JPH04310657A - Digital vtr - Google Patents

Abstract

PURPOSE:To enable dubbing in a short time by rotating a rotary head drum at high speed when dubbing to record a digital video signal reproduced by one digital VTR with other digital VTR is performed. CONSTITUTION:Plural digital VTRs are prepared and the dubbing to record a digital video signal reproduced with one prescribed digital VTR by other digital VTR is performed. At this time, rotary head drums 10 and 20 of a digital VTR are rotated at (n)-fold speed, magnetic tapes 3 and 4 are travelled at the (n)-fold speed and the dubbing can be performed in 1/n time. Thus, in correspondence to the travelling speed of the magnetic tapes 3 and 4 and the rotation speed of the rotary head drums 10 and 20, the dubbing can be performed at high speed and the dubbing can be performed at the time shorter than the real recording time of the video signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital VTR that converts video signals into digital data and sequentially records and reproduces them on tracks formed at an angle on a magnetic tape, and particularly relates to a dubbing technique using this digital VTR.

0002

2. Description of the Related Art Video signals and audio signals are recorded on a magnetic tape by forming one diagonal track per unit time using a helical scan type rotary head device.
In order to reproduce this, it has been put into practical use to digitize video signals and audio signals and record and reproduce them. This is because digitalization allows for high-quality recording and playback.

By the way, in the case of a VTR that performs recording and playback using a helical scan type rotary head device, the rotational speed of the rotary head drum to which the magnetic head is attached is kept at a constant speed synchronized with the vertical synchronization signal of the video signal. Recording and playback are performed in a controlled manner, and the rotational speed of the rotary head drum is hardly changed depending on the recording mode or playback mode, and when recording or playing back signals such as video signals, the time axis is greatly compressed and recorded.
Previously, it was impossible to reproduce it. Therefore, when performing so-called dubbing, in which multiple VTRs are used to reproduce the signals recorded on each track of one magnetic tape and record the reproduced signals on another magnetic tape, it is necessary to It required the same amount of time as the actual recording time of the signal. For example, when dubbing a magnetic tape on which one hour's worth of video signals has been recorded, it takes one hour.

0004

However, when dubbing with a VTR, it is inefficient to require the same amount of time as the actual recording time of the video signal.

SUMMARY OF THE INVENTION In view of this problem, it is an object of the present invention to provide a digital VTR that allows dubbing in a short time.

[0006]

[Means for Solving the Problems] The present invention provides a digital VTR that converts a video signal into digital data and records and reproduces it on a magnetic tape using a rotating magnetic head attached to a rotating head drum, as shown in FIG. Prepare multiple digital VTRs and use one predetermined digital VTR.
When dubbing a digital video signal played back by another digital VTR to record it on another digital VTR, the rotary head drums 10 and 20 of the digital VTR are rotated at n times the speed, and the magnetic tapes 3 and 4 are rotated at n times the speed. This allows dubbing to be performed in 1/n of the time it takes to run.

[0007]

[Operation] By doing this, dubbing can be performed in a short time, which is shorter than the actual recording time of the video signal.

[0008]

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

[0009] This example is applied to a digital VTR for recording digital video signals, and recording and reproduction are performed by the rotary head drum 1 shown in FIG. This rotary head drum 1 has a magnetic tape 2 wound around its circumferential surface at 180 degrees, and has a pair of double azimuth heads (hereinafter referred to as a first
(referred to as a double azimuth head). At this time,
The distance between the leading head HL and the trailing head HT is set to GL, and the leading head HL and the trailing head HT are fixed at a height offset of one track pitch (in the direction of the rotational axis of the drum). Furthermore, there is another set of double azimuth heads (hereinafter referred to as the second double azimuth head) at a position 180° opposite to this double azimuth head.
Install. This second double azimuth head, like the first double azimuth head, is composed of a leading head HL' and a trailing head HT', each having a different azimuth angle, and their positional relationship is also different from that of the first double azimuth head. Similarly (
That is, the interval is GL and the step is one track pitch). In addition,
The azimuth angles of both leading heads HL and HL' are the same, and the azimuth angles of both trailing heads HT and HT' are also the same.

Recording/reproduction on the magnetic tape 2 by the rotary head drum 1 having this configuration is performed in a first mode in which a digital video signal is recorded by the first and second double azimuth heads, and in a first mode in which digital video signals are recorded by the first and second double azimuth heads. Three modes are available: a second mode and a third mode in which the digital video signal is recorded only by the camera.

In this case, the first mode is used when recording and reproducing high-definition video signals, and the leading head HL, the trailing head HT, and the second double azimuth head, which constitute the first double azimuth head, are used in the first mode. The leading head HL' and the trailing head HT' forming the recording and reproducing head record and reproduce video signals one track at a time in order. That is, as shown in FIG. 3, the tracks formed on the magnetic tape 2 in the first mode are the track TL recorded and reproduced by the preceding head HL of the first double azimuth head, and the track TL recorded/reproduced by the leading head HL of the first double azimuth head.
The track TT recorded and reproduced by the trailing head HT of the double azimuth head, the track TL' recorded and reproduced by the leading head HL' of the second double azimuth head, and the trailing head HT of the second double azimuth head. Track TT' recorded and reproduced by head HT'
are formed in sequence. Note that in the following description, this first mode will be referred to as an HD mode.

[0012] The second mode is used when recording and reproducing NTSC video signals, and is 1/1 of the HD mode.
A magnetic tape 2 is run at a speed of 2, and a leading head HL and a trailing head H forming a first double azimuth head.
Recording and reproduction of video signals are performed alternately one track at a time. That is, as shown in FIG. 4, the tracks formed in the second mode are the tracks TL recorded and reproduced by the preceding head HL of the first double azimuth head, and
Tracks TT to be recorded and reproduced by the trailing head HT of the first double azimuth head are sequentially formed. Note that in the following description, this second mode will be referred to as the standard mode.

[0013]The third mode is also used when recording and reproducing NTSC video signals.
/4, The magnetic tape 2 is run at 1/2 the speed of the standard mode, and the leading head HL and trailing head HT forming the first double azimuth head alternately record and reproduce video signals one track at a time. conduct. However, in the case of this third mode, the preceding head H is rotated twice by the rotating head drum.
L and trailing head HT record and reproduce one track at a time, and the tracks are scanned every rotation of the rotary head drum. That is, as shown in FIG. 5, the tracks formed in the third mode are recorded and recorded by the leading head HL of the first double azimuth head.
A track TL to be reproduced and a track TT to be recorded and reproduced by the trailing head HT of the first double azimuth head are sequentially formed. In this third mode, the tape speed is 1/2 that of the standard mode, but the scanning interval of each head is also 1/2, so
The pitch of each track will be the same as in standard mode. Therefore, compared to the standard mode, the recording time can be doubled on the same tape, but the amount of information recorded in one field is approximately halved. Note that in the following description, this third mode will be referred to as a long-time mode.

In this example, when dubbing a magnetic tape recorded in HD mode, the rotary head drums 10 and 20 are rotated at twice the normal speed, and the magnetic tape is rotated at twice the normal speed. The vehicle was designed to run at a speed of . The configuration for performing this dubbing will be explained below using FIG. 1.

In FIG. 1, numeral 3 indicates a magnetic tape on which digital video signals have been recorded, and numeral 4 indicates a magnetic tape on which digital video signals reproduced from the magnetic tape 3 are recorded. The recorded signals on the magnetic tape 3 are reproduced by four magnetic heads arranged on the rotary head drum 10 of the reproduction side VTR. As with the rotary head drum 1 shown in FIG. 2, these four magnetic heads include a leading head HL and a trailing head HT, which constitute the first double azimuth head.
and the preceding head H constituting the second double azimuth head.
L', trailing head HT'. Further, each magnetic head HL, HT, HL', HT' is supported by a rotating head drum 10 via a bimorph plate 11, and by applying a predetermined control signal to this bimorph plate 11,
The height of each magnetic head HL, HT, HL', HT' can be changed. In this case, the rotary head drum 10 of this example is designed to be able to rotate at twice the normal rotation speed during dubbing in HD mode.

[0016] Then, the reproduction signals of the magnetic heads HL, HT, HL', HT' of the rotary head drum 10 are supplied to reproduction amplifiers 31a, 31b, 31c, 31d via rotary transformers (not shown), The preceding heads HL and HL' output by the reproduction amplifiers 31a and 31c
The reproduced signal is supplied to one and the other fixed contacts of the changeover switch 32. Further, reproduction signals of the trailing heads HT 1 and HT ′ outputted by the reproduction amplifiers 31 b and 31 d are supplied to one and the other fixed contacts of the changeover switch 33 . This changeover switch 32,
The switching 33 is performed in conjunction with the rotation of the rotary head drum 10. That is, each time the rotary head drum 10 rotates 180 degrees, the movable contact alternately selects one fixed contact and the other fixed contact.

Then, the two-channel reproduction signals obtained at the movable contacts of the changeover switches 32 and 33 are transmitted to the equalizer 3.
The signal is supplied to detection circuits 35a and 35b via 4a and 34b. In addition, the reproduced signal obtained from the movable contacts of the changeover switches 32 and 33 is supplied to PLL circuits (phase locked loop circuits) 36a and 36b to generate a clock synchronized with the reproduced signal, and this clock is sent to the detection circuit 35a. ，
35b, and digital data is detected from the reproduced signal in synchronization with the clock. Then, the detected digital data is supplied to time base collectors 37a and 37b to correct the time axis. In this case, the time axis is corrected based on the reference clock output by the oscillator 38. Then, the corrected digital data is sent to the error correction circuits 39a and 39.
b, and the error-corrected digital data is supplied to output terminals 40a and 40b of the reproducing VTR.

In this case, the equalizers 34a, 34 of this example
Each of the reproduction signal processing circuits from the error correction circuits 39a and 39b to the error correction circuits 39a and 39b is capable of signal processing of data up to a transmission rate twice the transmission rate of normal recording digital data. At this time, if necessary, constants set in each circuit may be changed depending on the transmission rate to cope with changes in the transmission rate. For example, the lock range of the PLL circuits 36a, 36b or the characteristics of the equalizers 34a, 34b are changed by changing the transmission rate.

Then, the two systems of reproduction data obtained at the output terminals 40a and 40b are supplied to the input terminals 41a and 41b of the recording side VTR, and the input terminals 41a and 41b are
The two systems of digital data obtained in the precoder 42a
, 42b. The precoders 42a and 42b are circuits that perform digital modulation for recording according to partial response class IV. And the precoder 42a
, 42b are supplied to movable contacts of changeover switches 43, 44. The switching of the changeover switches 43 and 44 is performed in conjunction with the rotation of the rotary head drum 20 of the recording side VTR. That is, the rotating head drum 20 is 18
Each time the movable contact rotates by 0°, the movable contact alternately selects one fixed contact and the other fixed contact. In addition, this recording side VTR
Each recording signal processing circuit is also capable of signal processing of data up to a transmission rate twice the transmission rate of normal recording digital data.

Then, the signals obtained at one and the other fixed contacts of the changeover switch 43 are sent to the recording amplifiers 45a and 45.
b, and the signals obtained at one and the other fixed contacts of the changeover switch 44 are supplied to recording amplifiers 45c and 45d. And each recording amplifier 45a, 45b, 45c,
The output of 45d is supplied to four magnetic heads HL, HT, HL', HT' arranged on the rotary head drum 20 via a rotary transformer (not shown). These four magnetic heads, like the rotary head drum 1 shown in FIG. It consists of a head HL' and a trailing head HT'. In addition, each magnetic head HL, H
T, HL', HT' are supported by a rotating head drum 20 via a bimorph plate 21, and by applying a predetermined control signal to this bimorph plate 21, each magnetic head HL, HT, HL', HT' The height can be changed.

Each recording amplifier 45a, 45b, 45 is attached to the magnetic tape 4 wound around the rotary head drum 20.
c, 45d to each magnetic head HL, HT, HL
', HT'.

Next, the operation when dubbing a magnetic tape recorded in HD mode using the configuration shown in FIG. 1 will be explained. During dubbing, each track is formed as shown in FIG. 3 and digital data is The recorded magnetic tape 3 is run at twice the tape speed when performing normal reproduction in HD mode. Further, the rotational speed of the rotary head drum 10 is set to twice the rotational speed when normal reproduction is performed in the HD mode. Then, all the reproduction heads (heads HL, HT, HL', HT') arranged on the rotary head drum 10 are used for reproduction. At this time, if the discrepancy between the inclination angle of the recording track and the scanning angle of the reproducing head caused by the running speed of the magnetic tape 3 being faster than the normal speed is so large that it cannot be corrected by the reproducing signal processing, a predetermined control is performed. A signal is applied to the bimorph plate 11 to control the reproducing head to correctly scan the recording track.

[0023] Then, the reproduced signals of each leading head HL, HL' and the reproduced signals of each trailing head HT, HT' are converted into digital data through separate signal processing systems, and are supplied to output terminals 40a, 40b. and playback side VTR
A recording side VTR connected to both output terminals 40a and 40b of
The two systems of digital data obtained at the input terminals 41a and 41b of the rotary head drum 20 are supplied to each leading head HL, HL' and each trailing head HT, HT' of the rotary head drum 20 via separate signal processing systems. Then, recording is performed on the magnetic tape 4 wound around the rotary head drum 20 using these four magnetic heads HL, HL', HT, and HT'. In this case, the running speed of the magnetic tape 4 is
The tape is run at twice the speed at which normal recording is performed in this mode (that is, the same speed as the running speed of the magnetic tape 3), and the rotational speed of the rotary head drum 20 is also twice the normal rotational speed. . Note that if the deviation between the track inclination angle and the recording head scanning angle caused by the running speed of the magnetic tape 4 being faster than the normal speed is so large that it is impossible to trace each specified track at all, the specified A control signal is applied to the bimorph plate 21 to control the recording head to scan at the correct angle.

The digital data recorded on the magnetic tape 3 in this manner is dubbed onto the magnetic tape 4. In this case, each magnetic tape 3, 4 is running at twice the normal speed, so it is faster than normal dubbing.
It can be done in /2 hours. In this case, since the signal recorded on the magnetic tape 3 is digital data, only data corresponding to a "1" signal or data corresponding to a "0" signal is recorded, and as in this example, a 1 Even if dubbing is performed at a time of /2, the changing period of this "1" signal or "0" signal will only be halved, and the playback circuit and recording circuit will not be able to cope with this change in transmission rate. If you can handle this, you will be able to dub without any signal deterioration.

[0025] In the above embodiment, an example has been described in which the present invention is applied to dubbing in HD mode for recording high-definition video signals, but it can also be applied to dubbing magnetic tape recorded in other modes. That is, if the running speed of the magnetic tape and the rotational speed of the rotary head drum are increased by the same ratio, the dubbing time can be correspondingly shortened. In this case, the running speed of the magnetic tape and the rotational speed of the rotary head drum may be increased by more than twice as long as the reproduction system circuit and the recording system circuit can cope with the corresponding transmission rate. Furthermore, in the above embodiment, the digital video signal played back from one VTR is recorded on one VTR, but it is also possible to prepare multiple recording VTRs so that multiple videos can be dubbed at the same time. It's okay.

Furthermore, it goes without saying that the present invention is not limited to the above-mentioned embodiments, but can take various other configurations.

[0027]

[Effects of the Invention] According to the present invention, dubbing can be performed at high speed corresponding to the running speed of the magnetic tape and the rotational speed of the rotary head drum, and dubbing can be performed in a short time that is shorter than the actual recording time of the video signal. It becomes like this.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a rotary head drum used in a VTR according to an embodiment.

FIG. 3 is an explanatory diagram showing recording tracks in HD mode according to one embodiment.

FIG. 4 is a configuration diagram showing recording tracks in standard mode and long-time mode according to one embodiment.

[Explanation of symbols]

1, 10, 20 Rotating head drum 2, 3, 4 Magnetic tape 11, 21 Bimorph board

Claims (1)

[Claims] Claim 1: In a digital VTR that converts a video signal into digital data and records and reproduces it on a magnetic tape using a rotating magnetic head attached to a rotating head drum, a plurality of digital VTRs are prepared, and a predetermined digital VTR is used.
The digital video signal played by TR can be transferred to other digital VT.
When dubbing recorded in R, the above digital VTR
A digital VTR characterized in that the rotary head drum is rotated at n times the speed and the magnetic tape is run at n times the speed so that dubbing can be performed in 1/n of the time.