JPS6129283A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To execute the excellent time correction and clamp action at reproduction by removing a sound signal at recording and producing non-signal period before and behind the m-numbered head switching point counted from the after- recording point in a vertical blanking period. CONSTITUTION:In a signal from an input terminal 1, a sound signal is removed in a gate circuit 2 which is driven based on a vertical blanking phase, and is made a digital signal in an A/D converter 3. Said signal and a signal through delay circuits 4-6 having certain delay periods are added to a switching circuit 7, which is driven by a head switching signal for synchronizing with a rotational phase of a rotating cylinder. Then a switching point is caused to come at an appropriate point in the vertical blanking period. Afterward the switching point is switched to l1. After the head is switched, said point is switched to l2. Next, the switching points are sequentially switched to l3 and l4. Their outputs are returned to analog signals by a D/A converter 9, and outputted from a terminal 10.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] Uninvented is the extremely short horizontal blanking period 79. Kake, Wle; From the nib, rough 4. The present invention relates to a magnetic recording/playback device (VFX).

[Background of the invention]

Development of high-definition television systems such as #T5C and PAL, which has much higher definition than current television systems, is underway. The signal band is Y (luminance signal) and C, in order to aim to more than double the resolution in the vertical and horizontal directions.

(Chromaticity signals) are both SOMHz. In order to transmit this signal in as small a band as possible (approximately 8 MEz'),
It has been proposed to perform 4-cross sampling between scanning lines and between frames, and its contents are detailed in, for example, Technical Report TEB 595-2 (March 1984) of the Television Television Society.

The signal after this band compression is P within the vertical blanking period.
A zero-level reference signal for a 6M audio signal, a chromaticity signal, and a reference/signal for horizontal synchronization separation are multiplexed. On the other hand, the horizontal blanking period is as short as only 0.7 μsec, and has a positive synchronization signal having the same polarity as the video signal.

A rotary helical scan type VTR for recording and reproducing such video signals has the following problems. Above BM
If you want to record and reproduce the Ilz band, especially on a small device such as a home-use V7'H, due to the restriction of the diameter of the cylinder in which the one-turn head is mounted, you will have to record by dividing the vertical period into multiple tracks. There is no choice but to adopt the so-called segment recording method. For this reason, a time base correction circuit (TBC) must be inserted into the reproduction circuit to completely correct the skidding that occurs when switching tracks. Conventionally, this skew correction has been carried out by making the phase of the horizontal synchronizing signal continuous before and after track switching immediately before the horizontal synchronizing signal (at the front porch where there is no video).

Therefore, considering the amount of skiing that occurs in the normal V7'R, the period of the front porch is several μs.
It was necessary to secure a level of ec. However, if the entire horizontal blanking period is only about 0.7 μsec, there is a problem that scratches (lack of signal) may occur during correction on the reproduced image.

For example, in order to stabilize the zero level of the chromaticity signal,
It is necessary to clamp the video signal to a certain level, and as described above, the reference signal that provides the timing for this clamping is within the vertical blanking period. Therefore, when there are multiple ski points in the vertical period, as in the case of the above-mentioned segment type VTR playback, the period from the first skew occurrence point to the next vertical blanking period is normal. I couldn't do the lamp,
For example, there is also the problem that the zero level of the chromaticity signal cannot be detected.

It is still young, and measures to solve these problems have not yet been disclosed.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems, and to improve the time axis correction and clamp operation during good playback even in VTRs that segment record video signals with extremely low horizontal synchronization periods. The goal is to provide a recording method.

[Summary of the invention]

For the above purpose, in the present invention, -vertical period fn C path is 2
The following recording method is used in the rotary two-head edge cal scan type VT- which performs segment recording by dividing into tracks of (an integer greater than or equal to). First, all audio signals within the vertical blanking period are removed. Then, based on the appropriately determined position of the vertical blanking period of the video signal, the video signal of the first vertical period is recorded on the first track, and the video signal of the second vertical period is recorded.

A predetermined period of time τ sufficient to correct the above-mentioned deviation.
record on the second track after a delay of Generally speaking, the 11th. The video signal is delayed by (an integer where 溪≦轴)−vertical period video signal 't-cm1l-1)τ, and then recorded on the No. 1 track. By this operation, the image is projected within one vertical interval, #A times the signal,
Since the input original signal is also delayed by (--1)τ,
By removing the audio signal and reducing the vertical blanking period with increased redundancy, the signal after the above operation is returned to the time relationship that matches the original signal input for each vertical blanking. do.

Furthermore, the no-signal period τ near the track switching point caused by the above operation is set to a certain potential and recorded. , and the switching phase of a known head switching signal generated in synchronization with the rotational phase of the rotating head (track switching phase) is positioned approximately at the center of the recording position on the track during the above-mentioned no-signal period τ. . During playback, skew correction is performed during this no-signal period τ based on the chromaticity switching signal described above, and this is clamped to a constant DC potential. This is to stabilize the level.

On the other hand, the audio signal removed from the vertical blanking period is recorded by means different from the video signal. For example, in a two-head helical scan VTR, a magnetic tape ``t-180'' is wound around a rotary cylinder equipped with a video head, and a video signal is transmitted to 180 degrees of the tape using the method described above.

It is sufficient to perform audio overlap recording in which the audio signal is recorded in the remaining portion.

[Embodiments of the invention]

Next, an embodiment of the present invention will be explained using the circuit block diagram of FIG. 1 and the signal waveform diagram of FIG. 2.

This figure shows an example of a 2-head, 4-segment recording type vrRO.

A video signal in the format shown in Figure 2 (al) is input to the input terminal 1. In Figure 2 (al), V is the video signal (Y,
C, 'includes a horizontal synchronizing signal), V-BLK is a vertical blanking period te@F), and the audio signal shown by A is multiplexed in a certain period of V-BLK. The signal from the input terminal 1 has the audio signal removed by the gate circuit 2 which is driven in accordance with the vertical blanking phase, resulting in the signal shown in FIG. Thereafter, the AD converter 3 converts the signal into a digital signal. This signal and a signal via a delay circuit 4'(1'', for example, configured with a shift register or the like) having a certain delay time (for example, 1H; B is a horizontal period), and a signal via a similar delay circuit 52, Furthermore, the delay circuit 6
' are applied to the switching circuits 7, respectively. Switching circuit 7
is driven by a control signal from input terminal 8. This control signal goes to 2 for a helical scan type VTR.

A known head switching signal (indicating which head is on the magnetic tape) synchronized with the rotational phase of the rotary cylinder as shown in FIG. 2(d) may be used. And V
- The switching point is set at an appropriate point in BLK, and after this point, the switching point is set to tl, after the primary head switching, to 4, and then to C8 and 4 in sequence,
If the output fl)A is converted back to an analog signal by the A converter 9, the signal shown in FIG. 2(C) is obtained at the output terminal 10. This f
FM modulated signal and recorded on magnetic tape.

2 (as shown by α in C1, for example, 1B (delay circuits 4, 5
．． A no-signal period of 6° is generated in the delay time of 6°, and a sufficient time margin for skinny correction during playback can be secured.

Moreover, since this no-signal period appears in synchronization with the phase of the head switching signal even during reproduction, the timing at which a correction operation should be performed can be easily detected. Also, as a result, the video signal immediately before the vertical blanking period is delayed by 3B in the above example compared to the input original signal shown in Figure 2 (a), but the vertical blanking period has increased redundancy by the amount removed from the audio signal. If the blanking period is shortened by f3E, the time relationship can be returned to match the original signal input for each vertical blanking.

As mentioned above, this is a 4-segment recording type VTR.
This is an example, but it goes without saying that the same method can be used if the number of segments is different.

Further, it is not necessary to limit the delay time of the delay circuits 4, 5.6 to 1B. In short, any amount is fine as long as there is enough time for ski correction, and as long as the audio signal can be removed to return the video signal to the time relationship that matches the input original signal for each vertical blanking. . Delay circuit 4, 5.6
may have different delay times.

Further, it is not essential to delay the signal after digitizing it via the AD converter 5, and it is also possible to perform delay processing as it is as an analog signal. Furthermore, the digital signal output from the switching circuit 7 may be modulated to that level without going through the DA converter 9 and recorded on the magnetic tape.

On the other hand, it is effective to set the no-signal period of, for example, 1B to a constant potential as shown by α in FIG. 2(C), and clamp this to a constant DC potential within the signal processing circuit.

This is especially effective when the horizontal blanking period is extremely short and there is not enough time to ramp it up, and as mentioned above, it is effective, for example, in stabilizing the zero level of the chromaticity signal. be. Note that the timing for performing this clamping can be easily detected from the head switching signal during playback.

In the above explanation, the method of recording audio signals has not been mentioned at all, but this will be described using FIG. 3 as an example of the case of a two-head helical scan type. In the figure, the components from input terminal 1 to l) A converter 9 may be the same as those in FIG. D
The output of the A converter 9 is converted into an FM modulated signal by the 1M modulator 11.

It is added to one end of the switching circuits 12cL and 12A. Input terminal 1
The signal is applied to the gate circuit 13, where the PCM audio signal portion is extracted based on the vertical blanking phase. Of course, the gate circuits 2 and 15'i may be combined into one switching circuit. Further, the PCM processor 14 converts the signal into a modulated wave suitable for recording on a magnetic tape.

It is added to the remaining one end of the switching circuit 12a; 12b. These two switching circuits 12α, 12b each also have an input terminal 8.
It is driven based on the head switching control signal from. The outputs are sent to two recording amplifiers 15eL.

It is applied to two video heads 16α and 16b via 15bf. The magnetic tape 17 has video heads 16g and 16A.
-i It is wound around the mounted rotating cylinder in a line slightly less than 180°. In this case, as in this embodiment, a separate switch circuit 12 is provided for each of the two video heads 16a and 16b.
By providing cL, 12b, and recording amplifier IF1, 15+61-, it is possible to realize audio overlap recording in which video is recorded in the 180° interval and audio is further recorded in the remaining interval as an extension thereof.

In the case of a segment recording VTR, it is optional whether to record the audio signal on the extension of each video track or every few tracks.J7. In each case on the pcI processor 14''':
This is achieved by converting the time axis.

I'll text you. Similarly, the processor 14 may be provided with a conversion function, for example by giving redundancy to the audio signal. 1 or more is a case where audio overlap recording is used, but it is not necessary to be limited to this, and the output of the gate circuit 13 is returned to an analog baseband signal, and bias recording is performed toward the end of the magnetic tape with a fixed head. It's okay.

Next, the faith recorded as described above! An embodiment for reproducing the data will be explained using the circuit block diagram in FIG. 4 and the signal waveform diagrams in FIGS. This figure shows a system for reproducing a signal recorded based on the embodiment of FIG. 3, and the video heads 16a, 16k and magnetic tape 17 may be the same as those shown in FIG. The operation will be explained below.

The reproduction output of the video heads 16a and 16h is provided by the reproduction amplifier 1.
After being amplified to an appropriate level by 8g and 18b, it is applied to switching circuits 19a and 19b. Switching circuit 19+! , 19A
is driven by a head switching signal synchronized with the rotational phase of the rotary head during playback from the input terminal 31, and as a result, 1
The output of 9a is a video signal, 19. The audio signals resulting from the above-mentioned overlap recording appear separately in the output of b.

The output of the switching circuit 19'a is demodulated by the 1M demodulator 2o and applied to the time axis correction circuit 21. A head switching signal is also led to this correction circuit 21, but this signal is synchronized with the no-signal period on the Eirin track created during recording. On the other hand, since skew is caused by signal processing during recording and occurs during this no-signal period, the correction circuit 21 performs skinny correction with sufficient time and margin based on the switching signal. be able to. As a result, the output of the correction circuit 21 includes the second output as shown in FIG. 5(a).
It is possible to obtain a video signal without time axis fluctuations such as skew, similar to that shown in Figure (cl).

The signal is then turned into a digital signal by the AD converter 22.

This signal, a signal via the delay circuit 23 (the delay time is the same as the delay circuit 6 in FIG. 3), a signal via the delay circuit 24 (also the same delay time as the delay circuit 5), and a signal via the delay circuit 25 (Similarly, the delay circuit 4 and the delay time are the same) t-signals are applied to the switching circuits 26, respectively. The switching circuit 26 is also driven by the head switching signal, and switches to fl during the vertical blanking period and immediately after that, to f2 after the next head switching point, and then to fs = f. If it is converted back to an analog signal by the fDA converter 27, a video signal similar to that shown in FIG. 2 (Al) can be obtained, as shown in FIG. 5(b). Join 28.

On the other hand, the output of the switching circuit 1Bb is demodulated by the PCM processor 29 and returned to the same signal as the input signal during recording. Further, after the signal is suitably phase-aligned with the signal from the input terminal 50 indicating the vertical blanking period after time axis correction, it is applied to the adder 28 .

The video signal and the audio signal are added in the adder 28,
A signal shown in FIG. 5(c) is output to the output terminal 32.

This is the same as the recording input signal shown earlier in FIG. 2 (cl), and it can be seen that the intended recording and reproducing operation can be completed.

□As mentioned above, by recording with a no-signal period at the head switching point where the track changes during recording, the no-signal period can be detected based on the phase of the head switching signal during playback. , here the skew correction can be performed with sufficient time. In addition, even in a state where there is skew before time axis correction, it is possible to perform clamping with sufficient time margin using this no-signal period based on the phase of the head switching signal, for example, to adjust the chromaticity. It is possible to stabilize the zero level of the signal.

〔Effect of the invention〕

As explained above, according to the present invention, a video signal with an extremely short horizontal blanking period can be transmitted to a segment recording type VTR.
Even in the case of recording, there is enough time to properly correct the skew that occurs at the head switching point during playback, and there will be no signal loss on the playback image.

In addition, for this purpose, by clamping the no-signal period formed during recording, even when there is a skew, there is a sufficient amount of time for recording, recording, and recording.
Hey. One. It is possible to stabilize the I zero level.

Furthermore, the timing for performing the skew correction and clamping can be easily detected from a known head switching signal.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram showing an embodiment of the present invention, Fig. 2 is a signal waveform diagram for explaining the invention, and Figs. 3 and 4 are circuit diagrams showing an embodiment of the invention. , FIG. 5 is a signal waveform diagram for explaining the present invention. 2... Gate circuit 3.22... AD converter 4.5, 6, 25, 24.25... Delay circuit 7.
26...Switching circuit 9,27...DA converter d20 dimension-1-I
ν -ノ2 2
G Procedural amendment (method) Name of the invention Relationship with the case of the person who amends the magnetic reproduction device 1 Patent applicant Name (
5101 Hitachi Manufacturing Co., Ltd. Agent Subject of personal amendment Application and specification

Claims (1)

[Claims] 1. A two-head segment recording type magnetic recording and reproducing device that records one vertical period of a video signal on a plurality of recording tracks, and furthermore, the time axis is compressed and the time axis is recorded within vertical blanking. In a device whose recording input is a video signal having a multiplexed audio signal, there is provided a circuit for removing the audio signal during recording, and an m-th (m is 1 or more) counting from the trailing edge of the vertical blanking period. A no-signal period of time τ is created before and after the head switching point (an integer of What is claimed is: 1. A magnetic recording and reproducing apparatus comprising: a circuit having a function of returning the data to the original signal; and a time axis correction circuit that performs skew correction during the no-signal period during playback. 2. The magnetic device according to claim 1, characterized in that the no-signal period in the vicinity of the switching point of the video head is at a constant potential, and this is clamped to a constant DC potential. Recording and playback device.