KR940002658Y1 - Caption decoder error correction apparatus - Google Patents

Abstract

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Description

Caption Decode Error Correction Device

1 is a synchronization extraction circuit for extracting conventional subtitle data.

2 is a caption decoder control circuit diagram using the vertical synchronization of FIG.

FIG. 3A is a configuration diagram of caption data for explaining FIG. 2, and (b) is a 21st vertical synchronous waveform diagram according to FIG.

4 is a block diagram of the subject caption decoder error correction system.

* Explanation of symbols for main parts of the drawings

1: envelope detection unit 2: first comparison unit

3: smoothing part 4: second comparing part

5: Oagate 6: Caption decoder control unit

The present invention relates to a caption decoder of V-Cal. In particular, the caption decoder, in which the caption is programmed in V-Cal, is used to reset the caption decoder controller to correct the error of the caption decoder due to signal blanking or unstable shifting operation of the tape. Caption decoder error correction device.

In general, the caption data is transmitted from the broadcasting station to the 21st line of the odd scan line when the part that does not appear on the screen of the TV video signal is transmitted as data in the 21st line of the odd scan line, and the receiving side detects and decodes the coded signal. It will be displayed as a letter on the screen. Also in the VRL, the vertical synchronization signal is detected from the composite video signal reproduced on the tape, and the caption data contained in the 21st line is extracted and displayed on the screen by the detected vertical synchronization signal.

FIG. 1 is a synchronous detection circuit for extracting a conventional caption data. As shown in FIG. 1, a clamp unit 100 for clamping a composite video signal CV1 reproduced in a VCl and a clamp unit 100 are provided. Synchronization detector 101 detects and outputs modified synchronization VS and horizontal synchronization HS from the clamped video signal, and vertical synchronization VS by low-pass filtering the synchronization signal detected by the synchronization detector 101. It consists of the low pass filter part 103 which extracts.

FIG. 2 is a caption decoder control circuit diagram using the vertical synchronization of FIG. 1, as shown in FIG. 2, which is enabled by a control signal CNT of a microcomputer input from the outside and is closed caption data in an external composite video signal CV1. And a caption decoder control unit 103 for synchronizing the detected caption data with vertical synchronization (VS) and generating stored character data corresponding to the caption data output from the caption decoder control unit 104. A character generator 104 and an adder 105 for synthesizing the character data generated by the character generator 104 and an external composite video signal and outputting them to the output terminal Vout.

The operation of the conventional subtitle decoder control circuit configured as described above is as follows.

First, when the composite video signal as shown in FIG. 3a is input, the clamp unit 100 clamps the input composite video signal and inputs the same to the synchronization detector 101. The sync detector 101 detects and outputs the horizontal sync (HS) and the vertical sync (VS) from the input composite video signal, and inputs the same to the low pass filter 102. The low pass filter 102 The low frequency filtering of the input synchronization signal detects the vertical synchronization V and inputs the same to the caption decoder controller 103 of FIG. At this time, the caption decoder control unit 103 is enabled by the control signal (CNT) of the microcomputer input from the outside to detect the caption data in the external composite video signal, and the detected caption data is vertically synchronized as shown in FIG. 3B. It is input to the character generator 104 in synchronization with (V). Accordingly, the character generator 104 generates the character data corresponding to the caption data of the caption decoder controller 103 and inputs it to the adder 105. The adder 105 generates the character data of the character generator 104. Data and an external composite video signal are synthesized to output a composite video signal carrying a caption signal to an output terminal Vout.

However, in such a conventional caption decoder control circuit, to extract the caption data contained in the 21st vertical retrace period of the composite video signal, a gate signal capable of checking the 21st scan line, such as 3b, should be produced. The vertical synchronization signal is used as a reference line for matching the scan signal with the 21st line of the scan line.

When the vertical synchronous signal is extracted from the video signal by using the synchronous detector, when no video signal is input or an unstable video signal is input, there is no vertical synchronous signal extracted by the synchronous detector, or a time delay or a synchronous width may be changed. . Such a change in the vertical synchronization signal causes a timing mismatch between the 21st detection gate signal made based on the vertical synchronization signal and the 21st line of the video signal, and thus the data contained in the 21st line cannot be checked. Will cause caption decoding to stop. If an error occurs in caption data detection, a lock phenomenon occurs in the caption decoder. After that, even if a normal video signal and a vertical synchronization signal are input to the caption decoder, the caption decoder must be reset. When the video signal is unstable during play of the caption error, the caption decoder controller needs to be reset.

In view of such a conventional problem, the orphan detects an envelope of a high frequency signal, which is a frequency-modulated video signal component scanned on a video tape, by using an envelope detector, and compares the detected envelope with a reference signal and a comparator to reproduce an image signal during tape playback. In the unstable part of the caption decoder to automatically reset the caption decoder error correction device to prevent the error of the caption decoder, the present invention will be described in detail with reference to the accompanying drawings as follows.

4 is a block diagram of the subject caption decoder error correction system of the present invention. As shown in the drawing, a high frequency signal RF, which is a frequency-modulated image signal component scanned from a video tape, is input to receive an envelope of the high frequency signal RF. A first comparator (2) for comparing the envelope detector (1) to be extracted, the envelope of the high frequency signal extracted from the envelope detector (1) and the set reference voltage (Vref1), and outputting a resultant voltage accordingly; A smoothing part 3 which extracts this part from the dropout part generated due to damage of the tape during video tape playback, and smoothes the input dropout signal DRout and outputs the DC voltage. A second comparison unit 4 which compares the output voltage of the smoothing unit 3 with the set reference voltage Vref2 and outputs a resultant voltage, and the first and second comparison units 2 and 3. Output voltage and output from micom A subtitle in the ORA gate 5 which logically sums and outputs the reset signal RS, and the composite image signal CV1 which is set and reset in accordance with the output signal of the OR gate 5 and is scanned from a tape and input. A caption decoder control unit 6 for detecting and outputting data in synchronization with the vertical synchronization VS, a character generating unit 7 for generating character data corresponding to the caption data of the caption decoder control unit 6, and the character; And an adder 8 for synthesizing the character data and the composite video signal CV1 output from the generation unit 7 and outputting them to the video output terminal VDout.

Referring to the operation, effects of the present invention configured as described above in detail.

When the high frequency signal RF, which is a video signal that is frequency-modulated and scanned from the video tape, is input, the envelope detector 1 detects the input high frequency signal RF, extracts only the envelope portion, and then, The first comparator 2 is inputted to the inverting terminal (-), and the first comparator 2 includes the reference voltage Vref1 (here, the reference voltage Vref1 = 1V) set at the envelope of the input high frequency signal RF and the non-inverting terminal +. ), When the envelope voltage of the high frequency signal RF is lower than the reference voltage, the first comparator 2 outputs a high signal, and when the envelope voltage of the high frequency signal RF is higher than the reference voltage Vref1, the low signal is output to the oragate 5. It is input to one input terminal of. On the other hand, when the video tape is played back, the dropout signal DR out is inputted from the dropout portion caused by damage to the tape, etc. (here, the dropout is caused by a lack of recording medium in magnetic recording. The transient level of the generated reproduction signal or the dropout of the signal) is smoothed through the smoothing unit 3 and input to the non-inverting terminal (+) of the second comparing unit 4 as a DC voltage. The second comparison unit 4 compares the voltage input from the smoothing unit 3 with the reference voltage Vref2 set in the inverting terminal (-), where the reference voltage Vref2 is 2.5V. When the drop out signal DR out input from the N / A signal is small, the low signal is inputted to the other input terminal to the oragate 5. Accordingly, the oA gate 5 sets and recaptures the caption decoder controller 6 by ringing the signals input from the first and second comparators 2 and 4 and the reset signals input from the microcomputer. Set. That is, as an example, when the drop out signal DR out input to the non-inverting terminal (+) of the second comparator 4 is greater than the reference voltage Vref2 due to the tape being damaged or the like during tape playback, the above-described first agent may be used. Since the comparator 4 outputs a high signal at its output, the oragate 5 outputs a high signal regardless of the reset signal of the first comparator 2 and the microcomputer to return the caption decoder control unit 6. Set.

In addition, when the video signal is not recorded on the tape or the video head cannot accurately track the tape track, such as shifting, at this time, the level of the high frequency signal RF or the high frequency signal RF is no signal. 1), the envelope detector 1 does not extract an envelope of the high frequency signal. As a result, a high signal is outputted at the output of the first comparator 2, and the high signal is transmitted through the oragate 5. 6) will be reset. If the tape is normal, a low signal is output from the output of the oragate 5 to set the caption decoder control section 96. The caption decoder control section 6 subtitles the composite video signal CV1 scanned from the video tape. The data is extracted, and the extracted caption data is input to the character generator 7 in synchronization with the vertical synchronizing signal VS. The character generator 7 generates character data corresponding to the input caption data and inputs it to the adder 8, and the adder 8 synthesizes the input character data and the composite image signal and outputs a video output terminal (VDout). Will output

As described in detail above, the present invention extracts an envelope of a high frequency signal, which is a frequency-modulated video signal component scanned from a video tape, by using an envelope detector, and compares the extracted envelope with a reference signal and a comparator to make the video signal unstable during tape playback. By automatically resetting the caption decoder control unit at the portion, an error of the caption decoder can be prevented.

Claims (1)

An envelope detector 1 extracting an envelope of the frequency-modulated high frequency signal RF and an envelope extracted from the envelope detector 1 and a reference voltage Vref1, and outputting a resultant voltage accordingly; The comparison section 2, the smoothing section 3 which smoothes the dropout signal DRout of the tape and outputs the DC voltage, and compares the output voltage of the smoothing section 3 with the reference voltage Vref2. The OR gate which sets and resets the caption decoder control unit 6 by ORing the second comparison unit 4 for outputting the resultant voltage and the output voltages of the first and second comparison units 2 and 3. 5) Caption decode error correction device characterized in that it comprises a.