JPS6276377A - Special reproducing device - Google Patents

Abstract

PURPOSE:To perform a special reproduction without providing a noise band by controlling only one V of tracking at every lXn cycle of Vs, storing a reproducing signal with the k-fold cycle of a control cycle and reproducing a picture in a reproduction at the speed of m/n of a recording time. CONSTITUTION:When a reproducing operation in a 1/2 slow reproduction is performed, the setting value of a speed control loop that controls the speed of a capstan motor 28 is set at 1/2 of the recording time and a tape speed is set at 1/2. And a reference signal R is given intermittently at every two Vs to perform the tracking. A given cycle becomes double of a normal reproducing time and according to that, the cycle of a polarity inversion command signal PR is made as the double, two Vs, of the normal reproducing time, consolidating the polarity of a tracking error signal. By the control of the tracking error signal, a reproducing signal PO that fluctuates in four V cycles can be obtained. A video signal generated from the reproducing signal PO with a video signal reproducing signal 16 is written n an internal memory in a storing and reading circuit 17 according to a write command signal, and it is read sequentially according to a picture scanning and is generated as an output video signal V.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a special playback device for a video tape recorder that uses a pilot method as a tracking method.

[Technical background of the invention]

Helical scan video tape recorder (hereinafter referred to as V
(referred to as TR), various special playback devices have been proposed that play back images at a tape speed different from that at the time of recording.

[Problems with background technology]

However, in special playback, as mentioned above, the magnetic tape is transported at a different speed than during recording, so the rotating head is moved at a different speed than during recording.

Noise bands will appear on the playback screen.

[Purpose of the invention]

The present invention has been made to address the above-mentioned circumstances, and its purpose is to provide a special playback device that can perform special playback without generating noise bands on the playback screen.

[Summary of the invention]

In order to achieve the above object, the present invention provides −(m
= 1 and n is an integer of 2 or more or m.

n is a relatively prime integer and m≧2. When playing at a speed of n≧1), 1 for every tXnV (t is a positive integer)
In addition to controlling the tiger and king by v, the reproduced video signal during tiger and king control is stored at a period k (k is a positive integer) times the tiger and king control period, and the image is generated based on this stored signal. It is designed to play.

[Embodiments of the invention]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings, but first, the present invention will be described in detail.

Generally, if a magnetic tape is transported at a recording speed of 1 (n is a positive integer of 2 or more), the relative relationship between the head locus and the recording track is determined by the period at which the rotating head scans the track (hereinafter referred to as IV). ) is repeated at a period n times larger than Therefore, if tracking control is performed by 1v for every nV,
At 1v, the head can be brought into almost a suitable tracking state (the state in which the head is on the track, hereinafter referred to as on-track). However, since the tape speed is different from that during recording, the head trajectory is slightly tilted with respect to the track.

By the way, in the tiger/king method using the pyro/g signal, it is easy to perform the tiger/king control by 1v for every nV as described above. Therefore, in pilot-type video tape recorders, during slow playback,
1 obtained from the on-track timing that appears every nv
By storing the field video signal and reading it at a timing when the rotary head is not on track, a reproduced image without noise bands can be obtained.

However, if so-called azimuth recording is performed, in which each track is recorded at a different azimuth, 1 (
When the video signal is played back at a speed of n (n is a positive integer), the video signal is on track, but the video signal is not played back every other time because the azimuth between the rotating head and the track is different.

Therefore, in the case of the azimuth recording method, it is sufficient to store the video signal at the timing that matches the anomalous signal. Note that the pilot signal is a low frequency signal, so
Tracking control can be performed regardless of anomalousness. Also, it is not necessary to memorize all of the noise-free video signals obtained in the above manner, but once every few times.
It is also possible to store the number of times.

It is also clear that the tracking may be controlled not at 1v at every nV but at 12 at every tXnV (t is a positive integer).

Furthermore, in general, if the tape is fed nine times at a speed of - (m, n are mutually prime integers, m≧2sn≧2) during recording, the relative relationship between the head trajectory and the recording track is such that the rotary head tracks the is repeated at a period n times the scanning 1v, so if tracking control is performed by 1v every nV,
Similarly to the above, a special playback screen without noise bands can be obtained. In this case as well, the tiger and king control may be performed only for a 1v period for every t x n v instead of for a 1v period for every nV.

In summary, the present invention provides the following advantages: when reproducing at a recording speed of -(mm = 1 and n is an integer of 2 or more or man is a relatively prime integer and m≧2.n≧1),
Tracking is controlled by 1v every tXnV (t is a positive integer), and k(
The reproduction video signal at the time of tiger and king control is stored at a period of (k is a positive integer) times, and an image is reproduced based on this stored signal.

Now, one embodiment will be described in detail with reference to the drawings. 1st
The figure is a block diagram showing the configuration of one embodiment. In the following description, a case where the present invention is applied to a so-called 8 mm VTR will be described as a representative example.

Now, the frequencies of the four pilot signals P are respectively f,
If f, , fs , f, then in 8mVTR,
These four frequencies f□ e Z kura efs=fa are f□−ft t =f s f −=fm ・・
・(1) f4 f□= f s - f * = 3fu
(2) However, fH: is set to satisfy the horizontal scanning frequency. Specifically, f l
”; 6.5 fm e-f z #7.
5 fII# fg #, 10.5 fHsf4
#9.5 Selected as fH.

The four pilot signals P having the above frequencies are applied to each video track 2 of the magnetic tape 1, as shown in FIG.
are recorded cyclically, one by one. Here, the frequency f
The 1-fs pyro signal P is recorded at ■azimuth,
It is assumed that the pilot signal P of frequency f*-fa is recorded at e azimuth. Also %X,,X.

denote the tape running direction and head scanning direction, respectively.

First, the reproduction operation during normal reproduction (reproduction at the same speed as during recording) will be explained with reference to FIG. Signals reproduced by heads 11 and 12 which are rotationally driven in a helical scanning manner are applied to a selector switch 15 via rotary transformers 13 and 14, respectively. Then, the switch 15 generates a continuous signal according to the head switch and the clock pulse Ps indicating the rotational phase of the heads 11 and 12.

The azimuths of rotation and de 11 and 12 are ■ and e”t, respectively.
', sb, head switching/4' Russ P Maro and rotation during playback, azimuth e of de 11, 12.

The relationship of e is as shown in FIG.

The reproduction output made continuous by the switch 15 is given to the video signal reproduction circuit 16 and the pandox filter BPF l &. The bandpass filter 18 extracts the pyro signal P included in the reproduced output and supplies it to the multiplier 19. The multiplier 19 multiplies the reproduced output of the noquilot signal P by the reference signal R in synchronization with the rotation and switching of the dots 11 and 12. The frequency of the reference signal R changes in synchronization with the switching of the rotary heads 11 and 12, fl-4f-→f3→f4→f,...
You can see the changes in the order of ・. As a result, the frequency fHe
The difference frequency signals of 3f11 are each passed through a bandpass filter B.
It is extracted at PF 20 and 21. These difference frequency signals are each subjected to level detection by level detection circuits 22 and 23, and a signal indicating the level difference between the two is outputted from the differential amplifier circuit 24. This signal is connected to the polarity inverting circuit 25 and the switch 26.
The polarity is unified for each track, and is output as a tracking error signal indicating the tracking deviation of the rotary head 11, 12.

Note that the signal selection operation of the switch 26 is controlled by a polarity inversion command signal Pa (polarity inversion at high level).

At the time of recording, the capstan motor 28 is controlled to the same speed as during recording by a speed control loop composed of a motor speed detector 291, a frequency dividing circuit 301, and a frequency discriminator 31. Therefore, by adding the tracking error signal to this loop via the adder 27, tracking can be performed.

At this time, the relationship between the trajectory of F and C and the trajectory of F and R is as shown in FIG. FIG. 3 is a diagram in which the relationship between the head trajectory (indicated by a broken line) and the track is developed with the horizontal axis as the time axis t.

As shown in FIG. A noise-free reproduced video signal vo is obtained. Therefore, at this time, the memory readout circuit 17
is not used, and image reproduction is performed according to the reproduction video signal vo.

Next, the reproduction operation when performing slow-motion reproduction will be explained with reference to FIG. First, the setting value of the speed control loop that controls the speed of the cab/stun motor 28 is set as the recording speed, and the tape speed is set as the setting value. In order to perform tiger and king control every 1V, a reference signal R is intermittently applied as shown in FIG. The order of giving is the same as during normal playback, f1 → f, → f, → f4 → f8, etc.
The cycle is twice that of normal playback. Accordingly, the period of the polarity reversal command signal P is also set to 2V, twice that of normal reproduction, and the polarities of the tiger and king error signals are unified.

If tracking and king control is performed using the tracking error signal obtained as described above, the head trajectory will become as shown in FIG. 4, and a reproduced signal PO that fluctuates at a period of 4V will be obtained.

Therefore, if this reproduction signal PO is made into a video signal by the video signal reproduction circuit 16, it is written into the internal memory of the storage/readout circuit 17 according to the write command signal PW, and this is sequentially read out according to image scanning to obtain the output video signal V. , a 1-hour slow playback image without noise bands can be obtained.

In general, in slow playback at 2P (P is a positive integer) double speed, one of the tracking control timings is as described above.
A good reproduced signal can be obtained every time. This is because the azimuth of the reproducing head and the on-track azimuth are different for every other azimuth. Therefore, in this case, 2n
The video signal vo may be written in V cycles. Further, tracking control may also be performed at this cycle.

Furthermore, the reproduction operation when performing one slow motion reproduction will be explained with reference to FIG.

In this case, the tape speed is set to 1, the reference signal R is intermittently applied at a cycle three times that of normal playback, and the polarity inversion signal PR is also set at a cycle three times that of normal playback, as shown in FIG. Take control. At this time, the head trajectory becomes as shown in FIG. 5, and a reproduced signal Po that fluctuates at a period of 3V is obtained. If the reproduced video signal vot obtained from this - the write command signal PQl shown in FIG. You can get the image.

Note that the write command signal PW may be set to Pw(2) (see FIG. 5), and the write timing may be thinned out to 1.

Similarly, during slow motion playback of 1 (n is an integer of 2 or more), for example, by performing nV same-cycle tracking control and writing the playback video signal Po at the timing when the tracking control is performed, the noise band is Although we have described slow playback above, it is also possible to obtain a playback image without noise bands in double speed playback, although we will omit detailed explanations.

As an example of double speed playback, Figure 6 shows double speed playback,
Figure 2g7 shows double speed playback. Further, FIG. 8 shows head trajectories in various special reproductions with arrows.

〔Effect of the invention〕

According to the special playback device of the present invention, special playback can be performed without generating noise bands on the playback screen.

[Brief explanation of drawings]

FIG. 1 is a professional diagram showing the configuration of one embodiment of the present invention.
Figures 2 to 7 are diagrams for explaining the operation of Figure 1;
FIG. 8 is a diagram showing the head trajectory during special playback. DESCRIPTION OF SYMBOLS 1... Magnetic tape, 2... Video track, 11°12... Rotating head, 13.14... Rotary transformer, 15.26... Switch, 16... Video signal reproducing circuit, 17 ...Memory readout circuit, 18°20.
21... Band pass filter, 19... Multiplier, 2
2.23... Level detection circuit, 24... Differential amplifier circuit, 25... Polarity inversion circuit, 27... Adder 31, 2
8... Cab stan motor, 29... Motor speed detector, 30... Branch circuit, 31... Frequency discriminator. Applicant's agent Patent attorney Suzue Takehiko□t T Zias ■ ○ ■ e ■
○ ■ e ■ eFigure 4

Claims (1)

[Scope of Claim] A video tape recorder that controls tracking of a rotary head according to the playback output of a plurality of pilot signals having different frequencies that are cyclically recorded one by one on a video track, m/n (m = 1 and n is an integer of 2 or more, or m, n is an integer that is relatively prime and m≧2,
a tape transport means for transporting the tape at a speed of n≧1); and a tape transport means for transporting the tape at a speed of n≧1); a tracking control means for controlling the tracking of the rotary head according to the playback output; a storage means for storing a video signal during tracking control at a period k (k is a positive integer) times the tracking control period; 1. A special playback device comprising: image playback means for playing back an image using a video signal stored in the image.