JPS61206953A - Method and device for discriminating speed of recording in magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To discriminate discordance of reproducing speed and recording speed automatically by utilizing drop-out signals that are generated when reproduction in which reproducing speed does not coincide with recording speed is going to be made. CONSTITUTION:Either of pairs of video heads 1a, 1b or 1c, 1d are connected to a head amplifier through reproduction head changing switches 2a, 2b corresponding to a reproduction mode. Pairs of video heads 1a, 1b or 1c, 1d are switched alternately synchronized with head switching pulse and pick up reproduction signals from a magnetic tape VT. The reproduction signals are amplified by a head amplifier 3 and outputted from the head amplifier 3 as reproduction output (RF output). A drop-out signal DP is inputted to a discriminating device 5, and discriminated whether it is a drop-out signal DP corresponding to drop-out of RF output generated by discordance of recording speed with the speed of presently executed reproduction.

Description

Detailed Description of the Invention "Field of Industrial Application" This invention provides a method for reproducing a recording on a magnetic tape written at two tape speeds, when the tape speed (recording speed) at the time of recording is The present invention relates to a method and apparatus for determining a recording speed in a magnetic recording/reproducing apparatus, which automatically determines whether the speed is different from the tape speed (reproducing speed) during reproduction.

"Prior Art" and "Problems to be Solved by the Present Invention" For example, in a four-head azimuth recording section type helical scan video tape recorder, FIGS.
), four different frequencies are recorded on the magnetic tape vT.
Two tracking pilot signals fl- and f4 are combined with an FM luminance signal and recorded for each track. When the recording speed is high, the track pitch W becomes large as shown in FIG. 4(a), and when the recording speed is low, the track pitch W becomes small as shown in FIG. 4(b). In either case, the video head width T is usually about 1.5 times the video track width W.

However, for example, if there is a section recorded at a low speed in the middle of a magnetic tape vT that is being played back at a high speed, the track pitch W in that low speed recording section will change as shown in Fig. 2(a). On the other hand, the video head width T becomes about three times as large, and signals are picked up from two tracks and each part of the adjacent tracks on both sides thereof. On the other hand, if there is a part recorded at high speed in the middle of the magnetic tape VT being played back at low speed, the track pitch W in that high speed recording part will change as shown in Fig. 3(a). On the other hand, the video head width T is about 0.75 times larger, and one video head cannot pick up the signal of one field. In either case, in order to reproduce high-quality images, it is necessary to switch the playback mode according to the respective recording speed, such as by changing the playback speed, head switching, and output timing control of the playback image signal. There is.

Conventionally, the playback mode was set by manual operations such as operating a switch, or by using a control written on the tape to detect the recording speed, and then automatically switch the playback mode according to the results of this determination. etc. were proposed.

``Means for Solving the Problems'' This invention was devised in view of the above-mentioned circumstances, and when reproducing recordings on a magnetic tape written at two tape speeds, the recording speed is The object of the present invention is to provide a recording speed determination method in a magnetic recording/recording/reproducing main device that automatically determines whether the recording speed is different from the reproduction speed, and a magnetic recording/reproducing apparatus capable of implementing this method.

In order to solve the above-mentioned problems, the present invention (this method) is designed to solve the above-mentioned problem. Focusing on the occurrence of dropouts, a dropout signal is generated that is synchronized with the dropout of the playback signal during playback, and based on the period of this dropout signal, it is possible to determine whether the recording speed is inconsistent with the current playback speed. A technical measure has been taken to determine whether or not the two devices match, and to output a playback mode switching signal if they do not match.

In addition, in order to carry out the above method, a dropout signal generation means for detecting a dropout in a reproduced signal and generating a dropout signal synchronized with the dropout, and Determine whether the recording speed is inconsistent with the speed,
A device is used which includes a discriminator that outputs a reproduction mode switching signal when there is a mismatch.

The above-mentioned determining means needs to be configured to output a reproduction mode switching signal only when a dropout signal of a predetermined period, which occurs when the reproduction speed is inconsistent with the recording speed, is repeated.

Therefore, the discriminating means inputs the dropout signal,
In addition, a first retrigger mono multivibrator whose time constant is set to be shorter than the dropout signal period that occurs when the recording speed does not match the playback speed, and the output thereof are input, and the time constant is set to be shorter than the dropout signal period that occurs when the recording speed does not match the playback speed. The second retrigger mono multivibrator, which is set longer than the cycle, and the second retrigger mono multivibrator are
'', and a flip-flop circuit that is inverted and outputs a reproduction mode switching signal when the counter counts a predetermined number.

Further, the time constants of the first and second retrigger mono multi-bye breaks of the above-described discriminating means are configured to be alternately switched between high-speed playback and low-speed playback by the playback mode switching signal. As a result, the circuit configuration is simplified.

"Example" Hereinafter, the method and apparatus according to the present invention will be described based on the first aspect.
This will be explained in more detail.

FIG. 1 is a block diagram showing a circuit of a recording speed determination device for a four-head azimuth recording section type helical scan type video tape recorder according to the present invention.

This video tape recorder includes a pair of video heads la and lb for standard speed playback (high speed playback) and a pair of video heads lc for half speed playback (low speed playback).

1d, and either one of the pairs is selected via a switch (not shown) or automatically switched as described below, depending on the playback mode. video head 1a, 1b or lc
, ld are connected to the head amplifier 3. magnetic tape VT
The above recording shows that either pair of video heads la, l
b or IC, 1d. A pair of video heads la, lb or lc, ld are switched alternately in synchronization with the head switching pulse to pick up a playback signal from the magnetic tape VT, and this playback signal is amplified by the head amplifier 3 and output as a playback output ( It is output from the head amplifier 3 as an RF ratio output.

Therefore, when the playback speed and recording speed match, the video head alternately traces each video track accurately, as shown in FIG. 4(C).
) The RF ratio output corresponding to the recording of each video track is obtained alternately in synchronization with the switching pulse shown in FIG. 4 (ψ).

In contrast, while playing at high speed (standard speed), slow speed (half speed)
When the recorded portion is played back, each video head diagonally traces the two video tracks and the adjacent tracks on both sides, as shown in Figure 2(a).
While the other video head is reading the recording, the level of the signal it reads drops. Therefore, in this case, Figure 2 (
When the head switching pulse shown in (b) is (@■'' (or 6L'), the RF ratio output output level decreases, a so-called dropout occurs in two vertical synchronization periods (2V) [Figure 2 (C )].

Additionally, when a high-speed (standard-speed) recorded portion is played back during low-speed (half-speed) playback, the width T of the video head becomes 0.75 times the track width W, as shown in Figure 3 (Xu). , 2v
Diagonally crosses the boundary of the recording track once every period, and
Since the recording azimuth angle and the reproducing azimuth angle match only once every 4V period, the RJ' output is accompanied by a dropout that becomes 0 at four vertical synchronizations of the head switching pulses as shown in Figure 3 (6). Become.

In either case, the above-mentioned RF ratio output is input to the dropout signal generating means 4. This dropout signal generating means 4 generates a primary dropout pulse DP which becomes "EI" when the RF ratio output level is below a predetermined value.
The dropout pulse detection circuit 41 outputs a dropout pulse DP', and the waveform shaping circuit 42 shapes the primary dropout pulse DP' into a rectangular wave signal and outputs a dropout signal Dr.

Therefore, the dropout signal generating means 4 to which the above-mentioned RF multiplied signal is input generates a dropout signal D as shown in FIG. 4(e) when the playback speed and recording speed match.
If a low-speed recorded portion is being played back during high-speed playback, a dropout signal Dr with a 2V cycle is output as shown in the mountain in Figure 2 (see the mountain), and furthermore, during low-speed playback, a high-speed If the recorded portion is being played back, the third
As shown in figure (d), the dropout signal L with a 4V cycle
) P will be output.

The dropout signal DP obtained in this manner is input to the determination means 5 described below, and the dropout signal DP is inputted to the determination means 5, and the dropout signal DP is inputted to the determination means 5, and the dropout signal DP is inputted to the determination means 5.
It is determined whether the dropout signal DP corresponds to F ratio output dropout.

This discrimination means 5 inputs the dropout signal DP and connects it to a first retrigger mono multivibrator 51 having a time constant shorter than the cycle of the dropout signal generated due to the discrepancy between the playback speed and the recording speed. , a second retrigger mono-multivibrator 52 which receives the output of this as an input and has a time constant longer than the period of a dropout pulse generated due to a discrepancy between the playback speed and the recording speed, and a first retrigger mono-multivibrator. 51, and count the number of outputs of the second retrigger mono multivibrator 5.
A counter 53 that is reset when the output of No. 2 becomes a low value and outputs a count-up signal when the count reaches a predetermined value or more, and a flip-flop circuit 54 that is inverted by the count-up signal and outputs a reproduction mode switching signal. It is made up of.

For example, in order to determine the discrepancy between the playback speed and the recording speed during high-speed playback, the time constant of the first retrigger mono multivibrator is shorter than 2V, for example, as shown in FIG. 2(e). , is set to 1.5v. Therefore, if
If a dropout signal is input at a cycle shorter than this, the output of the first retrigger mono multivibrator 51 remains at t@H'', so the output of the second retrigger mono multivibrator 52 After the time corresponding to the time constant has elapsed, the output of the second retrigger mono-multivibrator 52 becomes "L", and therefore the counter 53 counts 1 based on the output of the first re-trigger mono-multivibrator 51. After that, the count is reset by stopping the output of the second retrigger mono multivibrator 52 without advancing the count.Also, the time constant of the second retrigger mono multivibrator 52 is set to be longer than 2V, e.g. If it is set to 2.5V, and a dropout pulse is input with a period longer than this, the signal output from the first retrigger mono multivibrator 51 will be Retrigger Mono Multi Pibrator 5
2, the output of the second retrigger mono multivibrator 52 becomes "L", so the counter 53
will repeat the count 1 and reset. However, when the dropout pulse is input at a 2v cycle, the output of the first retrigger mono multi-by-break 51 becomes a pulse signal that is on for 1.5v at a 2v cycle, as shown in FIG. 2(e). , whereby the second retrigger mono-multivibrator 52 is retriggered,
The output of this device maintains the "H" state as shown in FIG. When reaches the specific number, the flip-flop circuit 54 is inverted and the reproduction mode switching signal (H”
or °1L").

In this way, the discrepancy between the playback speed and the recording speed during high-speed playback is determined, and the playback mode switching signal resulting from the determination automatically switches the playback speed, head used, video signal processing circuit, etc. It becomes possible to perform switching.

A discrepancy between the playback speed and recording speed during low-speed playback can be caused by, for example,
Similarly, by setting the time constant of the first retrigger monomultivibrator 51 to 3V and the time constant of the second retrigger monomultivibrator 52 to 5V, as shown in FIG. 3(e), It is determined. In this embodiment, the output of the flip-flop circuit 54 is also
These time constants can be set to 1.5V, 2.5V for high-speed playback, and 3V, 5V for low-speed playback using the playback mode switching signal.
Since the configuration is such that the switching is made between the two discriminating circuits, the circuit configuration is clearly simplified compared to the case where two discriminating circuits having different time constants for high-speed playback and low-speed playback are provided.

Of course, the present invention is not limited to the one embodiment described above, and it is obvious that various modifications can be made without departing from the scope of the claims.

For example, it is possible to apply the present invention to a magnetic recording and reproducing device that can perform recording and reproducing at standard speed and double speed. Furthermore, it is possible to apply the present invention not only to a 4-head magnetic recording/reproducing apparatus but also to a 2-head magnetic recording/reproducing apparatus.

"Effects of the Invention" As explained above, according to the invention, when a low-speed recorded part is about to be played back during high-speed playback, or when a high-speed recorded part is about to be played back during low-speed playback, By using the dropout signal that occurs when playback is attempted where the speed and recording speed do not match, it is possible to automatically determine the mismatch between the playback speed and the recording speed, and output is generated along with this determination. The reproduction mode switching signal makes it possible to automatically change the reproduction speed, the type of head used, the signal processing circuit, etc. Additionally, this dropout signal may occur due to reasons other than the discrepancy between the playback speed and the recording speed, but the only way to determine whether or not the dropout signal is due to a discrepancy between the playback speed and the recording speed is to Since it is determined, there is no possibility of malfunction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit of a recording device discriminating device in a four-head azimuth recording section helical scan video tape recorder according to the present invention, and FIG. A schematic diagram showing the relationship with the head. Figure 2) to (f) are signal waveform diagrams of various parts of the circuit during high-speed playback of the low-speed recording part, and Figure 3 (a) to (0 is the low-speed recording part of the high-speed recording part. Figure 2 (a) to (0) during playback
Figure 4 (a) is a recording pattern diagram for high-speed recording, Figure 4 (6) is a recording pattern diagram for low-speed recording, and Figures 4 (C) to (the peaks indicate the difference between the playback speed and recording speed). These are waveform diagrams of the head switching pulse, reproduction output (RF ratio output, and output of the dropout pulse forming circuit 4) when they match. 4. Dropout; δ formation means, 5. Discrimination. Means, 51...first retrigger mono multivibrator, 5
2-...Second retrigger mono multi pie break, 53
...Counter, 54...Flip-flop circuit, v'r...Magnetic tape. Figure 3 VT (e) Do 0 Tsua 7 Chi To 1 Ki Dρ (Ha1shisu)

Claims (4)

[Claims] (1) During playback, a dropout signal synchronized with the dropout of the playback signal is generated, and based on the period of this dropout signal, it is determined whether or not the recording speed is inconsistent with the playback speed. 1. A method for determining a recording speed in a magnetic recording/reproducing device, the method comprising: outputting a reproduction mode switching signal when (2) A dropout signal generation means that detects a dropout in the playback signal and generates a dropout signal synchronized with the dropout, and whether the recording speed is inconsistent with the playback speed based on the dropout signal. A recording speed discriminating device for a magnetic recording/reproducing apparatus, comprising: discriminating means for discriminating whether or not the two discs match, and outputting a reproduction mode switching signal when there is a mismatch. (3) The first judgment means receives a dropout signal and the time constant is set to be shorter than the dropout signal period that occurs when the recording speed is inconsistent with the playback speed.
a second retrigger mono multivibrator whose output is input and whose time constant is set longer than the dropout signal period, and an output of the first retrigger mono multivibrator. The magnetism according to claim 2, comprising a counter that counts and is reset by stopping the output of the second retrigger monomultivibrator, and a flip-flop circuit that is inverted when the counter counts a predetermined value. A recording speed determination device in a recording/reproducing device. (4) A patent in which the time constants of the first and second retrigger mono-multivibrators are alternately switched between a high-speed reproduction time constant and a low-speed reproduction time constant by the reproduction mode switching signal. A recording speed determination device in a magnetic recording/reproducing device according to claim 3.