JPS6175687A - Detection circuit of horizontal overlap position in teletext - Google Patents

Abstract

PURPOSE:To lighten the character signal discriminating burden imposed on a microcomputer and to prevent the error in transmission contents by taking out color burst signals from video signals in such a manner as delaying a horizontal synchronizing signal a little, integrating said color burst signals with the aid of a waveform shaping circuit to generate one pulse signal either counting up or counting down a counter. CONSTITUTION:A color burst signal of a video signal transmitted from an input terminal 1 is taken out by a color burst gate 8, and is further tuned at 3.5mHz to take out securely the color burst signal of 3.5mHz. This color burst signal is integrated and its waveform is shaped by a waveform shaping circuit 9, and transmitted to a clock input terminal 10 as one pulse. A counter 4 either counts up or counts down this pulse. Thus, a pulse of 10H in an odd field and that of 273H in an even field are discriminated to be at the same position. Namely, the fact that positions of pulses of 10H-21H in the odd field and those of pulses of 273H-28H in the even field are related is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application]
The present invention relates to a horizontal superimposition position detection circuit in teletext broadcasting, which detects H to 21H and even fields 273H to 284H as being mutually related.

[Prior Art] Conventionally, in teletext broadcasting, when extracting a character signal from an input video signal, the character signal was simply extracted, and then the signal content was determined by a microcomputer.

This places a burden on the microcomputer, and since there is no correlation between the H positions of the odd and even fields of the video signal, there are problems such as transmission malfunctions.

[Problems to be Solved by the Invention] The present invention aims to reduce the burden on the microcomputer and to reduce errors in transmitted content as much as possible by defining the H position.

C. Means for Solving Problems] The present invention has been made to achieve the above objects, and
A vertical and horizontal separation circuit for separating a vertical synchronization signal and a horizontal synchronization signal from a video signal, a delay circuit for delaying the separated horizontal synchronization signal and creating a gate signal that matches the position of the color burst signal; A color burst gate circuit extracts a color burst signal from a video signal using a gate signal of a delay circuit, and a waveform shaping circuit extracts the color burst signal from the color burst gate circuit, integrates and shapes the waveform to form one pulse. ,
a counter that is reset by the vertical synchronization signal separated by the separation circuit and counted by the waveform shaping circuit,
21H and even-numbered feel routes 273H to 284H are detected in relation to each other.

[Operation: Vertical and horizontal separation circuits separate vertical and horizontal synchronization signals from the video signal. The counter is reset by a separate vertical synchronization signal.

Further, the color burst signal is extracted from the video signal by slightly delaying the horizontal synchronization signal, and furthermore, it is tuned at 3.58 MHz to ensure that only the color burst signal component of this 3.58 MHz is extracted. This is integrated by a waveform shaping circuit, and
A single pulse signal is generated that is output only to the horizontal synchronization signal on which the color burst signal is superimposed. The pulses generated by this waveform shaping circuit cause the counter to count up or count down. As a result, the character sampling lines after IOH in odd-numbered fields and after 273H in even-numbered fields are detected as mutually related positions.

[Example] Hereinafter, one embodiment of the present invention will be described based on the drawings.

In Figure 1, (1) is an input terminal for a video signal, and this input terminal (1) is connected to a vertical and horizontal separation circuit (2) for separating a vertical synchronization signal and a horizontal synchronization signal from the video signal.
The vertical synchronizing signal output terminal (3) of this vertical/horizontal separation circuit (2) is connected to the clear terminal (5) of the counter (4).
) is combined with The horizontal synchronization signal output terminal (6) of the vertical and horizontal separation circuit (2) is coupled to a delay circuit (7) for producing a gate signal that slightly delays the horizontal synchronization signal to match the position of the color burst signal. , and is further coupled to a color burst gate circuit (8) for extracting a color burst signal from the video signal from the input terminal (1) and extracting a color burst signal which is a 3°58 MHz color subcarrier signal. A waveform shaping circuit (9) for integrating a 3.58 MHz signal and shaping the waveform to obtain one pulse is coupled to the output side of the color burst gate circuit (8). (
The output terminal of 9) is coupled to the clock input terminal (10) of the counter (4), and the output side of the counter (4) is a horizontal position output terminal (11).

Next, the operation of the circuit configured as above will be explained. Assume that a video signal as shown in FIGS. 2a and 2b is input to the input terminal (1). In this Figure 2 a and b, 1, 2, 3. . . 525 represents the number of the horizontal scanning line, and hereinafter, nH represents the n-th horizontal scanning line number. Also, among this IH ~ 525H,
Odd fields are from IH to 263.5H.

263.5H to 525H are even fields.

Further, (12) is a television video signal, (13) is a vertical synchronizing signal, (14) is a color burst signal, (15) is a character sampling line, and (T) is a vertical blanking period.

Here, the vertical and horizontal separation circuit (2) separates the vertical synchronization signal and horizontal synchronization signal from the video signal, and outputs the output terminal (
3) Reset (initialize) the counter (4) with the vertical synchronization signal output from the output terminal (6).6 Also, when the horizontal synchronization signal output from the output terminal (6) is sent to the delay circuit (7), the position of the color burst signal is A gate signal for extracting the color burst signal is created by slightly delaying the horizontal synchronization signal to match the color burst signal. The color burst signal of the video signal sent from the input terminal (1) is transmitted to the color burst gate circuit (
8) and further tuned at 3.58 MHz to reliably extract a 3.58 MHz color burst signal. The extracted color burst signal of 3.58 MHz is integrated and waveform-shaped by a waveform shaping circuit (9) to form one pulse, which is sent to the clock input terminal (10) of the counter (4). Then, the counter (4)
Now count up or count down this pulse. Therefore, it is determined that IOH in the odd field and 273H in the even field are at the same position.

That is, the positions of IOH to 21H in the odd field and 273H to 284H in the even field are detected as being related to each other.

Therefore, the vertical blanking interval character sampling line (15
) is accurately extracted.

[Effects of the Invention] Since the present invention is configured as described above, odd field I/O is performed based on the color burst signal after the vertical synchronization signal.
The positions after H and the even field after 273H can be sequentially detected as mutually related positions, and therefore,
The burden of character signal discrimination by a microcomputer can be greatly reduced, and errors in transmitted content will not occur.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a horizontal superimposition position detection circuit according to the present invention, and FIG. 2 is a waveform diagram of a video signal. (1)...Video signal input terminal, (2)...Vertical,
Horizontal separation circuit, (4)...Counter, (7)...Delay circuit, (8)...Color burst gate circuit, (9
)...Waveform shaping circuit. Applicant Zene La Rumi K.i.

Claims (1)

[Claims] (1) Vertical and horizontal separation circuits for separating the vertical and horizontal synchronization signals from the video signal, and a delay circuit for delaying the separated horizontal synchronization signals and creating gate signals that match the position of the color burst signal. , a color burst gate circuit that extracts a color burst signal from a video signal using the gate signal of this delay circuit, and a waveform that extracts a color burst signal from this color burst gate circuit, integrates and shapes the waveform, and forms one pulse. 1. A detection circuit for detecting a horizontal superimposition position in teletext broadcasting, comprising: a shaping circuit; and a counter that is reset by a vertical synchronizing signal separated by the separation circuit and counted by the waveform shaping circuit.