JPS59103479A - Video tape recorder - Google Patents

Abstract

PURPOSE:To attain the recording and reproduction at a recording and reproducing band of an existing home use VTR by recording a transmission signal of a text broadcast while expanding it by n-times and reproducing the signal while compressing it to 1/n-times in the recording and reproduction of a text broadcast signal by a VTR. CONSTITUTION:V and H of an input signal P1 are detected by a timing generating circuit 5, a control signal P2 is transmitted to a control circuit 2 at the rise of a vertical synchronizing signal and a signal P3 having a width of t2 delayed by t1 from the fall of the horizontal synchronizing signal is transmitted to a clock detecting circuit 4. When a clock detecting circuit 4 detects a text signal in 2.86MHz, the clock of a CCD1 is changed and the delay time is changed into 2H from 1H and restored after 2H. The clock is doubled at reproduction and the signal is compressed and restored into the text signal in 2.86MHz. The blank produced for the compression is muted and corrected by a correcting circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helical scan type video tape recorder (hereinafter referred to as V
TR).

Configuration of conventional example and its problems In recent years, teletext systems are being put into practical use.

A teletext system is a new broadcasting service that separates characters or graphics, superimposes them onto the vertical retrace period of a television broadcast video signal, and then selectively receives them using a home receiving device and displays them on a television receiver. It is well known that

The transmission signal format of this teletext is 5.727272 Mb
It is sent in it/sec. In other words, in order to record and reproduce this signal, the signal band must be 2.86 MHz.
! must be maintained. By the way, in recent years home VTR
Although the popularity of VTRs is remarkable, the frequency band that can be recorded and played back by these VTRs is approximately 2 MHz. Furthermore, even a VTR whose luminance signal band was extended by using a comb filter had a frequency of barely 2.5 MHz, making it completely impossible to record and reproduce teletext signals.

OBJECTS OF THE INVENTION The present invention eliminates the disadvantages of the prior art as described in 1. It provides a video tape recorder that can record and play back teletext signals without making any major changes to the conventional home VTR. '
The purpose is to

Structure of the Invention In order to achieve the above object, the video tape recorder of the present invention is a helical scan type video tape recorder, in which one predetermined horizontal scanning period within the vertical blanking period is divided into n horizontal scanning periods (n = natural number). This configuration includes a means for expanding and recording the recorded portion, and a reproducing means for compressing and reproducing the expanded and recorded portion at the time of reproduction.

According to this configuration, the frequency band recorded and played back on the video cheap player is reduced to i by a predetermined section, and even with the recording and playback band that current home VTRs have,
This makes it possible to distribute and reproduce teletext signals.

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

FIG. 1 is a diagram explaining the principle of the present invention, in which (a) is a vertical synchronizing signal period, (b) is an equivalent pulse period, (c) is a period in which a teletext signal can be superimposed, and (d) is a video signal period. The numbers 1 to 7 are schematic representations of the number of horizontal scanning periods (hereinafter referred to as H) after the vertical synchronization signal @ (hereinafter referred to as ■). Suppose now that a teletext signal is sent superimposed on the 8th H as shown in FIG. 1(a). Since the band of this (aθ) is 2.86 MHz, it cannot be recorded or played back on a conventional home VTR.
Stretch it twice and create a waveform like the one shown in Figure 1 (b) at °C1.

At this time, the 2.86 band of (bl) of @8H becomes 2 Mtl z, making it possible to record and reproduce sufficiently. Here, the information of the 4th H is completely erased, but since it is within the vertical retrace period, there is no information to begin with, so there is no problem. Now, if you record a waveform like the one shown in Figure 1 (b) and then play it back, you can compress the 8th H and create a waveform like the first one (c). Although it is necessary to insert the jH information in FIG. 3(c), since it is within the vertical retrace period, it is sufficient to use a dark level, and only the horizontal synchronizing signal ■ needs to be inserted.

FIG. 2 is a circuit block diagram of the main parts of a video tape recorder in one embodiment of the present invention. (1) is an input signal (P) when the reference clock CK is given from the control circuit (2).
This is a CCD that outputs the signal 1) with an IH delay, and the output signal is input to a low-pass filter (3). The clock detection circuit (4) detects the clock at the beginning of the teletext signal. During recording, it detects a 2.86 MHz clock, and during playback, it detects a 2.86/n MH2 clock (however, n is a natural number and is assumed to have been expanded by 0 times during recording). The timing generation circuit (5) receives an input signal (
This detects the V signal and H signal of Pl) and forms the timing necessary for the present invention. The control circuit (2) includes a clock detection circuit (4) and a timing generation circuit (5).
), a switch (
It performs switching control between SWυ and a switch (SWz) that allows the delayed signal to pass, and also provides a correction command to the correction circuit (6).

(7) is an inverter, (8) is an input terminal, and (9) is an output terminal.

Now, as shown in FIG. 1, it is necessary to extend the H period in which the teletext signal is superimposed. An example of extending the H period to twice that length is shown in FIG. 2 and the circuit shown in FIG. This will be explained with reference to FIG. 8, which is a waveform diagram of each part. First, during recording, an input signal (Pl) is input to the input terminal (8). The timing generation circuit (5) detects V and H of this video signal (Pl), detects the rising edge of the vertical synchronizing signal and sends the signal (P2) to the control circuit (2), and at the same time A signal @(P3) is sent to the clock detection circuit (4) with a delay (tl) from the falling edge of the synchronization signal and a width of the rising edge (tl). These (11) ([2) are set to detect the clock line at the beginning of the teletext signal, and are i, NIOμSec during recording.

t2≠8 psec, and 1t-10X during playback
Although nμ8eCst is set to about ≠8Xnμsec, (tl) may be made longer. Here, n
is expanded by a factor of 1 during recording and shows t here. Now, the clock detection circuit (4) detects whether or not there is a 2.86M1 (z clock) of the teletext signal when the signal (P3) is high, and in the detected H section, the clock is high like the signal (P4). Output.

The falling edge of this signal (P4) is made to be synchronized with the next horizontal synchronization signal. The control circuit (2) outputs the CCD drive clock CK, that is, the signal (P5) from the time the signal (P2) becomes high. This clock CK delays the input signal (P+) of CCD (1) by IH. Next, the control circuit <2) receives the signal (P
If the clock CK is to be output at the falling edge of 4), it goes without saying that the clock CK should be switched to the falling edge of the signal (r's).
The signal (Pl) is switched based on the information.

In other words, the clock CK is output and the signal after IH or more from C (
P6), the signal @ (Py) is inverted, and the signal (P4
) is synchronized with the signal (pll) 2H after the falling edge of "
Invert the C signal (Pl). This completes the series of operations. In other words, from the point when the vertical synchronization signal is more than IH, a signal delayed by IH is output, and the H section on which the teletext signal is superimposed is extended by changing the clock frequency given to the CCD (11) by 1'1. When the decompression is completed, the video signal is switched to the undelayed video signal and output.As a result, the output signal M (PM) has a waveform as shown in Fig. 8.The teletext phase superimposed on the 8th H is as follows. , No. 8'
Stretched as H, band, L-4 Lee = 1.48
MHz, and can be recorded and played back even on home VTRs.

Next, the operation during reproduction will be explained using FIGS. 2 and 4. The reproduction input signal (Pi) is passed through while the signal (Pl) is 1, and is also input to the CCD (1) at the same time. Here, CCD (IJ clock (Pρ is)
− is. The clock detection circuit (4) detects the clock at the beginning of the teletext signal, but it is expanded twice and recorded.
86, so the first clock frequency is MHz.

In addition, (t3) and (t4) of the signal (P3) are also switched to approximately twice the (tl) and (tl) during recording, respectively.
If ([2)] is set to a long I in advance, there is no need to switch. Now, after detecting the 2-86 MHz glock, at the falling edge of the signal (P,) synchronized with the next horizontal synchronization signal, the control circuit (2) switches the clock sent to the CCD (1) from CK to CK. , at the same time signal (Py)
(Ps) is inverted in the IH section. As a result, the 8th H
The signal is compressed. As a result, a waveform like the signal (Pi) is output. Here, the extended section cylinder 8'
In order to prevent H from being output, the correction circuit (6) performs muting during the 8th section.For this purpose, the signal (P9) is sent to the correction circuit (6).At this time, , 8th'
Since HIA ill lacks the H synchronization signal, it may be added by the correction circuit (6). Also, since it is okay to output the signal on the 8th day, the correction circuit (6'
) is not necessary. In this way, the final output (P+o) is loaded.

Here, the teletext phase reproduced in the 8th H is 286MH
It goes without saying that it has the same waveform as the input signal at the time of recording, which has a band of z.

Further, the cutoff frequency of the LPF (3) may be appropriately switched between recording and reproduction. That is, during recording, an LPF with a low cutoff frequency that passes A''-MHz is used, and during reproduction, it is switched to an LPF that has a high cutoff frequency that passes 2.86 MHz.

FIG. 5 shows a block diagram of a circuit that takes into consideration the switching of the LPF (3) and the addition of a horizontal synchronizing signal in the correction circuit (6). The circuit of this embodiment is almost the same as the circuit shown in FIG.
I" OQ OIJ, its changeover switch (SWs) (SW4), changeover signal (P+z)
CP, s) is added, and a timing generation circuit (5) is used to add a horizontal synchronization signal to the correction circuit (b).
A signal (PI3) has been added.

In the above embodiment, expansion and compression are set to double, but any integral multiple may be used. Although it is of course possible to expand and compress numbers other than integers,
The circuit system becomes complicated, which is not desirable.

Moreover, in each of the above-mentioned embodiments 1, 4th H and 5th H.

The 6th H is omitted and C is played back, but the section where the teletext signal is superimposed is between the scanning line number button 10H and the 21st H in the vertical retrace section, and the teletext signal near the teletext signal in this section is Even if the number l is missing, there is no effect on the video signal.

Furthermore, in each of the above embodiments, CC is used as the delay time fRS.
Although D(1) is used, it is of course possible to use a digital memory. In this case, various methods can be considered, such as taking in the input signal as binary values of high and low in synchronization with the first clock, or processing it by A/D conversion.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, one predetermined horizontal scanning period □ within the vertical retrace period is expanded and recorded into n horizontal scanning periods, and the expanded and recorded portion is recorded during playback. Since the teletext signals are compressed and reproduced in -, it is possible to record and reproduce teletext signals with a wide frequency band. Furthermore, for example, a clock detection circuit, a timing circuit 1. IIIJ control circuit, CCD
, a correction circuit, etc., it is possible to realize a video tape recorder capable of recording and reproducing text broadcasting with a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a circuit block diagram of main parts of a video tape recorder according to an embodiment of the present invention, and Fig. 8 is a diagram showing the main parts of a video tape recorder according to an embodiment of the present invention. Among the signal waveforms, FIG. 4 is a waveform diagram of each part of the circuit shown in FIG. 2 during reproduction, and FIG. 5 is a circuit block diagram of the main parts of a video tape recorder in another embodiment. (1) ・CCD, +2) ...control circuit, (3
) 0001) ・LPF, (4) -... Clock detection@path, (5)... Timing generation circuit, (6)
...Correction circuit agent Yoshihiro MorimotoOS ci::c5 Q! Hard-C
-497-

Claims (1)

[Scope of Claims] 1. Recording means for expanding and recording one predetermined horizontal scanning period within the overlap blanking period into n horizontal scanning periods (n = natural number);
A video tape recorder comprising a reproducing means for compressing and reproducing the expanded and recorded portion at the time of reproduction. 2. The recording means and the reproducing means include a clock detection circuit,
The apparatus comprises a timing circuit, a control circuit, and a CCD, and extends one horizontal scanning period in which a teletext signal within a vertical retrace period detected by the clock detection circuit is superimposed into n horizontal scanning periods. Claim 1, wherein the clock signal is recorded, and when reproduced, the n horizontal scanning periods detected by the clock detection circuit are compressed into one horizontal scanning period and reproduced.
Videotape recorder as described in Section. 3. The clock detection circuit is 2.86MHz in the recording system.
3. The video tape recorder according to claim 2, wherein the video tape recorder is configured to detect a □MHz clock in the playback system. 4. In the n horizontal scanning period during which the recorded signal is expanded by n times and is reproduced, the reproduced signal is input to the CCD and at the same time the reproduced signal is corrected by the correction circuit in claim 2. or the videotape recorder according to item 8. 5. Low-pass filter connected to the output end of CCD □
5. A video tape recorder according to any one of claims 2 to 4, wherein the video tape recorder is equipped with a low-pass filter and has a structure in which the cutoff frequency of the low-pass filter is switched between recording and reproduction.