KR20020015844A - Circuit for automatically detecting wide screen - Google Patents

Abstract

PURPOSE: A circuit for automatically detecting a wide screen is provided to detect a letter box signal appearing at the upper and lower sides of the wide screen of a 4:3 television receiver to automatically expand the screen in the vertical direction. CONSTITUTION: A low pass filter(1) eliminates noise of an input image. The first comparator(2) compares an input signal with a black level signal in order to judge if the input signal is a letter box signal. A selector(3) passes an active signal within an over-scan region to process only effective images. A counter(4) carries out resetting operation for every vertical synchronous signal. The first divider(5) divides signals counted by the counter by a predetermined number of times. An adder(6) adds up the signal output from the first divider and the previous output signal. A DFF1(7) averages the output signal of the adder. The second divider(8) divides the output signal of the DFF1 by a predetermined number of times. The second comparator(9) outputs an enable signal when the number of black signals is larger than a predetermined reference value. A DFF2(10) latches the enable signal and outputs the signal to a vertical expansion circuit(11).

Description

Wide screen automatic detection circuit {Circuit for automatically detecting wide screen}

The present invention relates to a wide screen detection circuit, and more particularly, to a wide screen automatic detection circuit for detecting a letter box signal appearing above and below a wide screen on a 4: 3 television receiver and automatically expanding the screen vertically. It is about.

In general, the current broadcast method has a 4: 3 aspect ratio, so most television receivers are set to 4: 3 aspect ratio.

However, in the future, the broadcasting method is shifting to 16: 9 aspect ratio, and accordingly, the television receiver is also being shipped for 16: 9.

As a result, in the future, since the input aspect ratio is diversified, it is necessary to be manufactured to cope with various aspect ratios inside the television.

When a wide screen is input under a 4: 3 aspect ratio television in a typical home, the user directly expands the screen vertically by hand using a physical device such as a knob or an adjustment button provided in the television, as shown in FIG. 1. The screen as shown in (a) is displayed as shown in (b) for viewing.

Therefore, in the present invention, when a wide screen is input to a 4: 3 screen, a wide screen (letter box signal) is automatically detected and a vertical extension signal is automatically output to a vertical expansion circuit so that a vertically extended image is displayed on the screen. The purpose is to provide an automatic detection circuit.

1 is a diagram of a screen state in a state where the wide screen is 4: 3 aspect ratio;

2 is a circuit diagram of automatic detection of a wide screen (letter box screen) according to the present invention.

Explanation of symbols on the main parts of the drawings

1: low pass filter 2: first comparator

3: selector 4: counter

5, 8 divider 6: adder

7, 10: D flip-flop 9: 2nd comparator

11: vertical expansion circuit

Technical means for achieving the above object is a low-pass filter for removing noise of the input image; A first comparator for outputting an enable signal to a black signal that is less than the reference value in comparison with the reference value ref1 for the black signal; A selector for passing only a valid signal region (active signal) of all video signals except an overscanned region among the signals compared and output from the first comparator; A counter that counts every vertical synchronous and outputs a counter after counting a predetermined number of times; A first divider dividing the signal counted by the predetermined number of times from the counter and outputting the signal by a predetermined number to reduce the load on the hardware; A protection circuit for averaging and outputting each field in case black is suddenly generated in units of a screen due to noise; A second comparator for outputting an enable signal when the number of black signals is greater than a preset reference value ref2 since the current signal is a letter box, that is, a wide screen; A second flip-flop has a feature of receiving the enable signal output from the second comparator as data and latching the output signal to the vertical expansion circuit.

The protection circuit includes an adder for adding the output signal and the previous output signal according to the number of times divided by the first divider, a first flip-flop for averaging the output signal of the adder, and an output signal of the first flip-flop The second divider outputs a predetermined number of times.

In addition, the vertical expansion circuit is characterized in that a separate function for adjusting the vertical expansion function in the automatic mode, manual mode according to the user's selection is added.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

2 is a diagram of a circuit for automatic detection of a wide screen (letterbox screen) according to the present invention.

The apparatus shown in FIG. 2 is a low pass filter 1 for noise removal of an input image, a first comparator 2 comparing with a black level signal ref1 to determine whether the input signal is a letterbox signal, A selector (3) for passing the active screen in the overscan area to process only the screen, a counter (4) for resetting for each vertical synchronization (Fv) signal, and a signal for counting a certain number of times and outputting a signal divided by a predetermined number of times. DFF1 (7) which averages and outputs the output signals of the adder (5), the adder (6) that adds the previous output signal, and the output signal according to the number of times divided by the first divider (5) (7) ), The second divider 8 for dividing the output signal of the DFF1 (7) by a certain number of times, and when the number of the black signals is larger than the preset reference value ref2, the signal that is currently input is the letter box, that is, the wide screen. To output And a DFF2 (10) for receiving and latching the enable signal output from the second comparator (9) and the second comparator (9) and outputting the data to the vertical expansion circuit (11).

Referring to the operation of the present invention configured as described above are as follows.

First, when the video signal is input, noise is removed through the low pass filter (1), and the letter box appearing on the top and bottom of the entire screen is black level, and thus the current signal is compared to a small signal. At this time, the reference value ref1 is set to about 10 and is less than 10, and a black signal is determined.

When the black signal is determined and output from the first comparator 1, the selector 3 filters and passes only the active signal to exclude the overscanned area of the signal.

When the counter signal 4 counts and outputs a signal for the black signal among the valid signals passed through the selector 3 at a predetermined number of times in the first divider 5 provided to reduce the load on the hardware. It divides into and outputs to the adder (6).

At this time, in order to output the averaged by field in case of black suddenly in the screen unit caused by noise, DFF1 (7) feeds back the signal about the previous output state and adds it with the current output signal in the adder (6) and averages it again. Will print.

The output signal is compared with the reference value ref2 of the second comparator 9, and if the number is large, the black signal is a letter box signal. The vertical extension signal is output.

Accordingly, the screen is vertically expanded and displayed automatically as shown in FIG. 2B without the user directly expanding the vertical screen using a physical device such as a knob.

If the signal for the 4: 3 aspect ratio is continuously received, since the signal for the black level detected by the first comparator 2 does not enter more than a predetermined number of times, the vertical expansion output signal is not finally applied to the vertical expansion circuit 11. The screen is normally displayed in 4: 3 aspect ratio.

On the other hand, the user may want to watch with the letterbox signal (2.35: 1, 16: 9 aspect ratio), so set the auto mode to automatically expand the screen vertically when the letterbox signal is input to the vertical expansion circuit, or manually You can set the manual mode to vertically expand the screen. Accordingly, the automatic mode button and the manual mode button should be provided on the remote control or the television function button.

Therefore, if the user wants to watch television with the letterbox signal state, the television screen is displayed with the letterbox signal unless the physical process for vertical expansion is performed in the manual mode.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the present invention described in the claims. Of course, such a change is of course within the scope of the present invention.

As described above, according to the present invention, it is possible to automatically detect a wide screen even by providing a small amount of hardware, and to automatically display a vertically expanded display by a vertical expansion circuit, thereby maximizing convenience in use.

Claims (3)

A low pass filter for removing noise of an input image; A first comparator for outputting an enable signal to a black signal that is less than the reference value in comparison with the reference value ref1 for the black signal; A selector for passing only a valid signal region (active signal) of all video signals except an overscanned region among the signals compared and output from the first comparator; A counter that counts every vertical synchronous and outputs a counter after counting a predetermined number of times; A first divider dividing the signal counted by the predetermined number of times from the counter and outputting the signal by a predetermined number to reduce the load on the hardware; A protection circuit for averaging and outputting each field in case black is suddenly generated in units of a screen due to noise; A second comparator for outputting an enable signal when the number of black signals is greater than a preset reference value ref2 since the current signal is a letter box, that is, a wide screen; And a second flip-flop for receiving an enable signal output from the second comparator as data and latching the data to a vertical expansion circuit. The method of claim 1, wherein the protection circuit An adder for adding the output signal and the previous output signal according to the number divided by the first divider, a first flip-flop for averaging the output signal of the adder, and an output signal of the first flip-flop at a predetermined number of times; A wide screen automatic detection circuit comprising a second divider for dividing and outputting. The method of claim 1, wherein the vertical expansion circuit Wide screen automatic detection circuit, characterized in that a separate function for adjusting the vertical expansion function to automatic mode or manual mode is added according to the user's selection.