JPS647555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for reproducing a color television signal, and more particularly, to a method and an apparatus for reproducing a color television signal. The luminance signal, the color signal, and the information signal are separated from the composite color television signal in which other information signals, such as high-frequency luminance signals, are frequency-converted and multiplexed. The present invention relates to a reproduction method and apparatus.

[Conventional technology]

The video signal band of conventional television signals is
Bandwidth was limited by the standard, and resolution improvements were limited. Also, if you really want to increase the resolution, remove the band limit of the standard and use, for example, instead of 4.2MH in the NTSC television system.
Measures such as transmitting at 6.0MHz were required.

[Problem that the invention seeks to solve]

With conventional television signals, it has been difficult to improve the resolution of television signals within the standard transmission band.

Therefore, the present invention transmits a color television signal having a luminance signal having a wider band than the transmission band within a predetermined transmission band such as a standard, and reproduces this brightness signal having a wider band on the receiving side. An object of the present invention is to realize a color television signal reproduction method that reproduces high-resolution, high-definition images, and a receiver for the same.

[Means for solving problems]

The present invention divides a brightness signal of a color television signal into a high-band brightness signal higher than a certain horizontal frequency and a low-band brightness signal lower than a certain horizontal frequency, modulates a subcarrier different from a color subcarrier with the high-band brightness signal, This modulated luminance signal is inserted into a region that is conjugate to the frequency domain of the modulated color signal in the vertical/temporal frequency domain of the television signal, thereby producing a low frequency luminance signal, a modulated color signal, and the above-mentioned frequency-converted modulated luminance signal. From the color television signal transmitted (including recording) through this multiplexing, the phase relationship of the subcarriers is used to separate and reproduce the low-band luminance signal, high-band luminance signal, and color signal. It was designed to do this. That is, here, two color difference signals are used to modulate a color subcarrier in which an adjacent scanning line with the same phase as a certain scanning line moves in one vertical direction for each field, and the high frequency component of the luminance signal is Another subcarrier is modulated in which an adjacent scanning line having the same phase as the scanning line moves in the opposite direction to the one direction mentioned above for each field, so that the signals can be separated and reproduced on the receiving side.

〔Example〕

First, to facilitate understanding of the present invention, NTSC
The color television signal of the system and the color television signal that is the input signal of the color television receiver of the present invention will be explained.

FIG. 1 schematically shows the relationship between fields and scanning lines of an NTSC TV signal.

When this is viewed from the left (direction perpendicular to the y-t plane), the relationship between fields and scanning lines is as shown in FIG. In the figure, circles represent scanning lines.

As is well known, the NTSC system is configured by modulating color subcarriers with color difference signals. In FIG. 2, +π indicates the phase relationship of the color subcarriers. If this is expressed by a frequency f in the time t direction (referred to as a temporal frequency) and a frequency ν in the vertical y direction (referred to as a vertical frequency), it becomes as shown in FIG. Note that, since it is point symmetrical about the origin, it is sufficient to show two quadrants.

First, the frequency fs indicates a spatiotemporal frequency based on interlaced scanning, as is well known. Also, the frequency fsc is
This is the spatio-temporal frequency corresponding to the color subcarrier of the NTSC signal. In addition, the luminance signal has the frequency origin, fs,
They exist as sidebands around fs', fs'' and fs. Modulated chrominance signals exist as sidebands around frequencies fsc and fsc'. These luminance signals and the baseband signal and sideband signal of the sidebands overlap each other,
It is desirable to limit the bandwidth in advance, as this may affect image quality. However, since some techniques for this are already known, their explanation will be omitted.

In the above explanation, the bands where vertical and temporal frequency components are vacant are indicated as f _Y and f _Y ' in the figure.
That is, if the spatiotemporal frequency domain expressed in two dimensions of time frequency f and vertical frequency ν is divided into four quadrants by orthogonal time frequency axis f and vertical frequency axis ν,
The modulated color signal is a subcarrier in the second and fourth quadrants.
It is distributed near fsc and fsc', and the first and third quadrants are empty (luminance signal components are present).

Therefore, in the vertical and temporal frequency domains of existing color TV signals, other information of color signals and brightness signals of existing color TV signals, such as horizontal high-frequency signal components of brightness signals that could not be transmitted in the past, can be transmitted. Convert frequency. In other words, another subcarrier is modulated with this high-frequency component, and this modulated luminance signal is divided into the above-mentioned first quadrant,
The new color is inserted into the region near the frequencies f _Y and f _Y ′ in the third quadrant, that is, the frequency region conjugate to the frequency region of the modulated color signal, and frequency multiplexed.
A TV signal is constructed.

FIG. 4 is a horizontal frequency distribution diagram for explaining the frequency conversion of the high frequency component _YH of the luminance signal mentioned above.

In a color TV signal based on the NTSC system, the luminance signal ranges from 0 to 4.2 MHz. Therefore, in order to transmit detailed image information, the high frequency component _Y
Move to 4.2MHz. In this way, the frequency-multiplexed TV signal is transmitted in the 4.2MHz band, and the high-frequency component Y _H of the luminance signal is transmitted at the receiver by the reverse operation described above.
Play.

FIG. 5 shows an embodiment of the overall configuration of a color television signal communication system including a color TV receiver according to the present invention.

In the figure, A, B, and C indicate a color television signal transmitting section, transmission medium (transmission in a broad sense including recording), and receiving section, respectively. In order to simplify the explanation, only the video signal section directly related to the present invention will be shown, and the explanation of the audio signal, synchronization signal, etc. will be omitted since they are the same as in the existing TV system.

The generating section A applies the luminance signal Y and color difference signals I and Q to a so-called well-known color encoder 1 to obtain a substantially standard NTSC signal, and also to a high-pass filter 2 to obtain a high-frequency luminance signal _YH . Then, the frequency is shifted by a frequency shift circuit 3. This circuit will be described later. At this time, as can be seen from FIG. 3, it is preferable to band-limit the frequency bandwidth of the high-frequency luminance signal _YH in the vertical direction and the time direction by a known method, since this reduces crosstalk.

The output of the color encoder 1 and the output of the frequency shift circuit 3 are added by an adder 4, and the expanded
The NTSC signal, this extended NTSC signal, is modulated by the transmitter 5 into a form suitable for transmission.

The transmission section B is usually a space for transmitting radio waves, but is not limited to a space and may be a recording medium or the like.

The receiving section C is a color television receiver according to the present invention, and operates in the opposite manner to that of the transmitting section, and will be described later.

In the embodiment shown in FIG. 5, since the luminance signal Y has a higher luminance component than the conventional one, a reproduced image with higher resolution can be obtained. Furthermore, by combining this with a conventionally proposed scanning line interpolation technique, a reproduced image of even higher quality can be obtained.

Next, an embodiment of the processing of the high frequency luminance signal _YH of the color television signal applied to the receiver of the present invention will be described. As mentioned above, the high frequency luminance signal Y _H is frequency converted (shifted) and transmitted to an empty area in the spatio-temporal frequency domain, and as an example of this, as shown in Fig. 3, The color signal is sent in the second and fourth quadrants, and the high-range luminance signal _YH is sent in the first and third quadrants. That is, the former color signal is transmitted using a subcarrier with a phase as shown in FIG. 2, and the latter high-range luminance signal is transmitted using a subcarrier with a phase as shown in FIG.

More specifically, according to the standard, the color signal is a subcarrier that has a phase relationship as shown in Figure 2, that is, the phase is inverted for each scanning line (line period) and has the same phase as the carrier wave of the current scanning line. The scanning line of the previous field is below the current scanning line (in terms of the number of scanning lines).
In the case of the NTSC system, it is modulated with a subcarrier that becomes the scanning line (262H before). On the other hand, the high-frequency luminance signal in the present invention has a subcarrier having a phase relationship as shown in FIG. The scanning line is modulated with a subcarrier that becomes the scanning line above the current scanning line (263H before in the case of the NTSC system).

First, an example of frequency shift in the generating section will be described. As is well known, if a signal with frequency fi is multiplied by a signal with frequency fo, a signal with frequency fi±fo can be obtained. For example, a signal of frequency fi-fo can be obtained by using a band-pass filter. Therefore, one method is to multiply the wideband 4.0 to 6.0 MHz signal by the fo = fsc / 2 = 3.58 / 2 [MHz] ≒ 1.8 MHz signal, as shown in Figure 8, to reduce the frequency to 2.2 to 4.2 MHz. Can be shifted. Note that when fi<fo, the vertical relationship of the shifted frequencies is reversed.

One method of obtaining a signal (subcarrier) of frequency fo is to employ a frequency related to the color subcarrier fsc, for example. For example, 1/2 this
You can divide the frequency into However, it is necessary to set the phase of each scanning line so that it has the above-mentioned relationship and to match the transmission and reception. Further, although an offset occurs in the phase at the end of the scanning line, it is natural to reset it at the beginning of the scanning line so that the conditions shown in FIG. 6 are satisfied. Now, the color subcarrier fsc
As is well known, this applies to sending and receiving. In the case of frequency division, four uncertainties can occur as shown in FIG. In other words, for the frequency fsc shown by the solid line,
There are four possible fsc/2 values as shown by the dotted lines. Which of these is the case can be easily identified in the receiving section by directly inserting this fsc/2 signal in bursts for a certain period of time into a part of the signal, such as the vertical synchronization part. Also, if this signal is not present, it can be identified as a normal NTSC signal.

Specifically, for example, if internal signal processing is performed using a clock signal with a frequency of 4 fsc, which is four times the color subcarrier fsc, pulses as shown in Fig. 9 will be generated, but which phase of the pulses will be generated? It only instructs whether to adopt. Therefore, in addition to the method of directly inserting the fsc/2 signal as described above,
There are various methods such as inserting a digital code.

Next, an embodiment of a method for separating the color signal component and the high-range luminance signal component _YH from the signal component in the receiving method of the present invention will be described.

FIG. 7 shows an example of a receiving circuit for this purpose (portion C in FIG. 5). To do this, first, the frame memory 16 extracts components that change from frame to frame. This includes a high frequency luminance signal _YH and a color signal C. This is filtered by a band pass filter 11.
Extract 2.2~4.2MHz components. This signal is passed through a 262H delay element 12 and a 1H delay element 13 (here, H is the horizontal scanning line period) to delay the signal.

This is led to difference circuits 14 and 15 as shown. The difference circuit 14 calculates the difference between the signal and the signal delayed by 262H. On the other hand, as can be seen from Figures 2 and 6,
Two color signals C with a 262H difference are in phase,
Since the luminance signal component Y _H is in reverse phase, only the Y _H component can be extracted. Similarly, only the color signal component C can be taken out from the difference circuit 15 which obtains the difference between two signals having a difference of 263H. As for the color signal, it is sufficient to perform demodulation in the synchronous detection circuit 17 as usual and extract the two color difference signal components I signal and Q signal. Also,
As for the luminance signal component _YH , the frequency shift circuit 18 returns the original value to 4.2 to 6.2M by reversing the process described above.
The frequency may be shifted to Hz (4.0 to 6.0 MHz in the first embodiment) and added to the luminance signal in the adder circuit 19.

That is, by extracting the signal of frequency fo using the method described above and multiplying it in the frequency shift circuit 18 to obtain the component of (fi - fo) + fo, the shifted component of frequency fi is obtained. be able to.

What is considered to be a problem in the present invention is image quality disturbance due to high-frequency luminance signal components, and this can be considered as follows.

(i) Interference can be avoided by subtracting the component obtained as described above from the original component.

(ii) If no deduction is made using an existing receiver, etc., the interference is caused by superimposing color signals on a black and white TV.
This is considered to be of the same degree as interference to a television receiver. That is, it is inverted for each frame, and the visual impact is considered to be small.

In addition to the methods shown in the embodiments, many modifications of the present invention are possible. Listed below.

(i) In the embodiment of the present invention, the NTSC signal system has been explained, but in the case of the PAL system, the signal system is as shown in FIG.・
Luminance and Chrominance Signals To Avoid Cross Color In
A.P.L. Color System (The
filtering of luminance and chrominance
signals to avoid cross-colour in a
PAL color, system) BBC Engineering (sept.1976)
It is possible to insert several high frequency signals (such as a high frequency luminance signal).

Furthermore, by taking advantage of the fact that there are generally two gaps, for example, in the case of PAL system, _YH is 5.5 to 5.5
It is also possible to insert 8MHz to 10.5MHz into _YH '.

(ii) As a method of eliminating imperfections in interlaced scanning and obtaining high resolution in the vertical direction, for example, doubling the number of scanning lines in the receiving section and converting interlaced scanning to sequential scanning, as appropriate. Of course, this method can also be freely adopted in combination with a method of increasing the number of scanning lines by insertion. Also,
Further, on the image sending side, the original image signal is obtained by sequential scanning, and it is converted into an interlaced scanning signal by filtering and subsampling of appropriate time and vertical frequencies (for example, by Kay Lucas (K.
Lucas), “Standards
for Broadcasting Satellite Services), IBA Technical Review (IBA)
Technical Review), No. 18, March 1982) may be combined with the designer's freedom.

(iii) The circuit shown in FIG. 7 for separating high-frequency luminance signals and color signals is merely an example. It is also possible to further pass the output of this circuit to the next circuit if necessary. In other words, by taking advantage of the fact that the phase is reversed between frames, it is passed through a filter to obtain the difference between frames, or by taking advantage of the fact that the phase is reversed between the scanning lines of the same field, it is possible to calculate the difference between the scanning lines. Passing it through a filter that detects the difference between the two is also useful for improving characteristics.

(iv) As mentioned above, for color difference signals and high-band luminance signals, it is preferable to band-limit the vertical frequency and temporal frequency in advance. There are known methods to limit the vertical frequency, such as summing the outputs using horizontal periodic delay lines. The same thing can be done in the time direction as well, just by replacing it with a frame delay element. In addition, regarding the luminance signal, f
=15Hz, ν=131 It is desirable to remove components near the band corresponding to the scanning line.

(v) In frequency bands where color signals and high-range luminance signals are superimposed, it is desirable to remove baseband luminance signal components in advance.

(vi) An example of the configuration of a filter for extracting color signals and high-range luminance signals is shown in FIG. However, the method is not limited to this, and various methods are possible. For the purpose of clarifying the circuit configuration and expression by transfer function,
The configuration including the configuration shown in FIG. 7 is shown below. Here, only the high-band luminance signal will be described.

● (1-Z ^-262H ) (BPF) ● (1-Z ^-262H ) (BPF) (-1+2Z ^-L -
Z ^-2L )/4 ● (1-Z ^-262H ) (BPF) (1-Z ^-525H )
...(In the case of Figure 7) ●(1-Z ^-263 ) (BPF) (1-Z ^-525H ) Or a combination of these.

In the case of color signals, a similar configuration can be achieved by replacing 262H and 263H.

Note that the gain may be determined as appropriate, including the function of the enhancer.

(vii) As is well known from the configuration of digital filters, the characteristics of the filter for sum or difference between fields can be further improved by using the following configuration, for example. That is, instead of 1-Z ^-263H -
1+2Z ^-263H -Z ^-525H .

Furthermore, when a signal passes through two or more routes, it is common practice to make the delay times as uniform as possible using ordinary techniques.

〔Effect of the invention〕

According to the present invention, a high-resolution image is obtained from a television signal in which high-resolution information is inserted into a three-dimensional frequency gap and transmitted within the range of current television signal standards. effective.

In other words, by inserting a 6MHz high-band luminance signal into the 4.2MHz signal band, it becomes possible to reproduce high-definition television video signals without changing current transmission equipment.

In addition, existing TV receivers can receive the current television signal by removing the high-band luminance signal from this transmission signal, making it possible to maintain compatibility with the current system.

In addition, techniques for doubling the scanning line or sequential scanning (so-called improved
By combining it with buoys (Improved TV) and the like, it becomes possible to display high-definition television images while maintaining compatibility by increasing the resolution in the horizontal and vertical directions.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the general concept of TV signals.
FIG. 2 is a general explanatory diagram showing the phase of the color subcarrier in the time-vertical domain, and FIG. 3 shows the spatio-temporal frequency and the arrangement of high-band luminance signal components added to the television receiver of the present invention. An explanatory diagram, FIG. 4 is a diagram showing a frequency shift in a high-band luminance signal, FIG. 5 is a block diagram showing an embodiment of a TV signal transmission system including a receiving section of the present invention, and FIG. 6 is a color diagram. An explanatory diagram showing the phase relationship of high-frequency signals in a TV signal. FIG. 7 is a block diagram showing an embodiment of the configuration of a filter for extracting the superimposed color signal and high-frequency luminance signal. FIG. FIG. 9 is an explanatory diagram showing the relationship between a subcarrier fsc and a signal of frequency fo for frequency shifting, and FIG. 10 is a frequency allocation diagram when applied to PAL. 1...Color encoder, 3...Frequency shift circuit, 12...Field (262H) delay element.

Claims (1)

[Claims] 1. A second color difference signal of two color difference signals among image signals obtained by scanning, in which an adjacent scanning line having the same phase as a certain scanning line moves in one vertical direction for each field. A modulated color signal obtained by orthogonally modulating one subcarrier wave and a high-frequency component of the luminance signal of the above image signal, and an adjacent scanning line having the same phase as a certain scanning line is in the opposite direction to the above one direction for each field. A first subcarrier inputting a composite color television signal obtained by frequency multiplexing a modulated luminance signal obtained by modulating a second subcarrier that moves on the luminance signal;
a second step of demodulating the high frequency component of the luminance signal from the composite color television signal and demodulating the two color difference signals by synchronous detection; a third step of synthesizing the luminance signal obtained from the composite color television signal excluding the high-frequency component of the luminance signal and the two demodulated color difference signals. How to play the signal. 2. Two color difference signals among the image signals obtained by scanning, the first subcarrier wave is orthogonally moved so that the adjacent scanning line having the same phase as a certain scanning line moves in one vertical direction for each field. Using the modulated color signal obtained by modulation and the high-frequency component of the luminance signal of the image signal, adjacent scanning lines having the same phase as a certain scanning line are moved in the opposite direction to the above one direction for each field. A modulated luminance signal obtained by modulating a second subcarrier is transmitted to a signal source of a composite color television signal that is frequency-multiplexed on the luminance signal, and a signal source of a composite color television signal that is frequency-multiplexed with the luminance signal; a first demodulating means for demodulating the high frequency component; a second demodulating means for demodulating the two color difference signals from the composite color television signal of the signal source by synchronous detection; and a high frequency component of the demodulated luminance signal. a luminance signal obtained from the composite color television signal excluding high-frequency components of the luminance signal, and means for synthesizing the two demodulated color difference signals.