JPH0720268B2 - Color television signal transmission / reception system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television signal processing system, and more particularly to a color television signal processing system for transmitting and receiving a wide band of color signals. .

(Prior Art) Conventionally, the color signal of a color television signal is modulated by at least one of two color difference signals so that the upper sideband of the modulated color subcarrier signal does not exceed the band of the composite color television signal. Had been band limited in advance. For example, in the PAL system, the two color difference signals (U signal and V signal) are both band-limited to 1.3 MHz, and in the NTSC system, the narrow band color signal (Q signal) is band-limited to 0.5 MHz.

(Problems to be solved by the invention) In order to widen the band of color signals by the technology used in the NTSC system, PAL system, etc., the band of multiple color television signals should be widened or the frequency of the color sub-carrier should be increased. I had to lower it. Increasing the band of the composite color television signal hinders effective use of transmission paths such as radio waves, or loses compatibility with the television broadcasting network to which frequencies are already assigned. Also, lowering the frequency of the color subcarrier is
You will lose all compatibility with existing color television systems. Therefore, it is difficult for the conventional technology to widen the band of the color signal while maintaining compatibility with the conventional method.

Even in the conventional technology, two color signals are divided into a wide band signal (I signal) and a narrow band color signal (Q signal) like the NTSC system, and Q
For the signal, the upper sideband of the modulated color subcarrier signal is band-limited so that it falls within the band of the composite color television signal, but for the I signal, the upper band is limited to a wider band than that of the composite color television signal. It is possible to widen only one of them.

For example, in the NTSC system, a composite color television signal band
At 4.2 MHz and a color subcarrier frequency of about 3.6 MHz, the I signal band is 1.5 MHz and the Q signal band is 0.5 MHz. In this case, the lower sideband of the modulated I signal is 2.1 to 3.6 MHz and the upper sideband is 3.6 MHz to 4.2 MHz. Therefore, the 2.1-3.0 MHz component is the single sideband (SSB) of the I signal. In the single sideband, it is not possible to separate and demodulate two color subcarriers whose phases are orthogonal to each other. Therefore, with this method, it is impossible to further widen the band of the narrow band color signal.

(Means for Solving the Problems) The purpose of the system of the present invention is to eliminate the above-mentioned drawbacks, without widening the band of a conventional composite color television signal, and without lowering the conventional color subcarrier frequency. An object of the present invention is to provide a color television signal transmission / reception system capable of transmitting two color difference signals in a wide band together.

That is, the color television signal transmitting and receiving system of the present invention,
In a color television signal transmission / reception method in which subcarriers whose phases are orthogonal to each other are amplitude-modulated by two band-limited color difference signals and superimposed on a luminance signal for transmission, the band limitation of the two color difference signals is performed by one line. Or, in one field cycle, one is switched from the wide band to the narrow band and the other is switched from the narrow band to the wide band alternately. Therefore, at least the wide band low-pass filter and the narrow band low-pass filter are switched to the encoder on the transmission side, and the switching is performed alternately. A signal generator is provided, and the two color difference signals are transmitted in a wide band together.

In a preferred embodiment of the present invention, one color difference signal is band limited by a wide band low pass filter, and the other color difference signal is band limited by a narrow band low pass filter. Only the high frequency component of 1 line or 1
It is characterized by comprising a receiving side decoder for alternately switching a field or a signal added with a signal delayed for one frame period in synchronization with the switching cycle of the encoder.

Furthermore, a preferred embodiment of the present invention demodulates only the color difference signals transmitted in a wide band, the demodulated signal is band-limited by a wide band low-pass filter, and the band-limited signal is one line. Alternatively, it is characterized in that it is provided with a receiving side decoder for alternately switching a signal delayed by one field or one frame in synchronization with the switching cycle of the encoder.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a configuration block diagram of a transmission side encoder of a first embodiment in a transmission / reception system of the present invention, and FIGS. 2 and 3 show an example of a reception side encoder corresponding to the encoder shown in FIG. 1 and other examples. It is a configuration block diagram.

In the encoder of FIG. 1, the luminance signal Y of the output of the matrix circuit 1 is directly input to the input of the adder circuit 10, and the two color difference signals C ₁ and C ₂ are input to the input a and the input b of the switch SW1 (2). Is entered. The switch SW1 conducts the input a and the output c and the input b and the output d when the switching signal x from the switching signal generator 6 is "0", and when the switching signal x is "1", the input a is conductive.
And output d and input b and output c are conducted. Switch SW1
The output c of (2) is a wide band low pass filter (wide band LP
F) 3 becomes an input, and the output d becomes an input of a narrow band low pass filter (narrow band LPF) 4. The cutoff frequency of wideband LPF3 is f _CW , that of narrowband LPF4 is f _CN , and f _CW > f _CN .

Next, the outputs of wide band LPF3 and narrow band LPF4 are switched respectively.
It becomes the input e and the input f of SW2 (5). Switch SW2
The operation of (5) is similar to that of the switch SW1, and the switching signals x and y for controlling them are the same signals and are output from the switching signal generator 6. The switching signal generator 6 is controlled by the synchronizing signal of the television signal, and generates the switching signals x and y having the contents described below in synchronization with the synchronizing signal.

Due to the configuration including the block from the switch SW1 (2) to the switching signal generator 6, the two color difference signals C ₁ and C ₂ are band-limited respectively. When the switching signals x and y are “0”, the color difference signal C ₁ is limited to the cutoff frequency f _CW and the color difference signal C ₂ is limited to the cutoff frequency f _CN , which is called state “0”. The opposite is true when the switching signals x and y are "1", which is called state "1".

The output g of the switch SW2 (5) modulates the sub-carrier product f _S becomes modulation input of the modulator 7. The output h of the switch SW2 (5) modulates the subcarrier f _S phase becomes modulation input of the modulator 8 is 90 ° shifted (9). The two modulated color difference signals C ₃ and C _{4, the} luminance signal Y, the burst signal and the synchronizing signal are added and multiplexed by the adder circuit 10 and then band-limited to the cutoff frequency f _Y or less by the low pass filter (LPF) 11. To be a composite color signal.

FIG. 4 shows an example of the configuration of the switching signal generator 6. The sync signal is input to the HV separator 12 and separated into a horizontal sync signal (hereinafter abbreviated as HD) and a vertical sync signal (hereinafter abbreviated as VD).
HD becomes the input of the NOR circuit 14 and the count input of the 1/2 counter 15, and VD becomes the input of the edge detector 13. Edge detector
13 outputs the signal i which becomes "0" only at the falling edge of VD. The NOR circuit 14 takes the signal i and the NOR of HD to obtain the signal j.
Is output. The signal j becomes the reset input of the 1/2 counter 15. The output of the 1/2 counter 15 becomes the above-mentioned switching signals x and y.

The operation of the fourth illustrated circuit will be described with reference to FIGS. 5 and 6. In both figures, the television scanning system is 525 lines and 2: 1 interlace, but the number of scanning lines is not limited to 525, and any other scanning system can be used as long as it is an interlace system. The symbols HD and VD and the signals i and j shown in FIGS. 5 and 6 are the same as those shown in FIG. In the state of odd field in FIG. 5, the edge signal i generated by VD becomes “0” and at the same time HD becomes “0”, and at the falling edge of VD.
The output signal j of the NOR circuit becomes "1". On the other hand, in the even field state, even if the signal i becomes "0", HD does not become "0" and the signal j is kept as "0". Signal j in FIG.
Is a reset input of the 1/2 counter 15, the switching signals x and y are always "0" in the first line of the odd field where the signal j is "1", that is, line 1. After that, 1/2 counter 15 counts HD as a counter input,
A switching signal whose state is inverted line by line, such as "1" for line 2 and "0" for line 3, is obtained. Therefore, the fourth
The circuit shown in the drawing is a switching signal generator 6 of the encoder shown in the first drawing.
When used as, the first illustrated circuit becomes a system for generating the state "0" and the state "1" for each line.

FIG. 7 shows a frequency spectrum (hereinafter, abbreviated as spectrum) of the composite color signal output from the encoder shown in FIG.
The spectrum 1 is the spectrum of the luminance signal Y and has frequency components O to f _Y. Spectrum m and n represents the spectrum of a color signal, that is two modulated color difference signals C ₃ and C _4. The spectrum m when the state "0" in the spectrum of the color difference signals C _3, spectrum n becomes a spectrum of the color difference signals C _4, when the "1" and vice versa. The spectrum m is calculated from the frequency f _S −f _CW to the frequency f _Y (hereinafter (f _S −f _CW ).
Abbreviated like ~ f _Y ), but in this spectrum (f _S −f _CW ) ~ (f _S −f _CN ) components include single sideband components and spectrum n components Since it does not exist, it is demodulated correctly on the decoder side. In addition, (f _S −f _CN ) to (f _S +
Although there are components of spectrums m and n in the band of f _CN ), both are double sidebands, so that they can be correctly demodulated. Since the state "0" and the state "1" are inverted for each line, both the color difference signals C ₃ and C ₄ actually have the spectrum m, but demodulation is possible because the band limitation alternately becomes a narrow band. There is no change.

Next, an example of the decoder according to the first embodiment of the present invention will be described with reference to FIG.

The transmitted composite color signal is a carrier color signal trap 2
1, sync separator 23 and band pass filter (abbreviated as BPF)
Applied to 22. The BPF 22 has a pass band of (f _S −f _CN ) to f _Y , and extracts only the band included in the carrier color signal from the composite color signal. The output of the BPF 22 is input to the synchronous detectors 25 and 26 and the subcarrier regenerator 24. Synchronous detector 25 and 26
Detects the output of BPF2 by the subcarrier of the given phase.

The outputs of the synchronous detectors 25 and 26 are each switch SW1 (28)
Input a and input b. The operation of the switch SW1 (28) is the first. The operation of the switch SW1 (28) of the encoder shown is the first.
This is the same as the switch SW1 (2) of the encoder shown. The output c of the switch SW1 (28) becomes the input of the broadband LPF 29 and BPF 30. The cutoff frequency of the broadband LPF 29 is f _CW , and its output is the input e of the switch SW2 (34). The pass band of BPF30 is f _{CN to} f _CW , and the high frequency components of the color difference signals are extracted. BP
The output of F30 becomes the input of 1H delay (abbreviated as 1 HDL) 31. 1
The output of HDL31 becomes the input of adder 33. Switch SW1 (2
The output d of 8) becomes the input of the narrow band LPF 32, and the cutoff frequency of the LPF 32 is f _CN . The output of the narrow band LPF 32 is the adder 33.
Will be input. Adder 33 outputs 1 HDL31 and narrow band BPF32
The output of is added and output. The output of the adder 33 is a switch SW
It becomes the input f of 2 (34). The operation of the switch SW2 (34) is similar to that of the switch SW1 (28). Switch SW2 (34) is output g is the original color difference signals C ₁ recovered chrominance signal C ₅ next (encoder side), the output h is the original chrominance signal C ₂ of the restored color difference signals
It becomes C ₆ . The switching signals x and y of the switch SW1 (28) and the switch SW2 (34) are the same signals, and are output from the switching signal generator 35. The switching signal generator 35 generates a switching signal synchronized with the encoder from the synchronization signal. For example, if the same circuit as shown in FIG. 4 on the encoder side is used as the switching signal generator 35, the same switching signal as on the encoder side can be obtained.

Due to the block configuration from the BPF 22 to the switching signal generator 35, when the switching signals x and y are “0”, the color difference signal C ₅ having the band of the cutoff frequency f _CW from the composite color signal and the frequencies 0 to 0 in the current line. Color-difference signal C ₆ in which the high frequency component (frequency f _{cn to} f _CW component) in the previous line is added to the f _CN component
Is obtained. This corresponds to the state "0" on the encoder side. Switching signal x, the high-frequency component (frequency f _CN and color difference signals C ₆ having a cut-off frequency f _CW contrary to the above, in the previous line to a component of a frequency 0 to F _CN in the current line when y is "1" .About.f _CW component) is added to obtain a color difference signal C ₅ .
This corresponds to the state "1" on the encoder side. If the same circuit shown in FIG. 4 as the encoder side is used as the switching signal generator, the state “0” and the state “1” are inverted line by line in synchronization with the encoder side.

As an embodiment of the present invention, the transmitting side is the encoder shown in FIG.
The receiving side uses the decoder shown in FIG. 2 and the circuit shown in FIG. 4 as a switching signal generator, and FIG. 8 shows the image characteristics when these are applied to the conventional NTSC system. Since it is the NTSC system, the scanning system has a field frequency of 59.94Hz and scanning line 5
25 2: 1 interlaces, the luminance signal band, that is, the composite color signal band is f _Y = 4.2MHz, the color subcarrier frequency is f _S = 3.58MHz, and the wideband color signal band is f _CW = 1.5M
The frequency band of Hz and narrow band chrominance signal is f _CN = 0.5MHz.

In FIG. 8, the horizontal axis represents the frequency MHz representing the signal band, which corresponds to the horizontal resolution on the screen. The vertical axis represents the vertical resolution on the TV. In the NTSC system, the resolution of 525 TV lines corresponds to the 6 MHz band. The area where the NTSC luminance signal can be reproduced on the image receiving side is shown by the alternate long and short dash line in Fig. 8. The horizontal and vertical resolutions are well balanced.
The vertical resolution is lower than 525 lines because the Kell coefficient is about 0.7. On the other hand, the NTSC narrow-band color signal can be reproduced only in the area p (shaded area on the right-downward side) in FIG. 8, and the image quality is determined by the horizontal resolution substantially determined by 0.5 MHz. As a result, the color spreads horizontally on a particular screen, making it difficult to see. On the other hand, when the present invention is used, the area in which the two color difference signals can be reproduced is an area obtained by adding the area q to the area p (diagonal left slant line diagram).

In this embodiment, the high frequency component of the color difference signal, that is, 0.5 MHz to 1.
Since the 5MHz component is transmitted every other line, the vertical resolution is limited to 525 / 4TV lines, but as you can see from Fig. 8, this value is well balanced with the band 1.5MHz. This does not impair the image quality improvement. Also
Since low-frequency components below 0.5MHz are transmitted on each line, the same resolution as before can be obtained.

As described above, by using the present invention, both of the two color difference signals can have a wide band. It should be understood that the region r can be transmitted in addition to the regions p and q shown in FIG. 8 unless the Kell coefficient and the interline flicker are taken into consideration. Further, when the composite color signal in this embodiment is received by the conventional NTSC receiver, since the encoder of this embodiment modulates the color difference signal by the same method as the NTSC system, the area q shown in FIG. 8 cannot be reproduced. Therefore, the same region p as in the conventional NTSC system is reproduced as it is. In this way, compatibility with conventional receivers is maintained.

The circuit shown in FIG. 9 is an example in which the decoder shown in FIG. 2 is improved, but the input of the BPF 30 for extracting the high frequency component of the color difference signal is made by averaging the preceding and following line signals (adder 37 and × 1 / It is possible to make the cutoff characteristics in the vertical direction of the region q in FIG. 8 more steep. 1 of 9th illustration
HDL39 is necessary to match the timing with the output of BPF32. A similar delay is needed for the Y signal circuit.

Next, a third example of the decoder of the first embodiment of the present invention will be described.
It will be described with reference to the drawings.

The configuration shown in FIG. 3 shows a simplified decoder as compared with the decoder shown in FIG. This decoder switches the sub carrier phase of the synchronous detector 25 by the switch SW1 (28) according to the switching signal x and demodulates the two color difference signals every other line. Since the switching signal is synchronized with the encoder, only the color difference signal transmitted in the wide band is demodulated. The demodulated signal is band-limited by wideband LPF29 and then switched to switch SW2.
It becomes the input e of (34). Furthermore, the output of the broadband LPF29 is 1 H
After being delayed by one line by DL31, it becomes the input f of the switch SW2 (34). The inputs e and f of the switch SW2 (34) are switched according to the switching signal y and become the input signals C ₇ and C _{8 of} the inverse matrix circuit 36. With the above circuit, the two color difference signals are demodulated every other line in the band of 1.5 MHz, and the signal one line before the signal of the non-demodulated gap is used as it is.

The characteristics shown in FIG. 10 are image characteristics when the decoder shown in FIG. 3 is used. The area t in FIG. 10 is the area of the color difference signal reproduced by the decoder shown in FIG. Since the color difference signals are demodulated only every other line, the vertical resolution is limited even in the band of 0.5 MHz or less, and the area s that should be reproducible is lost. However, the area t is well balanced in the horizontal and vertical resolutions, and the advantages of the present invention can be sufficiently exerted.

Next, a second embodiment according to the present invention will be described. In this case, the case of applying to the NTSC system as in the first embodiment will be considered. In the first embodiment so far, the switching signals x and y are set to the fifth value.
As shown in FIG. 6 and FIG. 6, the system is reset once for each frame, but in the second embodiment, this is a system for resetting once every two frames. Then, the band of the transmitted color difference signal changes as shown in FIG. In FIG. 11, lines 1, 3, 5, ... Show odd-numbered field lines, and lines 2, 4, 6, ... Show even-numbered field lines. Comparing the frame 1 and the next frame, the frame 2, the two and the color difference signals C ₁ and C ₂ are not required to occur once every two frames, and the frequency f _CW for all lines.
You can see that it is transmitted in a wide band. Therefore, for a line sent in a narrow band of frequency f _{CN in} a certain frame, if the high frequency components of frequencies f _{CN to} f _CW are extracted from the signal of the same line in the previous frame and added to the low frequency component of the current line, The original two color difference signals C ₁ and C ₂ for all the lines in each frame are demodulated as wideband signals.

Specifically, the BPF30,1 HDL31,
As shown in FIG. 12 (a), the circuit including the adder 33 is BP
F30, 1 frame delay (abbreviated as 1 FrDL), may be changed to a circuit including an adder 33. However, in the case of video, 1 FrDL
Since double image disturbance occurs when 40 is used, Fig. 12 (b)
As shown in the figure, it is necessary to detect the motion of the image by the motion detection circuit 41, turn on the 1 FrDL40 circuit for a stationary pixel, and turn on the 1 HDL31 circuit for a moving pixel.

FIG. 13 shows an example of image characteristics in the second embodiment.
An area obtained by combining the areas u and v in the figure is an area of a color difference signal that can be transmitted for a still image. The resolution in the vertical direction is significantly improved as compared with the characteristic shown in FIG. 8, and the transmission area is increased by the area v. However, as for the moving image, only the area u can be transmitted as in the case of FIG.

Also in the decoder shown in FIG. 3 and the decoder shown in FIG.
12 Modifications similar to those shown in the figure can be applied to this embodiment. FIG. 14 shows a concrete example of generating a reset signal once in two frames. Sub-delivery items are HD, VD
Use the one that is phase locked to. When the NOR of the signal i indicating the falling edge of VD and the signal w indicating the timing when the subcarrier changes from negative to positive in FIG. 14 is obtained, a reset signal can be generated once in two frames.

The present invention can be used not only in the NTSC system but also in the PAL system, for example. Even with the NTSC system, the color difference signal band is 1.5M.
It can be higher than Hz. Further, it may be provided not for each switching line between the wide band and the narrow band but for each field.
In this case, the decoder shown in the 2nd, 3rd, and 9th form will convert all 1 HDL into the 12th.
A far field may be changed to one field delay by the method shown in the figure. When switching for each field, the vertical resolution of the high frequency component of the color difference signal is Can be transmitted.

(Effects of the Invention) As described above, by using the system of the present invention, a conventional color television signal transmission / reception system such as NT
While maintaining compatibility with the SC and PAL systems, it is possible to transmit and receive the two color difference signals in a wide band together, and a higher quality color image than before can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a transmission side encoder of a first embodiment in the system of the present invention, and FIGS. 2 and 3 are configurations of one example and another example of a reception side decoder corresponding to the encoder shown in FIG. FIG. 4 is a block diagram, FIG. 4 is a diagram showing an example of a switching signal generator configuration of an embodiment of the present invention, FIGS. 5 and 6 are signal waveform diagrams for explaining the operation of the circuit shown in FIG. FIG. 7 is a frequency spectrum diagram of a composite color signal shown in the encoder shown in FIG. 1, FIG. 8 is a diagram showing an example of image characteristics when the system of the present invention is applied to the NTSC system, and FIG. FIG. 10 is a diagram showing an improved example of the decoder shown in FIG. 10, FIG. 10 is a diagram showing image characteristics by the decoder shown in FIG. 3, and FIG. 11 is a diagram showing transmission bands of two color difference signals in the second embodiment of the present invention. 12 (a) and 12 (b) are different from the configuration of the first embodiment of the second embodiment. FIG. 13 is a circuit diagram illustrating one example of image characteristics according to the second embodiment, and FIG. 14 is a diagram illustrating a reset signal necessary for the second embodiment. It is a figure which shows an example of a method. 1 Matrix circuit 2,28 ...... Switch SW1,3,29 ...... Wide band LPF 4,32 ...... Narrow band LPF, 5,34 ...... Switch SW2 6,35 ...... Switching signal generator 7,8 ...... Modulator, 9,27 …… 90 ° shift 10,33,37 …… Adding circuit, 11 …… LPF 12 …… HV separator, 13 …… Edge detector 14 …… NOR circuit, 15 …… 1/2 Counter 21 …… Carrier color signal trap, 22,30 …… BPF 23 …… Synchronous separator, 24 …… Subcarrier regenerator 25,26 …… Synchronous detector 31,39 …… 1 HDL (delayer) 36… … Inverse matrix circuit, 38 …… 1/2 multiplier 40 …… 1 FrDL (1 field delay device) 41 …… Motion detection circuit

Claims (3)

[Claims] 1. In a color television signal transmission / reception system in which subcarriers whose phases are orthogonal to each other are amplitude-modulated by two band-limited color difference signals and superimposed on a luminance signal for transmission, the bands of the two color difference signals are provided. Since the limit is alternately switched from wide band to narrow band and the other from narrow band to wide band with one line or one field period, the transmitting side encoder has at least a wide band low pass filter, a narrow band low pass filter and the alternating And a switching signal generator for switching between the two color difference signals, and transmitting the two color difference signals in a wide band together. 2. A signal in which one color difference signal is band-limited by a wide band low pass filter and a signal in which the other color difference signal is band limited by a narrow band low pass filter include only the high band component of the one color difference signal. A receiver decoder which alternately switches a signal added with a signal delayed for one line, one field, or one frame in synchronization with a switching cycle of the encoder.
A color television signal transmission / reception system according to the item. 3. A color difference signal transmitted in a wide band is demodulated, and the demodulated signal is band-limited by a wide band low-pass filter, and the band-limited signal is converted into one line, one field or one frame. 2. The color television signal transmitting / receiving system according to claim 1, further comprising a receiving side decoder that alternately switches the signal delayed for a period in synchronization with the switching cycle of the encoder.