JPH0352278B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for transmitting a color television (hereinafter abbreviated as TV) signal, and more specifically, a method for transmitting a wideband TV signal through a limited band transmission medium. The present invention relates to a TV signal transmission method for transmitting (broadly defined transmission including recording, etc.) and reproducing fine images.

[Background of the invention]

Conventional TV signal bands were limited by each standard, and their resolution was limited. Also,
If you really want to increase the resolution, remove the band limit of the standard and use the NTSC television system.
Measures were needed, such as transmitting at 6.0MHz instead of 4.2MHz.

For this reason, conversely, there were problems such as difficulty in improving the resolution of TV signals within the standard range.

[Purpose of the invention]

An object of the present invention is to provide a method for transmitting high-definition TV signals that can be directly received by existing TV receivers (that is, while maintaining compatibility with current standards).

[Summary of the invention]

In order to achieve the above object, the present invention transfers and transmits high-frequency luminance signal components to the frequency gaps in both the time and vertical frequency domains of the TV signal, and extracts them on the receiving side. It is characterized by reproducing a high-definition TV signal by restoring the original high-band luminance signal.

[Embodiments of the invention]

First, the principle of the present invention in the case of an NTSC signal will be explained. FIG. 1 schematically shows the relationship between TV signal fields and scanning lines.

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.

In the NTSC color television system, as is well known, color signals are constructed 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 in the time t direction (referred to as a temporal frequency) and a frequency v in the vertical y direction (referred to as a vertical frequency), it becomes as shown in FIG. In addition, since it is point symmetrical about the origin, it is sufficient to show two quadrants.

First, the frequency s indicates a spatio-temporal frequency based on interlaced scanning, as is well known. Also, the frequency sc is
This is the spatio-temporal frequency corresponding to the color carrier frequency of the NTSC signal. Also, the luminance signal has the frequency origin, s,
The chrominance signals exist as sideband waves around the frequencies s′, s″, and s.The chrominance signals exist as sideband waves around the frequencies sc and sc′.The baseband signals and sideband signals of these luminance signals are mutually exclusive. Since overlapping signals may interfere with image quality, it is desirable to limit the bandwidth in advance.However, since some techniques for this are already known, we will not discuss them here.

In the above explanation, the bands where the vertical and temporal frequency components are vacant are indicated by _Y and _Y ' in the figure.

That is, if the spatiotemporal frequency domain expressed in two dimensions of time frequency and vertical frequency v is divided into four quadrants by orthogonal time frequency axis and vertical frequency axis v,
The carrier color signal is a subcarrier in the second and fourth quadrants.
They are distributed near sc and sc', and the first and third quadrants are vacant (or are not used very effectively).

Therefore, the present invention can improve existing color TV signals in the time and vertical frequency domains.
The color signal of the signal, other information of the luminance signal, for example, the horizontal high-frequency signal component of the luminance signal, which could not be transmitted in the past, is frequency-converted to obtain the frequencies _Y and _Y ' in the first and third quadrants described above. A new color TV signal is constructed by inserting the signal into the region shown in , that is, a frequency region conjugate with the frequency region of the carrier color signal, and frequency multiplexing the signal.

FIG. 4 is an explanatory diagram for explaining the frequency conversion of the high frequency component _YH of the luminance signal in one embodiment of the TV signal generation method of the present invention.

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 42MHz 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 implementing the color television signal generation method according to the present invention.

In the figure, A, B, and C respectively indicate a color television signal generation section, transmission (transmission in a broad sense including recording) medium, and reception section. 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 and synchronization signal will be omitted since they are the same as in the existing TV system.

The generating section A adds the luminance signal Y and the color difference signals I and Q to a so-called well-known color encoder 1 to obtain an almost standard NTSC signal, and also adds this luminance signal to a high-pass filter 2 to obtain the high-frequency luminance signal. Y get _H. 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 Figure 3, the high-frequency luminance signal Y _H
It is preferable to band-limit the frequency bandwidth in the vertical direction and the time direction using 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
NTSC signal (referred to as Extended Definition NTSC signal)
get. This expanded NTSC signal is modulated by the transmitter into a form suitable for transmission.

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

The receiving section C performs an operation opposite to that of the receiving 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, the high-frequency luminance signal, which is an important part of the present invention,
An example of _YH processing will be described. As mentioned above, the present invention is to frequency-convert (shift) and transmit the high-frequency luminance signal Y _H to an unoccupied region in the spatio-temporal frequency domain.
As shown in the figure, 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 according to the present invention has a subcarrier having a phase relationship as shown in FIG. The scanning line of the field is modulated with a subcarrier that is 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 ₁ is multiplied (modulated) by a signal with frequency ₀ , a signal with frequency ₁ ± ₀ can be obtained. Then, a signal in the lower sideband of frequencies _1-0 , for example, can be obtained using _a bandpass filter. Therefore, as shown in Figure 8, one method for ₀ is ₀ = sc / 2 =
3.58/2 [MHz] ≒ 1.8MHz signal, wideband 4.0~
By multiplying the 6.0MHz signal, the frequency can be shifted to 2.2-4.2MHz. Note that when ₁ < ₀ , the vertical relationship of the shifted frequencies is reversed.

One way to obtain a signal (subcarrier) with a frequency of ₀ is to use a frequency related to the color subcarrier _SC, for example. For example, this is divided into 1/2. However, it is necessary to ensure that the phase has the above-mentioned relationship for each scanning line 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 _SC
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 _SC shown by the solid line,
There are four possibilities for _CS /2 as shown by the dotted lines. Which of these is the case can be easily identified by the receiving section by directly inserting the _SC /2 signal in bursts for a certain period of time into a part of the signal, such as the vertical synchronization part. Also, without this signal, 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 _Sc , which is 4 _times as large as each subcarrier Sc, pulses as shown in Fig. 9 will be generated, but which of these pulses will occur? It only instructs whether to use phase pulses. Therefore, in addition to the method of directly inserting _{the Sc} /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-frequency luminance signal _YH component from the signal component in the receiving section 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 is the high-range luminance signal Y _H and the color signal C
including. Pass this through a bandpass filter 112.2
Extract the ~4.2MHz component. This signal is passed through a 262H delay element 12 and a 1H delay element 13 (here, H is a horizontal scanning period) to delay the signal.

This is led to difference circuits 14 and 15 as shown. The difference circuit 14 calculates the difference with the 262H delayed signal. 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. The color signal may be demodulated by the synchronous detection circuit 17 as usual, and the two color difference signal components I signal and Q signal may be extracted. In addition, as for the luminance signal component _YH , the frequency shift circuit 18 converts the original value from 4.2 to
The frequency may be shifted to 6.2 MHz (4.0 to 6.0 MHz in the first embodiment) and added to the luminance signal in the adder circuit 19.

That is, ₀ is extracted using the method described above, and this is multiplied by the frequency shift circuit 18 to obtain ( ₁ −
By obtaining the component of ₀ ) + ₀ , it is possible to obtain the shifted and restored component of frequency ₁ .

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 due to the superimposition of the color signal 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 embodiments 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. 10.
Luminance and Chrominance Signals To Avoid Cross Color In
A.P.L. Color System (The
filtering of luminance and chrominance
signals to avoide crosscolour in a PAL
(colong system) BBC Engineering (sept.1976)), similarly two signals (such as high-frequency luminance signals) in a three-dimensional (i.e., time-frequency domain, vertical frequency domain, and horizontal frequency domain) gap. It is possible to insert

Furthermore, by generally providing two gaps, for example, in the case of PAL system, 5.5 to 8MHz for _YH ,
It is also possible to insert 8 to 10.5MHz into YH _' .

(ii) As a method to eliminate imperfections in interlaced scanning and obtain high resolution in the vertical direction, for example, a method of doubling the scanning lines in the receiving section and converting interlaced scanning to sequential scanning, as well as an appropriate method. Of course, the present method can be freely adopted in combination with a method of increasing the number of scanning lines by inserting the number of scanning lines. Furthermore, there is a method in which the original image signal is obtained by sequential scanning on the image transmission side, and is converted into an interlaced scanning signal by filtering the appropriate time and vertical frequency and cutting out 2:1 (for example, by Kay Lucas (K.
Lucas), “Standards Broadcasting Satellite Service”
for Broadcasting Satellite Services)”, IBA Technical Review (IBA
Technical Review), No. 18, March 1982) may be combined at the designer's discretion.

(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 scanning lines of the same field, it is possible to calculate the difference between scanning lines. Passing it through a filter that detects the difference between the two is also useful for improving characteristics.

(iv) As described 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 luminance signals, for 2.2 to 4.2MHz on which color signals etc. are superimposed,
=15Hz, v=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 brightness signals is shown in FIG. However, the method is not limited to this, and various methods are possible.

For the purpose of clarifying the relationship between the circuit configuration and the expression by the transfer function, 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 _-263H ) (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 _−526H .

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, by inserting high-resolution information into gaps between three-dimensional frequencies, it is possible to transmit high-resolution image information within the range of current television signal standards.

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

Furthermore, by combining the scanning line technology with doubling or sequential scanning technology (so-called Improved TV) on the transmitting side and the receiving side, or on the receiving side,
By increasing the resolution in the horizontal and vertical directions, it is possible to display high-definition television images while maintaining compatibility.

[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 color subcarriers in the time-vertical domain, and FIG. 3 is an explanatory diagram showing the spatio-temporal frequency and the arrangement of high-frequency luminance signal components, which is an embodiment of the present invention. 4 is a frequency component distribution diagram showing a frequency shift in an embodiment of the present invention, FIG. 5 is a block diagram showing an embodiment of the television signal processing method of the present invention, and FIG. 6
FIG. 7 is an explanatory diagram showing the phase relationship of high-frequency signals in one implementation of the present invention. FIG. FIG. 8 is a frequency component distribution diagram showing the frequency relationship of frequency shift in one embodiment, FIG. 9 is an explanatory diagram showing the relationship between subcarrier _SC and a signal of frequency ₀ for frequency shift, and FIG.
The figure is a frequency allocation diagram when the present invention is applied to PAL. 1...Color encoder, 3...Frequency shift circuit, 12...Field (262H) delay element.

Claims (1)

[Claims] 1. A color television signal transmission method comprising a television signal generation section that generates a color television signal, a transmission section that transmits the color television signal, and a reception section that receives the color television signal via the transmission section. In the above, the signal generating section converts information other than the color signal of the color television signal into two frequencies in both the time and vertical directions using a subcarrier different from that of the color signal.
The transmission unit transmits the color television signal including the other information, and the reception unit transmits the color television signal by performing an operation opposite to that of the signal generation unit. A color television signal transmission method characterized in that the other information is extracted from the first quadrant and the third quadrant.