JPS6126385A - Decoder for teletext - Google Patents

Abstract

PURPOSE:To eliminate the adverse influence such as drop-out at reproduction by decoding a teletext signal latter by 1H period in case an error signal generates an error pulse in 1H period when a reproduction character signal from a magnetic recording and reproducing device is inputted. CONSTITUTION:Reproduction and error signals from a magnetic recording and producing device 9 are transmitted to an input processing part 11 of a decoder 10. Here, when the eorror signal generates an error pulse, such action as to decode a teletext signal latter by one horizontal period is executed. The teletext signal in an H section where the error signal will not generate the error pulse is selected, transmitted to a main memory 12, stored and decoded in an output processing part 13, afterwards, it is outputted to a CRT14. Thus the decoding of a character signal can be executed without being influenced by drou-out, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a teletext decoder capable of decoding reproduced teletext signals from a magnetic recording and reproducing device.

Conventional configuration and its problems At present, teletext systems are being put into practical use.
Along with this, the demand for recording and reproducing teletext signals is also increasing. The transmission signal of this teletext is 5.7272
This is a format that is sent at 72 Mbit/sec. In order to record and reproduce this signal, a signal band of 2.86 M is required.
This means that H2 must be secured.

However, the currently popular home VTR has a recording and reproducing band of about 2 to 2.5 MH2, and therefore cannot record and reproduce teletext at all. Therefore, the inventors of the present invention have made various proposals for recording and reproducing teletext signals. For example, by shifting the FM carrier frequency of a VTR to a higher frequency band, recording and reproducing only the luminance signal during the period when the teletext signal exists, and extending the recording and reproducing band, it is possible to record and reproduce the teletext signal. be.

In fact, according to the method described above, teletext signals can be almost perfectly recorded and reproduced, but there is one problem. That is, if a dropout occurs during recording and reproduction of a teletext signal, incorrect information will be reproduced and an error will occur.

Furthermore, once a conventional teletext decoder recognizes that there is a teletext signal in a predetermined horizontal section with respect to a vertical synchronization signal, it then selectively decodes only that recognized section. If a dropout occurs, the incorrect information is decoded as is and sent to the CRT.
7, which produced an unsightly image.

FIG. 1 shows a signal waveform diagram in a conventional example.

The first prisoner is an input video signal indicating a vertical retrace period. The teletext signal T1 is superimposed on the 10th H to the 21st H, and in the example, it is superimposed on the 16th H. Here, H indicates a horizontal synchronization signal. This enlarged view is shown in Figure 1 (B).
It is. Now, when this signal is recorded and played back, it is shown in Figure 1 (C
) Suppose that dropout occurs at the timing shown in (). Here, the high level in FIG. 1(C) indicates that dropout has occurred. The reproduced waveform at this time becomes as shown in FIG. 1(D), and the teletext signal T1 becomes erroneous information due to dropout, and an error occurs.

OBJECT OF THE INVENTION The object of the present invention is to provide a teletext decoder that can accurately decode a teletext signal in a reproduced signal from a magnetic recording/reproducing device without being affected by dropouts or the like. It is.

Structure of the Invention In order to achieve the above object, the present invention provides a method in which a reproduction signal and an error signal are inputted from a magnetic recording and reproducing device, and the error signal generates an error pulse from a plurality of teletext signals superimposed on the reproduction signal. This system is configured to decode the teletext signal of one horizontal period in which the teletext signal is not displayed, and thereby enables accurate decoding without being affected by dropouts or the like.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, the case of recording in a magnetic recording/reproducing device will be explained using the waveform diagram of FIG. 2. In FIG. 2, the image signal is a video signal, and tB) is its enlarged waveform. In the present invention, the video signal undergoes the following processing. First, the teletext signal portion is stored, and then in a plurality of predetermined horizontal periods, the video signal A is replaced with the stored signal to form a composite signal, which is then recorded in a plurality of recording and reproducing devices. In other words, the enlarged waveform B becomes a composite signal C as shown in FIG. 2(C). Here, the composite signal C shows an example in which the 2H section immediately after the teletext signal T1 is replaced, and the signal T2. T3 is exactly the same signal as signal T1. The waveform obtained by recording and reproducing this composite signal C is
It is shown in Figure fEl. Here, it is assumed that a dropout signal occurs in the section shown in FIG. 2(D), as in the conventional example. The teletext signal T1 of the reproduced signal E is affected by dropout and becomes erroneous information, but T2. T3 is reproduced accurately. Therefore, T2. A teletext decoder such as T3 that decodes only accurately reproduced teletext signals can perform decoding without being affected by dropouts.

Therefore, according to the present invention, the error signal is sent to the decoder together with the reproduction signal from the magnetic recording/reproduction device, and when the error signal generates an error pulse, the teletext signal after one horizontal period is decoded. This configuration method can be easily modified using software that is installed inside the decoder, but the concept will be explained in detail with reference to FIG.

Assume that a reproduced input signal A, such as that of a third prisoner, is input to the decoder. Teletext signals are T, , T2. Indicated by T3. This teletext signal does not need to be limited to three sections, and may be multiple sections. Simultaneously with the reproduction input signal A, an error signal is also input from the magnetic recording and reproduction apparatus. This error signal is a signal indicating a reproduction error such as a dropout that occurs during reproduction, and is generated in the magnetic recording/reproducing apparatus, and a high level indicates an error pulse.

Now, an example of the relationship between the sections in which character signals are decoded and error signals is shown in FIG. 3(B) fc) fD). Under normal conditions, as shown in Fig. 3 (Bl), the first section ['r, that is, the @16H period, of the teletext signal is recognized and this n is used as decode information. (C)
When the error signal generates an error pulse as shown in , the next interval T2. In other words, the software is designed to use the 17th H period as decoding information. In this way, it is possible to decode the teletext signal in section T2 in which no dropouts or the like occur.

Next, as shown in FIG. 3(D) in sections T, , and T2, when both error signals generate error pulses, the teletext signal in the next section 'r3, that is, the 18th H period, is decoded as information. Just say that. Here, in the next vertical period, the process returns to the beginning and starts decoding again from the 16th H period of section T1.

In this way, by always decoding the section where no error pulse occurs, 1-close, it is possible to prevent errors caused by the decoder.

Here, various error signals generated inside the decoder may be added to the input error signal to operate as a new error signal.

Although various circuit configurations can be considered for the magnetic recording/reproducing apparatus during recording, a block diagram of the main circuit configuration is shown next. FIG. 4 is the most basic block diagram, which is composed of a memory circuit (2), a control circuit (3), and a switch (4). It is detected in the video signal input from the input terminal (1), and then a predetermined H section switch (4) is switched to the storage circuit (2) side. Here, a-d are input video signals, control signals,
Switch signal, output signal, also memory circuit (2)
It may be a digital memory having a file Φ converter, an end converter, a RAM, etc., or a CCD. When using a digital memory, the stored teletext signal can be reproduced any number of times, so it is possible to read out multiple H sections from the section in which the character signal was originally inserted. Furthermore, as described above, when the teletext signal is at the end of the vertical retrace period, it is also possible to store it for one vertical period and read it out multiple times in a predetermined H period from the next vertical synchronizing signal.

However, when using a CCD, with this circuit configuration, the storage signal is inserted only in the IH interval immediately after the H interval where it was originally inserted, and it is not possible to insert multiple H intervals or insert it after the next vertical synchronization signal. becomes impossible.

FIG. 5 shows a circuit block diagram that allows character signals to be inserted into a plurality of H sections using a CCD. In this case, this processing is realized by inserting a CCD into the feedback circuit system.

Figure 6 shows the waveforms of each part of the block diagram in Figure 4, ia)
~fd) correspond to a to d in FIG. Before the teletext section T1, for example, writing is started from the vertical synchronization signal with a write pulse of the control signal S, and when there is no teletext signal, it is reset with the reset pulse of the control signal S. From the next H interval in which the teletext signal is detected, one or more H intervals, for example T2.
The T3 section is read out and replaced with the video signal a by switch (4) and combined. As a result, an output signal d is obtained. Therefore, T2. The signal in the T3 interval is exactly the same as the signal in the T1 interval.

With this configuration, the recorded signal is reproduced and sent to the teletext signal decoder. This is shown in FIG. FIG. 7 shows only the reproduction system. Magnetic recording and reproducing device (9)
The reproduced signal and the error signal are sent to the input processing unit αD of the decoder (11), and the above-mentioned operation is performed in the input processing unit αC inside the decoder 00, and the error signal is converted into a teletext signal in the H section in which no error pulse occurs. Select this and store it in main memory (2
), the teletext signal is stored, and after being decoded by the output processing section (to), it is output to the CRTa.

This makes it possible to decode character signals without being affected by dropouts or the like.

Effects of the Invention As is clear from the above description, the teletext decoder of the present invention performs IH when an error signal generates an error pulse during the IH period when a reproduced character signal from a magnetic recording/reproducing device is input. By decoding the teletext signal after the period, the teletext signal can be accurately decoded without being affected by dropouts that occur during playback.

[Brief explanation of drawings]

Fig. 1 is a signal waveform diagram for explaining the conventional example, Figs. 2 and 3 are signal waveform diagrams for explaining the present invention, and Fig. 4 is a signal waveform diagram for explaining the present invention.
5 and 5 are block diagrams for explaining processing during recording, FIG. 6 is a signal waveform diagram based on FIG. 4, and FIG. 7 is a block diagram of the reproduction system of the present invention. (2)...Memory circuit, (3)...Control circuit, (9)
...Magnetic recording/reproducing device, 00...Decoder, αB・
・・Input processing section, U-・・Main memory, α3・Output processing section agent Yoshihiro Morimoto Figure 1/ , 27 (5672910///2/P1416/
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tetstit7tzrttxrztmFigure 7 - 11 drops 11 drops--cruel

Claims (1)

[Claims] 1. A reproduction signal and an error signal are inputted from a magnetic recording/reproduction device, and from a plurality of teletext signals superimposed on the reproduction signal, there is one horizontal line in which the error signal does not generate an error pulse. A decoder for teletext broadcasting that decodes a teletext signal for a period. 2. The teletext decoder according to claim 1, wherein the error signal is a dropout signal from a magnetic recording/reproducing device. 3. Claims characterized in that when an erroneous pulse occurs during a period in which a teletext signal is superimposed, the teletext signal after one or several horizontal periods is decoded only during that one vertical period. The teletext decoder according to item 1.