JPH11213312A - Magnetic recording and reproducing device and intermittent magnetic recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make continue to surely record a video signal regardless of the occurrence of a clogging during intermittent recording. SOLUTION: In a magnetic recording and reproducing device 1, video heads 16a and 16b are switched to reproducing operation during a pause of intermittent recording, and whether a clogging occurs or not is detected by a clogging detection circuit 6. When an intermittent driving command signal (a) is outputted from an intermittent driving command circuit 23, video heads 16a and 16b are switched to recording operation to execute intermittent recording. Hereafter, intermittent recording and clogging detection are successively repeated in the same cycle. If a clogging signal (h) is inputted from the clogging detection circuit 6 to a head selection circuit 7, video heads 16a and 16b whose clogging was detected are switched to other unused video heads 16c and 16d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for detecting clogging of a video head in intermittent magnetic recording and a change in an input recording video signal, and an intermittent magnetic recording method.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus (VTR), clogging of a video head not only makes recording on a magnetic tape incomplete or impossible, but also makes such recording incomplete. Is used, even when the data is reproduced on a normal VTR or the like having a video head without clogging, a large amount of noise may be generated in the reproduced video, or the video may not be displayed at all.

Contrary to the above, even when a normally recorded magnetic tape is reproduced by a clogged video head, a large amount of noise may be generated or no image may be reproduced at all, as described above.

[0004] The clogging phenomenon can be easily detected through the monitor screen during reproduction, but when clogging during recording is to be detected, for example, the recording is temporarily stopped during the recording. Need to switch to playback.

[0005] For example, a conventional video head clogging detection device disclosed in Japanese Patent Application Laid-Open No. 2-103710 is used for an intermittent magnetic recording device for security monitoring, and intermittently outputs a video signal to a magnetic tape. The clogging of the video head is automatically detected during the pause period during the intermittent recording for recording, so that the detection can be performed without any hindrance to the recording operation.

In a conventional magnetic recording / reproducing apparatus equipped with a video head clogging detecting device, after detecting the clogging, a cleaning roller or the like is applied to the video head to wipe off the magnetic powder of the magnetic tape attached to the video head. Was like that.

[0007]

As described above, in the conventional intermittent magnetic recording apparatus, the clogging is detected and the video head is cleaned by utilizing the idle period during the intermittent recording. In some cases, it cannot be restored to a normal video head. For example, problems such as when the magnetic powder adhered to the video head cannot be sufficiently removed even if the cleaning roller is applied to the video head, or when a normal recording cannot be performed due to abrasion or breakage of the video head and a sufficient reproduction envelope cannot be output. Had occurred. In the case of an intermittent magnetic recording device used for security monitoring, it is fatal that no data is recorded. In addition, since the pause period of intermittent recording is used for cleaning the video head, if the pause period of intermittent recording is short, sufficient cleaning time cannot be obtained. Furthermore, since no video is recorded during cleaning, the two functions of clogging detection and cleaning of the video head cannot be simultaneously realized depending on the intermittent recording mode set in the VTR. There is no time to clean the head, and both clogging detection and cleaning of the video head cannot be performed.)

Further, the conventional magnetic recording / reproducing apparatus employs T-1
In the case of intermittent recording on a 20-hour tape, recording can be performed for as long as 960 hours. In such a long-term monitoring mode, 2/960 = 1/480, thus one field every 480 fields, ie 60 per second.
The field recording apparatus records an image at 480/60 = 8 seconds, and thus at a rate of one field every 8 seconds. However, the interval between droppings is long, and 7+ (59/60) is not recorded.
The state is not monitored at all for seconds. Therefore,
Even a magnetic recording / reproducing device that can be monitored for a long time,
Actually, there has been a problem that the monitoring time density is reduced to be unsuitable for practical use, or is unsuitable for monitoring a state that changes in a short time.

Further, in the conventional magnetic recording / reproducing apparatus, when performing intermittent recording, a mechanical switch is provided at a monitoring place, light and sound are provided so that the recording operation is not continued unnecessarily in a state where the image is not changed. When a detection signal (hereinafter referred to as an alarm signal) is input by installing a sensor that detects temperature, temperature change, infrared rays, etc., the mode is switched from long-term intermittent recording mode to recording mode with short time intervals. I was By receiving the alarm signal, it is possible to reliably record the video at the required moment. Recently, there is a case where a device called a motion detector that directly detects a change in a video signal is used without using a mechanical switch or a sensor. Therefore, expensive field memories, AD and DA conversion circuits, and the like were required because of the necessity of holding the video signal.

As described above, the conventional magnetic recording / reproducing apparatus has a problem that the cost of the entire apparatus is increased because the number of electric circuit components for holding a temporally past video signal is increased. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a magnetic recording and reproducing apparatus and a magnetic recording / reproducing apparatus capable of reliably recording a video signal even when clogging occurs during intermittent recording. It is intended to provide an intermittent magnetic recording method.

It is another object of the present invention to monitor a short-term change of a video signal even in a long-time monitoring mode and record a necessary video signal without leaking.

[0013]

According to the present invention, there is provided a magnetic recording / reproducing apparatus comprising: a multi-channel video head for recording / reproducing on / from a magnetic tape; a recording head amplifier for supplying a recording signal to these video heads; In a magnetic recording / reproducing apparatus for performing intermittent recording on a magnetic tape, the apparatus includes a reproducing head amplifier for amplifying a video signal reproduced by a video head and a head changeover switch for switching the video head between a recording operation and a reproducing operation. A recording / reproduction command means for generating a recording command signal for operating the recording head amplifier during a recording period and generating a reproduction command signal for operating the reproduction head amplifier and a head switching command signal for switching a head switch in other periods. Detects the clogging of the video head and issues a clogging signal. A clogging detecting means for, in which a head selection means for selecting the video head has not been determined that the blockage among th the video head detects the occurrence of the clogging signal.

In the magnetic recording / reproducing apparatus according to the present invention, the clogging detecting means compares the envelope of the video signal reproduced by the reproducing head amplifier with a predetermined envelope value indicating that the video head is clogged. A reproduction envelope comparison circuit; and a clogging output circuit for detecting clogging of the video head and generating a clogging signal in accordance with the comparison signal of the reproduction envelope comparison circuit.

Further, in the magnetic recording / reproducing apparatus according to the present invention, the clogging detecting means includes a demodulating circuit for demodulating a reproduced video signal by the reproducing head amplifier, and a synchronizing signal for separating a synchronous signal from the demodulated reproduced video signal. A separation circuit; and a clogging output circuit that detects clogging of the video head and generates a clogging signal in accordance with the presence or absence of the synchronization signal.

In the magnetic recording / reproducing apparatus according to the present invention, the clogging detecting means compares the envelope of the video signal reproduced by the reproducing head amplifier with a predetermined envelope value indicating that the video head is clogged. A reproduction envelope comparison circuit, a clogging output circuit for detecting clogging of the video head and generating a clogging signal in accordance with a comparison signal of the reproduction envelope comparison circuit, and demodulating a reproduction video signal by the reproduction head amplifier A demodulation circuit;
A video signal comparing circuit for comparing the demodulated reproduced video signal with the input video signal, and a predetermined magnitude change between the past reproduced video and the current input video based on the comparison signal of the video signal comparing circuit. And an alarm output circuit for generating an alarm signal if there is, and a motion video detection circuit for outputting a motion video detection signal only when the alarm signal is generated without generating the clogging signal.

Further, in the magnetic recording / reproducing apparatus according to the present invention, a multi-channel video head for recording / reproducing on / from a magnetic tape, a recording head amplifier for supplying a recording signal to these video heads, and reproduction by the video head In a magnetic recording / reproducing apparatus that includes a reproducing head amplifier that amplifies a video signal and a head changeover switch that switches the video head between a recording operation and a reproducing operation and performs intermittent recording on the magnetic tape, A recording / reproducing command means for generating a recording command signal for operating the recording head amplifier and for generating a reproducing command signal for operating the reproducing head amplifier and a head switching command signal for switching a head switch during other periods; Demodulation circuit that demodulates the video signal reproduced by the head amplifier A video signal comparing circuit for comparing the demodulated reproduced video signal with the input video signal; and an alarm signal if there is a change between the past reproduced video and the current input video based on the comparison signal of the video signal comparing circuit. And an alarm output circuit for generating an alarm.

Further, the magnetic recording / reproducing apparatus according to the present invention further comprises a recording mode switching circuit for switching to a recording mode having a higher intermittent recording time density in response to the alarm signal.

An intermittent magnetic recording method according to the present invention comprises a video head of a plurality of channels and performs an intermittent recording on a magnetic tape. The intermittent magnetic recording method generates a recording command signal during a predetermined intermittent recording period. During the other period, a reproduction command signal is generated, and the clogging of the video head used for intermittent recording is detected based on the video signal reproduced by the reproduction command signal, and when the clogging is detected, The intermittent recording is performed by switching to a video head of a channel which is not determined to be clogged among the video heads.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes an intermittent magnetic recording / reproducing device, and 2 denotes a recording / reproducing command circuit. Reference numeral 3 denotes a reproduction envelope comparison circuit, 4 denotes a clogging output circuit, and 5 denotes a clogging signal output terminal, and these constitute a clogging detection circuit 6. Further, 7 is a head selection circuit, and 8 and 9 are head selection switches.

The intermittent magnetic recording / reproducing apparatus 1 is configured as follows.

That is, in FIG. 1, reference numeral 11 denotes a video signal input terminal, 12 denotes a recording signal processing circuit, and 13ab and 13c.
d is a recording head amplifier (HA), 17a, 17b, 17
c and 17d are reproducing head amplifiers (HA), 14a and 14
Reference numerals b, 14c, and 14d denote head selector switches for a recording (hereinafter, referred to as REC) side and a reproducing (hereinafter, referred to as PB) side. Reference numeral 15 denotes a rotating drum on which video heads 16a, 16b, 16c, and 16d are mounted. The pair of video heads 16a and 16b
5 are provided at opposing positions and have different azimuth angles from each other.
Also, c and 16d are provided at opposing positions on the rotating drum 15, and have different azimuth angles. Furthermore, video heads 16a and 16c have different azimuth angles, and video heads 16b and 16d have different azimuth angles. The video signal input from the input terminal 11 is converted into an FM signal for magnetic recording by the recording signal processing circuit 12, and then sent from the head selection switch 8 to the recording head amplifier 13ab or the recording head amplifier 13cd, where the recording signal c Is output as This recording signal c is supplied to the head changeover switches 14a and 14b or the head changeover switches 14c and 14c.
Via 14d, it is supplied to either video head 16a, 16b or video head 16c, 16d.
The recording command signal d is supplied to the recording head amplifiers 13ab and 13cd and the head changeover switches 14a, 14b, 14c and 14d, and the reproduction head amplifiers 17a, 17b,
A reproduction command signal e is supplied from the recording / reproduction command circuit 2 to 17c and 17d.

Reference numerals 18ab and 18cd denote reproduction changeover switches. These reproduction changeover switches 18ab and 18c
Command signals from the drum controller 25 are supplied to the video heads 16a, 16b, 16c, 16c.
d is switched in synchronization with the timing of tracing the magnetic tape 19. The head selection circuit 7 has two pairs of video heads 16a and 16b and 16c and 16d.
The head selection switch 8 selects either the recording head amplifier 13ab or the recording head amplifier 13cd during recording, and the head selection switch 9 selects the reproduction changeover switches 18ab and 18c during reproduction.
Control is performed so as to select any one of d. Normally, the video heads 16a and 16b have a head width of 58 μm and are used for the SP mode (2 hour mode), and the video heads 16c and 16d have a head width of 26 μm and the EP mode (6 hours). Mode).

A capstan shaft 20 is driven by a capstan motor 21 to run the magnetic tape 19. Reference numeral 22 denotes a capstan controller that outputs a speed command b to the capstan motor 21, 23 denotes an intermittent drive command circuit, and 24 denotes a drum motor. This drum motor 2
4 is controlled by the drum controller 25 so that the rotation speed and the phase are synchronized with the vertical synchronization signal separated from the video signal. Further, the capstan motor 21 is controlled by the intermittent drive command signal a output from the intermittent drive command circuit 23.
Is controlled so that the magnetic tape 19 runs at a predetermined running pitch.

Next, the intermittent recording operation in the above apparatus will be described.

FIG. 2A shows an intermittent drive command signal output from the intermittent drive command circuit 23, and FIG. 2B shows the motor speed of the capstan motor 21. Here, the capstan motor 21 is intermittently driven in synchronization with the intermittent drive command signal a in accordance with a series of speed commands b forming a trapezoidal pattern of acceleration, constant speed, deceleration, and stop output from the capstan controller 22. You. The trapezoidal pattern varies depending on the intermittent drive control type. In the following, a case where intermittent recording is performed using the video heads 16a and 16b of the four channels will be described, but the same applies to intermittent recording using the remaining pair of video heads 16c and 16d.

FIG. 2C shows the video heads 16a and 16a.
b shows the timing of supplying the signal current for the recording signal. As shown here, the supply of the signal current starts before and after the rotation speed of the capstan motor 21 reaches the maximum. In such a running record, the video heads 16a, 1
Since it is not necessary to make a head step of 6b much, two-hour mode recording, which is normal continuous recording, can also be performed by the video heads 16a and 16b. However,
In this case, it is necessary to keep the speed of the capstan motor 21 constant. Here, one field of the video signal,
That is, a field recording method in which the intermittent recording current is supplied to the video heads 16a and 16b only for a period corresponding to a half rotation of the rotating drum 15 is adopted.

The operation described above is the same in the conventional intermittent magnetic recording / reproducing apparatus 1. Here, during intermittent recording, the head changeover switches 14a and 14b are
Switching is performed between the B-side as described below.

That is, during intermittent recording, the intermittent drive command circuit 23 applies an intermittent drive command signal a as shown in FIG. The time interval Tμsec differs depending on the recording mode of the intermittent recording, and is set longer in the long time mode in which the number of video signal field drops is large.

FIG. 2D shows a recording command signal d. When the intermittent command signal a is applied to the recording / reproducing command circuit 2, the recording command signal d is applied to the recording head amplifier 13ab, and the video heads 16a, 16b Starts the recording operation. The recording command signal d is applied to the recording head amplifier 13ab earlier in time by Tl than the recording signal c, so that recording is not performed in a transient state when the recording head amplifier 13ab rises. At the same time, the recording command signal d from the recording / reproducing command circuit 2 is
a, 14b, and is switched to the REC side.

Here, since the intermittent magnetic recording / reproducing apparatus 1 uses the field recording method, the video heads 16a and 16b
, A video signal for one field is supplied at the same time, and the video heads 16a and 16b on the designated side trace the magnetic tape 19, and a recording signal is recorded on the magnetic tape 19 over a period of one field.

FIG. 2E shows a reproduction command signal e output from the recording / reproduction command circuit 2. This reproduction command signal e
Is applied to the reproducing head amplifiers 17a and 17b from the recording / reproducing command circuit 2 immediately after the intermittent recording is completed, and the reproducing operation is started. At the same time, the head changeover switch 14
a and 14b are switched to the PB side, the recording head amplifier 13ab is cut off from the video heads 16a and 16b, and the reproducing head amplifiers 17a and 17b are connected to the video heads 16a and 16b. That is, when the intermittent recording is completed, the magnetic tape 19 is kept stopped,
When performing the next intermittent recording, the magnetic tape 19 is driven again. Therefore, if the magnetic head 19 is switched to the reproduction side after the end of the intermittent recording, the reproduction level of the recorded video signal can be detected.

FIG. 2F shows the reproducing head amplifiers 17a and 17a.
7b shows a reproduced video signal reproduced. The reproduced video signal f is obtained by amplifying the video signals from the video heads 16a and 16b by the reproduction head amplifiers 17a and 17b, and is switched by the reproduction changeover switch 18ab and the head selection switch 9 to generate the clogging detection circuit. 6 is sent to the reproduction envelope comparison circuit 3. The switching timing of the playback changeover switch 18ab is instructed by the drum controller 25, and the video head 16
a and 16b are synchronized with the timing of tracing the magnetic tape 19.

In the case of running recording, since the reproduction track angle is smaller than the recording track angle, the envelope of the reproduced video signal has a triangular waveform rising upward as shown in FIG. 2 (f). In FIG. 2F, m is a predetermined envelope value set in the reproduction envelope comparison circuit 3 in advance. In the field recording method, tracing is performed during reproduction by the video head used for recording. Therefore, the reproduction envelope comparison circuit 3 compares the trace with a predetermined envelope value m, and a comparison signal g indicating the result of the magnitude comparison. Can be obtained.

Here, a case where the video heads 16a and 16b are clogged will be described.

FIG. 2G shows the comparison signal g, and FIG. 2H shows the clogging signal h. The clogging signal h is output from the clogging output circuit 4 to the clogging signal output terminal 5. Since the reproducing head amplifiers 17a and 17b are generally designed to have an amplifier gain of about 60 dB, the video heads 16a and 16b
Assuming that the reproduced video signal detected at b is 200 μV, the amplifier output is about 200 mV. Video head 16a,
If 16b is in a good condition without clogging, the outputs of the reproducing head amplifiers 17a and 17b are maintained at 200 mVpp or more. Even if clogging occurs and the envelope output value of the reproduced video signal decreases, 100 mVpp
At present, a relatively good image quality can be maintained, but when the value is less than this, the image quality is rapidly deteriorated, and the reproduced image shows a head clogging phenomenon. Therefore, if the envelope value m is set to about half the reproduction envelope voltage value of a good video head, the video head 16 used for recording can be used.
The head clogging can be sufficiently detected simply by switching a and 16b to the reproducing side.

As one example of the circuit configuration of the reproduction envelope comparison circuit 3, since the reproduction video signal is an FM signal of 3 to 5 MHz, the amplitude of the reproduction envelope is amplified by a band amplifier which amplifies this band to 20 dB or more. For example, a configuration is possible in which an envelope is detected using an AM detector using a diode, and a comparator that uses the envelope value m as a comparison reference level is used.

The comparison signal g obtained by the reproduction envelope comparison circuit 3 in this manner is output to the clogging output circuit 4 of the next stage.
Is applied to The role of the clogging output circuit 4 is as follows. That is, since the reproduced envelope is a triangular waveform or a flat waveform slightly flattened at a flat portion, if a constant comparison signal g is obtained over the entire one-field period as shown in FIG. Not necessarily. Here, if the comparison signal g is obtained even once in this field at the end of one field period (t ₀ ), it is determined that the field is not clogged, and the comparison signal g is obtained even once in one field period. If not, this field is determined to be clogged. However, in the field recording method, a video signal several fields before is reproduced due to a problem such as a step in which the head is attached to the rotary drum 15, but even if it is not the immediately preceding video signal, several fields (two to three fields) are reproduced.
The clogging can be detected by the previous signal reproduction, and the damage that a video signal cannot be recorded due to the clogging can be minimized. Further, when clogging is continuously detected over several fields to be reproduced, a circuit for determining that clogging is present is added, so that clogging can be more reliably caught.

As described above, the magnetic recording / reproducing apparatus according to the first embodiment switches the video heads 16a and 16b to the reproducing operation while the intermittent recording is stopped, as shown in FIGS. 2 (a) to 2 (h). When the clogging is detected and the intermittent drive command signal a for the next cycle is applied, the video heads 16a and 16b are switched to the recording operation again to execute the intermittent recording. , The intermittent recording and the clogging detection are repeated. And the clogging signal h
Is input to the head selection circuit 7, head switching is performed from the video heads 16a and 16b, for which clogging has been detected, to the other, unused video heads 16c, 16d. In the intermittent recording after the head is switched, the clogging is similarly detected.

In this way, the video head in which clogging is detected is automatically switched to the other video head in which clogging is not detected, and intermittent recording is continued. Although switching from the video heads 16a and 16b to 16c and 16d has been described, the same applies to switching from 16c and 16d to 16a and 16b.

Further, even when clogging is detected by both the video head 16a and the video head 16d, field recording can be continuously performed using the remaining video heads 16b and 16c, and vice versa. is there. However, in such a case, the single azimuth recording is performed in the conventional intermittent magnetic recording.

Embodiment 2 FIG. 3 is a block diagram showing a configuration of a clogging detection circuit used in the magnetic recording / reproducing apparatus according to the second embodiment. The clogging detection circuit 60 according to the second embodiment employs a reproduction signal demodulation circuit 26 and a vertical synchronization separation circuit 28 instead of the reproduction envelope comparison circuit 3 in the clogging detection circuit 6 according to the first embodiment.
Here, the reproduced video signal f is input to the reproduced signal demodulation circuit 26, and the demodulated video signal is further inputted to the vertical synchronization separation circuit 2.
8 to separate the vertical synchronizing signal and output it to the clogging output circuit 4. When the vertical synchronizing signal is not output during reproduction, it is possible to determine that the video signal has not been recorded correctly and the video head is clogged. h is output. Other circuit configurations are the same as those of the first embodiment.

In the second embodiment, the presence / absence of a reproduced video signal, that is, clogging of the head is detected based on the presence / absence of a vertical synchronization signal. However, clogging can be detected by detecting the presence / absence of a horizontal synchronization signal. .

Embodiment 3 FIG. 4 is a block diagram showing a configuration of the magnetic recording and reproducing apparatus according to the third embodiment. This magnetic recording / reproducing apparatus has a motion detecting circuit 61 instead of the clogging detecting circuit 6 of FIG. Motion detection circuit 61
Is composed of a reproduction signal demodulation circuit 26 and a video signal comparison circuit 29, and outputs the motion comparison signal i to the intermittent drive command circuit 23 together with the motion detection signal terminal 30. In addition,
The head selection circuit 7 is configured such that a head selection command (not shown) is appropriately given from the outside to switch the video head.

Next, the operation of the third embodiment will be described with reference to the signal waveform diagram of FIG.

The reproduced video signal f shown in FIG.
The reproduced signal is output from the reproduction signal demodulation circuit 26 to the video signal comparison circuit 29 as a past video signal (a video signal several fields before being reproduced during the intermittent recording stop). On the other hand, the current video signal input from the video signal input terminal 11 is also input to the video signal comparison circuit 29 and compared with the past video signal. Therefore, it is possible to compare the past input video signal several fields before the intermittent recording reproduced during the intermittent recording stop with the currently input video signal without using a memory. The video signal comparison circuit 29 can detect a change in the luminance level of the video signal, for example, by subtracting two video signals and taking a difference value between the two signals. Further, the change of the chroma signal can be detected by adding or subtracting two video signals depending on whether the field is an odd field or an even field. Further, a specific point in one field (for example, the 50th scanning line or 55-6
It may be configured to detect only a change in the video signal of the 0th scanning line).

The comparison circuit 29 functions as an alarm output circuit, and when it is determined that there is a change in the video signal exceeding a predetermined reference value, as shown in FIG. The motion comparison signal i rising to the level is output to the motion detection signal terminal 30 as an alarm signal. Therefore, by switching the magnetic recording / reproducing apparatus which has been operating in the intermittent recording mode for a long time when the alarm signal is detected to the recording mode in which the time interval is short,
Only necessary images can be reliably recorded.

Embodiment 4 Also, as shown in FIG.
By providing a configuration in which the motion comparison signal i is also supplied to the intermittent drive command circuit 23, it is possible to increase the recording density of the intermittent recording operation when it is determined that the video has motion. That is, if the intermittent drive command circuit 23 is configured to switch and output the control signal of the capstan controller 22 when the motion comparison signal i is input, the capstan motor 2 is switched when the motion is detected.
1, the recording speed can be continued by further increasing the rotation speed and setting a shorter time interval for intermittent recording. By switching to the recording mode in which the time Tμsec of the intermittent drive command signal a shown in FIG. 2A is set shorter, the density of the recording signal with respect to time can be automatically increased.

Embodiment 5 FIG. In the magnetic recording / reproducing apparatus according to the fifth embodiment, a change in a video signal can be more accurately determined using a clogging signal and a motion comparison signal.

FIG. 5 is a block diagram showing a configuration of a motion detection circuit 62 used in the magnetic recording and reproducing apparatus according to the fifth embodiment. This motion detection circuit 62 is used in place of the motion detection circuit 61 in FIG. In FIG. 5, while the reproduced video signal f is input to the reproduced envelope comparison circuit 3, it is also input to the reproduced signal demodulation circuit 26. The reproduction envelope comparison circuit 3 compares a predetermined envelope value m with the envelope of the reproduction video signal f,
The clogging signal h as the comparison result is input to the video signal comparison circuit 29. Further, the recording signal c is input to the video signal comparison circuit 29 from the input video terminal 11. As a result, only when the clogging signal h is not output from the clogging output circuit 4 (when there is no clogging), the reproduced video signal f output from the reproduced signal demodulation circuit 26 and the recording input from the input video terminal 11 are recorded. The signal c and the video signal comparing circuit 2
9, the motion comparison signal i can be generated as an alarm signal when the motion of the video is detected.

By detecting the clogging of the video head as described above, a video signal having a low reproduction level is not inputted to the video signal comparing circuit 29.
Can prevent motion detection errors.

Further, when only the motion detection is performed and the presence or absence of a change in the event at the shooting location is determined based on the presence or absence of the movement in the video signal, if head clogging occurs, The subsequent image changes naturally. for that reason,
When the motion detection is performed only by the video signal comparison circuit 29, the video signal comparison circuit 29 detects the change in the video signal and records the intermittent recording even if no change in the event actually occurs. Malfunction such as changing the mode. However, in the fifth embodiment, since the motion is detected using the detection of clogging of the video head, the recording signal is not input to the video signal comparison circuit when the clogging of the video head is detected.
Prevent erroneous detection and enable highly accurate motion detection.

Further, if the motion detection signal i is inputted to the intermittent drive command circuit 23, the rotation speed of the capstan motor 21 is increased and the rotation speed of the capstan motor 21 is increased when the motion is detected, as in the fourth embodiment. Therefore, the density of the recording signal with respect to time can be increased. The clogging signal h can also be supplied to the head selection circuit 7 to switch the video head.

In the above-described first to fifth embodiments, the description has been given of the one using the 4-channel video head.
A magnetic recording / reproducing apparatus having a channel video head can more reliably record necessary video signals.

[0057]

Since the present invention is configured as described above, it has the following effects.

In the magnetic recording / reproducing apparatus according to the first aspect, intermittent recording for intermittently recording a video signal on a magnetic tape is performed, and the video head is switched to the reproducing mode during a pause during the intermittent recording. The video head traces the recording track of the magnetic tape recorded before this, and a reproduced video signal is obtained. At this time,
If the video head is clogged, a clogging signal is input to the head selection means, and the clogged video head is replaced with a video head that has not been detected yet (a video head that has not been used yet). Head is included).

In the magnetic recording / reproducing apparatus according to the second aspect, when the video head is clogged, the envelope of the reproduced video signal is smaller than the predetermined envelope value indicating that the video head is clogged. Become. Therefore, clogging can be detected by detecting a decrease in the envelope of the reproduced video signal.

Further, in the magnetic recording / reproducing apparatus according to the third aspect, the reproduced video signal reproduced by the video head is demodulated, and the demodulated reproduced video signal is inputted to the sync separation circuit.
By detecting the presence or absence of a synchronization signal output from the synchronization separation circuit, clogging of the video head can be detected.

Further, in the magnetic recording / reproducing apparatus according to the fourth aspect, only when the clogging is not detected, the video signal inputted at present is compared with the reproduced video signal recorded in the past so that the video signal is reproduced. Can be accurately detected. By switching the recording mode of the intermittent recording according to the detection signal, the intermittent recording density can be increased.

In the magnetic recording / reproducing apparatus according to the fifth aspect, the video head is switched to the reproduction mode during the intermittent recording pause, and the video head traces the recording track of the magnetic tape recorded before that. The video signal recorded in the past is reproduced. By comparing the reproduced video signal with the currently input video signal, a change in the video signal can be detected.

In the magnetic recording / reproducing apparatus according to the sixth aspect, the recording mode of the intermittent recording is switched according to a detection signal that detects the movement of an image from a change in a video signal.
Intermittent recording density can be increased. Further, the motion can be detected accurately by comparing the past video and the current video with a simple circuit configuration without using an expensive field memory and AD and DA conversion circuits. Then, it is possible to eliminate the necessary loss of the recorded video by the motion detection signal. Further, only when the clogging is not detected, the change of the video signal can be accurately detected by comparing the currently input video signal with the reproduced video signal recorded in the past.

In the intermittent magnetic recording method according to the seventh aspect, even if clogging occurs during the intermittent recording, the video signal can be reliably recorded.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a signal waveform diagram showing operation timing of the present invention.

FIG. 3 is a block diagram showing a configuration of a clogging detection circuit used in a second embodiment.

FIG. 4 is a block diagram showing a configuration of a magnetic recording and reproducing device according to a third embodiment.

FIG. 5 is a block diagram showing a configuration of a detection circuit used in a fifth embodiment.

[Explanation of symbols]

1 intermittent magnetic recording / reproducing device, 2 recording / reproducing command circuit,
3 playback envelope comparison circuit, 4 clogging output circuit, 5 clogging signal output terminal, 6,60 clogging detection circuit, 7 head selection circuit, 8, 9 head selection switch, 11 video signal input terminal, 12 recording signal processing circuit , 13 recording head amplifier, 14 head changeover switch, 15 rotary drum, 16 video head, 17 reproduction head amplifier, 19 magnetic tape, 20 capstan shaft, 21 capstan motor, 22 capstan controller, 23 intermittent drive command circuit, 24 Drum motor, 25 drum controller, 26 reproduced signal demodulation circuit, 28 vertical sync separation circuit, 29 video signal comparison circuit, 30 motion detection output terminal, 61, 62 motion detection circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/91 H04N 5/91 F

Claims (7)

[Claims] 1. A video head of a plurality of channels for recording and reproducing on and from a magnetic tape, a recording head amplifier for supplying a recording signal to these video heads, a reproducing head amplifier for amplifying a video signal reproduced by the video head, and A magnetic recording / reproducing apparatus for performing intermittent recording on the magnetic tape, comprising: a head changeover switch for switching the video head between a recording operation and a reproducing operation; and a recording command signal for operating the recording head amplifier during intermittent recording. And a recording / reproducing command means for generating a reproducing command signal for operating the reproducing head amplifier and a head switching command signal for switching a head switch during other periods, and detecting a clogging signal of the video head. Clogging detection means for detecting the occurrence of the clogging signal. A magnetic recording / reproducing apparatus comprising: a head selecting means for selecting a video head which is not determined to be clogged among the video heads. 2. A reproduction envelope comparison circuit for comparing an envelope of a video signal reproduced by the reproduction head amplifier with a predetermined envelope value indicating that the video head is clogged, 2. The magnetic recording / reproducing apparatus according to claim 1, further comprising a clogging output circuit that detects clogging of the video head and generates a clogging signal in response to a comparison signal of a comparison circuit. 3. The clogging detection means includes: a demodulation circuit for demodulating a video signal reproduced by the reproduction head amplifier; a synchronization separation circuit for separating a synchronization signal from the demodulated reproduction video signal; 2. A magnetic recording / reproducing apparatus according to claim 1, further comprising a clogging output circuit for detecting clogging of said video head and generating a clogging signal. 4. A reproduction envelope comparison circuit for comparing an envelope of a video signal reproduced by the reproduction head amplifier with a predetermined envelope value indicating that the video head is clogged, A clogging output circuit for detecting clogging of the video head and generating a clogging signal in response to a comparison signal of a comparison circuit; a demodulation circuit for demodulating a video signal reproduced by the reproducing head amplifier; A video signal comparing circuit for comparing the video signal with the input video signal; and an alarm signal if a predetermined change between the past reproduced video and the current input video based on the comparison signal of the video signal comparing circuit. An alarm output circuit that generates a motion video detection signal only when the clogging signal is not generated and the alarm signal is generated 2. The magnetic recording / reproducing apparatus according to claim 1, further comprising: a moving image detecting circuit. 5. A video head of a plurality of channels for recording and reproducing on and from a magnetic tape, a recording head amplifier for supplying a recording signal to these video heads, a reproducing head amplifier for amplifying a video signal reproduced by the video head, and A magnetic recording / reproducing apparatus for performing intermittent recording on the magnetic tape, comprising: a head changeover switch for switching the video head between a recording operation and a reproducing operation; and a recording command signal for operating the recording head amplifier during intermittent recording. Recording / reproduction command means for generating a reproduction command signal for operating the reproduction head amplifier and a head switching command signal for switching a head changeover switch during other periods, and demodulation for demodulating a reproduced video signal by the reproduction head amplifier. Circuit, and the demodulated reproduced video signal and the input video. A video signal comparing circuit for comparing the image signal with an image signal; and an alarm output circuit for generating an alarm signal if a change is made between a past reproduced video and a current input video based on the comparison signal of the video signal comparing circuit. A magnetic recording / reproducing apparatus characterized by the above-mentioned. 6. The magnetic recording / reproducing apparatus according to claim 4, further comprising a recording mode switching circuit for switching to a recording mode having a higher time density of intermittent recording in response to the alarm signal. apparatus. 7. An intermittent magnetic recording method comprising a plurality of channels of video heads and performing intermittent recording on a magnetic tape, wherein a recording command signal is generated during a predetermined intermittent recording period and a reproduction command signal is generated during other periods. And detects clogging of the video head used for intermittent recording based on the video signal reproduced by the reproduction command signal. When the clogging is detected, it is determined that the video head is clogged. An intermittent magnetic recording method characterized in that intermittent recording is performed by switching to a video head of a channel that is not used.