JPH0346147A - Mode switching device for video tape recorder - Google Patents

Abstract

PURPOSE:To prevent distortion of video and sound from being generated by changing the traveling speed of a tape corresponding to the change of speed for recording information on the magnetic tape by detecting a speed switching signal recorded in a control track. CONSTITUTION:In the recording state of an SP mode, when an instruction signal is inputted from an operation input part 1 for setting an EP mode, a speed switching signal recording circuit 2 outputs a speed switching signal 21 and a control head 3 records the signal 211 to the control track of the magnetic tape. On the other hand, a tape switching circuit 4 controls the rotation of a capstan motor 5 to the traveling speed corresponding to the EP mode. While such a magnetic tape is reproduced with the SP mode, the control head 3 reproduces the signal 211, which is recorded in the control track, and a control circuit 7 instructs a reproducing mode, which is instructed by the signal 211, based on the output of a speed switching signal detecting circuit 6. The tape speed switching circuit 4 changes the tape speed and the distortion of video and sound can be prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mode switching device for a video tape recorder, and more specifically, when the tape running speed is switched when recording information on a magnetic tape, The present invention relates to a device that prevents disturbances in video and audio when the switched portion is played back.

(Prior art) While recording information on a magnetic tape, the recording mode is set to S, for example.
When switching from P mode to EP mode, when playing back the magnetic tape, the tape running speed suddenly changes at the point where the recording mode changes, so it takes a considerable amount of time for the servo to follow this mode change. was. That is, as shown in FIG. 7, after reproducing the change point a of the recording mode on the magnetic tape at time t0 until time tzz when the servo actually follows, time T1
It required

(Problem to be Solved by the Invention) Therefore, during this time T, that is, from the time when the recording mode change point on the magnetic tape is reproduced until the servo actually follows the image on the screen and There were problems with the audio being distorted and the playback screen being very ugly.

In addition, if the recording mode changes point a is entered in the state of intermittent slow playback, the change in recording mode cannot be detected, and even though the recording mode has changed from SP mode to EP mode, , there was also the problem that normal video could not be obtained because intermittent slow playback continued in SP mode.

The present invention has been made in view of the above circumstances, and its purpose is to quickly follow the servo at the mode change point when reproducing a magnetic tape on which information in different recording modes has been continuously recorded. An object of the present invention is to provide a mode switching device for a video tape recorder that prevents the occurrence of video and audio disturbances during mode change point reproduction.

(Means for Solving the Problems) In order to solve the above problems, a mode switching device for a video tape recorder according to the present invention responds to a recording mode switching signal inputted from an operating section when recording information on a magnetic tape. a speed switching signal recording means for recording a speed switching signal indicating a tape speed corresponding to the recording mode after switching on a control track of the magnetic tape; and a speed switching signal recording means is recorded on the magnetic tape by the speed switching signal recording means. and a tape speed switching means for switching the tape speed to a speed corresponding to the recording mode input from the operation input section after the information is recorded on the magnetic tape. a speed switching signal detecting means for detecting the speed switching signal that has been detected, and a speed switching signal detected by the speed switching signal detecting means,
The magnetic tape apparatus is configured to include a control means for controlling the running speed of the magnetic tape to the switched running speed.

(Function) With the above configuration, when information is recorded on a magnetic tape, the speed switching signal recording means switches the speed to indicate the tape speed corresponding to the switched recording mode based on the recording mode switching signal input from the operation input section. The signal is recorded on a control track of the magnetic tape. After a predetermined period of time, the tape speed switching means switches the tape speed to a speed corresponding to the recording mode input from the operation input section. On the other hand, when the speed switching signal recorded on the magnetic tape is detected by the speed switching signal detection means during reproduction of the magnetic tape on which information is recorded in this manner, the control means controls the speed switching signal based on the detected speed switching signal. , the tape speed switching means is controlled so that the running speed of the magnetic tape becomes the detected running speed. That is, since predictive control is performed prior to actual servo control so that the next recorded mode is achieved, subsequent servo tracking is performed in an extremely short time.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the electrical configuration of the mode switching device of the present invention.

In the same figure, the output of the manual operation section (2), which inputs recording or playback start instructions, mode switching instructions, etc., is led to the speed switching signal recording circuit 2.
The output is given to the control head 3 as a speed switching signal indicating the recording speed on a magnetic tape (not shown). Further, the other output of the speed switching signal recording circuit 2 is given to the tape speed switching circuit 4 as a switching instruction signal for instructing switching of the tape speed. The control head 3 records the applied speed switching signal on a predetermined control track of the magnetic tape.

Further, the tape speed switching circuit 4 controls the rotation of the capstan motor 5 after a certain period of time based on the led switching instruction signal, so that the tape speed changes to the speed of the mode instructed by the switching instruction signal. Control the tape running speed.

On the other hand, the control head 3 shows various control signals reproduced from the control track of the magnetic tape.
The output of the speed switching signal detection circuit 6 is led to a speed switching signal detection circuit 6, and the output of the speed switching signal detection circuit 6, which detects the speed switching signal from the guided control signal, is given to a control circuit 7. The output of the control circuit 7 is led to the tape speed switching circuit 4 as a control signal based on the speed switching signal. Based on this control signal, the tape speed switching circuit 4 controls the rotation of the capstan motor 5.
The running speed of the magnetic tape is controlled so that the tape speed corresponds to the subsequent recording mode.

Next, the operation of the mode switching device having the above configuration will be explained with reference to FIGS. 3 and 4. However, FIG. 3 shows the operation timing during recording, and FIG. 4 shows the operation timing during reproduction. In addition, in this embodiment, the recording mode is set to S.
An example of switching from P mode to EP mode will be explained.

First, the operation during recording will be explained.

Assume that information is being recorded on a recording track of a magnetic tape in SP mode by a video head (not shown). In this recording state, when an instruction signal 111 for setting the recording mode to EP mode is input from the operation input section l at time t1, the speed switching signal recording circuit 2 transmits a speed signal to the control head 3 indicating the EP mode. Since the control head 3 outputs the switching signal 211, the control head 3 records this speed switching signal 211 on the control track of the magnetic tape. On the other hand, after outputting the speed switching signal 211 to the control head 3, the speed switching signal recording circuit 2 instructs the tape speed switching circuit 4 to change the tape running speed from SP mode to time t15, which is slightly later than time t2. E
By outputting a switching instruction signal to switch to P mode,
At time t15, the tape speed switching circuit 4 controls the rotation of the capstan motor 5 to control the running speed of the magnetic tape to a speed corresponding to the BP mode (see FIG. 3(C)).

Next, a case will be described in which a magnetic tape on which information is recorded in this manner is reproduced.

While reproducing the magnetic tape in the SP mode, the control head 3 sequentially reproduces various control signals recorded on the control track of the magnetic tape and outputs them to the speed switching signal detection circuit 6.

Then, at time t3, when the speed switching signal 211 is reproduced by the control head 3, the speed switching signal detection circuit 6 detects this speed switching signal 211 and outputs the speed switching signal 211 to the control circuit 7. Based on the speed switching signal 211, the control circuit 7 outputs a control signal 711 instructing the tape speed switching circuit 4 to the reproduction mode indicated by the speed switching signal 211 at time t. From time t4 when this control signal 711 is applied, the tape speed switching circuit 4 decelerates the rotation of the capstan motor 5 so as to enter the instructed playback mode, and changes the tape speed of the magnetic tape to the speed corresponding to the SP mode. [See FIG. 4(C)].

Therefore, at time T, when the magnetic tape was at a speed corresponding to SP mode, at time T, E
The speed stabilizes at the speed corresponding to P mode, but since this time TI is T1>T, the servo pull-in time is shorter than before, and the period of video and audio disturbance on the playback screen is reduced accordingly. becomes shorter.

FIG. 2 shows an embodiment in which the mode switching device of the present invention is applied to a video tape recorder that performs digital noise reduction using a frame memory.

That is, in this embodiment, when a change point in the recording mode is reproduced, a still image is output on the reproduction screen, thereby completely preventing image disturbance.

In the figure, 11 is an operation input section, 12 is a speed switching signal recording circuit, 13 is a control head, 14 is a tape speed switching circuit, 15 is a capstan motor, 16 is a speed switching signal detection circuit, and 17 is a control circuit. , these structures are the same as those of the embodiment shown in FIG. 1, so their explanation will be omitted here. In this embodiment, in addition to the above configuration, a new video writing stop circuit 18, an open/close switch 19, a digital memory 20, and a tape running stability determination circuit 21 are provided.

That is, the output of the speed switching signal detection circuit 16 is led to a new video writing stop circuit 18, which prohibits writing of new video based on the signal from the speed switching signal detection circuit 16. The output of 18 is led to the opening/closing control input of the opening/closing switch 19. Open/close switch 19
A video signal Sl reproduced from a magnetic tape by a video head (not shown) is guided to one terminal a, and the other terminal is connected to an input of a digital memory 20. The output of the digital memory 20 is output as a still image to a monitor (not shown). Further, the output of the servo circuit 22 indicating the servo state is led to the tape running stability determining circuit 21, and the tape running stability determining circuit 21 indicates the determination result of the stable state of tape running.
The output of No. 1 is led to the opening/closing control input of the opening/closing switch 19.

The open/close switch 19 maintains the ON state in a normal state in which no write stop signal is given from the new video write stop circuit 18, and also indicates stability from the tape running stability determination circuit 21 in the OFF state. When a signal is applied, it switches to the ON state.

Next, the operation of the mode switching device having the above configuration will be explained with reference to FIGS. 5 and 6. However, although both FIG. 5 and FIG. 6 show the operation timing during playback, FIG. 5 shows the case where conventional servo pull-in is performed, and FIG.
This shows a case where the predictive control shown in the figure is performed. Further, in this embodiment, a case will be described using as an example a case where the recording mode is switched from SP mode to EP mode. Note that since the operation during recording is the same as in the above-described embodiment, only the operation during reproduction will be explained here.

While reproducing the magnetic tape in the SP mode, the control head 13 sequentially reproduces various control signals recorded on the control track of the magnetic tape and outputs them to the speed switching signal detection circuit 16. Then, at time 1h, the speed switching signal 211 is sent by the control head 13.
, the speed switching signal detection circuit 16 detects this speed switching signal 211 and reproduces the speed switching signal 2.
11 is output to the new video writing stop circuit 18 and the control circuit 7. In the new video writing stop circuit 18, based on this speed switching signal 211, the time t? Since the OFF signal is output to the open/close switch 19 at
9 is in the OFF state. Therefore, digital memory 20
Then, at time t, the digital still image stored immediately before (indicated by "H" level in FIG. 5(d)) is output to the monitor.

At this time, from the speed switching signal detection circuit 16, the control circuit 1
If the speed switching signal 211 is not output for 7,
Since the servo circuit 22 performs servo control similar to the conventional one, the magnetic tape decelerates the rotation of the capstan motor 15 at a time t later than the time t when the recording mode on the tape actually changes. However, at time t1°, the tape speed becomes stable at a level corresponding to the EP mode. Then, at the stable time t and a slightly later time t, the tape running stability determination circuit 21 determines that the tape running is stable, and therefore outputs a control signal to the open/close switch 19 at this timing, and outputs a control signal to the open/close switch 19 at this timing. Switch 19 is turned on. As a result, transmission of digital still images is stopped at time t, and from then on, transmission of digital still images is stopped at time t.
Normal playback image in P mode [r in Figure 5 (a)
l, j levels] will be output to the monitor.

On the other hand, at time t from the digital memory 20, a digital still image [indicated by "H" level in FIG. For speed switching signal 211
is output, the control circuit 7 controls the tape speed switching circuit 14 to instruct the tape speed indicated by the speed switching signal 211 at time t, based on the speed switching signal 211. A signal 711 is output. From time tl□ when this control signal 711 is applied, the tape speed switching circuit 14 decelerates the rotation of the capstan motor 5 so that the specified playback mode is achieved, and changes the tape speed of the magnetic tape to correspond to the SP mode. control the speed. Therefore, at time t11, which is T1 hours after time t12 at which the magnetic tape was at a speed compatible with SP mode, the tape speed becomes stable at a tape speed compatible with EP mode. Then, at time t14, which is slightly delayed from the stable time t13, the tape running stability determination circuit 21 determines that the tape running is stable. Switch 19 is turned on.

As a result, the transmission of digital still images is stopped at time 4, and from then on, normal playback images in EP mode (indicated by "L" level in FIG. 6(d)) are output to the monitor. become.

In addition, although the above embodiment describes the case where the playback mode is switched from SP mode to EP mode, the present invention is not limited to this case, and the present invention can also be applied to, for example, when switching from EP mode to SP mode. It is possible. Further, even when a tape speed change point is reached during intermittent slow playback, it is possible to detect the speed switching signal in advance, so that a normal slow playback image can be obtained in the second case as well.

(Effects of the Invention) The mode switching device for a video tape recorder according to the present invention records a speed switching signal on a control track on a magnetic tape, and detects this speed switching signal during playback, thereby controlling information recording on the magnetic tape. Since the tape running speed is changed in accordance with the speed change, it is possible to reduce disturbances in video and audio caused by reproducing tape speed change points. Further, by outputting a still image to a monitor at the tape speed change point during playback, disturbances in video and audio can be completely prevented.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the electrical configuration of a mode switching device for a video tape recorder according to the present invention, and Fig. 2 shows the same device applied to a video tape recorder that performs digital noise reduction using a frame memory. A block diagram showing an example, Figure 3 is an operation timing diagram during recording, Figure 4 is an operation timing diagram during playback, and Figure 5 is an operation 7447 when masking with a still image without predictive control.
9 and 6 are operation timing diagrams when predictive control and still image masking are used together, and FIG. 7 is an operation timing diagram during playback by a conventional apparatus. 1.11... Operation input section 2.12... Speed switching signal recording circuit 3.13.
...Control head 4.14...Tape speed switching circuit 5, I5...Capstan motor 6.16...Speed switching signal detection circuit 7.17...Control circuit 18...New video writing Stop circuit 19...Open/close switch 20...Digital memory 21...Tape running stability determination circuit 22...Servo circuit

Claims (1)

[Claims] 1) When recording information on a magnetic tape, based on a recording mode switching signal input from an operation input section, a speed switching signal indicating a tape speed corresponding to the recording mode after switching is transmitted to the magnetic tape. A speed switching signal recording means for recording on a control track of the tape; and after the speed switching signal is recorded on the magnetic tape by the speed switching signal recording means, the tape speed is adjusted to a speed corresponding to a recording mode input from an operation input section. tape speed switching means for switching; speed switching signal detection means for detecting the speed switching signal recorded on the magnetic tape when playing back the magnetic tape on which information is recorded in this manner; and detection by the speed switching signal detection means. 1. A mode switching device for a video tape recorder, comprising: control means for controlling the running speed of the magnetic tape to the switched running speed based on the switched speed switching signal.