JPH0993546A - Noise blanking circuit for edtv reinforcement signal of television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a reinforcement signal noise at the reception of an EDTV-II broadcast signal apparently with an inexpensive and simple configuration. SOLUTION: The circuit is constituted of an EDTV identification signal detection circuit 9 detecting an EDTV broadcast identification signal from a broadcast video signal Stv to generate and output a detection signal Spt, a control circuit 5 generating and outputting a control signal Sctl corresponding to a synchronization period when a video by the broadcast video signal Stv is not in existence while the detection signal Spt is detected, an on-screen video signal generating circuit 6 that generates and outputs an on-screen video signal Srgb2 and generates and outputs a blanking signal Sblk corresponding to a display period of the on-screen video signal Srgb2 and an input period of the control signal Sclt, and a changeover circuit 7 that receives the blanking signal Sblk and selects the broadcast video signal Srgb1 when the blanking signal Sblk is not received or selects the on-screen video signal Srgb2 when the blanking signal Sblk is received.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a screen aspect ratio of 4:
3 television receiver, EDTV system NTS
The present invention relates to an EDTV reinforcement signal noise blanking circuit of a television receiver capable of suppressing video noise appearing on a screen by an EDTV reinforcement signal when receiving a television broadcast.

[0002]

2. Description of the Related Art Conventionally, NTSC television broadcasting has been performed in Japan and the United States. In recent years, for the purpose of improving the image quality of NTSC television broadcasting, E, which is an image quality improving method that maintains compatibility with NTSC television broadcasting.
The DTV-II system NTSC television broadcasting has been put into practical use.

The NTSC television broadcast is generally a so-called normal aspect video with a ratio of the horizontal and vertical directions of the video (aspect ratio) = 4: 3.
(Aspect ratio) = 16: 9, etc., so-called wide aspect video broadcasting is also increasing in recent years. Also, EDT
The V-II system NTSC television broadcasting is premised on the broadcasting of wide aspect video.

Therefore, when a television receiver having a normal aspect screen of (aspect ratio) = 4: 3 receives these broadcast images, the normal aspect image is displayed as it is on the full screen, and the wide aspect ratio is displayed. The video was displayed in the center of the display screen excluding the top and bottom edges.

A conventional television receiver having a normal aspect screen will be described with reference to the drawings. FIG. 4 is a block diagram of a conventional television receiver, and FIG.
(A) to (e) are signal waveform diagrams of each part of the same, and FIGS. 6 (a) and (b) are screen display examples of the same.

In the figure, α is a television receiver, A is an on-screen display circuit, 1 is a tuner / IF / demodulation circuit,
2 is an external input terminal, 3 is an input switching circuit, 4 is a video signal processing circuit, 5 is a control circuit, 6 is an on-screen video signal generation circuit, 7 is a broadcast video signal / on-screen video signal switching circuit, and 8 is a CRT. is there.

The television receiver α according to the present embodiment displays a broadcast image and a character image such as a channel number on the CRT 8.
An on-screen display circuit A is provided for displaying on the screen in a superimposed manner.

The television receiver α shown in FIG. 4 has a tuner / IF / demodulation circuit 1, an external input terminal 2, an input switching circuit 3, a video signal processing circuit 4, a control circuit 5, and an on-screen video. It is composed of a signal generation circuit 6, a broadcast video signal / on-screen video signal switching circuit 7, and a CRT 8.

The tuner / IF / demodulation circuit 1 receives and selects an arbitrary television broadcast signal Stv from a broadcasting station,
Intermediate frequency amplification and demodulation, and output as composite video signal (composite video signal) Scmp1.

A composite video signal Scmp2 from an external VTR (video tape recorder) or the like is input to the external input terminal 2.

The input switching circuit 3 includes the tuner / IF /
The composite video signal Scmp1 from the demodulation circuit 1 and the composite video signal Scmp2 from the external input terminal 2 are selectively switched,
Output as composite video signal Scmp.

The video signal processing circuit 4 color-decodes the input composite video signal Scmp to generate a broadcast video 3
The primary color signal Srgb1 is output and the composite video signal S is output.
Separates and outputs the synchronization signal Ssync from cmp.

The control circuit 5 generates and outputs a control signal Sctl including channel number data and display position data.

The on-screen video signal generating circuit 6 displays the character image of the channel number corresponding to the channel number data of the control signal Sctl at the display position on the screen corresponding to the display position data of the control signal Sctl. The image 3 primary color signal Srgb2 is generated and output in synchronization with the synchronization signal Ssync. Also, the on-screen video signal S which is the display period of the character image of the channel number
The blanking signal Sblk is output according to the display period of rgb2.

The broadcast video signal / on-screen video signal switching circuit 7 responds to the level of the blanking signal Sblk from the on-screen video signal generating circuit 6 by changing the level of the blanking signal Sblk from the on-screen video signal generating circuit 6. The video 3 primary color signal Srgb2 and the broadcast video 3 primary color signal Srgb1 from the video signal processing circuit 4 are selectively switched and set to 3
It is output as the primary color signal Srgb.

The CRT 8 receives the three primary color signals Srgb and displays an image on the screen.

The conventional television receiver adopts such a configuration, and the operation of the conventional example will be described below. CRT8
On the screen, the area where the broadcast video is displayed is defined as the main image area Fm, and the area where it is not displayed is defined as the non-image area Fn.

The blanking signal Sblk output from the on-screen video signal generation circuit 6 has a high level only during the horizontal period during which the character image of the channel number is output, and has a low level during the other horizontal periods, so that the CRT8 display is performed. The broadcast image and the on-screen image are superimposed and displayed on the main image portion Fm on the screen, and nothing is displayed because the black level signal is given to the upper and lower non-image portions Fn.

By the way, the EDTV system NTSC television broadcast signal Stv includes the NTSC television broadcast signal S
For the purpose of improving the image quality while maintaining compatibility with tv, the 53rd (316th) horizontal period to the 232nd (495th) horizontal period are provided to the main image portion Fm and the 23rd (28th) of the synchronization signal Ssync.
6) Horizontal period to 52nd (315th) horizontal period and 23rd period
The 3rd (496th) horizontal period to the 262nd (525th) horizontal period correspond to the non-image portion Fn, and the vertical resolution enhancement signal, the vertical time resolution enhancement signal, and the horizontal resolution enhancement signal are superimposed during the horizontal period. There is.

[0020]

However, in the conventional television receiver α, the EDTV-II system NTS is used.
When trying to receive the C television broadcast signal Stv,
As the reception electric field strength of the broadcast radio wave is reduced, distortion is generated, and multiple reflections are generated in the propagation path, the reinforcing signal is superimposed as noise N from the main image portion Fm to the non-image portion Fn of the display image. The image of the broadcast video 3 primary color signal Srgb1 is shown in FIG.
As shown in FIG. 6A, the display image by the three primary color signals Srgb becomes as shown in FIG. 6B, and as a result, the quality of the display image is deteriorated.

In particular, since the main image portion Fm is a moving image of multiple colors and the non-image portion Fn is a still image of a single color, the noise N of the non-image portion Fn is particularly noticeable.

As a measure for reducing the noise N, a reinforcement signal reducing circuit (not shown) such as a filter circuit may be added to the video signal processing circuit 4. However, in this method, the noise N removing process, that is, the signal. Since it is directly processed, it has a drawback that it necessarily causes an increase in circuit scale and an increase in initial cost.

Here, the present invention is an EDTV of a television receiver capable of apparently suppressing reinforcing signal noise at the time of receiving an EDTV-II broadcast signal with an inexpensive and simple structure.
A reinforcement signal noise blanking circuit is provided.

[0024]

In order to solve the above-mentioned problems, the present invention employs the following novel characteristic constitution means. That is, a first feature of the present invention is to provide an EDTV identification signal detection circuit that detects an EDTV broadcast identification signal from a broadcast video signal and generates and outputs a detection signal, and the broadcast video signal when the detection signal is detected. A control circuit for generating and outputting a control signal corresponding to a synchronizing period in which the image does not exist, and generating and outputting an on-screen image signal, and corresponding to a display period of the on-screen image signal and an input period of the control signal. An on-screen video signal generation circuit for generating and outputting a blanking signal, and the blanking signal is input, the broadcast video signal is input when the blanking signal is not input, and the on-screen video signal is input when the blanking signal is input. EDTV reinforcement signal noise blanking of a television receiver comprising a signal switching circuit for selectively outputting It is a road.

A second feature of the present invention is that the control circuit comprises:
It is an EDTV reinforcement signal noise blanking circuit of a television receiver that also performs display control of the on-screen video signal.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a television receiver having a normal aspect screen according to an embodiment of the present invention will be described with reference to the drawings. FIG.
2A is a block diagram of a television receiver according to an embodiment of the present invention, FIGS. 2A to 2E are signal waveform diagrams of respective parts, and FIGS. 3A and 3B are screen display examples.

In the figure, β is a television receiver, B is an on-screen display circuit / EDTV reinforcement signal noise blanking circuit, 1 is a tuner / IF / demodulation circuit, 2 is an external input terminal, 3 is an input switching circuit, 4 Is a video signal processing circuit, 5
Is a control circuit, 6 is an on-screen video signal generation circuit, 7
Is a broadcast video signal / on-screen video signal switching circuit, 8
Is a CRT, and 9 is an EDTV identification signal detection circuit.

The television receiver β shown in FIG. 1 has a tuner / IF / demodulation circuit 1, an external input terminal 2, an input switching circuit 3, a video signal processing circuit 4, a control circuit 5, and an on-screen video. Signal generation circuit 6, broadcast video signal / on-screen video signal switching circuit 7, CRT 8, and ED
It is composed of a TV identification signal detection circuit 9.

The tuner / IF / demodulation circuit 1 receives and selects an arbitrary television broadcast signal Stv from a broadcasting station,
Intermediate frequency amplification / demodulation is performed and output as composite video signal (composite video signal) Scmp1.

The external input terminal 2 receives a composite video signal Scmp2 from an external VTR (video tape recorder) or the like.

The input switching circuit 3 includes the tuner / IF /
The composite video signal Scmp1 from the demodulation circuit 1 and the composite video signal Scmp2 from the external input terminal 2 are selectively switched,
Output as composite video signal Scmp.

The video signal processing circuit 4 color-decodes the input composite video signal Scmp to generate a broadcast video 3
The primary color signal Srgb1 is output and the composite video signal S is output.
Separates and outputs the synchronization signal Ssync from cmp.

The control circuit 5 generates and outputs a control signal Sctl including channel number data, display position data, and the presence or absence of a detection signal Spt described later.

The on-screen video signal generation circuit 6 displays the character image of the channel number corresponding to the channel number data of the control signal Sctl at the display position on the screen corresponding to the display position data of the control signal Sctl, and nothing further. An on-screen image three primary color signal Srgb2 displaying a blanking image corresponding to the image portion Fn is generated and output in synchronization with the synchronization signal Ssync. Also, on-screen video 3
The blanking signal Sblk is output in accordance with the display period of the primary color signal Srgb2, the EDTV-II identification signal period, and the upper and lower non-image area Fn display periods.

The broadcast video signal / on-screen video signal switching circuit 7 responds to the level of the blanking signal Sblk from the on-screen video signal generating circuit 6 by changing the level of the blanking signal Sblk from the on-screen video signal generating circuit 6. The video 3 primary color signal Srgb2 and the broadcast video 3 primary color signal Srgb1 from the video signal processing circuit 4 are selectively switched and set to 3
It is output as the primary color signal Srgb.

The CRT 8 receives the three primary color signals Srgb and displays an image on the screen.

The EDTV identification signal detection circuit 9 detects the EDTV identification signal superimposed on the 22nd horizontal period and the 285th horizontal period of the composite video signal Scmp, and detects the EDTV identification signal.
When the TV identification signal is detected, the detection signal Spt is output.

The television receiver β of this embodiment adopts such a configuration, and the operation of this embodiment will be described below.

The blanking signal Sblk output from the on-screen video signal generation circuit 6 is at a high level only during the horizontal period during which the character image of the channel number is output and during the horizontal period corresponding to the non-image area Fn, and other horizontal levels. Since the level is low during the period, the image by the broadcast image signal Srgb1 is as shown in FIG. 3 (a), but the broadcast image and the on-screen image are superimposed on the main image part Fm on the CRT8 display screen. While being displayed, an arbitrary on-screen image instructed by the control circuit 5 is displayed on the upper and lower non-image portions Fn, and the display image by the three primary color signals Srgb is shown in FIG.
As a result of (b), the noise N is apparently masked.

In the present embodiment, the display color of the on-screen signal Srgb2 displayed on the non-image area Fn of the CRT8 display screen can be set arbitrarily. Generally, black is used as the display color, but as an example, when the display color is set to white or cyan with an intermediate gradation, a wide aspect broadcast image is continuously received. CR
It is also possible to prevent the occurrence of the burn-in phenomenon on the T8 screen or to improve the visual effect of the display image.

[0041]

As described above, by applying the EDTV reinforcing signal noise blanking circuit of the television receiver of the present invention to a television receiver having a normal aspect screen, reinforcement at the time of receiving an EDTV broadcast image is provided. Video noise due to signals and the like can be apparently suppressed, and the image quality can be maintained high.

Further, since it has no effect on the conventional NTSC television broadcasting signal, there is an advantage that compatibility between NTSC television broadcasting and EDTV system NTSC television broadcasting can be maintained.

Further, since the configuration is such that the on-screen display circuit provided in most of the television receivers is effectively used, the on-screen display processing and the noise blanking processing can be carried out at the same time, and a new additional component is added. There is an advantage that the initial cost can be suppressed to a minimum by suppressing it to a very small extent.

[Brief description of drawings]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention.

2 (a) to (e) are signal waveform diagrams of respective portions.

[FIG. 3] Same as above. (A) and (b) are examples of screen display.

FIG. 4 is a block diagram of a conventional television receiver.

5 (a) to 5 (e) are signal waveform diagrams of respective portions.

FIG. 6 Same as above. (A) and (b) are examples of screen display.

[Explanation of symbols]

α, β Television receiver A On-screen display circuit B On-screen display circuit and EDTV reinforcement signal noise blanking circuit 1 Tuner / IF / demodulation circuit 2 External input terminal 3 Input switching circuit 4 Video signal processing circuit 5 Control circuit 6 On Screen video signal generation circuit 7 Broadcast video signal / on-screen video signal switching circuit 8 CRT 9 EDTV identification signal detection circuit

Claims (2)

[Claims] 1. An EDTV identification signal detection circuit that detects an EDTV broadcast identification signal from a broadcast video signal and generates and outputs a detection signal, and synchronization in which no video of the broadcast video signal exists when the detection signal is detected. A control circuit that generates and outputs a control signal corresponding to a period, and generates and outputs an on-screen video signal, and generates a blanking signal corresponding to a display period of the on-screen video signal and an input period of the control signal. An on-screen video signal generation circuit for outputting, and a signal switch for selecting and outputting the broadcast video signal when the blanking signal is not input, and the on-screen video signal when the blanking signal is input. EDTV reinforcement signal noise blanking circuit of television receiver characterized by comprising a circuit and Road. 2. The EDTV reinforcement signal noise blanking circuit for a television receiver, wherein the control circuit also controls display of the on-screen video signal.