JP2714460B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an intermittent magnetic recording apparatus that performs so-called dropped frames by recording a video signal one feed or one frame at a time by running a magnetic tape intermittently. Below "T / L VTR"
More specifically, the present invention relates to a recording position control means for preventing overwriting at a joint between a previous recording portion and a current recording portion.

[Conventional technology]

In the conventional T / L VTR, when the recording is stopped once and the recording is started again, the seam portion between the previous recording unit and the current recording unit is overwritten. Hereinafter, the overwriting process will be described.

FIG. 3 is a plan view showing a magnetic tape running system of a helical scan type VTR, (1) a cassette containing a magnetic tape, (2) a magnetic tape supply reel in the cassette (1), and (3) a magnetic tape. Tapes, (4), (5) and (6) are guide rollers for guiding the magnetic tape (3) on the entrance and exit sides, (7) is a full-width erasing head, (8) is an impedance roller, and (9) is audio. An erasing head, (10) is a control head, (11) is a capstan, (12) is a pinch roller, (13) is a take-up reel, and (14) is a rotating drum having a magnetic head.

FIG. 4 is a diagram schematically showing a positional relationship between a video signal (15) recorded on a magnetic tape (3) and a control signal (16) and a recording pattern thereof.
As shown, the magnetic tape (3) is wrapped around a drum (14), but here it is assumed that it is merely in contact for simplicity.

Further, as shown in FIG. 3, the positions of the drum (14) and the control head (10) are far apart, and the video signal (15) and the CTL signal (1) corresponding to the input signal at a certain time.
The recording position of (6) is a distant position as shown in FIG. 4 (a), but for simplicity of explanation, as shown in FIG. 4 (b), the drum (14) and the control head (10) ) Are located at the same position, and when a certain video signal (15) is recorded, the following description will be made assuming that the corresponding CTL signal (16) is recorded immediately below.

Next, the video signal (15) and the CTL signal (16) are recorded when the recording is actually performed using the conventional VTR, the running of the magnetic tape (3) is once stopped, and then the recording is started again. A schematic diagram of the pattern is shown in FIG. 5, and the details will be described below. The arrow in the figure indicates the direction of travel of the magnetic tape (3), and the hatched portion indicates the previously recorded area. First, the magnetic tape (3) is moved in the direction of the arrow to record the image to the position shown in FIG.

Next, when recording is started again, the magnetic tape (3) is automatically rewound in the reverse direction (from right to left in the figure) to the position shown in FIG. 5 (b), and then FIG. 5 (c). The recording is started from the position of the recording pattern shown by (17) in FIG.

Therefore, in the area between (15) and (17) in the figure, the current recording is overwritten, and the previous recording is erased.

In the conventional VTR, as described above, the reason for moving the magnetic tape (3) in the reverse direction or the forward direction at the start of recording or overwriting the recording is as follows.

The reason why the magnetic tape (3) is rewound in the reverse direction is to match the phase of the CTL signal recorded this time with the phase of the CTL signal recorded previously. This is to prevent a situation in which the phase of the CTL signal is deviated between the previous recording and the current recording, because the synchronization is lost during reproduction and the image is disturbed.

The feeding in the forward direction is for improving the familiarity between the drum (14) and the magnetic tape (3). When the recording is started from the stop state, the recording is not immediately started because the magnetic tape (3) is slackened. Therefore, it is necessary to run the magnetic tape (3) in the forward direction to some extent before starting recording.

The reason for performing the overwriting is to make the seam between the previous record and the present record inconspicuous. Ideally, when starting recording, it is desirable that the current recording start from the end of the previous recording. However, starting the recording as it is from the position where the magnetic tape (3) is stopped is described in the above 2nd. More difficult than one reason. Further, when the magnetic tape (3) is rewound and then sent in the forward direction, it is difficult to control the connection of the current recording immediately after the previous recording. Also, even if there is an unrecorded gap between the previous record and this record,
The image during playback is distorted and unsightly. Therefore, a method of performing overwriting even if the record written last time is somewhat lost is generally used.

In the VTR of the continuous recording method, the amount of loss of recorded information due to the overwriting described above is small, and does not cause a serious problem.

[Problems to be solved by the invention]

However, the T / L VTR has a problem that a satisfactory image cannot be reproduced because a part of the screen information recorded last time is lost each time a new recording is performed.

For example, if continuous recording in the 2H mode has a portion that has disappeared due to overwriting for one second, in intermittent feed recording in the 960H mode, the erased portion can be as long as eight minutes.

The present invention has been made in order to solve the above-described problems, and the previous recorded portion and the current recorded portion do not overlap, and an unrecorded portion generated between the previous recorded portion and the current recorded portion is not removed. The aim is to obtain a minimal T / L VTR.

[Means for solving the problem]

The present invention rewinds and stops the magnetic tape by a predetermined length when recording is stopped, and when the recording is resumed, the magnetic tape is fed forward by the length necessary to remove the slack of the magnetic tape. Detecting the feed length and starting the search for the CTL signal, either when the CTL signal is no longer detected, or when the forward feed length of the tape slightly exceeds the rewind length from when recording is resumed, A means for restarting recording at an earlier time is provided.

[Action]

According to the present invention, the position at which recording is resumed is from the previous recording stop position or a position slightly beyond the previous recording stop position, so that overwriting is not performed, Frame drop recording can be performed only by leaving a short unrecorded portion between the recorded portions.

(Example of the invention)

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

The difference of this embodiment from the conventional example is that the sequence control means of the capstan motor in the process of once stopping from the recording state and then starting recording again is partially changed.

FIG. 1 is a diagram for explaining a driving state of a magnetic tape according to this embodiment. The magnetic tape and the CTL head are temporarily stopped when recording is performed, and then when recording is started again. The relative position is schematically shown.

 Hereinafter, the operation of this embodiment will be described.

When a stop is instructed at the position shown in FIG. 1A while recording is performed on the magnetic tape 3, the magnetic tape 3 is moved in the reverse direction as shown in FIG. 1B. It stops at the position where it has been rewound by length s from left to right in the figure.

Next, when the restart of the recording operation is instructed, the magnetic tape (3) moves in the forward direction (right to left in the figure).
The search for the CTL signal (16) is started from the position shown in FIG. 1 (c) sent by the length t necessary to remove the slack, and while the CTL signal (16) is detected, recording is started. The detection operation of the CTL signal is continued without shifting to the state, but as shown in FIG. 1 (d), when the CTL signal is no longer detected, the recording is started immediately. However, in FIG. 1C, the detection of the feed length of the tape is also performed together with the start of the search for the CTL signal, and the feed length in the forward direction including t in FIG. Even if the return length exceeds s, CTL
If a signal is detected, the recording is forcibly started from the position where the sum of the tape feed length u after the start of the search for the CTL signal and the tape feed length t slightly exceeds the rewind length s. Be started. This is because even if the detection of the CTL signal is continued for some reason, the current recording operation must be performed when the forward feed length u + t of the tape reaches a position slightly exceeding the rewind length s. It is to start. Eventually, the recording operation is restarted at the time when the CTL signal is no longer detected or when the forward length of the tape slightly exceeds the rewind length, whichever is earlier.

The length s of rewinding the magnetic tape (3) in the reverse direction in FIG. 1 (b) and the length t of the magnetic tape (3) fed in the forward direction in FIG. 1 (c) are set to have a relationship of s> t. Further, the tape feed length u from the start of the search for the CTL signal is set to have a relationship of (s−t) <u slightly longer than st.

FIG. 2 is a flowchart of this embodiment, FIG. 2 (a) is a flowchart when shifting from the recording state to the stop state, and FIG. 2 (b) is a flowchart when shifting from the stop state to the recording state again.

First, the flowchart of FIG. 2A will be described. When the stop instruction enters during recording, temporarily stopping the capstan motor in S _1. Next, returning only winding length s of the magnetic tape (3) in the opposite direction at S _2, stopping the capstan motor at the position S _3.

Next, the flowchart of FIG. 2B will be described. When recording command during stop state entering, by driving the capstan motor in S _4, to run the magnetic tape (3) in the forward direction. Next, in S _5, also began to search for CTL signal from the position sent by the tape length t, when it is no longer detected CTL signal recording is started at S _7. On the other hand, when the CTL signal has been detected, the tape feed length from the start of the search of the CTL signal S ₆ is determined whether exceeds u, CTL signal when the tape feeding length does not exceed u And the recording is started when the tape feed length exceeds u.

Such sequence control can be easily performed by a microcomputer.

〔The invention's effect〕

As described above, according to the present invention, when recording is stopped, the magnetic tape is rewound and stopped by a predetermined length, and when the recording is resumed, the magnetic tape is moved in the forward direction by a length necessary to take up the slack of the magnetic tape. When the CTL signal is no longer detected, or when the CTL signal is no longer detected, or when the recording is resumed, the tape's forward feed length is rewound. A control means is provided to restart recording at a time when the length is slightly exceeded or whichever is earlier, so that overwriting is not performed and the CTL signal erased part at the previous recording is detected. Even if the error is made, the current recording can be performed at a slight interval from the previous recording part.

[Brief description of the drawings]

FIG. 1 is a diagram showing the positional relationship between a magnetic tape and a CTL head for explaining the operation of one embodiment of the present invention, FIG. 2 is a flowchart of a drive control sequence for the magnetic tape of this embodiment, and FIG. FIG. 4 is a plan view showing a running system of a magnetic tape of a helical scan type VTR to which this embodiment and the conventional example are applied. FIG.
FIG. 5 is a schematic diagram for explaining a positional relationship between L signals, and FIG. 5 is a diagram showing a positional relationship between a magnetic tape and a CTL head for explaining an operation of a conventional control sequence. (3) Magnetic tape, (10) CTL head, (11)
…… Capstan, (15) …… Video signal recording track,
(16) Control signal. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] A means for rewinding and stopping the magnetic tape by a predetermined length when a stop command is received during recording, and for removing a slack in the magnetic tape when receiving a recording start command after stopping the recording. Means for detecting the forward feed length of the tape further from the point in time when the tape is forwarded by the necessary length, and generating an output when the forward feed length after the recording start command slightly exceeds the rewind length, A search for a control signal is started from the start of the detection operation of this means, and a means for generating an output when the control signal is no longer detected, and a video recording is started in response to the earlier output of the outputs of the two means. And a magnetic recording / reproducing apparatus.