JPH08140059A - Scanning line converter - Google Patents

Abstract

PURPOSE: To provide a scanning line converter capable of scanning line converting not demodulated color difference signals but chrominance signals modulated as they are, improving operation, lowering the cost and miniaturizing. CONSTITUTION: C signals supplied from a YC separation circuit 1 are scanning line converted in a scanning line conversion circuit 4a for the C signals as they are without being demodulated. So as to realize the conversion, the codes of tap coefficients for respective scanning lines are controlled so as to be inverted for the respective scanning lines viewing from the input side of a vertical filter 45 by a tap coefficient changeover control circuit 7a and the tap coefficients are controlled to let the polarity of modulation be inverted for the respective scanning lines viewing from the output side of the vertical filter 45 by the tap coefficient changeover control circuit 7a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning line conversion device used in video equipment such as a television receiver. Further, the present invention particularly provides a scanning line conversion device which is capable of scanning line conversion of a color signal as it is modulated rather than a demodulated color difference signal, is easy to use, and is low in cost and small in size. Has an aim.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional scanning line conversion device. The input composite signal (composite video signal) is input to the YC separation circuit 1. The YC separation circuit 1 separates the composite signal into a luminance (Y) signal and a color (C) signal. C
The signal remains quadrature modulated by the color subcarrier. The configuration of the YC separation circuit 1 can be both analog and digital, and the YC separation method is 3
Dimensional separation, two-dimensional comb-shaped separation, separation by a one-dimensional bandpass filter, etc. are considered. It should be noted that the YC separation circuit 1 may use a built-in television receiver.

The form of each of the Y and C output signals of the YC separation circuit 1 is limited by the circuit of the next stage. The Y signal output needs to be a digital signal because the Y signal scanning line conversion circuit 3 in the next stage has a digital circuit configuration. Therefore, when the YC separation circuit 1 has a digital configuration, the digital Y signal may be output as it is. YC for analog configuration
It is necessary to add an A / D converter to the final output stage of separation. On the other hand, the C signal output form needs to be adapted to the configuration of the color demodulation circuit 2 in the next stage.

In the color demodulation circuit 2, the C signal is converted into the color difference signal (R
-Y, BY or I, Q). Color demodulation circuit 2
Like the YC separation circuit 1, there are two possible configurations for analog and digital.

The output signal of the color demodulation circuit 2 needs to be a digital signal because the color signal scanning line conversion circuit 4 in the next stage has a digital circuit configuration. Therefore, when the color demodulation circuit 2 has a digital configuration, the digital signal may be output as it is. In the case of the analog configuration, it is necessary to add an A / D conversion unit to the final output stage of the color demodulation circuit 2. Further, since the color difference signal has a narrower band than the luminance signal, the color demodulation circuit 2 generally lowers the rates of the two color difference signals to multiplex (MPX) in order to save the circuit.

Each of the two scanning line conversion circuits 3 and 4 is composed of a series connection circuit of a memory and a vertical filter.
The Y signal supplied to the Y signal scanning line conversion circuit 3 is written in the memory 31 only in the scanning line which is the scanning line conversion target according to the control signal from the writing / reading control circuit 6. Done). The written Y signal is read at the display timing on the screen of the television receiver according to the control signal from the writing / reading control circuit 6. The control signal is a sync separation / timing generation circuit 5 to which an input composite signal is supplied.
Is generated based on the timing signal generated from the synchronization signal.

Thinning out of the scanning lines due to scanning line conversion,
A signal discontinuity caused by reading the same scan line many times, that is, aliasing interference at the time of vertical sample rate conversion is eliminated by the vertical filter 32 in the next stage.
The vertical filter 32 is composed of a transversal filter having one scanning line as a unit delay, and scanning line conversion is performed by switching the tap coefficient for each line. The tap coefficient switching control is performed by the tap coefficient switching control circuit 7. Tap coefficient switching control circuit 7
The reference timing of the control by is generated by the sync separation / timing generation circuit 5 as in the case of the control of the memory 31.

An example of tap coefficient switching is shown in FIG. In the figure, the circles on the left side show the scanning lines on the input side, and the circles on the right side show the scanning lines on the output side. As shown in the figure, the mixing ratio of the scanning lines from the input side is switched for each scanning line on the output side by the tap coefficient of the vertical filter 32, whereby the same image is displayed with the number of scanning lines converted. The function of this vertical filter is to insert a value of zero into the signal on the input side and once uprate it to the least common multiple of the number of input and output scan lines, and apply a vertical LPF to eliminate aliasing, and then output it. It is equivalent to thinning out the number of scanning lines.

In the example shown in FIG. 4, the scanning lines on the output side are densely drawn so as not to change the shape of the figure by scanning line conversion. The side scanning lines are output at the desired timing.
At this time, there is a time difference between the input and the output, but the time difference is absorbed by the input and output of the memory 32.

The scanning line conversion for the color difference signals is similarly performed by the memory 41 and the vertical filter 42 in the color signal scanning line conversion circuit 4 similar to the Y signal scanning line conversion circuit 3. The signal demodulated into the color difference signal may be treated in the same manner as the Y signal except for the difference between the color matrix and the signal band.

The Y signals and color difference signals after scanning line conversion output from the scanning line conversion circuits 3 and 4 are supplied to output circuits 8 and 9, respectively. The output circuit converts the signal according to the specifications of the connection destination and outputs it to the outside. As a simple example, digital Y signals and color difference signals are only D / A converted and output as analog signals. In this case, the output is an analog Y, color difference signal. In addition, a separated video signal separated into a Y signal and a C signal (hereinafter, separated Y /
When the C signal is required, the color difference signal needs to be remodulated into the C signal, and when the composite signal is required, the Y signal and the C signal need to be combined.

FIG. 6 shows, as another conventional example, an apparatus in which the arrangement of the memories in the scanning line conversion circuits 3 and 4 and the vertical filter circuit is reversed. In this example, the signal on the output side (the signal after scanning line conversion) is created before the signal is stored in the memory, and the signal on the output side is stored in the memory. Since the signal on the output side is generated at the same time as the signal on the input side, it is necessary to accelerate the operation speed of the vertical filter to match the output side when enlarging an image. The operation of the other blocks is similar to that of the conventional example shown in FIG.

[0013]

Generally, the input / output of consumer video equipment (television receiver, etc.) is a composite signal or a separated Y / C signal. Therefore, the C signal is demodulated into a color difference signal and scanning line conversion is performed. However, it is preferable to use not a scanning line conversion device that re-modulates to generate a C signal, but a device that can perform scanning line conversion on a C signal as it is. However, in the configuration example according to the conventional technique, since the color signals are demodulated into the color difference signals and then the scanning lines are converted, the color demodulation circuit 2 is required. When the form of the color signal of the output signal is a modulated color signal with a color burst signal (a signal orthogonally modulated by a color subcarrier), a so-called C signal, the color difference signal must be modulated again after the scanning line conversion. However, the circuit scale and cost are increased. Further, depending on the characteristics of the color demodulation / remodulation circuit, the color signal may be deteriorated. Considering the case where the color demodulation circuit 2 is configured by an analog circuit, D / A and A / D conversion are required, and when configured by a digital circuit, a large circuit and a complicated configuration are required to improve ACC characteristics and the like. .

According to the present invention, not the demodulated color difference signal but the color signal (C signal) as it is modulated can be converted into the scanning line and output in the form of the C signal, which is convenient and easy to use. It is an object of the present invention to provide a scanning line conversion device that can be manufactured at low cost and can be downsized.

[0015]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a luminance signal scanning line conversion circuit which has a luminance signal as an input and is composed of a memory and a vertical filter connected in series, and a color subcarrier. And a read / write control for adjusting the write and read timings of the two memories by inputting a color signal in a state of quadrature modulation by a And a coefficient switching control circuit that switches tap coefficients of the two vertical filters for each scanning line, and converts the number of scanning lines by adjusting the timing of writing and reading and switching the tap coefficient for each scanning line. In the scanning line conversion device for performing the above, the coefficient switching control circuit is configured such that each of the coefficient switching control circuits is viewed from the input side of the vertical filter in the color signal scanning line conversion circuit. A vertical filter in the color signal scanning line conversion circuit so that the sign of the tap coefficient for the scanning line is inverted for each scanning line and the modulation polarity of the scanning line output from the vertical filter is inverted for each scanning line. The present invention provides a scanning line conversion device characterized by switching control of the tap coefficient of.

[0016]

EXAMPLE FIG. 1 shows the configuration of an example. The same parts as those in the conventional example are designated by the same reference numerals. The form of each of the Y and C output signals of the YC separation circuit 1 is limited by the circuit of the next stage. In the case of this embodiment, since the scanning line conversion circuits 3 and 4a in the next stage are both digital circuits, the Y and C output signals must be digital signals. Therefore, the YC separation circuit 1
When is a digital configuration, the digital signal may be output as it is. In the case of an analog configuration, it is necessary to add A / D conversion to each output final stage of YC separation.
It should be noted that the YC separation circuit 1 may use a built-in television receiver.

As for the output from the YC separation circuit 1, the Y signal is Y
The C signal is supplied to the signal scanning line conversion circuit 3 and the C signal scanning line conversion circuit 4a. Scanning line conversion circuit 4a for C signal
The signal supplied to C is quadrature modulated with a color subcarrier.
Since it is a signal, there is no need to multiplex the signal as in the conventional example, and no demodulation processing is required. Each of the scanning line conversion circuits 3 and 4a is composed of a series connection circuit of a memory and a vertical filter.

Operation of the Y signal scan line conversion circuit 3 (writing / writing
The operations controlled by the read control circuit 6 and the tap coefficient switching control circuit 7a) are the same as those in the conventional example, and therefore the description thereof is omitted here.

Next, the operation of the C signal scanning line conversion circuit 4a will be described. The operation of the memory 41 is the same as the conventional example. A big difference from the conventional example is the tap coefficient switching control of the vertical filter 45 by the tap coefficient switching control circuit 7a. Examples of tap coefficient switching are shown in Figs. 2 (a) and 2 (b). In both (a) and (b) of the figure, the circle on the left side indicates the scanning line on the input side, and the circle on the right side indicates the scanning line on the output side. Further, the symbols attached to the respective circles represent the symbols of the color burst signal indicating the modulation state of the color signal (C signal). As shown in the figure, the mixing ratio of the scanning lines from the input side is switched for each scanning line on the output side by the tap coefficient of the vertical filter 45,
The same image is displayed with the scanning line number converted. The function of this vertical filter is to remove all the signs of the tap coefficients, and then, as in the conventional example, insert a value of zero into the signal on the input side and once uprate it to the least common multiple of the number of input and output scanning lines. This is equivalent to applying a vertical LPF that eliminates aliasing and thinning out the number of scanning lines on the output side.

Here, attention is paid to the polarity of modulation of the C signal, that is, the code of the color burst (the code within the circle). The burst code on the input side is inverted for each scanning line as shown in the figure. Therefore, when the scanning line conversion similar to that in the conventional example is performed in consideration of this code, as shown in the figure, the sign of the tap coefficient for each scanning line is inverted for each scanning line when viewed from the input side. You can do this. In addition, in order to output a normal C signal to the output side, a filtered C signal is output.
With respect to the signal, the tap coefficient is set so that the polarity of modulation (symbol in circle) is inverted for each scanning line when viewed from the output side. FIG. 2 shows an example of a sequence of tap coefficients of a vertical filter in which these two elements (inversion of the sign of the tap coefficient for each scanning line and inversion of the modulation polarity for each scanning line) are combined.

In the above example, since the color frame on the input side is not detected during scanning line conversion,
When the sign of the C signal of the scanning line on the output side displayed at the same place as the input side is stored as shown in FIG.
) And the case of reversing ((b) in the same figure). In either case, the sign (C
The signal modulation polarity) is inverted for each line, and this scanning line conversion does not deviate from the standard of the normal NTSC signal. Therefore, it is not necessary to newly provide a circuit for detecting a color frame.

Further, in the present embodiment, as in the conventional example, the scanning lines on the output side are densely drawn so that the shape of the figure does not change due to the scanning line conversion. However, when a part of the screen is enlarged and displayed, , Output the scanning line on the output side at the timing at which it is desired to be displayed. At this time, there is a time difference between input and output,
This time difference is absorbed by the memory input / output.

The Y and C signals after the scanning line conversion, which are respectively output from the scanning line conversion circuits 3 and 4a, are given to the output circuits 8 and 9, respectively. The output circuit converts the signal according to the specifications of the connection destination and outputs it to the outside. As a simple example, the Y signal and the C signal are only D / A converted and output as analog signals. In this case, the output is an analog separated Y / C signal. If a composite signal is required, it is necessary to combine the Y and C signals. However, a modulation circuit for remodulating a color difference signal into a C signal as in the conventional example is unnecessary.

Usually, in consumer video equipment, there are many interfaces in the above two signal forms (composite signal and separated Y / C signal), and scanning line conversion can be performed by C signal without interposing a color difference signal. This embodiment that can output is convenient.

FIG. 3 shows another embodiment in which the arrangement of the memory and the vertical filter in the scanning line conversion circuits 3 and 4a is reversed. In this example, an output side signal (scan line converted signal) is created before the signal is stored in the memory, and the output side signal is stored in the memory. The signal on the output side is generated at the same time as the signal on the input side, so when enlarging the image,
It is necessary to speed up the operation speed of the vertical filter to match the output side. The operation of the other blocks is similar to that of the embodiment shown in FIG.

[0026]

As described above, in the scanning line conversion apparatus of the present invention, not the demodulated color difference signal but the color signal as it is modulated (quadrature-modulated by the color subcarrier is added, and the color burst signal is added. A signal, a so-called C signal, can be converted into a scan line and output in the form of the C signal. Generally, input / output of consumer video equipment is generally performed by a composite signal or a separated Y / C signal, so scanning line conversion can be performed by the C signal without a color difference signal, and a signal in the C signal format can be obtained. This scan line conversion device that can output is very convenient.

Further, since the present scanning line conversion apparatus can perform scanning line conversion without demodulating the color signals, a color demodulation circuit is not required, and the color difference signals are remodulated even when outputting in the C signal form. Since a modulation circuit is not required, cost reduction and downsizing can be achieved, and deterioration of a color signal, which is apt to occur in the past due to the characteristics of a color demodulation and re-modulation circuit, can be prevented. The scanning line conversion device according to the second aspect is suitable for a video device in which an output signal can be a composite signal (composite video signal) and input / output is a composite signal.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a diagram illustrating an example of tap coefficient switching of a vertical filter.

FIG. 3 is a block diagram of another embodiment.

FIG. 4 is a diagram showing an example of tap coefficient switching of a conventional vertical filter.

FIG. 5 is a block diagram of a conventional example.

FIG. 6 is a block diagram of a conventional example.

[Explanation of symbols]

 1 YC separation circuit 3 Y signal scanning line conversion circuit 4a C signal scanning line conversion circuit 5 Sync separation / timing generation circuit 6 Writing / reading control circuit 7a Tap coefficient switching control circuit 8, 9 Output circuit (D / A converter) ) 31,41 Memory 32,45 Vertical filter

Claims (2)

[Claims] 1. A brightness signal scanning line conversion circuit comprising a memory and a vertical filter connected in series, and a color signal orthogonally modulated by a color subcarrier as an input, and a memory and a vertical filter. A scanning line conversion circuit for color signals, which is connected upright with a writing / reading control circuit for adjusting the writing and reading timings of the two memories, and tap coefficients of the two vertical filters are switched for each scanning line. A scan line conversion device configured to convert the number of scan lines by adjusting the write and read timings and switching the tap coefficient for each scan line, the coefficient switch control circuit comprising: When viewed from the input side of the vertical filter in the color signal scanning line conversion circuit, the sign of the tap coefficient for each scanning line is inverted for each scanning line, A scanning line conversion device, wherein the tap coefficient of the vertical filter in the color signal scanning line conversion circuit is switched and controlled so that the modulation polarity of the scanning line output from the vertical filter is inverted for each scanning line. . 2. The scanning line conversion device according to claim 1, wherein the luminance signal output from the luminance signal scanning line conversion circuit and the color signal output from the color signal scanning line conversion circuit are combined. And a scanning line conversion device comprising an output circuit for outputting a composite video signal.