JPH02150188A - Television broadcast receiving circuit - Google Patents

Abstract

PURPOSE:To improve the definition of a display picture by time-compressing a picture signal in a second television broadcast system at a small aspect ratio, forming a mask signal in synchronization with the picture signal in the second television broadcast system in a part generated with the compression, and superimposing it. CONSTITUTION:When a discriminating circuit 7 discriminates that a received television signal is for the second television broadcast system at the small aspect ratio, the second received television signal is added through a first switching circuit 5 to a second signal processing circuit 11, a processing such as time-compression is executed, and the signal is outputted to a superimposing circuit 15 as the second picture signal. To the superimposing circuit 15, the mask signal corresponding to the time difference between the first and second picture signals is added from a mask signal generating circuit 13 by an instruction from the discriminating circuit 7, the mask signal is superimposed to the second picture signal, and outputted through a second switching circuit 17 to a picture display device side. Thus, even when the picture at the small aspect ratio is reproduced on the picture display device at the large aspect ratio, awkwardness is eliminated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a television broadcast receiving circuit, and in particular to a color television receiver capable of receiving a plurality of television broadcasts with different ratios of horizontal stripes on the image screen, so-called aspect ratios. The present invention relates to an improvement in a television broadcast receiving circuit suitable for.

[Problems to be solved by conventional techniques and inventions] In recent years,
The development of high-definition televisions, such as HDTV and other television broadcasting systems, that widen the baseband frequency band and increase the number of scanning lines to clearly reproduce detailed images on a wide screen is progressing.

High-definition television broadcasting systems such as HD TV,
Since the broadcasting system is different from the currently popular NTSC television broadcasting system, for example, television listeners need a color television receiver capable of receiving high-definition television broadcasting.

On the other hand, since the current N'T'SC format television broadcasting is widely used, it is expected that there will be a strong demand for receiving NTSC format television broadcasting using color television receivers for high-definition television broadcasting. be done.

However, the aspect ratio of the current NTS C television broadcasting system is 4:3 as shown in Figure 4A, but the high-definition television broadcasting system currently being considered for standardization is 4:3 as shown in Figure 4B.
For example, it is relatively horizontal, such as 16:9.

Therefore, when receiving NTSC television broadcasts on a color television receiver for high-definition television broadcasts, due to the difference in aspect ratio, the reproduced image of the NTSC television broadcasts as shown in Figure 5A (
There is a risk that the shaded areas) may protrude from the top and bottom of a color display device, for example, a color cathode ray tube.

If you use NT on a color CRT for high-definition television broadcasting,
If the image of SC television broadcasting is to be completely reproduced, the fifth
As shown by the diagonal lines in Figure B, it is expected that the received NTSC television signal will be time-compressed and reproduced in the center of the horizontally elongated color cathode ray tube, leaving margins on both sides.

However, when an image is reproduced in the center of a color cathode ray tube in this way, both the left and right edges of the reproduced image become visible, making it extremely unsightly.

The present invention was made under these circumstances.

TV broadcast reception that improves the unsightly appearance of an image display device by making it difficult to see both edges of the image even when an image from a TV broadcasting system with a small aspect ratio is reproduced on an image display device for TV broadcasting with a large aspect ratio. The purpose is to provide information on circuits.

[Means for Solving the Problems] In order to solve such problems, the present invention provides a system in which at least the selected received television signal has a predetermined aspect ratio in a first television broadcasting system or in this first television broadcasting system. A determination circuit is formed to determine which of the second television broadcasting formats has an aspect ratio smaller than that of the first and second television broadcasting formats. a first signal processing circuit that connects a first switching circuit that selectively switches the received television signal to the discrimination circuit, processes the first received television signal and outputs a first image signal; The first switching circuit is connected to a second signal processing circuit that processes the received television signal and outputs a second image signal temporally compressed according to the aspect ratio of the first received television signal. are doing.

Furthermore, a mask signal generation circuit that generates a mask signal with a time width corresponding to the time difference between the first and second image signals is connected to the discrimination circuit, and the second signal processing circuit The second image signal is connected to a superimposition circuit that superimposes the mask signal at least before or after the second image signal, and selectively receives the first and second image signals from the first signal processing circuit and the superimposition circuit. A second switching circuit is connected thereto.

[Function] In the television broadcast receiving circuit of the present invention equipped with such means, the received television signal is applied to the first switching circuit and the discrimination circuit, and the discrimination circuit converts the received television signal into the first television broadcast system. If it is determined that it is related to the above, a first determination signal is output to the first and second switching circuits. Therefore, the first received television signal related to the first television broadcasting system is processed by the first signal processing circuit via the first switching circuit, and the first image signal is processed via the second switching circuit. It is output to the image display device side.

When the determination circuit determines that the received television signal is related to the second television broadcasting method, a second determination signal is output to the first and second switching circuits, and the second determination signal is outputted to the first and second switching circuits. The received television signal is passed through the first switching circuit to the second switching circuit.
The signal is applied to the signal processing circuit, undergoes processing such as temporal compression, becomes a second image signal, and is output to the superimposition circuit.

To this superimposition circuit, a mask signal corresponding to the time difference between the first and second image signals is added from the mask signal generation circuit according to instructions from the discrimination circuit, and the mask signal corresponding to the time difference between the first and second image signals is applied before or after the second image signal, or before and after the second image signal. The mask signal is superimposed and the second
It is output to the image display device side via the switching circuit.

[Implementation example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a television broadcast receiving circuit according to the present invention.

In the figure, a channel selection circuit 1 selects a desired television channel from a received television signal from a receiving antenna and converts it into a composite color television intermediate frequency signal, and is connected to a demodulation circuit 3.

The demodulation circuit 3 amplifies the composite color television intermediate frequency signal and performs AM detection, for example, and is connected to the first switching circuit 5 and the broadcast system discrimination circuit 7.

The broadcast system discrimination circuit 7 determines whether the demodulated signal demodulated by the demodulation circuit 3 is a high-definition television broadcast system, for example, HDTV or NTSC.
It determines whether it is a broadcasting system by comparing and determining the synchronization signal frequency of the received TV signal and the number of images within a unit time.
If it is a TV child TV number, the first discrimination signal is outputted, and if it is an NTSC television signal, the second discrimination signal is outputted to the first switching circuit 5 and the second switching circuit 17.
It has a function of outputting an instruction signal to a blanking generator 13, which will be described later, when determining that it is a television signal.

The first switching circuit 5 switches the demodulation circuit 3 between the HDTV signal processing circuit 9 and the NT based on the discrimination signal from the broadcast system discrimination circuit 7.
It is selectively connected to the SC signal processing circuit 11 through φ switching, and the demodulated signal is sent to the HDTV signal processing circuit 9 by the first discrimination signal, and the N'1' signal is transferred to the HDTV signal processing circuit 9 by the second discrimination signal.
The signal is output to the SC signal processing circuit 11.

The HDTV signal processing circuit 9 receives the demodulated HDTV signal.
■ Signal processing of various types of transmission signals such as luminance signals, color signals, synchronization signals, etc. from the child TV program is performed, and the first color image signal as shown in Figure 2 A is processed to form a predetermined high-resolution scanning line. It is connected to the second switching circuit 17.

The NTSC signal processing circuit 11 has a conventionally known circuit configuration that separates a luminance signal, a color signal, and a synchronization signal from a demodulated NTSC television signal, performs various types of signal processing, and outputs a second color image signal. At the same time, as shown in FIG. 2B, the data is temporally compressed and output to the superimposing circuit 15.

The degree of compression in the NTSC signal processing circuit 11 is
NTS for color cathode ray tubes for TV television broadcasting system
This is temporal compression that allows the reproduced image of the C television broadcasting system to fit, and as shown in Figure 2B, a blanking period of 12.5% before and after the second color image signal per scanning line of 25% is obtained. It's like being exposed.

As shown in FIG. This is what is output. Note that this blanking pulse is at a level that displays a black image.

This superimposition circuit 15 superimposes a blanking pulse before and after each scanning line on the second color image signal from the NTSC signal processing circuit 11,
This is what is output to. Note that FIG. 2B shows a state in which a blanking pulse is superimposed.

The second switching circuit 17 receives the first
Alternatively, the second discrimination signal determines whether the first color image signal from the HD TV signal processing circuit 9 or N'I'SC
It selectively switches the second color image signal from the signal processing circuit 11, and is a color cathode ray tube circuit (not shown).
It is connected to the.

Next, the present invention configured as described above will be explained in detail.

A received television signal from a receiving antenna is selected to a desired channel by a channel selection circuit 1, AM demodulated by a demodulation circuit 3, and a test wave signal is applied to a first switching circuit 5 and a broadcast system discrimination circuit 7.

When the broadcast system discrimination circuit 7 discriminates that the received television (No. 3) is an HDTV television signal, the first discrimination signal
is output to the switching circuit 5 and the second switching circuit 17.

Therefore, the demodulated signal from the demodulation circuit 3 is applied to the HD TV signal processing circuit 9 via the first switching circuit 5 for signal processing, and the second color image signal is applied to the HD TV signal processing circuit 9 via the second switching circuit 17. The image is then output to a color cathode ray tube circuit, and an image is reproduced on the entire color cathode ray tube with an aspect ratio of 16:9 as shown in FIG.

On the other hand, the broadcast system discrimination circuit 7 converts the received television signal into NTSC.
When it is determined that the signal is a television signal, the second determination signal is switched to the first signal.
The first switching circuit 5 switches the demodulation circuit 3 into the NTSC signal processing circuit 1.
1, the demodulated signal is processed into a signal including temporal compression, and the second color image signal is sent to the superimposition circuit 1.
Added to 5.

Since the broadcast system discrimination circuit 7 outputs an instruction signal indicating that the signal is an NTSC television signal to the blanking generator 13, a blanking pulse is output from the blanking generator 13 to the superimposing circuit 15.

The superimposition circuit 15 superimposes blanking pulses before and after the second color image signal for each -scanning line (see FIG. 2B), and applies them to the second switching circuit 17.

The second switching circuit 17 outputs a second image signal to the color cathode ray tube circuit in response to the second discrimination signal, and the image is reproduced on the color cathode ray tube with an aspect ratio of 16:9, as shown by diagonal lines in FIG.

In this image, an image based on an NTSC television signal is reproduced in the center of the screen, and both sides of the image are blanked in black to mask both edges of the reproduced image, so that the image is reproduced with good pixel quality.

Note that by changing the level of the blanking pulse, it is possible to blanking mask the blanking areas on both sides of the reproduced image with any color other than black.

In addition, in the present invention, by superimposing a mask signal containing additional information such as characters or a clock in addition to the mask signal consisting of a simple blanking pulse, additional information can be added to the left or right of the reproduced image of the color cathode ray tube, or to the left and right margins. Can be displayed.

The mask signal generation circuit may be formed accordingly.

Further, each of the above-mentioned circuits can be connected directly or indirectly as long as the respective functions are not impaired.

The present invention can also be implemented in a configuration in which an HDTV television signal and an NTSC television signal are obtained through separate channel selection circuits and demodulation circuits, and the present invention is applicable to a configuration in which at least a tuned reception television signal is processed. Good to have.

[Effects of the Invention] As explained above, the present invention distinguishes between the first and second television broadcasting systems having different aspect ratios, and based on the result of this determination, determines the image signal of the second television broadcasting system having a small aspect ratio. At the same time as compressing the time, a mask signal synchronized with the image of the second television broadcasting system (a) is formed and superimposed on the part generated by the time compression, and the image signals of the first and second television broadcasting systems are Since the configuration is such that the output is switched to the image display device side, even if a television broadcast image with a small aspect ratio is reproduced on an image display device for a television broadcast system with a large aspect ratio, the mask pattern will not be displayed alongside the image. As a result, both edges become difficult to see, and the image quality on a single-image display device deteriorates.

Furthermore, if a mask signal containing additional information such as characters or a clock is superimposed on an image signal of a television broadcasting system having a small aspect ratio, there is an advantage that the additional information can be displayed in the margin of a single-image display device.

Note that the present invention is not limited to high-definition television broadcasting such as HDTV television broadcasting, but can be widely applied to switching reception between television broadcasting systems having a larger aspect ratio than the television broadcasting system currently in practical use, such as the NTSC system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a television broadcast receiving circuit according to the present invention, and FIGS.
FIG. 3 is a diagram illustrating the state in which an image is reproduced using the first and second image signals, FIG. 4 A and B are diagrams illustrating the aspect ratio, and FIG.
Figures A and B are diagrams showing a state in which an image of a television broadcast system with a small aspect ratio is reproduced on a screen of a television broadcast system with a large aspect ratio. ■・・Tuition selection circuit 3・・Demodulation circuit 5・・First switching circuit 7・・Discrimination circuit (broadcast system discrimination circuit) 9...First signal processing circuit (HD TV signal processing circuit) 11・...Second signal processing circuit (NTSC signal processing circuit) 13...Mask signal generation circuit 5 ・ 7 ・ (Blanking generator) ・Superimposition circuit ・Second switching circuit

Claims (1)

[Claims] (1) A first signal that outputs a first image signal by signal processing a first received television signal according to a first television broadcasting method having a predetermined aspect ratio among at least selected received television signals. a processing circuit and said received television signal;
A second received television signal according to a second television broadcasting system having an aspect ratio smaller than that of the first television broadcasting system is subjected to signal processing, and is temporally compressed according to an aspect ratio of the first received television signal. a second signal processing circuit that outputs a second image signal; a determination circuit that determines whether the received television signal corresponds to the first or second television broadcasting system; and determination from the determination circuit. a first switching circuit that selectively switches the first and second received television signals to the first and second signal processing circuits based on the results; and a first switching circuit that selectively switches the first and second received television signals to the first and second signal processing circuits; a mask signal generation circuit that generates a mask signal having a time width corresponding to the time difference; a superimposition circuit that superimposes the mask signal at least before or after the second image signal in each scanning line; and the first signal processing. said first from the circuit and the superimposed circuit.
and a second switching circuit that selectively switches the second image signal.