JPS58212647A - Video tape recorder - Google Patents

Abstract

PURPOSE:To prevent the generation of a noise bar on a reproduced picture and to obtain a fine picture by synchronizing the timing to switch a reproducing mode with a head switching pulse for a rotary head at prescribed width. CONSTITUTION:An output signal (d) of a mode alteration switch 11 is inputted to a timing circuit 14. A head switching pulse (c) to indicate head switching and turning position is inputted to a frequency dividing circuit 16 and the timing circuit 14. The output of the frequency dividing circuit 16 is inputted to a delay circuit 17 of which delay width can be changed and the output of the delay circuit 17 is supplied to a capstan controlling circuit 6 and the timing circuit 14. The output of the timing circuit 14 is inputted to a delay circuit 18 of which delay width can be changed and an output signal from the delay circuit 18 is inputted to the capstan controlling circuit 6 and a capstan motor braking circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a helical scan type video tape recorder (hereinafter abbreviated as VTR), which has a simple configuration and can provide good slow motion playback images. be.

As is well known, helical and scan type VTRs [stop, move, stop, move...
By repeating . . . , a slow motion playback image can be obtained. However, since the scanning trajectory of the rotating head on the magnetic tape when the tape is stopped is different from the recording trajectory, it is not possible to accurately scan one recording trajectory.
As a result, a period in which the reproduced signal level is decreased occurs.

If this period in which the reproduced signal level is reduced is located near the vertical synchronizing signal, a good image can be obtained without substantially generating noise bars on the television receiver.

As described above, in order to obtain a good slow motion reproduction image by repeatedly stopping and moving the magnetic tape, it is possible to obtain by optimizing the timing of stopping and the timing of movement.

However, when switching from normal playback to slow-motion playback, or from slow-motion playback to normal playback, the switch occurs the moment you press the conventional playback mode switch, so a noise bar will appear on the playback screen at the time of the switch. There is a problem that a good image cannot be obtained.

According to the present invention, when switching the playback mode, the timing at which the playback mode is actually switched is determined based on the signal from the playback mode changeover switch using a head-switching pulse of the rotary head at a timing at which no noise bar is generated on the playback screen. It is composed of

The present invention will be explained below based on the illustrated embodiments. In FIG. be done. 4 is an FC and head that detects a pulse signal with a period corresponding to the rotational speed of the capstan motor 2, that is, a rotational speed signal, and its output is amplified by an amplifier 6 and sent to the capstan and control circuit 6.
is input. Reference numeral 7 indicates a control head which is recorded at intervals of one frame during recording. The signal is input to a delay circuit 9 whose width can be changed.

The output signal of the delay circuit 9 is input to the capstan motor brake circuit 1o.

Reference numeral 11 denotes a playback mode changeover switch, which can be switched by the user to either the normal playback side 120 or the slow motion playback side 13. The output signal d of the mode changeover switch 11 is input to the timing circuit 14. Reference numeral 16 denotes an input terminal for a head switching pulse C that indicates head switching and rotational phase of two rotating magnetic heads (not shown) attached to a known rotating head cylinder (not shown), and is connected to the frequency dividing circuit 16 and The signal is input to the timing circuit 14. The output of the frequency dividing circuit 16 is input to a delay circuit 17 whose delay width can be changed, and its output is supplied to the capstan control circuit 6 and the timing circuit 14. The output of the timing circuit 14 is a delay circuit N1 whose delay width can be changed.
8, and the output signal of the delay circuit 18 is input to the capstan control circuit 6 and also to the capstan motor brake circuit 1o.

The six capstan control circuits are configured to control the speed of the capstan motor 2 according to the signal from the FG head 4, and to control the phase of the capstan motor 2 according to the control signal reproduced by the control head 7. .

The capstan motor brake circuit 1o includes a control signal delay circuit 9 and a mode switching signal delay circuit 18.
In response to the output signal, a brake signal of a predetermined width is applied to the capstan motor 2 to stop the capstan motor 2.
is configured to apply.

Next, the operation of the embodiment of the present invention when switching from normal playback to slow motion playback and from slow motion playback to normal playback will be described with reference to FIGS. 2 and 3.

In FIG. 2, (a) 2-head helical scan V
It shows the state in which the recording tracks of the TR are repeatedly arranged, and each scale on the horizontal axis indicates the time of one field, and also indicates the timing of the head changeover switch. The vertical axis shows the range of chip movement, and each scale indicates how much the tape runs in one frame time during recording or normal playback.

At the same time, each division represents the recording track width. The head gap angles of the two video heads are slightly different, resulting in azimuth recording.

Therefore, in the recording trunk pattern of FIG.
Trunks recorded by the A head are represented by odd numbers, and tracks recorded by the B head are represented by even numbers. Odd-numbered tracks can only be played back by the A-head, and even-numbered trunks can only be played back by the B-head.

The thick line in FIG. 2 (2L) represents the head movement when switching from normal playback to slow motion playback with the configuration of the present invention, and the broken line represents the head movement when switching from conventional normal playback to slow motion playback. It shows head 1 and 1 traces.

3) are respective reproduction envelope waveforms. The head switching pulse C is shown in FIG. 2(C). As described above, since azimuth recording is performed, only odd-numbered trunks can be reproduced in the A head during the high (H) level period of the head switching pulse C, and only even-numbered trunks can be reproduced in the B head during the low (L) level period.

FIG. 2(d) shows the playback mode selector switch 11 in FIG.
This is the output signal of
By operating 1, you can, for example, set high (H) during normal playback.
) level (low motion playback) Obtain a signal called low (L) level. Conventionally, slow-motion playback was performed from normal playback to static mode based on the signal d determined by the user's operation timing, resulting in the trajectory shown by the broken line in Fig. Figure 2(e) shows the output signal of the timing circuit 14 in Figure 1, and shows the output signal of the timing circuit 14 in Figure 1. Even if the playback mode changeover switch 14 is changed at the timing, the output signal e of the timing circuit 14 is not changed to the head switching pulse C shown in FIG. 2(C).
It is configured to synchronize with the falling edge of

Output signal e of the timing circuit 14 [see Fig. 2 (8)]
is delayed by the delay circuit 18 as shown in FIG. 2(f). The fall of the output signal f of the delay circuit 18 becomes the timing for the capstan motor 2 to start braking.
At this timing, the capstan motor brake circuit 10 outputs a brake signal k shown in FIG. 2(k) to stop the capstan motor 2.

FIG. 2(g) shows the output signal of the frequency dividing circuit 16 of FIG. 1, and the head switching ζ pulse C shown in FIG. 2(C)
is divided by h, and for slow motion playback, the frequency is divided by h.
Becomes speed. Note that if you want to change the slow motion playback speed, you can change the frequency division ratio of the frequency divider circuit 16.

FIG. 2(h) shows the waveform of the output signal g of the delay circuit 17 of FIG. 1, and the output signal g of the frequency dividing circuit 16 shown in FIG. 2(g) is delayed. The rise of the output signal of this delay circuit 17 becomes the timing of acceleration in slow motion reproduction.

FIG. 2(i) shows a control signal obtained from the control head 7, and this control signal i is, for example, the lower end of the head trace in FIG. 2(a) at the center of each frame on the vertical axis (0, 5, 1, 6, 2, 5, etc.) is played.

This control signal i is amplified by an amplifier 8 and input to a delay circuit 9, resulting in a waveform shown in FIG. 2 (0). - The falling edge of signal j delayed from control signal i becomes the timing of deceleration in slow motion playback,
From this timing, capstan motor brake circuit 1
0 outputs the brake signal k shown in FIG. 2 (6) to stop the capstan motor 2.

Similarly, the capstan motor 2 starts moving the magnetic motor 1 at the rising edge of the 11- signal obtained by dividing and delaying the bed switching pulse c'1, and transmits the control signal 1. By repeating the movement and stopping of stopping and starting at the falling edge of the delayed signal, you can slow down from normal playback without generating noise bars.
Motion playback can be performed.

As another configuration example, the capstan motor 2 may be stopped not at the timing when the head switching pulse is delayed but at the timing when the first reproduction control signal after switching the reproduction mode is delayed.

Next, the operation of the embodiment of the present invention when switching from slow motion playback to normal playback will be explained with reference to FIG.

In FIG. 3, (a) shows a state in which the recording track pattern is repeatedly arranged as in FIG. The dashed line represents the head impression when switching from conventional slow-mo playback to normal playback.

FIG. 3(b) shows the respective reproduction envelope waveforms.

FIG. 3(C) shows a head switching pulse.

FIG. 3(d) shows the output signal of the playback mode selector switch 11 shown in FIG. When the playback is switched to the normal playback, the head ejection trace is shown by the broken line in FIG. 3(a) and the playback envelope is shown by the broken line in FIG. 3(b). Depending on the timing of switching the playback mode, the playback envelope may further decrease, and the control pull-in time also varies depending on the control characteristics of the capstan control circuit 6, making it difficult to obtain a good playback image. .

FIG. 3(8) is an output signal of the timing circuit 14 of FIG. 1, which synchronizes the switching timing from slow motion playback to normal playback with the falling edge of the head switching pulse.

There is a signal f in which the waveform of FIG. 3 (6) is delayed, and this signal f is manually input to the capstan control circuit 6.
The rising timing is the acceleration timing for switching to normal reproduction, and the reproduction envelope becomes the solid line in FIG. 3(b), which is always good.

Thereafter, during the period in which the output signal f of the delay circuit 18 is at a high (H) level, the normal reproduction mode is set, and since it is not necessary for the brake signal of the capstan motor brake circuit 1o, it is configured to be prohibited.

FIG. 3(g) is a waveform obtained by frequency-dividing the head switching pulse C of FIG. 3(0) by four, and is delayed by the delay circuit 17 to become the waveform shown in FIG. 3(middle). As described above, the rising edge of the signal waveform (in FIG. 3) is the timing of acceleration in slow motion playback. During slow motion playback, there is a moving period and a stopping period of the magnetic tape, so by inputting this signal to the timing [1M14, the output signal e of the timing circuit 14 is set during the magnetic tape stopping period and at the rising edge of the head switching pulse C. It can be configured to coincide with the falling timing.

In addition, as another configuration, the output signal of the timing circuit 14 may be synchronized with the rise or fall of the head switching pulse during the movement period during slow motion reproduction.

3(i) shows the control signal reproduced from the control head 7, and FIG. 3(0) shows the output signal of the delay circuit 9 which delays the control signal. Delay circuits 9.1 and 18 in Fig. 1 are for obtaining the acceleration or deceleration timing of the capstan motor 2, respectively, and the delay time is optimized depending on the inertia moment of the capstan motor, starting torque, etc. Since the delay times are different, the optimum time can be set according to the motor specifications of the capstan motor 2.

Further, in the present invention, in order to improve the reproduction envelope when switching from normal reproduction to slow motion reproduction or vice versa, the track width of the recording/reproducing rotary magnetic head may be made wider than the recording track width.

As is clear from the above description, the present invention has a simple configuration and eliminates the noise bar, which greatly degrades the quality of the playback screen when switching between normal playback and slow motion playback, by always keeping the playback mode switching timing constant. This is an excellent feature of obtaining a good playback screen with no visible blemishes. As is clear from the above explanation, the playback mode cannot be changed even when switching from normal playback to static playback, static playback to normal playback, reverse 1x speed playback to static playback, static playback to reverse 1x speed playback, etc. It goes without saying that the same effect can be obtained by keeping the timing constant.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts showing one embodiment of the present invention;
3 and 3 are diagrams showing head ejection traces, envelope waveforms, and main signal waveforms when switching from normal playback to slow motion playback and vice versa in the embodiment of the present invention. 1...magnetic tape, 2...capstan motor, 2'&...capstan, 3...mark pinch roller, 4...FG head, 6...・・・・・・
Capstan control circuit, 7... To control, 7)", 9, 17.18... Delay circuit, 1
0... Capstan motor brake circuit, 11
......Playback mode selector switch, 14...
- Timing circuit, 16... Head switching pulse input terminal, 16... Frequency dividing circuit. Name of agent: Patent attorney Toshio Nakao and one other person
ゝ5 +−ゝ−

Claims (2)

[Claims] (1) It is configured to perform slow motion playback by repeatedly stopping and moving the magnetic tape. and a magnetic tape running means for intermittently moving the magnetic tape including a capstan motor and a vinyl roller, a braking means for applying a brake to the capstan motor to stop it, and switching between normal playback and slow motion playback. 1. A video tape recorder comprising: a reproduction mode switching means; and a timing processing means for receiving an output signal of the reproduction mode switching means and controlling the magnetic tape running means at a predetermined timing. (2) The video tape recorder according to claim (1), wherein the timing processing means is configured to synchronize with a head switching pulse of the rotary head at a predetermined width.