GB2342760A

GB2342760A - Tape recorder with temporary memory

Info

Publication number: GB2342760A
Application number: GB9908445A
Authority: GB
Inventors: Kikuo Sagara
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1998-10-14
Filing date: 1999-04-13
Publication date: 2000-04-19
Anticipated expiration: 2019-04-13
Also published as: DE19940225B4; JP2000125242A; GB9908445D0; GB2342760B; DE19940225A1

Abstract

Device and method to record a video signal on a magnetic tape 6 without interruption during periods when direct recording of the input signal 14 onto the tape is not possible (eg. during rewind, power failure or tape replacement). This is achieved by use of a storage circuit 10 to store the input signal during these periods. The stored signal is transferred to the tape once recording becomes possible again.

Description

2342760 MAGNETIC TAPE RECORDING DEVICE AND VIDEO SIGNAL RECORDING METHOD

BACKGROUND OF THE INVENTION

This invention relates to a magnetic tape recording device and signal recording method for recording only a video signal or audio and video signals on a recording medium such as a magnetic tape.

Fig. 6 is a block diagram showing a prior art magnetic tape recording devices for recording video signals (referred t o hereafter as VTR). In the figure, reference numeral 1 denotes a rotating drum, and 2 denotes a pair of video heads mounted on the rotating drum 1. Reference numeral 3 denotes a drum motor for driving the rotating drum 1. Reference numeral 4 denotes a capstan motor for rotating a capstan 4a. Reference numeral 5 denotes a pinch roller, 6 denotes a videotape in the form of magnetic tape, and 7 denotes a servo circuit for controlling the drum motor 3 and capstan motor 4. Reference numeral 8 denotes a recording signal processing circuit for converting a video signal into a recording signal which can be recorded on the videotape 6. Reference numeral 11 denotes a character generating circuit, 12 denotes a superimposing circuit which superimposes characters on the video signal, and 13 denotes a control circuit for controlling the servo circuit 7, recording signal processing circuit 8, and the like.

Next, the recording operation of this VTR will be described.

An input video signal Vin, which for example is supplied from a monitor camera, not shown, is input to the superimposing circuit 12 and control circuit 13. The servo circuit 7 which is connected to the control circuit 13 causes the drum motor 3 to rotate in synchronism with the input video signal (Vin), and causes the capstan motor 4 to 1 rotate at a predetermined speed corresponding to the recording speed set on the VTR. The videotape 6 is wound at an inclined angle on the rotating drum 1, and runs at a predetermined speed between the capstan 4a and the pinch roller 5.

Time and other information is generated in the character generating circuit 11, and supplied as character signals to the superimposing circuit 12. In the superimposing circuit 12, these character signals are superimposed on the input video signal, and output to the recording signal processing circuit 8. In the recording signal processing circuit 8, the processed video signal is recorded by the video heads 2 on the videotape 6.

A variation of VTR is a time lapse VTR which thins out or decimates video signals so as to permit recording for long periods of time using the same length of tape. For example, whereas an ordinary VTR records a video signal of 60 fields per second In the normal recording mode, in the extended recording mode of a time lapse VTR, a video signal of 20 fields per second is recorded by recording only one field in every three fields. Therefore, using such a time lapse VTR, 18 hours of video signals can be continuously recorded on a tape which permits 6 hours recording in normal recording mode.

For recording images picked up by a monitor camera, for example, it may not be necessary to record a video signal of 60 fields per second as it is when recording television broadcasts, and in this case a time lapse VTR which can record for long time periods such as described above, is used. Also, in a time lapse VTR, the same tape can automatically be overrecorded excepting for images which it is desired to save for a longer time. When the video signal is recorded automatically by the VTR, the recording operation is terminated when the end of the tape recording

2 area is detected, the tape is rewound back to the beginning, and recording is resumed after the rewinding.

In the prior art VTR described above, the following problems arise when the video signal is recorded on videotape 6.

In general, when a video signal is over-recorded for repeatedly using the same videotape 6, recording begins from the beginning of the tape, the recording operation is temporarily terminated when the tape has been recorded to the end, the videotape 6 is rewound to the beginning, and recording is then resumed. When the tape is being rewound by the VTR, input video signals cannot be recorded on the videotape 6. Even when plural videotapes are provided and the video signal is recorded on these tapes one after another, the situation is almost the same. In other words, when recording on the first videotape has finished, recording of input video signals cannot resume while the first tape is being removed from the VTR and the second tape is being inserted into the VTR. Therefore, input video signals cannot be recorded for a certain time during which the videotape is being replaced. Recording on the videotape is.also interrupted if there is an interruption of power supply to the VTR.

Thus, there was a problem in that video signals could not be recorded while the tape was being rewound or replaced, or there was a power supply failure.

SUMMARY OF THE INVENTION

It is therefore an object of this invention, which was conceived in view of the aforesaid problems, to provide a video signal recording method and magnetic tape recording device wherein a video signal can be saved without interruption during periods when recording on tape is impossible, such as when a tape is being rewound or 3 replaced, or when there is a power supply failure.

According to the invention, there is provided a magnetic tape recording device for recording an input video signal on magnetic tape, comprising:

recording means for recording the input video signal on said magnetic tape; storage means for storing said input video signal; and control means for causing said input video signal to be stored at least in a period when recording said input video signal on said magnetic tape is impossible.

Accordingly, video signals which could not be recorded on the video tape while the tape was being rewound or replaced, or during a power failure, can now be saved.

It may be so arranged that said control means causes the video signal to be transferred from the storage means to said magnetic tape after said period when the recording on said magnetic tape is impossible ends.

It may be so arranged that the magnetic tape recording device may further comprise comprising selecting means; wherein said control means causes the video signal to be read from the storage means after after said period when the recording on said magnetic tape is impossible ends; said selecting means selects and outputs either the video signal read from said storage means or said input video signal bypassing the storage means; said recording means records the video signal output by said selecting means; and said control means causes said selecting means to select the video signal stored in said storage means after said period when the recording on said magnetic tape is impossible ends so that the video signal read from said storage means is transferred to said magnetic tape.

It may be so arranged that the control means causes 4 said selecting means to select the input video signal bypassing the storage means after the transfer of the video signal from the storage means to the magnetic tape is completed.

It may be so arranged that the selecting means outputs said video signal read from said storage means when recording on said magnetic tape resumes after said magnetic tape has run to the end.

Accordingly, the video signal acquired while the tape is rewinding can be recorded on the videotape.

It may be so arranged that the control means causes said storage means to intermittently store said video signal.

Accordingly, the video signal acquired while the tape is rewinding can be recorded on the videotape without any break.

It may be so arranged that the control means causes the magnetic tape to run at the speed for normal recording, while causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number; causes one field in every n fields of the input video signal to be written in said storage means, with n being an integer greater than 1; and causes the video signal to be transferred to and recorded on said magnetic tape at said first rate while causing the magnetic tape to run at the speed for normal recording.

It may be so arranged that the control means causes the magnetic tape to run intermittently at an average speed which is 1/m of the speed for normal recording, with m being an integer greater than 1, while causing one field in every m fields of the input video signal to be recorded, said input video signal being supplied at a first rate of p fields per second, with p being a predetermined number; causes one field in every m fields of the input video signal to be written in said storage means, and causes the video signal to be transferred to and recorded on said magnetic tape at the first rate of p fields per second, while causing the magnetic tape to run at the speed for normal recording.

It may be so arranged that the magnetic tape recording device further comprises detecting means for detecting that no more recording area is available on said magnetic tape and generating a detection signal upon such detection, and the control means causes said input video signal to be written in said storage means when said the detection signal is generated.

Accordingly, the video signal acquired while the tape is rewinding or during tape replacement can be recorded on the videotape.

The magnetic tape recording device may further comprise a backup power supply to supply at least to said storage means to enable said input video signal to be written in said video signal when an external power supply to the recording device is interrupted.

Accordingly, a video signal supplied by a monitor camera, for example, can be stored even during a power failure, and the video signal can be recorded on the videotape without any break.

The storage means may comprise a replaceable storage medium.

There is therefore no need to transfer the video signal to the videotape, with the result that the video signal stored by the storage means can be recorded at normal speed as in the case of the video signal recorded on the videotape without performing intermittent recording.

6 According to another aspect of the invention, there is provided a method for recording a video signal on magnetic tape using a magnetic tape recording device, comprising the steps of: (a) recording the input video signal on said magnetic tape; and (b) storing said input video signal in a storage means at least in a period when recording said input video signal on said magnetic tape is impossible.

The method may further comprise the step of: (c) transferring the video signal from the storage means to the magnetic tape after said period when recording said input video signal on said magnetic tape is impossible ends.

The method may further comprise the steps of: (d) superimposing a character signal on said video signal; and (e) supplying said video signal on which said character signal is superimposed to said magnetic tape and storage means.

Accordingly, it is easy to verify the continuity of the video signal.

The method may further comprise the steps of (f) rewinding said magnetic tape when no more recording area is available on said magnetic tape; (g) storing said input video signal in said storage means; and (h) transferring said video signal from said storage means to said magnetic tape when recording by said magnetic tape is resumed after rewinding.

Accordingly, the video signal can be repeatedly recorded automatically without replacing the tape, and there is no break in the recorded image over a long time period.

The method may further comprise the steps of: (i) storing said input video signal in said storage means 7 after no more recording area is available on said magnetic tape and at least until a new magnetic tape is inserted, and (j) transferring the video signal from said storage means to said new magnetic tape when recording is started on said new magnetic tape.

Accordingly, recording can be made on new videotapes one after another without any break in the video signal during tape replacement.

The step (b) of storing the video signal in said storage means may comprise storing intermittent video signal; and said step (a) of recording the video signal on the magnetic tape may comprise recording intermittent video signal.

Accordingly, by having the video signal transferred from the storage means to the videotape, breaks in images recorded over a long time are eliminated.

It may be so arranged that said step (a) of recording comprises causing the magnetic tape to run at the speed for normal recording, and causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number; said step (b) of storing comprises causing one field in every n fields of the input video signal to be written in said storage means, with n being an integer greater than 1; and said step (c) of transferring comprises causing the video signal to be transferred to and recorded on said magnetic tape at said first rate while causing the magnetic tape to run at the speed for normal recording.

It may be so arranged that said step (a) of recording comprises causing the magnetic tape to run intermittently at an average speed which is 1/m of the speed for normal recording, with m being an integer greater than 1, and causing one field in every m

8 fields of the input video signal to be recorded, said input video signal being supplied at a first rate of p fields per second, with p being a predetermined number; said step (b) of storing comprises causing one field in every m fields of the input video signal to be written in said storage means; and said step (c) of transferring comprises causing the video signal to be transferred to and recorded on said magnetic tape at the first rate of p fields per second, and causing the magnetic tape to run at the speed for normal recording.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a block diagram showing a magnetic tape recording device according to an embodiment of the invention.

Fig. 2 is a block diagram showing a storage circuit according to the embodiment of Fig. 1 Fig. 3A and Fig. 3B are schematic diagrams showing an ordinary and intermittent recording.

Fig. 4 is a block diagram showing a magnetic tape recording device according to another embodiment of the invention.

Fig. 5 is a block diagram showing a magnetic tape recording device according to another embodiment of the invention.

Fig. 6 is a block diagram showing a conventional magnetic tape recording device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will now be described referring to the attached drawings.

Fig. 1 is a block diagram showing a video recording device which is a magnetic tape recording device according 9 to an embodiment of the invention, the same symbols being assigned to identical or equivalent parts of the prior art device shown in Fig. 6.

In Fig. 1, reference numeral 1 denotes a rotating drum, and 2 denotes a pair of video heads mounted on the rotating drum 1. Reference numeral 3 denotes a drum motor, 4 denotes a capstan motor for rotating a capstan 4a, 5 denotes a pinch roller, 6 denotes a videotape in the form of magnetic tape cassette, and 7 denotes a servo circuit which controls the drum motor 3 and capstan motor 4. Reference numeral 8 denotes a recording signal processing circuit which converts the video signal into a recording signal, 9 denotes a selecting circuit, 10 denotes a storage circuit which stores an input video signal, 11 denotes a character generating circuit which generates characters, 12 denotes a superimposing circuit which superimposes characters on the video signal, and 13 denotes a control circuit which controls the servo circuit 7 and the recording signal processing circuit 8. Reference numeral 14 denotes an input terminal for receiving an input video signal which is supplied from a monitor camera, not shown, for example, and 15 denotes an end detector for detecting an end of the tape 6.

This video recording device is different from the conventional VTR in that a signal from the superimposing circuit 12 which is processed in the recording signal processing circuit 8 and is recorded on the videotape 6, is also stored in the storage circuit 10. The selecting circuit 9 comprises two video signal input terminals Ia and Ib and is connected to the control circuit 13. When the input terminal Ia is selected by the selecting circuit 9, the video signal stored in the storage circuit 10 is output, and when the input terminal Ib is selected, the input video signal Vin input directly from the superimposing circuit 12, - i i.e., bypassing the storage circuit 10, is output.

Fig. 2 is a block diagram showing an example of the construction of the storage circuit 10. In Fig. 2, reference numeral 101 denotes an A/D converter which converts an analog video signal into a digital video signal, 102 denotes a latch circuit, 103 denotes a memory circuit for storing the digital coded video signal, 104 denotes a latch circuit, 105 denotes a D/A converter for performing digital/analog conversion, and 106 denotes a memory controller for performing data write/read control.

Next, the operation of this video recording device will be described referring especially to the storage circuit 10 and selecting circuit 9.

When an input video signal Vin is supplied to the input terminal 14, it is simultaneously supplied via the superimposing circuit 12 to the storage circuit 10 and input terminal Ib of the selecting circuit 9. When the videotape 6 begins to run and record a video signal, the selecting terminal Ib of the selecting circuit 9 is selected, and the video signal output from the selecting circuit 9 to the recording signal processing circuit 8 is recorded on the videotape 6 by the video heads 2.

At the same time, in the storage circuit 10, the input video signal Vin is converted to a digital signal by the A/D converter 101, and is latched as a digital signal in field units by the latch circuit 102. The latched digital signal is written to a memory circuit 103 at locations of the addresses specified by the memory controller 106. When the input terminal Ia of the selecting circuit 9 is selected, reading of the video signal from the memory circuit 103 begins. During such operation, the memory controller 106 specifies the address, the read video signal is latched by the latch circuit 104, and the signal is converted by the D/A converter 100' into an analog read signal Vout. This

11 read signal Vout is input to the input terminal Ia of the selecting circuit 9, and sent to the video heads 2 via the recording signal processing circuit 8.

After the video signal from the storage circuit 10 is output by the selecting circuit 9 and recorded on the videotape 6, the input terminal Ib of the selecting circuit 9 is again selected so that the original video signal is supplied to the recording signal processing circuit 8, and recorded on the videotape 6.

Change-over to the input terminal Ib in the selecting circuit 9 may be performed at a point in time when writing catches up with reading in the storage circuit 10, i.e., when reading from the storage circuit 10 is no longer possible.

In the magnetic tape recording device of the embodiment under consideration, the video signal Vin is temporarily recorded by the memory circuit 103 of the storage circuit 10 at times when a video signal cannot be recorded on the videotape 6, such as when the tape is being re-wound or replaced, and subsequently, when the selecting circuit selects the input terminal Ia, this unrecorded part of the video signal is read from the memory circuit 103 and output to the recording signal processing circuit 8. Therefore, by temporarily storing in the memory circuit 103, a video signal which could not be recorded on the tape 6, automatic recording can be performed without any break in an image picked up by a monitor camera, for example.

It is noted that during the period when the video signal is transferred from the storage circuit 10 to the tape 6, the direct recording of the video signal, i.e., the recording of the video signal bypassing the storage circuit 10 on the tape is impossible. Accordingly, the image picked up during this period needs to be written in the storage circuit 10 first, and subsequently transferred to the tape 12 6.

Time or other information may be superimposed as a character signal on the video signal in the superimposing circuit 12. Therefore, the continuity of the video signal may easily be determined from the superimposed character signal.

The video signal which is supplied to the storage circuit 10 may be always written in the storage circuit 10. As an alternative, the control circuit 13 may cause the video signal to be written only for the periods when the direct recording of the video signal (recording of the video signal bypassing the storage circuit 10) on the video data, including the period when the video signal is transferred from the storage circuit 10 to the tape, as well as the period when the recording on the tape is impossible at all.

The period when the recording of the input video signal onto the tape directly is impossible at all may be the period when the tape is being rewound after the recording reaches to the end of the tape, or the period when the tape is replaced with a new one, or the external power supply is interrupted.

The recording on the tape may be made at the same rate as the input video signal, or intermittently, extracting one field in every predetermined number of fields of the input video signal, as in a time lapse VTR.

The intermittent recording is schematically illustrated in Fig. 3B, in contrast to an ordinary recording in Fig. 3A. In the ordinary recording, all the fields of the input video signal, supplied at a rate of 60 fields per second for example, are recorded. In other words, the video signal is recorded on the tape at the same rate (e.g., 60 fields per second) as the rate of the input video signal. In the intermittent recording, one field out of every predetermined number of fields, e.g., three fields, is extracted, and

13 recorded. If one field out of every three fields is extracted, the rate of recording is 20 fields per second. In Fig. 3B, the fields with hatching are those which are not recorded.

First, let us consider a situation where the video signal is recorded on the tape at the same rate (e.g., 60 fields per second) as the rate of the input video signal, and the same tape is repeatedly used by over-writing the old video signal.

Assume that r6cording begins from the beginning of the tape. When it is detected by the end detector 15 that no more recording area is available, a command is issued by the control circuit 13 to write the video signal to the storage circuit 10. Simultaneously, the control circuit 13 outputs a command to the servo circuit 7 to rewind the tape 6 back to the beginning, and magnetic recording is resumed from the beginning of the tape. The video signal read from the storage circuit 10 is first recorded, before direct recording of the input video signal begins. The aboveoutlined process will now be described in further detail.

When the input video signal is directly recorded on the tape, the tape is made to run at the speed for normal recording, and the input terminal Ib of the selecting circuit 9 is selected, so that the video signal is input to the recording signal processing circuit 8 directly from the superimposing circuit 12 to be recorded on the tape 6, and it is also supplied to the storage circuit 10.

When the end of the tape is detected by the end detector 15, the rewinding of the tape is started, and the control circuit 13 issues a"write command for the video signal to be stored by the storage circuit 10 during the rewinding.

Thus, during rewinding, the video signal is written in the storage circuit 10 at a lower rate (e.g., 20 fields).

14 e.g., extracting one field in every n fields (e.g., 3 fields) of the input video signal. By such decimation, the stored video signal has been effectively compressed to a data length of 1/n (e.g., 1/3) as compared to the input video signal, or an ordinary continuous recorded image.

When the videotape 6 has been rewound to the beginning and recording is resumed, the input terminal Ia is selected by the selecting circuit 9 due to a command from the control c1rcuit 13, and a command is also given by the control circuit 13 to read from the storage circuit 10. A video signal is therefore input to the recording signal processing circuit 8 from the storage circuit 10, and recorded on the tape 6. Thus, the video signal is transferred from the storage circuit 10 to the tape 6. The video signal is transferred at the rate of 60 fields per second (which is identical to the rate of the input video signal, or the rate at which the direct recording on the tape is effected). Since this video signal has been compressed to 1/n (e.g., 1/3) data length during write, it can be read at a rate n times (e.g., three times) the rate of the real-time. During this transfer, the tape is made to run at the speed for normal recording. For this purpose, a command is given to continuously read video signals stored in the storage circuit 10 in a time sequence.

In this way, a video signal stored while the tape was rewound is transferred to the tape.

If the time required to rewind the tape is represented by X (e.g., three minutes), the video signal stored in the storage circuit during this time has a data length which can be read in X/n (e.g., if X = 3 minutes and n = 3 as assumed above, X/n = 1 minute). To record data stored in the storage circuit 10 which can be read in X/n (e.g., one minute) on the tape 6, the same length of time, i.e., X/n (e.g., one minute) is required. During this interval, the image of the scene picked up by a monitor camera, for example, cannot be recorded directly on the tape, so it must first be stored in the storage circuit 10. Similarly, during the period X/n (e.g., one minute), required to transfer the data stored in the storage circuit 10, the image of the present scene cannot be directly recorded on the tape.

The total time which the transfer of the video signal from the storage circuit to the tape takes before the video signal acquired by the monitor camera, for example, can be directly recorded to the tape, i.e., the time from the beginning of the transfer begins and until the writing from the storage circuit catches up with the reading into the storage circuit, with the reading effected at a rate n times the rate of writing, is Y X/(n-1) When n 3, Y = 3, as in the example under consideration, Y = 1.5, i.e., one minute and thirty seconds. In other words, the the writing from the storage circuit 10 catches up with the reading, and at this point in time, the selecting circuit may be turned to select the terminal Ib.

After the transfer is thus completed, and the terminal Ib is selected, the recording of the input video signal directly (bypassing the storage circuit 10) onto the tape 6 is resumed.

It is therefore sufficient if the storage circuit 10 have a storage capacity for approximately X/(n-1) (one minute and thirty seconds) including the time required to transfer the video signal to the tape 6. However, if the memory areas from which video data has been read are used for writing new video signal, the storage capacity needed is for X/n, i.e. , for the video signal acquired by the monitor camera, for example, during the rewinding.

In this way, the video signal (acquired by a monitor 16 camera, for example) during rewinding can therefore also be recorded on the same tape 6 without any break.

A summary of the operation of the embodiment described above is given below.

In the normal state when the input video signal can be directly (bypassing the storage circuit) recorded, the control circuit 13 causes the tape torun at the speed for normal recording, while causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number (e.g., 60).

When the tape is recorded to the end and it is detected that no more recorded area is available, the tape is rewound, (so that the input video signal cannot be directly recorded,) the control means 13 causes one field in every n fields of the input video signal to be written in said storage circuit, with n being an integer (e.g., 3) greater than 1.

When the rewinding is completed, and recording on the tape becomes possible, the video signal is transferred from the storage circuit to the tape. For this purpose, the control circuit 13 causes the video signal to be transferred to and recorded on the tape at said first rate while causing the tape to run at the speed for normal recording.

After the transfer is completed, the recording of the input video signal directly (bypassing the storage circuit 10) onto the tape is resumed.

In this way, the video signal can automatically be repeatedly recorded, and there is no break in the video signal over a long time period.

Let us know consider a situation where repeated overrecording is performed using a time lapse VTR.

In a time lapse VTR, as already mentioned, the length of time for which the video signal can be recorded using the same tape can be extended. For instance, 17 in the case of a time lapse VTR which records one field in every m fields, the recording time can be extended to m times that of the normal recording time. As an example, m 3, so that 18 hours of extended recording can be achieved using a tape capable of recording 6 hours of a video signal in the normal continuous recording mode. The tape is made to run intermittently at an average speed which is 1/m (e.g., 1/3) of the speed for normal recording.

When the tape end is detected by the end detector 15 and no more recording area is found available, the tape begins rewinding, and one field in every m (e.g., three) fields of video signal is written to the storage circuit 10.

When the tape has been rewound to the beginning and the video signal starts to be recorded on the tape 6, the video signal is read continuously from the storage circuit 10. The tape is made to run at an average speed which is identical to the speed for normal recording, and the video signal from the storage circuit 10 is transferred and recorded at a rate identical to the rate for normal recording (i.e., 60 fields per second). Hence, as in the case of the embodiment described above, the video signal acquired by a monitor camera, for example, during rewinding can be recorded on the tape 6 in 1/m (e.g., 1/3) of the time it takes to rewind the tape. In other words, if the rewinding time is X minutes g., 3 minutes), the video signal recorded by the storage circuit 10 can be recorded on the tape 6 in X/m (one minute). Applying the same analysis as in the embodiment described above, it takes the length of time X/(m-1) for the writing of the storage circuit 10 catches up with the reading.

When the transfer is completed, the selecting circuit 9 may be switched to the terminal Ib, to begin the recording of the video signal bypassing the storage circuit 10 on the 18 tape.

The tape is now made to run intermittently, at an average speed which is 1/m the speed for normal recording, and the input video signal is recorded intermittently, extracting one field in every m fields (e.g., 3 fields).

In this way, the video signal acquired by a monitor camera, etc. during rewinding can be recorded on the same tape 6 from the beginning of the tape without any break in the video signal.

A summary of the operation of the time lapse VTR of the embodiment described above is given below.

In the normal state when the input video signal supplied at a first rate of p fields per second can be directly (bypassing the storage circuit) recorded, with p being a predetermined number (e.g., 60), the control circuit 13 causes the tape to run intermittently at an average speed which is 1/m of the speed for normal recording, with m (e.g., 3) being an integer greater than 1, while causing one field in every m fields of the input video signal to be recorded so that the video signal is recorded at at a second rate of q fields per second, with q (e.g., 20) being equal to P/M.

When the tape is recorded to the end and it is detected that no more recorded area is available, the tape is rewound, (so that the input video signal cannot be directly recorded,) the control means 13 causes one field in every m fields of the input video signal to be written in said storage means.

When the rewinding is completed, and recording on the tape becomes possible, the video signal is transferred from the storage circuit to the tape. For this purpose, the control means 13 causes the video signal to be transferred to and recorded on the tape at the first rate of p fields (e.g., 60 fields) per second, while causing the tape to run

19 at the speed for normal recording.

After the transfer is completed, the recording of the input video signal directly (bypassing the storage circuit 10) onto the tape is resumed, while the tape is made to run intermittently at an average speed which is 1/m (e.g., 1/3) of the speed for normal recording.

In this way, the video signal can automatically be repeatedly recorded, and there is no break in the recorded image over a long period of time.

In the embodiments described above, the same tape is repeatedly used for recording. As an alternative, plural video tape cassettes may be provided and, when recording has been completed up to the end of one tape 6, this is detected by the end detector 15, and the tape 6 is replaced by a new tape 6 instead of repeatedly over-recording as in the previously described embodiments.

Specifically, in the magnetic tape recording device comprising the storage circuit 10 for recording the input video signal and the selecting circuit 9 which selects and outputs either the video signal stored in this storage circuit 10 or the input video signal Vin, the input video signal Vin supplied while the tape is being replaced, is stored in the storage circuit 10, and, immediately after replacement, the video signal is read from the storage circuit 10 and recorded on the new tape. Therefore, the video signal can be recorded on new tapes one after another without any break in the recorded signal.

As shown in Fig. 4, a back-up power supply 16 may be provided to back up the storage operation by the storage circuit 10. Consequently, even if external power supply to the magnetic tape recording device is interrupted, the input video signal Vin can be stored by the storage circuit 10. In the example shown in Fig. 4, the backup power supply is connected to the storage circuit 10, character generating circuit 11, superimposing circuit 12 and control circuit 13. Therefore, by storing the video signal supplied by a monitor camera without fail even in the event of a power failure, the video signal can be recorded on the tape 6 without a break.

The memory 103 of the storage circuit 10 may comprise a replaceable semiconductor memory, in the form of a memory card. The video signal is recorded in this semiconductor memory and when this memory is full, the memory is replaced by a new memory. Consequently, video signals stored in the storage circuit 10 need not be transferred to the tape 6.

In this case the selecting circuit 9 need not be provided, and the output of the superimposing circuit 12 may be connected directly to the recording signal processing circuit 8, and the video signal stored in the storage circuit 10 may be output via an output terminal 17, as shown in Fig. 5.

In this way, if the storage circuit 10 is a replaceable memory, and the memory and tape are used alternately, there is no need to transfer the video signal from the storage circuit 10 to the tape 6 when the tape is replaced by a new tape in the image recording device, and there is also no need to record this part of the video signal intermittently (even in a situation where the direct recording on the tape is made at a rate identical to the rate for normal recording). However, to make full use of the relatively limited storage capacity of the storage circuit, the writing In the storage circuit may be made intermittently, extracting one field in every plural fields.

Various modifications are possible without departing from the scope of the invention.

For example, the selecting circuit 9 used in the embodiments of Fig. 1 and Fig. 4 may be eliminated, if the storage circuit 10 is used as a buffer when the input video 21 signal is recorded on a real-time basis, i.e., in time with (and with a minimum delay with respect to) the input of the video signal to the input terminal 14. In such a case, a certain fixed area of the storage circuit 10 may be used for temporarily storing the video signal, before the video signal is read and transferred to the tape.

The video signal supplied to the input terminal 14 is not limited to one supplied from a monitor camera, but may be a signal obtained by receiving a broadcast signal.

22

Claims

CLAIMS:

1. A magnetic tape recording device for recording an input video signal on magnetic tape, comprising: recording means for recording the input video signal on said magnetic tape; storage means for storing said input video signal; and control means for causing said input video signal to be stored at least in a period when recording said input video signal on said magnetic tape is impossible.

2. The magnetic tape recording device as defined in Claim 1, wherein said control means causes the video signal to be transferred from the storage means to said magnetic tape after said period when the recording on said magnetic tape is impossible ends.

3. The magnetic tape recording device as defined in Claim 2, further comprising selecting means; wherein said control means causes the video signal to be read from the storage means after after said period when the recording on said magnetic tape is impossible ends; said selecting means selects and outputs either the video signal read from said storage means or said input video signal bypassing the storage means; said recording means records the video signal output by said selecting means; and said control means causes said selecting means to select the video signal stored in said storage means after said period when the recording on said magnetic tape is impossible ends so that the video signal read from said storage means is transferred to said magnetic tape.

23 4. The magnetic tape recording device as defined in Claim 3, wherein said control means causes said selecting means to select the input video signal bypassing the storage means after the transfer of the video signal from the storage means to the magnetic tape is completed.

5. The magnetic tape recording device as defined in Claim 3, wherein said selecting means outputs said video signal read from said storage means when recording on said magnetic tape resumes after said magnetic tape has run to the end.

6. The magnetic tape recording device as defined in Claim 5, wherein said control means causes said storage means to intermittently store said video signal.

7. The magnetic tape recording device as defined in Claim 5, wherein said control means causes the magnetic tape to run at the speed for normal recording, while causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number; causes one field in every n fields of the input video signal to be written in said storage means, with n being an integer greater than 1; and causes the video signal to be transferred to and recorded on said magnetic tape at said first rate while causing the magnetic tape to run at the speed for normal recording.

8. The magnetic tape recording device as defined in Claim 5, wherein said control means causes the magnetic tape to run intermittently at an average speed which is 1/m of the speed for normal 24 recording, with m being an integer greater than 1, while causing one field in every m fields of the input video signal to be recorded, said input video signal being supplied at a first rate of p fields per second, with p being a predetermined number; causes one field in every m fields of the input video signal to be written in said storage means, and causes the video signal to be transferred to and recorded on said magnetic tape at the first rate of p fields per second, while causing the magnetic tape to run at the speed for normal recording.

9. The magnetic tape recording device as defined in any of Claims 1 to 8, further comprising detecting means for detecting that no more recording area is available on said magnetic tape and generating a detection signal upon such detection, wherein said control means causes said input video signal to be written in said storage means when said the detection signal is generated.

10. The magnetic tape recording device as defined in Claim 1, further comprising a backup power supply to supply at least to said storage means to enable said input video signal to be written in said video signal when an external power supply to the recording device is interrupted.

11. The magnetic tape recording device as defined in Claim 1, wherein said storage means comprises a replaceable storage medium.

12. A method for recording a video signal on magnetic tape using a magnetic tape recording device, comprising the steps of:

(a) recording the input video signal on said magnetic tape; and (b) storing said input video signal in a storage means at least in a period when recording said input video signal on said magnetic tape is impossible.

13. The method as defined in Claim 12, further comprising the step of: (c) transferring the video signal from the storage means to the magnetic tape after said period when recording said input video signal on said magnetic tape is impossible ends.

14. The method as defined in Claim 12, further comprising the steps of: (d) superimposing a character signal on said video signal; and (e) supplying said video signal on which said character signal is superimposed to said magnetic tape and storage means.

15. The method as defined in Claim 12, further comprising the steps of (f) rewinding said magnetic tape when no more recording area is available on said magnetic tape; (g) storing said input video signal in said storage means; and (h) transferring said video signal from said storage means to said magnetic tape when recording by said magnetic tape is resumed after rewinding.

16. The method as defined in Claim 12, further comprising the steps of: (i) storing said input video signal in said storage means after no more recording area is available on said magnetic 26 tape and at least until a new magnetic tape is inserted, and (j) transferring the video signal from said storage means to said new magnetic tape when recording is started on said new magnetic tape.

17. The method as defined in any of Claims 12 to 16, wherein said step (b) of storing the video signal in said storage means comprises storing intermittent video signal; and said step (a) of recording the video signal on the magnetic tape comprises recording intermittent video signal.

18. The method as defined in Claim 12, wherein said step (a) of recording comprises causing the magnetic tape to run at the speed for normal recording, and causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number; said step (b) of storing comprises causing one field in every n fields of the input video signal to be written in said storage means, with n being an integer greater than 1; and said step (c) of transferring comprises causing the video signal to be transferred to and recorded on said magnetic tape at said first rate while causing the magnetic tape to run at the speed for normal recording.

19. The method as defined in Claim 12, wherein said step (a) of recording comprises causing the magnetic tape to run intermittently at an average speed which is 1/m of the speed for normal recording, with m being an integer greater than 1, and causing one field in every m fields of the input video signal to be recorded, said input video signal being supplied at a first rate of p fields per second, with p being a predetermined number; said step (b) of storing comprises causing one field in 27 every m fields of the input video signal to be written in said storage means; and said step (c) of transferring comprises causing the video signal to be transferred to and recorded on said magnetic tape at the first rate of p fields per second, and causing the magnetic tape to run at the speed for normal recording.

20. A tape recording device comprising: recording means for recording an input signal on a tape and storage means for storing an input signal at least when recording of the input signal on the tape is suspended.

21. A magnetic tape recording device substantially as hereinbefore described and as shown in Fig. I and Fig. 2, or Fig. 4, or Fig. 5.

22. A method of recording a video signal on a magnetic tape substantially as hereinbefore described with reference to Figs. 1, 2, 3A and 3B, or Fig. 4 or Fig. 5.

28 Amendments to the claims have been filed as follows CLAIMS:

1. A magnetic tape recording device for recording an input video signal on magnetic tape, comprising: recording means for recording the input video signal on said magnetic tape; storage means for storing said input video signal; and control means for causing said input video signal to be stored when recording said input video signal on said magnetic tape is impossible; and selecting means; wherein said control means causes the video signal to be read from the storage means after said period when the recording on said magnetic tape is impossible ends; said selecting means selects and outputs either the video signal read from said storage means or said input video signal bypassing the storage means; said recording means records the video signal output by said selecting means; and said control means causes said selecting means to select the video signal stored in said storage means after said period when the recording on said magnetic tape is impossible ends so that the video signal read from said storage means is transferred to said magnetic tape and causes said input video signal to be written in said storage means while the stored video signal is transferred from said stortge means to said magnetic tape.

OL 2. The magnetic tape recording device as defined in Claim 1, wherein said control means causes said selecting means to select the input video signal bypassing the storage means after the transfer of the video signal from the storage means to the magnetic tape is completed.

3. The magnetic tape recording device as defined in Claim 1, wherein said selecting means outputs said video signal read from said storage means when recording on said magnetic tape resumes after said magnetic tape has run to the end and been rewound.

4. The magnetic tape recording device as defined in Claim 3, wherein said control means causes said storage means to intermittently store said video signal.

5.

I I -4

5. The magnetic tape recording device as defined in Claim 3, wherein said control means causes the magnetic tape to run at the speed for normal recording, while causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number; causes one field in every n fields of the input video signal to be written in said storage means, with n being an integer greater than 1; and causes the video signal to be transferred to and recorded on said magnetic tape at said first rate while causing the magnetic tape to run at the speed for normal recording.

The magnetic tape recording device as defined in Claim 3, wherein said control means causes ithe magnetic tape to run intermittently at an average speed which is 1/m. of the speed for normal recording, with m being an integer greater than 1, while causing one field in every m fields of the input video signal to be recorded, said input video signal being supplied at a first rate of p fields per second, with p being a predetermined number; causes one field in every m fields of the input video signal to be written in said storage means, and causes the video signal to be transferred to and recorded on said magnetic tape at the first rate of p fields per second, while causing the magnetic tape to run at the speed for normal recording.

7. The magnetic tape recording device as defined in any of Claims 1 to 6, further comprising detecting means for detecting that no more recording area is available on said magnetic tape and generating a detection signal upon such detection, wherein said control means causes said input video signal to be written in said storage means when said the detection signal is generated.

8. The magnetic tape recording device as defined in Claim 1, further comprising a backup power supply to supply at least to said storage means to enable said input video signal to be written in said video signal when an external power supply to the recording device is interrupted.

9. The magnetic tape recording device as defined in Claim 1, wherein said storage means comprises a replaceable storage medium.

10. A method for recording a video signal on magnetic tape using a magAetic tape recording device, comprising the steps of:

(a) recording the input video signal on said magnetic tape; (b) storing said input video signal in a storage means when recording said input video signal on said magnetic tape is impossible; and (c) transferring the video signal from the storage means to the magnetic tape after said period when recording said input video signal on said magnetic tape is impossible ends, storing said input video signal in said storage means also when said stored video signal is transferred from said storage means to said magnetic tape.

11. The method as defined in Claim 10, further comprising the steps of(d) superimposing a character signal on said video signal; and (e) supplying said video signal on which said character signal is superimposed to said magnetic tape and storage means.

12. The method as defined in Claim 10, further comprising the steps of (f) rewinding said magnetic tape when no more recording area is available on said magnetic tape; (g) storing said input video signal in said storage means; and (h) transferring said video signal frorn' said storage means to said magnetic tape when recording by said magnetic tape is resumed after rewinding.

13. The method as defined in Claim 10, further comprising the steps of.

(i) storing said input video signal in said storage means after no more recording area is available on said magnetic tape and at least until a new magnetic tape is inserted, and 0) transferring the video signal from said storage means to said new magnetic tape when recording is started on said new magnetic tape.

14. The method as defined in any of Claims 10 to 13, wherein said step (b) of storing the video signal in said storage means comprises storing a video signal intermittently; and said step (a) of recording the video signal on the magnetic tape comprises recording a video signal intermittently.

15. The method as defined in Claim 10, wherein said step (a) of recording comprises causing the magnetic tape to run at the speed for normal recording, and causing the video signal to be recorded at a first rate of p fields per second, with p being a predetermined number; said step (b) of storing comprises causing one field in every n fields of the input video signal to be written in said storage means, with n being an integer greater than 1; and said step (c) of transferring comprises causing the video signal to be transferred to and recorded on said magnetic tape at said first rate while causing the magnetic tape to run at the speed for normal recording.

33 16. The method as defined in Claim 10, wherein said step (a) of recording comprises causing the magnetic tape to run intermittently at an average speed which is I /m of the speed for normal recording, with in being an integer greater than 1, and causing one field in every in fields of the input video signal to be recorded, said input video signal being supplied at a first rate of p fields per second, with p being a predetermined number; said step (b) of storing comprises causing one field in every m fields of the input video signal to be written in said storage means; and said step (c) of transferring comprises causing the video signal to be transferred to and recorded on said magnetic tape at the first rate of p fields per second, and causing the magnetic tape to run at the speed for normal recording.

17. A magnetic tape recording device substantially as hereinbefore described and as shown in Fig. I and Fig. 2, or Fig. 4, or Fig. 5.

18. A method of recording a video signal on a magnetic tape substantially as hereinbefore described with reference to Figs. 1, 2, 3A and 3B, or Fig. 4 or Fig.