JPS63219286A - Low-noise television system - Google Patents

Abstract

PURPOSE:To suppress a noise preventing overmodulation from being generated, by transmitting a luminance signal after applying preemphasis on the high frequency area of the luminance signal corresponding to the amplitude of a low frequency component. CONSTITUTION:A signal inputted from a color camera, etc., is inputted to a matrix circuit 1, and the luminance signal Y is generated, and is separated to three systems. In first system, first signal is obtained by processing the signal Y with a flat high frequency area. In second system, second signal is obtained by processing the signal Y with a pre-emphasis frequency characteristic by which a gain is raised according to the increase of a frequency at the high frequency area. In third system, a mixing ratio K of the first signal to the second signal is calculated by a K component generation circuit 8 based on the low frequency component of the signal Y. And the first signal and the second signal are synthesized in a form of the third signal=(first signal)X(1-K)+(second signal)XK, then, the third signal is generated, and broadcasting is performed setting the third signal as the luminance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low-noise television system that improves image quality while suppressing an accompanying increase in noise when transmitting and receiving television broadcast images.

[Conventional technology]

From the broadcasting station side, the luminance signal component 'f 4 is processed with almost flat characteristics up to the region exceeding IviHz, is transmitted by amplitude modulation, and color subcarriers are superimposed at positions of 3 and 5 aMHz. In normal television receivers, in order to prevent problems such as cross color due to insufficient separation of the luminance signal component and color signal component, the luminance signal component is given 2 to 3 MF (a descending characteristic from Z onwards).High-resolution image reception In this machine, the luminance signal component and the color signal component are completely separated using a comb filter, and the luminance signal component is processed with flat characteristics.

[Problem that the invention seeks to solve]

In high-resolution receivers, the bandwidth of the luminance signal is wider than in normal receivers, so noise also increases. Improving resolution does not necessarily lead to improvement in image quality.

As a measure to expand the usable bandwidth of the luminance signal while suppressing noise, it is possible to pre-emphasize the amplitude of the luminance signal on the transmitting side and de-emphasize it on the receiving side, but it is also possible to amplitude modulate the luminance signal. With the current transmission method, pre-emphasis using the normal method would cause overmodulation in the broadcaster, and existing TV receivers that do not have a de-emphasis function would cause an unnatural feeling on the screen.
All 1. I didn't work.

The purpose of this invention is to effectively perform pre-emphasis and de-emphasis while preventing overmodulation of broadcasting equipment and maintaining compatibility with existing receivers. ] This invention is comprised of a broadcaster and a receiver.

In a typical embodiment of this invention, the broadcaster includes:
The luminance signal component of a color video signal obtained by a camera or the like is separated into three systems.

In the first system, a first signal is obtained by processing a luminance signal with flat frequency characteristics.

In the second system, a second signal is obtained by processing the luminance signal with a pre-emphasis frequency characteristic in which the gain increases as the frequency increases in a high frequency region.

In the third system, a mixing ratio K between the first signal and the second signal is calculated based on the low frequency component of the luminance signal.

Here, the value of K is 1 when the amplitude of the low frequency component is minimum (0%), decreases as the amplitude of the low frequency component increases, and when the amplitude of the low frequency component is maximum (100%) OVC
Become.

The first signal and the second signal are (first signal)
X(1-K) + (second signal) The luminance signal (third signal) in the received television signal is separated into three systems.

In the first system, the third signal is processed with flat frequency characteristics to obtain the fourth signal.

In the second system, the $3 signal @all broadcast side Brien Fascist processes it with the opposite de-emphasis frequency characteristic to obtain the fifth signal.In the third system, the third
The K is calculated based on the low frequency component of the signal.

Then, the fourth signal and the fifth signal are combined in the form (fourth signal)X(K-1)+(fifth signal)XK, and this is used as a luminance signal to display an image.

As exemplified in the embodiments described above, in the present invention, on the broadcasting side, depending on the low frequency component in the luminance signal, the difference between the flat frequency characteristic and the predetermined pre-emphasis frequency characteristic in the high frequency region is determined. The luminance signal is controlled and transmitted with a frequency characteristic that changes continuously, and on the receiving side, depending on the low frequency component in the received luminance signal, a flat frequency characteristic and de-emphasis, which is the opposite of the pre-emphasis described above, are generated. The received luminance signal is controlled using a frequency characteristic that continuously changes between the received luminance signal and the frequency characteristic to obtain a luminance signal for displaying an image.

[Function] The amplitude of each frequency component of the luminance signal is large in the low frequency region and small in the high frequency region. Therefore, the modulation degree in amplitude modulation is highly dependent on the amplitude of the low frequency component of the luminance signal, and when the amplitude of the low frequency component is the minimum, there is a large margin in the modulation degree; When this is the case, there is almost no margin for the degree of modulation.

In this invention, when the amplitude of the low frequency component of the luminance signal is small, the broadcasting side applies sufficiently large pre-emphasis based on the desired pre-emphasis frequency characteristics (
When the amplitude of the low frequency component in K-1) is large, the pre-emphasis application rate Ki is lowered. As a result, it is possible to perform pre-emphasis as close to desired frequency characteristics as possible within the range allowed by the modulation degree while always avoiding overmodulation.

On the receiving side, the original luminance signal is reproduced by the reverse procedure to that on the broadcasting side, and an image is displayed based on this, but the noise in the image is greatly suppressed by the above-mentioned Brian Assis, and the visual psychological You will notice an even greater reduction in noise. In addition, when receiving images using such a receiver, it is possible to vary the de-emphasis frequency characteristic around a specified value, or to vary the value determined by the low frequency component of the luminance signal around a specified value. By doing, etc.
By adjusting the amount of high-frequency components in the luminance signal used for display, it is also possible to adjust the definition of the screen according to your preference.The above-mentioned broadcast can be received by a receiver that does not have a ready-made de-emphasis function. In this case, if the pre-emphasis level applied by the broadcaster is appropriate, the definition of the screen will increase, making it seem like the image quality is better than before, so it is important to be compatible with these TV receivers. You can get sex. However, if the pre-emphasis on the broadcasting side is excessive, the high-frequency components of the luminance signal will become excessive in existing conventional receivers, causing an unnatural feeling on the screen, so care must be taken.

The above-mentioned high frequency region of the luminance signal generally refers to the frequency region above 0-5 to I MHz, and the pre-emphasis frequency characteristic may be a linear rising characteristic such as x2 db per octave, or a non-linear rising characteristic. However, when making settings, it is necessary to consider the above-mentioned noise reduction effect and compatibility with existing receivers that do not have a de-emphasis function.

[Embodiment 1] FIG. 1 shows a video signal processing section on the broadcasting side q A signal input from a color camera or the like enters a matrix circuit 1, where a luminance component Y is generated. A part of this component Y is connected to the delay circuit 2.
The other part of the luminance component Y passes through the pre-emphasis frequency characteristic circuit 4 and the delay circuit 5 and enters the amplitude control circuit 3. Another part of the luminance component Y passes through the pre-emphasis frequency characteristic circuit 4 and the delay circuit 5 and enters the amplitude control circuit 6. , passes through a low-pass filter 7 and enters a K component generation circuit 8. Here, the passband of the filter 7 is from about 0.5 MHz downward. The K component generating circuit 8 is an amplifier having linear or non-linear input/output characteristics and configured to obtain outputs of K and (1-K) in accordance with the magnitude of the input amplitude. The outputs of the amplitude control circuits 3 and 6 are summed by a synthesizer 9 and sent to the color encoder 10.
It is determined according to the control signal (1-K) and K generated by the component generating circuit 8.

Here, the characteristics of the pre-emphasis frequency characteristic circuit 4 are as follows:
As shown in Fig. 3, the gain is flat below the frequency fo, and the gain increases at a rate of 12 db per off tarp above the frequency fo, and the frequency foO value is 0.5 MHz.
The characteristic of the K component generating circuit 8 is determined by the straight line A or the curve E shown in FIG.
, C, etc., when the amplitude of the low frequency component of the luminance signal below 0.5 MHz is maximum (100%), it is 0, and when the amplitude of the low frequency component is 00, it is l, and there is a continuous Therefore, when the amplitude of the component below 0.5 MHz in one luminance signal is small, the proportion of the output of the amplitude control circuit 6 in the signal components added by the synthesizer 9 increases,
The degree to which high frequency components are pre-emphasized in the broadcast luminance signal is high. On the contrary, 0,5 MI(z
When the amplitude of the following components is large, the proportion of the amplitude control circuit 3 output in the added signal components increases, and the luminance signal is processed and broadcast with nearly flat characteristics, resulting in overmodulation. 0 Figure 2 shows the luminance signal processing part on the image receiving side.The received color video signal enters the color decoder 11, and a part of the obtained luminance signal component Yr passes through the delay circuit 12 and is shaken. It enters the width control circuit 13. Further, another part of the luminance signal component Yr enters the diffusion frequency characteristic circuit 14, passes through the delay circuit 15'iz, and enters the amplitude control circuit 16. Yet another part of the luminance signal component yr is filtered through a low pass filter 1'7.
(passes from 0 to 0.5 MHz) to the K component generation circuit 1.
entering the sun. Similar to the circuit 8 in FIG. 1, the K component generating circuit 18 generates K and (1-K) according to the characteristics shown in FIG.
) and feed these outputs to amplitude control circuits 16 and 13, respectively.

The outputs of the amplitude control circuits 13 and 16 are (1-K), respectively.
and K, which are added in the combiner 19,
This serves as a luminance signal input to the matrix 20.

Here, the characteristics of the de-emphasis frequency characteristic circuit 14 are such that the gain decreases above the frequency fo as shown in FIG.
The signal that has passed through the pre-emphasis frequency characteristic circuit 4 is
When passed through this de-emphasis frequency characteristic circuit 14, its characteristics are determined so that it becomes the original signal. Although it is difficult to return the signal to its original form, the closer the value of K is to 1 and strong pre-emphasis is performed, the better it is possible to return it to the luminance signal before pre-emphasis. There is no effect on fidelity.

[Embodiment 2] FIG. 6 shows a luminance signal processing section on the broadcasting side. Here, unlike the example construction, the amplitude controller 3 in the first system of the luminance signal output from the IJ control unit is omitted, and the pre-emphasis frequency characteristic circuit 4 is replaced with the one shown in FIG. As shown in FIG.
By controlling the output of , and adding this output luminance signal component to the luminance signal Y that has passed through the delay circuit 2 in the synthesizer 9, the same effect as in the first embodiment can be obtained. This composite signal enters the color encoder 10.

FIG. 7 shows the luminance signal processing section on the image receiving side. Here, similarly to the broadcast side shown in FIG. 6, the amplitude controller 13 (FIG. 2) in the first system is omitted, and the de-emphasis frequency characteristic circuit 34 in the second system is used as a pre-emphasis A circuit with the same characteristics as the frequency characteristic circuit 24 is used, and a polarity inversion circuit 30 is interposed between the amplitude control circuit 16 and the synthesizer 20.

Therefore, on the broadcasting side, a high frequency component for pre-emphasis by the circuit 24 is added to the luminance signal Y processed with flat characteristics in an amount corresponding to the amplitude of the low frequency component, and then broadcast. A high frequency component for de-emphasis, which is similar to the high frequency component for pre-emphasis added on the broadcasting side, is created by the circuit 34, and only the above amount is subtracted from the received luminance signal Yr, resulting in the original luminance signal. A display luminance signal with characteristics close to Y can be obtained.

[Embodiment 3] FIG. 9 shows a luminance signal processing section on the broadcasting side. Here, the use of the amplitude control circuit 6 and the component generation circuit 8 in the second embodiment is omitted, and the nonlinear amplifier 3 is used instead.

M) One half of the luminance signal from the IJ box 1 is filtered by a low-pass filter 41 to obtain a component below the frequency f○ where emphasis starts to be applied, and this is supplied to the synthesizer 9.

Furthermore, the luminance signal enters the non-linear amplifier 42, and as shown in FIG. 11, when the amplitude is large, both the low and high frequency components of the luminance signal are amplified, and when the input amplitude is small, it is enhanced. obtains an output that hardly changes.

This output is supplied to a circuit 24 having a pre-emphasis frequency characteristic as shown in FIG. and the output of the pre-emphasis frequency characteristic circuit 24 to obtain a broadcasting luminance signal, which is sent to the color encoder IO.

In this device, the high frequency component of the luminance signal is superimposed on the low frequency component and enters the nonlinear amplifier 42, but in the input/output characteristics shown in Figure il1, the input is biased by the low frequency component, and then the high frequency component is superimposed on the low frequency component. It can be seen that amplification is occurring. Therefore, the amplitude of the low frequency component is 0.
When the amplitude is close to , the amplification gain of the high frequency component is extremely large, and as the amplitude of the low frequency component increases, the amplification gain of the high frequency component decreases.As a result, the amplitude control circuit 6 of FIG.
It is possible to obtain the same effect as when the amplitude of the high frequency component is controlled by the component.

FIG. 1O shows the luminance signal processing portion of the receiver. One half of the received luminance signal Yr passes through all of the low-pass filters 51 and is supplied to the synthesizer 19 in the same manner as on the broadcasting side, and the other half of the luminance signal yr is supplied to the nonlinear amplifier 42 and the pre-emphasis frequency on the broadcasting side, respectively. Nonlinear amplifier 5 with the same characteristics as the characteristic circuit 24
After passing through 2 and pre-emphasis frequency characteristic circuit 34-, the polarity is inverted in circuit 30 and supplied to synthesizer 19. The output is added to obtain a display luminance signal, which is input into the matrix 20. This operation is almost the same as the embodiment shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, the high frequency region of the luminance signal is pre-emphasized and broadcast according to the amplitude of the low frequency component, and de-emphasis is performed on the receiver side, thereby preventing overmodulation and reducing noise. Can be suppressed. Moreover, when this broadcast is received with a normal TV receiver that does not have a de-emphasis function, there will be no noticeable discomfort on the screen, and on the contrary, the definition will be improved. Compatibility is also achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the luminance signal processing section on the broadcasting side in the first embodiment of the present invention, FIG. 2 is a block diagram of the luminance signal processing section on the receiving side in the same embodiment, and FIG. 3 f#j:
1. FIG. 4 is a characteristic diagram of the pre-emphasis frequency characteristic circuit 4 in FIG. 1. FIG. 5 is a characteristic diagram of the de-emphasis frequency characteristic circuit 14 in FIG. 6 is a block diagram of the brightness signal processing section on the broadcasting side in the second embodiment of the present invention, and FIG.
The figure is a block diagram of the luminance signal processing part on the receiving side in the same embodiment, FIG. 8 is a characteristic diagram of the pre-emphasis frequency characteristic circuit 24 in FIG. 6, and FIG. A block diagram of the luminance signal processing part of
FIG. 10 is a block diagram of the luminance signal processing section on the image receiving side in the same embodiment, and FIG. 11 is a characteristic diagram of the nonlinear amplifier 52 in FIG. 10. 2 and 12... Delay circuit (circuit that obtains flat frequency characteristics), 3 and 13... Amplitude control circuit (circuit that makes the amplitude dependent on the low frequency component), 4... Pre-emphasis frequency characteristic circuit, 5 and 15...delay circuit, 6 and 16...
...Amplitude control circuit (circuit that makes it dependent on the amplitude of low frequency components), 7 and 17...Low pass filter, 8 and 18...
・K component generation circuit (circuit that detects the amplitude of low frequency components,
9 and 19...Synthesizer, 14. Self-de-emphasis frequency characteristic circuit. Patent applicant: Agent of Nippon Television Broadcasting Network Co., Ltd.
Tetsu Shimizu 2 people / [! 1 year old 2 figure Maro Figure 77

Claims (1)

[Claims] (1) Consisting of a broadcaster and a receiver, the broadcaster processes the low frequency components in the luminance signal with flat frequency characteristics, and processes the high frequency components in the luminance signal by increasing the amplitude amplification as the frequency increases. is between a pre-emphasis frequency characteristic that increases according to a predetermined slope and a flat frequency characteristic, and the amplitude of the low frequency component in the luminance signal is small depending on the amplitude of the low frequency component in the luminance signal. The receiver has a means for continuously controlling and transmitting the received luminance signal with a frequency characteristic approaching the pre-emphasis frequency characteristic and approaching the flat frequency characteristic when the low frequency component is large. The low frequency components in the received luminance signal are processed as they are, and the high frequency components in the luminance signal are processed between the flat frequency characteristic and the de-emphasis frequency characteristic, which is the opposite of the pre-emphasis frequency characteristic, and are processed as they are in the received luminance signal. Depending on the amplitude of the low frequency component of 1. A low-noise television system characterized by having means for obtaining a brightness signal for image display by controlling the brightness.