JPS62242482A - Teletext signal processor - Google Patents

Abstract

PURPOSE:To prevent a teletext signal from being deteriorated by extracting only the teletext signal from a TV signal, correcting its error and then superposing the corrected signal again to the TV signal. CONSTITUTION:A TV signal including the teletext signal is inputted from a TV signal input terminal 1. A character signal extracting circuit 2 extracts character signal data from the TV signal and supplies the extracted data to an error correcting circuit 4 through a time base converting circuit 3. The circuit 4 corrects the error of the character signal data and then supplied the corrected data to a character signal superposing circuit 6 through a data synchronizing signal adding circuit 5. The circuit 6 superposes the character signal to the TV signal and outputs the superposed signal from an output terminal 7. On the other hand, the parallel charcter signal converted by a serial/parallel conversion circuit 8 is decoded by a decoding circuit 9 and a character/graphic pattern is displayed on a display device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a teletext signal processing device using a shortened difference-set cyclic code that can be decoded by a majority circuit with information bits of 190 bits and parity pits of 82 bits, for example. It is something.

Conventional technology In November 1985, coded transmission type teletext broadcasting was started. When characters and graphics are encoded and transmitted, they have the disadvantage of being extremely susceptible to bit errors on the transmission path. Therefore, in this coded transmission system, as a protection measure against bit errors in the transmission path, error correction is performed using a (272,190) shortened difference set cyclic code that can be decoded by a majority circuit (Reference: Radio Technology Council Board ``Report on Coded Transmission Teletext Broadcasting'' (1985).

Conventionally, when broadcasting a television signal including this teletext signal, the relay station receives the teletext signal and simply amplifies it and sends it. The system simply recorded and played back the video signal directly as a video signal.

Problems to be Solved by the Invention As described above, when broadcast wave relaying or recording/reproduction of television signals including teletext signals, noise, group delay distortion, or drops occur as the number of relays increases, or as the number of recording/reproductions increases. There is a problem in that quality deterioration of character signals due to outs etc. is cumulative.

An object of the present invention is to reduce the quality deterioration of the character signal.

Means for Solving the Problems In the character signal processing device of the present invention, the output of the character signal sampling circuit is connected to a time axis conversion circuit, the output of the time axis conversion circuit is connected to an error correction circuit, and the output of the character signal sampling circuit is connected to an error correction circuit. The serial data output of the correction circuit is connected to a data synchronization signal addition circuit, and the output of the data synchronization signal addition circuit is connected to a character signal superimposition circuit.

According to the above structure, the present invention extracts the teletext signal every time a television signal including a teletext signal is broadcasted or recorded and reproduced, and relays or records the teletext signal after error correction. This reduces the quality deterioration of character signals due to noise, group delay distortion, dropouts, etc.

Embodiments Hereinafter, teletext signal processing apparatuses according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a teletext signal processing device according to a first embodiment of the present invention.
2 is a character signal extraction circuit, 3 is a time axis conversion circuit, 4 is an error correction circuit, 6 is a data synchronization signal addition circuit, 6 is a character signal superimposition circuit, and 7 is a television signal signal input terminal. 8 is a serial-parallel conversion circuit, 9 is a character signal decoding device, and 10 is a display device.

FIG. 2 is a text signal waveform diagram for explaining the signal processing process in the teletext signal processing device shown in FIG. 1. Hereinafter, the operation of the teletext signal processing circuit shown in FIG. Explain.

A teletext signal shown in FIG. 2a whose quality has deteriorated between relay stations or on a transmission line is input from a television signal input terminal 1 and is supplied to a character signal extracting circuit 2 and a character signal superimposing circuit 6. In the character signal extraction circuit 2, character signal data containing errors due to quality deterioration as shown in FIG. 2 is extracted from the input television signal and is supplied to the time axis conversion circuit 3. In the time axis conversion circuit 3, the character signal data is delayed by a certain period of time and then supplied to the error correction circuit 4. In the error correction circuit 4, after correcting errors in the character signal data, the corrected serial character signal data shown in FIG.

The data synchronization signal adding circuit 6 adds a data synchronization signal shown in FIG. 2d to the corrected serial character signal data (waveform shown in FIG. 2e) and supplies it to the character signal superimposition circuit.

In the character signal superimposing circuit 6, the character signal is again superimposed on the television signal, and is outputted from the television signal output terminal 7 in the waveform shown in FIG. Further, the character signal converted into parallel data in the serial-parallel conversion circuit 8 undergoes character code decoding processing in the character signal decoding circuit 9, and a character/graphic pattern is displayed on the display device 1o.

As described above, according to the present invention, only the character signal is extracted from a television signal that includes a teletext signal with degraded quality, and after error correction is performed, the character signal is superimposed on the television signal again. Deterioration of broadcast signals can be reduced.

A character signal processing device according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of a teletext signal processing apparatus according to a second embodiment of the present invention, where 3 is the time axis conversion circuit in FIG. 1, 4 is the error correction circuit in FIG. 1, and 6 is the block diagram in FIG. 20 is an input terminal for character signal data output from the character signal extracting circuit 2 shown in FIG. 1; 21 is a memory; 22 is a write control circuit; 23 is a read control circuit; Bit syndrome register, 26
is a majority circuit, 26 is a 272-bit shift register, 2
7 is a sign inversion circuit, 28 is a switch, 29.30 is an input terminal of switch 28, 31 is an output terminal of switch 28,
32 is a synchronizing signal generation circuit, and 33 is a character signal output terminal.

FIG. 4 is a text signal waveform diagram for explaining the signal processing process in the teletext signal processing circuit of FIG. 3. Below, FIG. 4 will be used to explain the operation of the teletext signal processing circuit of FIG. explain.

The waveform in FIG. 4a is character signal data containing errors extracted from the television signal by the character signal superimposition circuit 2 in FIG. 21 and written into the memory 21 by the write control circuit 22. The character signal data written in the memory 21 is sent to the read control circuit 23, where the transfer bit rate is converted as shown in Figure 4, and the data is divided into multiple parts (two in Figure 4) and read out to prevent errors. The signal is supplied to an 82-bit syndrome register 24 and a 272-bit shift register 26 of the correction circuit 4. 82
A syndrome is calculated in the bit syndrome register 24, and a correction signal is outputted to the majority circuit 25 and sign inversion circuit 27 according to the result. 2
The character signal data shifted from the 72-bit shift register 26 is corrected bit by bit by the correction signal from the majority circuit 26 in the sign inversion circuit 2. The corrected character signal data is supplied to the input terminal 29 of the switch 28 of the data synchronization signal addition circuit 6. switch 2
8, the input terminal 30 and the output terminal 31 are connected until the character signal data is input to the input terminal 29 of the switch 28.
is connected, and the synchronization signal generation circuit 32 outputs a synchronization signal (waveform shown in FIG. 4 C) consisting of a clock run-in (CRI) and a framing code (FC), and during the character signal data period, the input terminal 29 and the output terminal 31 is connected, a character signal in which a data synchronization signal is added to the beginning of the character signal data divided into two parts is outputted from the output terminal 33 as shown in FIG. 4(d). The two character signals outputted from the output terminal 33 are superimposed on different H's of the television program signal in the character signal superimposing circuit 6 shown in FIG. 1 with the waveform shown in FIG. 4 O.

As described above, according to the present invention, as shown in the first embodiment, deterioration in the quality of character signals can be reduced, and at the same time, for example,
The bit rate of character signals can be lowered when recording on a VTR or the like. In particular, the recording area width of current home VTRs is approximately 2 MIIz, which is 5.73 Mbit.
/! It is impossible to record a teletext signal with a bit rate of 160. However, in the present invention, by lowering the bit rate of the text signal, it is possible to reduce the bit rate of the text signal.
Recording to TR is also possible.

Although the present invention has been described assuming that the number of superimposed teletext signals is one, even when a plurality of character signals are continuously superimposed, it is possible to have two error correction circuits and use the two error correction circuits in parallel. This can be handled by switching to .

Effects of the Invention As described above, according to the present invention, it is possible to reduce deterioration in the quality of text signal data when broadcasting or recording/reproducing television signals including text broadcasting signals. At the same time, it also becomes possible to record and reproduce character signals on a recording medium with a narrow bandwidth, such as a home VTR.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a teletext signal processing apparatus according to a first embodiment of the present invention, FIG. 2 is a waveform diagram of a character signal showing the processing process of a character signal according to the first embodiment, and FIG. 4th block diagram of a teletext signal processing device according to a second embodiment of the invention;
The figure is a waveform diagram of a character signal showing a character signal processing process according to the second embodiment. 2... Character signal sampling circuit, 3... Time axis conversion circuit, 4... Error correction circuit, 6...
...Data synchronization signal addition circuit, 6...Character signal superimposition circuit, 8...Series-parallel conversion circuit, 9...
...Character signal decoding circuit, 1°...Display device, 21...Memory, 22.Paper "°Writing control circuit, 23...Reading control circuit , 24゛'°"82
Bit syndrome register, 25°゛°°“majority circuit, 26...272 bit shift register, 2
7...Sign inversion circuit, 28...Switch, 32...Group synchronization signal generation circuit. Name of agent: Patent attorney Toshio Nakao, 1st person, 2nd person
figure

Claims (2)

[Claims] (1) In a teletext signal processing device equipped with an error correction circuit using a shortened difference set cyclic code, the output of the character signal acquisition circuit is connected to a time axis conversion circuit, and the output of the time axis conversion circuit is connected to the A teletext signal connected to an error correction circuit, wherein the serial data output of the error correction circuit is connected to a data synchronization signal addition circuit, and the output of the data synchronization signal addition circuit is connected to a character signal superimposition circuit. Processing equipment. (2) The output of the error correction circuit is connected to a serial-parallel conversion circuit, and the output of the serial-parallel conversion circuit is connected to a character signal decoding circuit. teletext signal processing equipment.