KR19990001151U - Weak signal determination circuit of video signal processing device - Google Patents

Abstract

The present invention relates to a video signal processing apparatus capable of receiving a broadcast signal displaying a blue back screen by a blue back mode control signal. A sync signal separator for separating and outputting a composite sync signal into a vertical sync signal and a horizontal sync signal among broadcast signals 20; A pulse generator 30 for generating window pulses synchronized with the horizontal synchronizing signal; An end gate 40 connected in parallel to the synchronous signal separator 20 and the pulse generator 30 and outputting a logical sum of the horizontal synchronous signal and the window pulse; A counter 50 that counts the output signal from the end gate 40 and stops counting the output signal from the end gate 40 upon application of a vertical sync signal from the sync signal separator 20; When the vertical synchronizing signal is applied, the microcomputer 60 which outputs an arbitrary blue back mode control signal when the count value counted to the counter 50 is equal to or greater than the preset count value is provided, thereby more accurately detecting the weak signal of the video device. To implement.

Description

Weak signal determination circuit of video signal processing device

The present invention relates to an image signal processing apparatus, and more particularly, to an apparatus for detecting a weak signal in an image signal.

The composite video signal used in televisions and video cassette recorders can be divided into a luminance signal representing the contrast of the photographed subject largely, a color signal representing the color of the subject, and a synchronization signal.

Here, the synchronizing signal has the same meaning as a signal used for synchronizing between a general transmitter and a receiver. In a television video signal, a horizontal synchronizing signal for determining that a horizontal scanning line starts and a vertical synchronizing for determining that a field starts It consists of a signal.

The synchronization signals in the video signals are used for other functions of the video device besides synchronizing the scanning lines. For example, a television or the like is provided with a channel automatic tuning function, and channel automatic tuning automatically stores only a broadcast channel among a plurality of receivable channels in the television. In order to perform the channel auto-tuning function, it is necessary to determine whether the reception channel is a broadcast channel, and whether or not the broadcast channel is generally determined as the presence or absence of a synchronization signal.

In the case of determining whether there is a synchronization signal as in the channel automatic tuning function, the broadcast signal is affected by noise during the transmission process. Therefore, when a predetermined number of synchronization signals are detected within a predetermined time, the broadcast signal is determined to include a synchronization signal. Method was used. For example, in the case of the NTSC system, it is determined that the signal includes the synchronization signal when 15 to 64 synchronization signals are detected within 2 msec.

On the other hand, a video cassette recorder employs a blue back function that prevents noise from appearing on a television screen by using this synchronization signal detection method in reverse.

In detail, if the number of synchronization signals detected within 2 msec is out of 15 to 64 (for example, 14 or 65), the video signal currently input through the tuner is an unreceivable signal (usually called a weak signal). In this case, the OSD (On Screen Display) in the video cassette recorder is driven. The blue back signal output by the OSD driving is provided to the television screen, so that the user can watch the noiseless blue back screen.

However, in the conventional weak signal determination method of determining whether to output such a blue back screen, as described above, only the number of pulses of the composite synchronization signal inputted without discriminating each synchronization signal (vertical and horizontal) or noise is uniformly counted. It was.

Therefore, in the related art, a criterion for judging a weak signal has been widespread, and an error often occurs during a noise detection process, thereby preventing a correct blue back screen from being provided.

Accordingly, an object of the present invention is to provide a weak signal determination device for providing a blue back screen to a television according to the number of noise detection in an image signal.

In order to achieve the above object, the present invention provides a video signal processing apparatus capable of receiving a broadcast signal displaying a blue back screen by a blue back mode control signal, and separates a composite sync signal from a broadcast signal into a vertical sync signal and a horizontal sync signal. A synchronization signal separator for outputting; A pulse generator for generating window pulses synchronized with the horizontal synchronizing signal; An end gate connected in parallel to the synchronizing signal separator and the pulse generator and outputting a logical sum of the horizontal synchronizing signal and the window pulse; A counter that counts the output signal from the end gate and stops counting the output signal from the end gate upon application of a vertical sync signal from the sync signal separator; When the vertical synchronizing signal is applied, a weak signal detecting circuit of the video signal processing apparatus is provided, comprising a microcomputer for outputting an arbitrary blue back mode control signal when the count value counted to the counter is equal to or greater than a preset count value. .

1 is a block diagram of a weak signal determination device according to the present invention,

2A is a signal waveform diagram generated from the sync signal separator and the pulse generator of FIG.

2B is a signal waveform diagram of FIG. 2A when noise is generated;

3 is a flow chart of a weak signal determination process according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10: tuner 20: sync signal separator

30: pulse generator 40: end gate

50: counter 60: microcomputer

The above object and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a block diagram of a weak signal determination apparatus according to the present invention.

As shown, the weak signal determining apparatus includes a tuner 10, a sync signal separator 20, a pulse generator 30, an end gate 40, a counter 50, a microcomputer 60).

First, the tuner 10 is configured to receive a broadcast signal of a channel corresponding to PLL data which is a tuning signal of the microcomputer 60 among a plurality of broadcast frequency signals transmitted from a broadcast system, and receives the received broadcast signal as a synchronization signal separator. Output to (20).

At this time, the sync signal separator 20 separates the horizontal sync signal H-sync and the vertical sync signal V-sync from the composite sync signal C-sync of the broadcast signal received from the tuner 10 and performs horizontal sync. The signal is provided to the end gate 40 and the vertical synchronization signal is provided to the counter 50 and the microcomputer 60, respectively.

The pulse generator 30 according to the present embodiment outputs a window pulse in synchronization with the horizontal synchronizing signal from the synchronizing signal separator 20.

Here, as shown in FIG. 2A, the window pulse becomes a high level after a predetermined time t1 elapses after the falling edge of the horizontal synchronizing signal, and the high level states P1 and P2 are shown. (P3) is switched to the low level before the predetermined time t2 at the rising edge of the horizontal synchronizing signal.

FIG. 2A shows a state in which no noise is detected in the horizontal synchronizing section, that is, an ideal output waveform diagram of the horizontal synchronizing signal.

However, referring to the case of FIG. 2B, it can be seen that a plurality of noises are generated in the high level periods P1, P2, and P3 of the window pulse. Therefore, if the number of such noise is counted by a counter 50 to be described later and a predetermined number or more is detected, it is determined as a weak signal.

Returning to the block diagram of FIG. 1 again, the end gate 40 logically combines the window pulse generated from the pulse generator 30 and the horizontal synchronization signal generated from the synchronization signal separator 20 and outputs the result to the counter 50. That is, the end gate 40 provides a high level output signal to the counter 50 when noise occurs in the horizontal synchronizing signal as shown in FIG. 2B.

The counter 50 counts the high signal provided from the end gate 40 for a predetermined time (in this embodiment, the counter is cleared when the vertical synchronization signal is applied, so that the number of noises in one field is counted), The counted value is applied to the microcomputer 60.

On the other hand, when the vertical synchronization signal is detected by the synchronization signal separator 20, the microcomputer 60 checks the count value provided by the counter 50 and compares it with the preset value. When the count value is equal to or greater than the preset value, the current tuner ( It is determined that the broadcast signal provided from 10) is a weak signal.

Therefore, the microcomputer 60 outputs a blue back mode control signal to an OSD (not shown), and the OSD outputs image data such that a blue back screen can be displayed on a monitor.

Next, the weak signal determination process according to the present invention together with the above-described configuration unit will be described in detail with reference to the flowchart of FIG. 3.

First, when a predetermined video signal is input from the tuner 10 to the sync signal separator 20, the sync signal separator 20 may generate a horizontal sync signal and a vertical sync signal among the complex sync signals of the video signal from the tuner 10. Separately, the horizontal synchronizing signal is provided to the end gate 40, and the vertical synchronizing signal is provided to the counter 50 and the microcomputer 60.

In addition, the horizontal synchronizing signal is provided to the end gate 40 in synchronization with the window pulse from the pulse generator 30, and the end gate 40 logically combines the horizontal synchronizing signal including the noise with the window pulse to counter 50. To provide.

On the other hand, when the first vertical synchronizing signal is input from the synchronizing signal separator 20 to the counter 50 and the microcomputer 60 (step 100), the counter 50 counts the high signal applied from the end gate 40 and The microcomputer 60 temporarily stores this count value (step 102).

In addition, the microcomputer 60 determines whether a second vertical synchronization signal is detected from the synchronization signal separator 20 (step 104).

As a result of the determination in step 104, if the second vertical synchronization signal is detected, the counter 50 stops counting the high signal (step 106), and the microcomputer 60 sets the applied count value to a preset value (e.g., 30). (Step 108).

If the count value does not exceed the preset count value, the microcomputer 60 determines that the video signal flowing from the tuner 10 is a normal signal and tunes to the corresponding channel (step 110).

However, if the count value is greater than or equal to the preset count value, the microcomputer 60 determines that the video signal flowing from the current tuner 10 is a weak signal. Accordingly, the microcomputer 60 sends a blue back mode control signal to the OSD, and the OSD outputs image data to the monitor so that the blue back screen can be displayed (step 112).

As described above, the present invention has the effect of more accurately determining the weak signal of the imaging device.

Claims (1)

An image signal processing apparatus capable of receiving a broadcast signal displaying a blue back screen by a blue back mode control signal, A synchronization signal separator (20) for separately outputting a composite synchronization signal of the broadcast signal into a vertical synchronization signal and a horizontal synchronization signal; A pulse generator (30) for generating window pulses synchronized with the horizontal synchronizing signal; An end gate (40) connected in parallel to the synchronization signal separator (20) and the pulse generator (30) and outputting an OR of the horizontal synchronization signal and the window pulse; A counter 50 that counts the output signal from the end gate 40 and stops counting the output signal from the end gate 40 upon application of the vertical sync signal from the sync signal separator 20; ; And a microcomputer 60 for outputting an arbitrary blue back mode control signal when the count value counted by the counter 50 is greater than or equal to a preset count value when the vertical synchronization signal is applied. Weak signal detection circuit.