JPH0564147A - Video tape recorder compatible with teletext - Google Patents

Abstract

PURPOSE:To record and reproduce an excellent teletext signal by using a gate pulse generated only for a teletext multiplex period to stop the operation of a Y/C separate circuit and a noise reduction circuit. CONSTITUTION:A gate pulse generating circuit 31 generates a gate pulse to gate a multiplexer position of a teletext. Then in the case of recording, changeover switches S1, S2 are turned off with a gate pulse from the circuit 31 to stop the operation of the Y/C separate circuit 1. Moreover, at reproduction, a moving contact (c) of a changeover switch S3 is thrown to the position of a stationary contact (a) according to the gate pulse from the circuit 31 and a changeover switch S4 is turned off to stop the operation of noise reduction circuits 17, 21. Through the constitution above, the teletext data are recorded without being subject to deterioration due to passing through the circuit 1 and are outputted to a teletext decoder without being subject to deterioration due to passing through the circuits 17, 21 at reproduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a teletext corresponding to a teletext that is effective when a teletext is used (especially when a subtitle broadcast is recorded and replayed) in the recording and the reproduction of a commercial broadcast in which teletext is multiplexed. Video tape recorder.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of image processing of a conventional video tape recorder.

In FIG. 1, a video signal received from a tuner (not shown) is guided to a Y / C separation circuit 1.

The Y / C separation circuit 1 is composed of a bandpass filter 2 for the 3.58 MHz band, a 1H delay line 3 and an adder 4. The video signal input to the Y / C separation circuit 1 is , And is guided to the adder 4 and the bandpass filter 2. The output of the bandpass filter 2 for extracting the color signal is led to the 1H delay line 3 and the low frequency conversion circuit 7, and the output of the 1H delay line 3 is led to the adder 4. Further, the output of the adder 4 is guided to the pre-emphasis circuit 5 for enhancing the high frequency component as a signal indicating the luminance signal.

The output of the pre-emphasis circuit 5 is
It is guided to the FM modulation circuit 6, and the output of the FM modulation circuit 6 is guided to the mixing circuit 8. Further, the output of the low-frequency conversion circuit 7 is guided to the mixing circuit 8, and the mixing circuit 8
Output of each of the changeover switches S5, S6 is guided to each of the video rotary heads 22, 23 via one of fixed terminals a, a and movable terminals c, c.

The other fixed terminals b, b of the changeover switches S5, S6 are led to the switching circuit 13 via the amplifier circuits 11, 12 provided corresponding to the respective switches S5, S6. The output is led to a high-pass filter 14 for extracting a luminance signal and a low-pass filter 19 for extracting a color signal converted into a low frequency band. The changeover switches S5 and S6 are controlled so that the movable terminal c is connected to the fixed terminal a side during recording and the movable terminal c is connected to the fixed terminal b side during reproduction. .. In addition, the switching circuit 1
Reference numeral 3 is for performing switching for converting a video signal reproduced from a predetermined recording track by each of the video rotary heads 22 and 23 into a series of video signals, and switching control is performed by a head switching pulse. ..

The output of the high-pass filter 14 is led to the noise reduction circuit 17 via the FM demodulation circuit 15 and the de-emphasis circuit 16, and the output of the noise reduction circuit 17 is led to the mixing circuit 18.

Further, the output of the low-pass filter 19 is led to a noise reduction circuit 21 through a high frequency conversion circuit 20 for converting the color signal into the original frequency band of 3.58 MHz, and the noise reduction circuit 21 outputs The output is
It is led to the mixing circuit 18. The noise reduction circuits 17 and 21 are generally cyclic noise reduction circuits.

In the above structure, the video signal received from the tuner is input to the Y / C separation circuit 1 and given to the adder 4 and the bandpass filter 2 of the Y / C separation circuit 1. The color signal separated by the bandpass filter 2 is delayed by 1H (1 horizontal scanning period) by the 1H delay line 3 and then given to the adder 4 and by the low-frequency conversion circuit 7 at a frequency band of about 630 to 690 KHz. After being converted to the low frequency range, the signal is supplied to the mixing circuit 8. The adder 4 extracts the luminance signal by adding the 1H-delayed phase-inverted chrominance signal to the supplied video signal and supplies it to the pre-emphasis circuit 5.

The luminance signal supplied to the pre-emphasis circuit 5 has its high frequency component enhanced, and then the next F
It is FM-modulated in the M modulation circuit 6 and given to the mixing circuit 8. Then, in the mixing circuit 8, the FM-modulated luminance signal and the low-frequency-converted color signal are mixed again, and each video rotary head 2 is passed through each changeover switch S5, S6.
2 and 23, and sequentially recorded on corresponding recording tracks of a recording medium (not shown). As described above, in each of the changeover switches S5 and S6, the movable terminal c is connected to the fixed terminal a side during recording.

On the other hand, at the time of reproduction, each changeover switch S5
In S6, the movable terminal c is connected to the fixed terminal b side. Therefore, the video signals reproduced from the corresponding recording tracks of the recording medium by the video rotary heads 22 and 23 are transmitted to the amplifier circuits 11 and 12 via the changeover switches S5 and S6.
Is supplied to the high pass filter 14 and the low pass filter 19 after being amplified to a required level and then alternately switched by the switching circuit 13 to be restored to a series of video signals.

The luminance signal separated from the video signal by the high-pass filter 14 is FM-demodulated in the next FM demodulation circuit 15, restored to the original frequency characteristic in the de-emphasis circuit 16, and then the noise reduction circuit 1
7, unnecessary noise components are removed, and the mixing circuit 18
Given to.

The color signal separated from the video signal by the low-pass filter 19 is converted into the original frequency band in the next high-frequency conversion circuit 20, and then the unnecessary noise component is removed in the noise reduction circuit 21. It is provided to the mixing circuit 18.

Then, the luminance signal and the chrominance signal are mixed again in the mixing circuit 18, and the original video signal is restored and outputted.

[0015]

In such a video tape recorder, when recording and reproducing a multiplexed signal of teletext, the Y / C separation circuit 1 is used at the time of recording.
Therefore, during reproduction, the noise reduction circuits 17 and 21
As a result, the teletext signal is deteriorated. Therefore, if such a teletext signal is input to the teletext decoder,
Since data errors frequently occur, there is a problem in that it is not possible to use teletext broadcasting of reproduced video by a video tape recorder.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a video tape recorder corresponding to a teletext capable of favorably recording and reproducing the teletext.

[0017]

In order to solve the above-mentioned problems, a teletext-compatible video tape recorder according to the present invention converts a received video signal into a luminance signal and a color signal by a Y / C separation circuit during recording. While separating, the separated luminance signal and chrominance signal are subjected to appropriate processing, then mixed again and recorded on a recording medium, and when reproduced, appropriate processing is performed on the separated luminance signal and chrominance signal reproduced from the recording medium. A gate pulse generator circuit that generates a gate pulse only during the character multiplex period, and a gate pulse generator circuit that generates a gate pulse during the character multiplex period. A recording stop circuit that stops the operation of the Y / C separation circuit based on the gate pulse generated by the pulse generation circuit, and a recording stop circuit during reproduction. Based on the gate pulse that is generated by Toparusu generating circuit a configuration in which a reproduction stop circuit stops the operation of the noise reduction circuit.

[0018]

[Operation] Multiple positions for teletext are set to 10 in the odd field.
H to 21H and even field 273H to 2
Up to 84H, the gate pulse generation circuit generates a pulse to gate this portion.

At the time of recording, the operation of the Y / C separation circuit is stopped in accordance with the gate pulse from the gate pulse generation circuit, so that the deterioration of the teletext signal recorded on the recording medium is prevented. Further, at the time of reproduction, the operation of the noise reduction circuit is stopped in accordance with the gate pulse from the gate pulse generation circuit, so that deterioration of the teletext signal reproduced from the recording medium is prevented.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the electrical construction of a video tape recorder for teletext according to the present invention.

In the figure, 1 is a Y / C separation circuit, 2 is a bandpass filter in the 3.58 MHz band, 3 is a 1H delay line, 4 is an adder, 5 is a pre-emphasis circuit,
6 is an FM modulation circuit, 7 is a low frequency conversion circuit, 8 is a mixing circuit,
11, 12 are amplifier circuits, 13 are switching circuits, 1
4 is a high pass filter, 15 is an FM demodulation circuit, 16 is a de-emphasis circuit, 17 is a noise reduction circuit,
Reference numeral 18 is a mixing circuit, 19 is a low-pass filter, and 20 is 3.
A high frequency conversion circuit for the 58 MHz band, 21 is a noise reduction circuit, 22 and 23 are video rotary heads, and S5 and S6 are changeover switches. These configurations are the same as those of the conventional video tape recorder described above. The same reference numerals are given here, and detailed description is omitted.

In addition to the above configuration, the video tape recorder of the present invention is provided with a gate pulse generating circuit 31 for inputting a video signal input and a video signal output, and between the 1H delay line 3 and the adder 4. Open / close switch S1
, An open / close switch S2 between the bandpass filter 2 and the low frequency conversion circuit 7, a changeover switch S3 between the noise reduction circuit 17 and the mixing circuit 18, and a switching switch S3 between the noise reduction circuit 21 and the mixing circuit 18. Open / close switch S4
And each of the switches S1 to S4.
The switching control is performed according to the gate pulse generated by the gate pulse generation circuit 31. In the changeover switch S3, the output of the de-emphasis circuit 16 is connected to one fixed terminal a, the output of the noise reduction circuit 17 is connected to the other fixed terminal b, and the input of the mixing circuit 18 is connected to the movable terminal c. It has been configured.

Further, the gate pulse generating circuit 31 has a changeover switch S7 having a fixed terminal a to which a video signal input is led and a fixed terminal b to which a video signal output is led, and a movable terminal c of this changeover switch S7. And a multi-vibrator 312, 313 connected in multiple stages to which the output of the vertical sync separation unit 311 is guided.

The first stage multi-vibrator 312 operates at the falling edge of the vertical synchronizing signal,
The "H" level is output for a period of 6H (≈63.5 μsec × 6). Further, the second-stage mono multivibrator 313 operates at the falling edge of the output of the first-stage mono multivibrator 312, and 12H (≈
The "H" level is output for a period of 63.5 μsec × 12). A timing chart of the gate pulse generation circuit 31 is shown in FIG. "H" of the gate pulse output from the second-stage mono multivibrator 313
The level period is a multiple period of teletext.

Further, each open / close switch S1, S2, S4
Is turned off only while the gate pulse output from the gate pulse generation circuit 31 is at the “H” level, and the changeover switch S3 is movable only while the gate pulse output from the gate pulse generation circuit 31 is at the “H” level. The terminal c is connected to the fixed terminal a side.

That is, at the time of recording the multiplexed video signal of the teletext, the open / close switches S1 and S are set during the superposition period of the teletext.
Since 2 turns off and the operation of the Y / C separation circuit 1 is stopped, the teletext is recorded on the recording medium without being deteriorated by the data passing through the Y / C separation circuit 1. Become.

When the recorded video signal of the teletext is reproduced, the changeover switch S is operated during the superposition period of the teletext.
The movable terminal c of 3 is connected to the fixed terminal a side, and
Since the open / close switch S4 is turned off to stop the operation of the noise reduction circuits 17 and 21, the teletext signal reproduced from the recording medium is not deteriorated by the noise reduction circuits 17 and 21.
It will be output to a teletext decoder (not shown).

As described above, since the deterioration due to the recording and reproduction of the teletext signal is extremely small, it is possible to reproduce the teletext in good condition without the occurrence of a data error during the reproduction.
Further, since the above operation is an operation in the vertical blanking period, it does not affect the video signal.

[0030]

The video tape recorder for teletext according to the present invention has a gate pulse generating circuit for generating a gate pulse only during the character multiplex period and a gate pulse generated by the gate pulse generating circuit during recording. A recording stop circuit for stopping the operation of the Y / C separation circuit on the basis of the operation, and a reproduction stop circuit for stopping the operation of the noise reduction circuit on the basis of the gate pulse generated by the gate pulse generating circuit during the reproduction. With such a configuration, when the commercial broadcast in which the teletext recorded on the video tape recorder is multiplexed is played back, the teletext can be used. In particular, the effect of recording and reproducing a video signal in caption broadcasting for a deaf person is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a teletext-compatible video tape recorder according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the gate pulse generation circuit.

FIG. 3 is a block diagram showing an electrical configuration of a conventional video tape recorder.

[Explanation of symbols]

 1 Y / C separation circuit 17, 21 Noise reduction circuit 31 Gate pulse generation circuit S1, S2 Open / close switch (stop circuit during recording) S3 Changeover switch (stop circuit during playback) S4 Open / close switch (stop circuit during playback)

Claims (1)

[Claims] 1. At the time of recording, the received video signal is separated into a luminance signal and a color signal by a Y / C separation circuit, and
The separated luminance signal and chrominance signal are subjected to appropriate processing and then mixed again to be recorded on a recording medium, and at the time of reproduction, reproduced from the recording medium and subjected to appropriate processing on the separated luminance signal and chrominance signal, and noise In a video tape recorder configured to reduce unnecessary noise by a reduction circuit and then mix and output again, a gate pulse generation circuit that generates a gate pulse only during the character multiplex period and this gate pulse generation during recording. A recording stop circuit for stopping the operation of the Y / C separation circuit based on the gate pulse generated by the circuit, and the noise reduction circuit based on the gate pulse generated by the gate pulse generation circuit during reproduction. A video tape for teletext, comprising a stop circuit at the time of reproduction for stopping the operation of Coder.