory control circuit, 501 …… Front scan line input terminal, 502…
... rear scanning line input terminal, 503 ... front field scanning line input terminal, 504 ... intra-field scanning line comparator, 505 ... inter-field scanning line comparator, 506 ... encoder, 507 ... calculator, 508 ... … Switch (S ₆ ), 509 …… Output terminal.

Claims (6)

[Claims] 1. A television signal which receives a television signal using an interlaced scanning method in which two consecutive fields form one frame, and scanning lines before and after interpolation for each field and a field before the field to be interpolated. In a signal conversion device that creates and inserts an interpolated scan line from a corresponding scan line in to convert to a new television signal, image information of an arbitrary scan line in the current field and adjacent scans adjacent to the arbitrary scan line. In-field correlation extraction means for extracting a correlation with image information of a line, and image information of a specific scan line corresponding to either the arbitrary scan line or the adjacent scan line in the field preceding the current field and the adjacent At least one of a correlation with image information of a scanning line or a correlation between image information of the specific scanning line and the arbitrary scanning line Based on the output signal of the intra-field correlation extracting means and the output signal of the inter-field correlation extracting means, and / or the image information of the arbitrary scanning line and / or the image of the adjacent scanning line. A signal conversion device comprising an interpolating means for creating the interpolation scanning line from information and / or image information of the specific scanning line. 2. The signal conversion device according to claim 1, wherein the adjacent scanning lines are obtained by delaying one horizontal scanning period by a line memory. 3. The signal conversion apparatus according to claim 1, wherein the image information of the specific scanning lines corresponding to the two scanning lines in the field before the current field is stored in the field memory in one vertical scanning cycle. A signal conversion device characterized by being obtained by delaying only. 4. The signal conversion device according to claim 1, wherein the interpolating means is configured to perform only on a luminance signal obtained by Y / C separating the television signal. A signal conversion device characterized by. 5. The signal conversion device according to claim 1, wherein the interpolating scan lines are created and inserted between the scan lines for each field after the television signal is converted to double speed. A signal conversion device characterized by being configured. 6. The signal converting apparatus according to claim 1, wherein the interpolating means interpolates an average of image information of the arbitrary scanning line and image information of the adjacent scanning line in a current field. A signal converter characterized in that it is configured to perform only on a color difference signal obtained by Y / C separation.