JPH01158655A - Rotary head type magnetic picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To cancel a back tracking by detecting that it is a track recorded by another magnetic head at the time of reproduction, changing the speed of a magnetic speed by the signal and skipping automatically a tracking for one frame. CONSTITUTION:When it is detected that it is the back tracking by an identifica tion signal recorded on the tape at the time of recording by a detecting circuit 13, the acceleration command circuit 12 is activated by the signal, and accelera tion signal is outputted to a speed control circuit 3 and a capstan motor 1 is accelerated. The count values of an FG counter 9 to count the output of a frequency engine 2 and a timer counter 10 are compared with each other by a comparator 11, when their difference becomes an odd number times as much as a tape length necessary for recording a video signal of one frame, the circuit 12 is controlled and the acceleration is terminated. Thus, the back tracking state of a miniature cylinder type helical scan system VTR can be automatically canceled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a head cylinder in which four magnetic heads having different azimuth angles are arranged at equal intervals.
In the winding of 00, the magnetic tape is wound spirally at the corner and run, and one of the four magnetic heads of nIJ is sequentially selected every 3/4 rotation of the head cylinder to wrap the magnetic tape on the magnetic tape. This relates to a rotary head type magnetic recording and reproducing device (VTR) of a helical scan type called a small cylinder type that sequentially records and reproduces one field of video signal as one recording trajectory.In particular, during reproduction,
The present invention is characterized by a control system that controls the relative positional relationship between the magnetic head and the magnetic tape so that the magnetic head used during recording performs reproduction.

Conventional technology Figure 2a shows a conventional two-head helical power scan VTR.
The head cylinder is shown. A magnetic tape 1 is wound around a 180 degree range around the outer circumference of a cylinder 2, and a pair of heads A and B with different azimuth angles of plus and 6 degrees are used alternately to generate one field (one screen) of video signals. One recording trajectory A, , B1. A2. B2. A3・
... is recorded on the magnetic tape 1. Further, during recording, a signal of one frame period indicating the rotational phase of the magnetic head A is sequentially recorded by the control head 3 as a control signal C.

FIG. 2 shows a small cylinder type heli-power cylinder type VTR having tape compatibility with the heli-power cylinder type VTR described above. In order to maintain tape compatibility, it is necessary to accurately match each other's recording track length 10 and inclination angle θ, so the diameter of the cylinder 5 is set to 2.
% of the head cylinder of a head type VTR, and four heads A, B, A', and B' with alternating azimuth angles are placed at 90 degree intervals on the circumference. It is placed. The tape 4 is wound around the outer circumference of the cylinder 5, that is, within a range of 270 degrees, so that the track length 10 is equal to 11, and θ. The running angle is determined so that θ1 is equal to θ1, and the tape is run at the same speed as the tape speed of a two-head type VTR.

When the cylinder 6 is rotated 46 times per second (in the case of NTSC system) and one field of video is recorded on one track, four heads run on the tape in the order of A, B, A', and B'. However, just before the head B records track A1 and finishes running on the tape, the B head has already arrived at the starting point and records the next track B1. Then, the A' head records track A2, and then the B' head records track B2. At this time, the control signal (C
TL) is recorded at a rate of one period for tracks A1 and B1, and one period for tracks A2 and B2. That is, signals indicating the rotational phases of the heads A and A' are alternately recorded on the tape as control signals, making it possible to draw the same recording locus on the tape as with a two-head type VTR.

Problems to be Solved by the Invention When a tape recorded using four heads in this manner is played back using the above playback method, it is impossible to distinguish between the trunk recorded on the A head and the track recorded on the A' head. ,
Track f recorded by head A: A phenomenon in which the track is reproduced by head A' (hereinafter referred to as back tracking) occurs with a probability of %. In this case, there is no problem because the azimuth angles match, but if there is eccentricity of the cylinder, the jitter component increases, resulting in an unsightly screen.

In order to reliably play back the recorded head, it is necessary to use some method during recording to separate the frames recorded by the A and B heads from the A.
By recording on the tape a signal that distinguishes the frames recorded by the ', B' heads, it is possible to determine whether or not the recording head is being used for reproduction during playback. As the above method, a method has been proposed in which the duty of the control signal is changed every frame.

However, even if the discrimination can be made, in order to extract from the back tracking, it is necessary to accelerate or decelerate the capstan and skip one frame.

However, conventionally there was no way to reliably skip one frame. The present invention is intended to solve these conventional problems and to provide a means that can reliably skip one frame from back tracking.

Means for Solving the Problems In order to solve the above problems, the rotating head type magnetic recording and reproducing apparatus of the present invention includes means for detecting that a trunk recorded by another magnetic head is being played back during playback. , a speed converting means for changing the speed of the 11J magnetic tape from the standard speed according to the detection signal, and a first counting means for counting a first count value according to the traveling distance of the magnetic tape during the speed change period; A second counting means that counts a second count value according to the passage of time during the MiJ gear shift period, and compares the first count value and the second count value, and the difference is determined in advance. The magnetic tape has means for stopping the operation of the speed converting means when the speed reaches the standard speed.

Effect According to the above configuration, the time to move the magnetic tape corresponding to n frames at standard speed is (n+1) or (n-1).
Since the magnetic tape can be moved by a frame, tracking can be automatically skipped by one frame.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a capstan motor control device according to an embodiment of the present invention, in which 1 is a capstan motor, and the well-known speed control is performed by the output of a frequency generator 2 that generates pulses with a frequency corresponding to the rotation speed of the capstan motor. By driving the circuit 3 and driving the motor drive circuit 7 via the mixing circuit 6, the motor 1 is rotated at a predetermined speed.

On the other hand, the phase comparator 5 outputs the reproduction control signal of the control head) and the output of the head switching pulse generator 8 based on the rotational phase of the rotary head cylinder.
A signal based on the phase difference is applied to the mixing circuit 6, and the phase of the capstan motor 1 is controlled to maintain a predetermined phase relationship between the reproduction control signal and the rotary head. It is configured like this.

The above is the same configuration as a conventional VTR of this type, and
The difference from TR is that a detection circuit 13 for detecting a back tracking state is provided in the conventional control system, and this detection signal drives an acceleration command circuit 12 and applies an acceleration signal to the speed control circuit 3. The comparator 11 compares the counts of the FG counter 9, which counts the output of the frequency generator 2, and the timer counter 1Q, and the comparator 11 accelerates the capstan motor 1. The present invention is configured to control the acceleration command circuit 12 to terminate the acceleration when the acceleration occurs.

To explain the operation in detail, when the detection circuit 13 determines that the back tracking state is present and a command signal a to start acceleration is input to the acceleration command circuit 12, the speed control circuit 3 operates to start acceleration. . At the same time, iJkiF
A Ci counter 9 and a timer counter 1o for counting stable lock signals are set together, and the counts of the FG counter 9 and timer counter 10 are input to a comparator 11 and compared. To change from the back tracking state to the normal tracking state, the capstan must be accelerated or decelerated during playback at the standard tape speed (back tracking state). After playing the tape longer or shorter by an odd multiple of the tape length a necessary for recording the signal, it is sufficient to return to the original standard tape speed.

In other words, if the frequency generator 2 is configured to generate FG pulses while driving a tape with tape length l for one frame, then ±(2m-1)X FG pulses are generated during the speed change period.
The speed change period may be controlled so that the count value is greater (or less) by the FG parnu number k than the count value due to running at a normal standard tape speed. For this purpose, the frequency of the clock signal is configured to generate pulses in one frame period, and the count value of the timer counter 10 during the speed change period and the FG
If the time when the difference in the counter count value becomes (2m - j) can be returned to.

Therefore, the comparator 11 has both counters 9.10
The configuration may be such that the acceleration command circuit 12 is controlled to stop acceleration when the counted value of .+-.(2m-1)Xk. However, if you end the acceleration at the moment when you have skipped an odd number of frames, there is a risk that it will go too far before decelerating and returning to the steady state, so ±(2tn-1)Xk
It needs to be a little less than that. This value is the VT
The optimum value may be selected depending on the R mechanism, speed change speed, etc. Further, in order to prevent damage to the tape due to malfunction due to some abnormality, etc., it is preferable to set the maximum value in the timer counter 10, and to terminate the acceleration when the maximum value is reached.

Effects of the Invention As described above, the rotating head type magnetic recording and reproducing apparatus of the present invention can automatically shift from the back tracking state to the normal tracking state quickly, and can cancel the back tracking of a small cylinder type helical force run-can type VTR. It is valid for

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of a rotary head type magnetic recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 2a is a block diagram of main parts. b is a 2-head helical scan type VTR1.
... Capstan motor, 2 ... Frequency generator, 3 ... Speed control circuit, 9 ... FG
Cow/re, 10... Tire counter, 11.
... Comparator, 12 ... Acceleration command circuit, 13 ... Both side output circuits. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
--Punutan motor at the temple Figure 1

Claims (1)

[Claims] Four magnetic heads with different azimuth angles alternately wrap a magnetic tape in a helical manner along head cylinders arranged at equal intervals, and run the magnetic tape in a spiral manner.
One of the four magnetic heads is sequentially selected every /4 rotation to sequentially record and reproduce video signals on the magnetic tape so that one field of video signal forms one recording locus, and at the time of recording, A one-frame period phase signal indicating the rotational phase of the head cylinder is recorded on the magnetic tape as a control signal, and the capping is performed so that the rotational phase and the reproduced control signal maintain a predetermined phase relationship during reproduction. A rotary head type magnetic recording and reproducing apparatus that controls a stun motor, the apparatus comprising a detecting means for detecting that a track recorded by another magnetic head is being reproduced during playback, and a detection signal from the detecting means for detecting the speed of the magnetic tape. a speed converting means for changing the speed from a standard speed; and a first speed converting means for changing the speed from a standard speed,
a first counting means for counting a count value, a second counting means for counting a second count value according to the passage of time during the shift period, and a second count means for counting the first count value and the second count value. A rotary head type magnetic recording and reproducing apparatus characterized in that the rotary head type magnetic recording and reproducing apparatus has a means for stopping the operation of the speed converting means and returning the magnetic tape to the standard speed when the difference reaches a predetermined value. .