JPH0570980B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a camera signal magnetic recording device, and more particularly to a device for switching video signals from a plurality of black and white or color video cameras and magnetically recording them on a magnetic tape. It is.

[Prior Art] A series of system equipment consists of a single black-and-white or color video camera or a plurality of black-and-white or color video cameras, a camera switching converter for controlling switching of these video cameras, and a monitor television. , has been widely used in banks and supermarkets for crime prevention and monitoring purposes. Furthermore, since magnetic recording devices (hereinafter abbreviated as VTR) have become popular for consumer use at low cost over the past few years, the system equipment described above can be combined with a VTR to record video camera signals on magnetic tape and later record the recorded contents. It became possible to inspect and analyze.

On the other hand, VTR recording time can now be up to eight hours, using the VHS system as an example, making it possible to cover normal business hours. However, it is troublesome to change the video cassette tape every day, and if you want to record for more than 8 hours, if the video cassette tape ends midway through,
Magnetic tape is used intermittently because it cannot be stored on book tape, and because recording is not continuous 24/7 and is broken into pieces over time, so-called frame-drop recording does not pose much of a problem in practice. A so-called intermittent recording VTR was developed, which records by moving the camera. When this is used, intermittent recording can be performed for 24 hours, 48 hours, or even longer periods of time on one video cassette tape, and the above-mentioned disadvantages can be solved.

In addition, if we incorporate the current normal recording, so-called continuous recording method, into this intermittent recording VTR, and make it possible to automatically convert the recording method using an external control signal, we can use the intermittent recording method during normal normal conditions. In the event of an emergency, if you send a control signal to the VTR, it will instantly convert to continuous recording, allowing you to record the situation at the scene in great detail.

Next, a conventional camera signal magnetic recording device will be explained. First, to explain the configuration of this device, this camera signal magnetic recording device mainly includes a plurality of video cameras, a camera switcher,
It consists of an intermittent recording type VTR and a continuous recording type VTR. More specifically, the plurality of video cameras are black and white or color video cameras. The camera switcher includes a synchronization signal generator that generates a field synchronization signal to match the timing of the vertical synchronization signal of each video camera's video signal, and a synchronization signal generator that sequentially switches the video signals of each video camera to output one video signal. and a video switch to
and a switching controller that controls switching of this video switch. A VTR includes a magnetic tape for recording video signals from a video camera and a mode selection switch for selecting intermittent recording or continuous recording of the video signal.
is output from.

Next, the intermittent recording operation of this device will be explained. During intermittent recording, a clock signal from the VTR is given to the switching controller, and the switching controller controls video switch switching using this clock signal.
Video signals from each video camera are sequentially switched and output from the video switch. One frame of video signals from each video camera corresponding to the switching position of this video switch is input to the VTR and recorded on magnetic tape, and the entire device remains in a standby state until the next clock signal is given to the switching controller. becomes. By repeating these operations, the video signals from each video camera are sequentially recorded one frame at a time on the magnetic tape.

Next, the continuous recording operation of this device will be explained. During continuous recording, a clock signal is not output from the VTR, and a clock signal fixed to a pre-specified video camera or a clock signal generated within the camera switch is given to the switch controller. The switching controller controls switching of the video switch using this clock signal, and the video signal of a designated video camera is derived from the video switch, or the video signals from each video camera are sequentially switched and derived. The video signals of the designated video camera corresponding to the switching position of the video switch or of each video camera that is sequentially switched are continuously recorded on the magnetic tape in the usual manner.

[Problems to be solved by the invention] In the case of continuous recording, there are times when it is usually an emergency and it is desired to use all video cameras to capture the constantly changing situation at the scene.
The video cameras are sequentially switched by a clock signal generated inside the camera switch, so that apparently all the video cameras are recorded.

However, this internal clock signal usually has a minimum
For example, if there are 8 video cameras, the time it takes for the switching to complete one cycle is approximately 0.5 seconds.
0.5 seconds x 8 = 4 seconds, so for a video camera, video signals are only recorded on magnetic tape every 4 seconds, and even though VTRs record continuously, all It becomes extremely difficult to clearly record the contents of the video camera.

Therefore, it seems possible to shorten the period of the internal clock signal, but this is not possible for the following reasons. In a VTR, in order to control the magnetic tape and rotating drum during playback, a so-called control signal is recorded on the magnetic tape in synchronization with the frame period of the video signal during recording, and this control signal and the internal clock of the video switch are If the signal cycles are not synchronized, one screen, or one frame signal, at the moment the video camera switches will appear to contain one field of the video camera before switching and one field of the video camera after switching. The upper one frame signal is recorded on the magnetic tape. If you play this back, the screens of both video cameras will appear as duplicates. The period of the internal clock signal is 0.5 seconds, and the frame period is 1/3.
If it is 0 seconds, the rate at which the above double screen appears is (1/30)/0.5 = 1/15, which is a level that does not pose a practical problem, but as the period of the internal clock signal is shortened, There was a problem that double screens frequently occurred, making it impractical.

One way to solve these problems is to connect a VTR to all video cameras, but this is not practical considering the cost, installation space, and the complexity of inspecting and analyzing recorded magnetic tape. It cannot be said that it is a method that can be used for

The present invention was made to solve this problem, and an object of the present invention is to provide a camera signal magnetic recording device that can obtain clear reproduced images without duplication even if the cycle of the clock signal of the camera switch is shortened. shall be.

[Means for Solving the Problems] A camera signal magnetic recording device according to the present invention provides video signals of a plurality of video cameras to a switching means while being synchronized by a synchronizing signal from a synchronizing signal generating means, and the switching means Each applied video signal is applied to a magnetic recording means while switching sequentially in synchronization with a frame synchronization signal generated from the video signal, and the magnetic recording means synchronizes the applied video signal with the above-mentioned frame synchronization signal for each frame synchronization. In this system, magnetic recording is performed continuously and sequentially.

[Function] In the present invention, the video signals of each video camera synchronized by the switching means are sequentially switched based on the frame synchronization signal.
Each video signal for each frame is given to the magnetic recording means, and each video signal for each frame is continuously recorded on the magnetic recording means for each frame period in synchronization with the above-mentioned frame synchronization signal, so that switching is performed. One field of the previous video signal and one field of the video signal after switching are not apparently recorded as one frame signal.

[Embodiment] As mentioned above, the shorter the period of the clock signal, the more clearly the current situation can be recorded. In the shortest case, the video camera is switched for each frame of the video signal, and this invention was developed based on this idea.

FIG. 1 is a block diagram of a camera signal magnetic recording device which is an embodiment of the present invention. First, the configuration of this device will be explained. In the figure, this camera signal magnetic recording device mainly includes a plurality of video cameras 1, a camera switch 2, an intermittent recording type VTR 3, a continuous recording type VTR 3, and a changeover switch 4.
It is composed of. To explain in more detail, the plurality of video cameras 1 include N black and white or color video cameras C1, C2, C3, C4,
...consists of CN. The camera switch 2 is
a synchronization signal generator 21 that generates a field synchronization signal for matching the timing of the vertical synchronization signal of each video signal from the N video cameras;
The video switch 22 includes a video switch 22 that sequentially switches video signals from different video cameras and outputs one video signal, and a switching controller 23 that controls switching of the video switch 22. To explain the structure of the VTR 3, a pair of video signal magnetic heads 302 and 303 are provided on the circumference of a rotating drum 301, facing each other at an angular interval of 180 degrees. A drum motor 305 drives the rotating drum 301 to rotate. Magnetic tape 3 on capstan 306
04 is in contact. capstan motor 30
7 rotates the capstan 306, causing the magnetic tape 304 in contact with the capstan to run. Video signal magnetic heads 302 and 303 rotate together with rotary drum 301 to helically scan magnetic tape 304. A video signal from the camera switch 2 is input to the VTR 3.
A recording signal processing circuit 309 performs signal processing for recording an input video signal onto a magnetic tape 304 using video signal magnetic heads 302 and 303. The vertical synchronization signal separation circuit 310 separates and extracts only a vertical synchronization signal (hereinafter referred to as a field synchronization signal corresponding to a frame synchronization signal to be described later) from the input video signal. Bistable multivibrator 31
1 converts the field synchronization signal into a frame synchronization signal with twice the period. Drum controller 312
is the drum motor 3 in synchronization with the frame synchronization signal.
The drum motor 305 is negatively controlled in response to a drum PG signal obtained by the drum motor 305 so that the drum motor 305 can rotate. Control head 308 records the frame synchronization signal on magnetic tape 304 as a control signal. A clock signal generating circuit 314 generates an intermittent recording control signal, ie, a clock signal, during intermittent recording.
The cabstan controller 313 controls the capstan to run the magnetic tape 304 intermittently at a fixed pitch during intermittent recording, and to run the magnetic tape 304 continuously in synchronization with a frame synchronization signal during continuous recording. A capstan PG signal obtained by the motor 307 is received to negatively control the capstan motor. The changeover switch 315 responds to the selection output of a mode selection switch (not shown) for selecting intermittent recording or continuous recording of the video signal, and outputs a frame synchronization signal during continuous recording and a clock signal during intermittent recording. Input to capstan controller 313. In addition, in response to the selection output of the mode selection switch, the changeover switch 4 is configured to
A clock signal from the VTR 3 is input to the switching controller 23, and a frame synchronization signal from the VTR 3 is input to the switching controller 23 during continuous recording.

Next, the intermittent recording operation of this device will be explained. When the intermittent recording mode is selected by the mode selection switch, the magnetic tape 304 of the VTR 3 is intermittently sent one frame of the video signal at preset time intervals, and at this time a clock signal is generated from the clock signal generation circuit 314. is output. This clock signal is given to the switching controller 23 via the switch 4, and the video switch 2
2 are sequentially switched in synchronization with the clock signal.
Thus, the VTR3 includes video cameras C1, C2,
Each video signal from C3,...CN is sequentially input one frame at a time to the video signal magnetic head 30.
2 and 303 are recorded on the magnetic tape 304.

FIG. 2 is a time chart showing the operation timing of each part of a camera signal magnetic recording device according to an embodiment of the present invention.

Next, the continuous recording operation of this apparatus will be explained with reference to FIG. Here, a case will be described in which there are four video cameras, but cases in which the number of video cameras is different can also be explained using the same concept as in the following explanation. When the continuous recording mode is selected by the mode selection switch, the synchronization signal generator 21
The field synchronization signal from C is given in parallel to each of the video cameras C1, C2, C3, and C4 of the plurality of video cameras 1, and the field synchronization signal from the video camera C shown in FIG.
1 signal, video camera C2 signal, video camera C
3 signal and the vertical synchronization signal timing of the video camera C4 signal. No matter which switching device the video switch 22 is in, the corresponding video camera signal is switched and input to the VTR 3, and a frame synchronization signal is generated through the vertical synchronization signal separation circuit 310 and the bistable multivibrator 311. The frame synchronization signal is applied to the switching controller 23 via the switch 4. The switching controller 23 generates a control signal that sequentially switches the video switch 22 every time a switching signal, which is a frame synchronization signal, is applied from the switching switch 4. Thus, as shown in FIG. 2, the output of the video switch 22 includes the video camera C1 signal, video camera C2 signal, video camera C3 signal, video camera C4 signal, video camera C1 signal, and video camera signal for each frame period. A video signal is obtained which switches sequentially from the C2 signal, . At this time, the rotary drum 301 is driven to rotate in synchronization with the frame synchronization signal, and the magnetic tape 304 is continuously run, so one field of the video signal before the video camera is switched and one field of the video signal after the video camera is switched. One field of the video signal is not apparently recorded as one frame signal. In addition, each video camera C1, C
The frame period of the video signals from VTR 2, C3, and C4 is synchronized with the period of the control signal of the VTR 3, and the frame synchronization signal is recorded directly on the magnetic tape 304 by the control head 308 of the VTR 3 as a control signal. The purpose of this control signal is to identify one frame of the video signal during playback.

In the above manner, the magnetic tape 30 of the VTR3 is
4, a video signal in which the video camera signal is sequentially switched every frame period, and a control signal synchronized with the frame period of this video signal are recorded.

Naturally, in a VTR without intermittent recording, no clock signal is output, so the switch 4 can be omitted and the frame synchronization signal from the bistable multivibrator 311 can be directly connected to the switching controller 23. Further, when there is only one video camera, if the input of the switching controller 23 is turned off, it can be used as a normal VTR.

Furthermore, in a normal VTR, the switching timing of the head switching signals of the video signal magnetic heads 302 and 303 precedes the vertical synchronization signal of the input video signal by several H (1H is one horizontal period of the video signal). There is no problem in replacing the head switching signal with a frame synchronization signal.

In the above-described camera signal magnetic recording device, when the VTR is in an intermittent recording mode and the switching of multiple video cameras is synchronized with the intermittent cycle, the corresponding camera signal is recorded in one frame of the magnetic tape. Therefore, the amount of magnetic tape used can be significantly reduced. Furthermore, in the event of an emergency, by operating the VTR continuously and switching between multiple video cameras frame by frame, it is possible to record the scene situation on magnetic tape in detail.

[Effects of the Invention] As described above, according to the present invention, the video signals of a plurality of video cameras are synchronized by the synchronization signal from the synchronization signal generation means, and are applied to the switching means.
The switching means applies each applied video signal to the recording means while sequentially switching it in synchronization with a frame synchronization signal generated from the video signal, and the recording means applies the applied video signal to the recording means in synchronization with the frame synchronization signal mentioned above. Since each video signal is magnetically recorded in sequence, even if the video signals from multiple video cameras are switched sequentially and recorded continuously on a VTR,
One field of the video signal before the video camera is switched and one field of the video signal after the video camera is switched are not apparently recorded as one frame signal. Therefore, it is possible to obtain a camera signal magnetic recording device that can obtain clear reproduced images without duplication.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a camera signal magnetic recording device which is an embodiment of the present invention. FIG. 2 is a time chart showing the operation timing of each part of a camera signal magnetic recording device according to an embodiment of the present invention. In the figure, 1 is a plurality of video cameras, C
1, C2, C3, C4,...CN is a video camera,
2 is a camera switch, 3 is a magnetic recording device (VTR),
301 is a rotating drum, 302 and 303 are video signal magnetic heads, 304 is a magnetic tape, 305 is a drum motor, 306 is a capstan, 307 is a capstan motor, 308 is a control head, 309 is a recording signal processing circuit, and 310 is a 311 is a bistable multivibrator, 312 is a drum controller, 313 is a capstan controller, 314 is a clock signal generation circuit, and 315 and 4 are changeover switches. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A plurality of video cameras; a synchronization signal generating means for generating a synchronization signal for synchronizing the video signals of each of the video cameras; A switching means for sequentially switching and outputting the video signals of each of the video cameras, and a magnetic recording means for sequentially magnetically recording the video signals from the switching means in synchronization with the frame synchronization signal every frame period. Also, camera signal magnetic recording device. 2. The magnetic recording means includes: vertical synchronization signal separation and extraction means for separating and extracting a vertical synchronization signal from the video signal from the switching means; and conversion means for converting the vertical synchronization signal into the frame synchronization signal. The camera signal magnetic recording device according to scope 1. 3. The magnetic recording means includes: a mode selection means for selecting continuous recording or intermittent recording of a video signal; an intermittent synchronization signal generation means for generating an intermittent synchronization signal in synchronization with the intermittent recording; and selection of the mode selection means. In response to the output, in the case of the continuous recording, outputting the frame synchronization signal to the switching means and the magnetic recording means;
In the case of the intermittent recording, the claim further comprises a control means for outputting the intermittent synchronization signal to the switching means and the magnetic recording means, and sequentially switching the video signals of the video cameras in response to the intermittent synchronization signal. The camera signal magnetic recording device according to item 1 or 2.