JPS61170974A - Device for magnetic recording and reproducing - Google Patents

Abstract

PURPOSE:To find a precise recording track position irrespective of the reproduction mode of a magnetic recording and reproducing device by calculating a phase difference between a recording track position signal and a reference one from the counted value of a counting circuit with a clock signal as a counter, for instance, and detecting a currently reproduced recording track position with the aid of the counted value. CONSTITUTION:A CTL detecting circuit 4 samples a CTL signal component among signals outputted from a shaping amplifier 3. Said component is inputted to a gate signal generating circuit 5 and its output is made a signal having a pulse width (t) in a waveform C. Accordingly, when the signal opens and closes a gate circuit 6, a CF signal is sampled in a waveform D. A counter7 counts a reference pulse (p) outputted from a timing circuit 8 at every field as a start signal, and stops its counting when the CF signal is inptuted. Accordingly, the result comes to the counted value N0 in proportion to the phase difference between the reference pulse P and the CF signal. When the counted value N0 decides the position of the CF signal, a discriminating circuit 9 discriminates the color field number of a currently reproduced video track.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording and reproducing device that records video signals using a helical scan method, and in particular, plays back (records) track position signals recorded together with video signals. ) The present invention relates to a magnetic recording/reproducing device suitable for performing the following operations.

[Conventional technology]

A video tape recorder (hereinafter referred to as VTR) that records video signals
Usually, video signals are recorded on tracks diagonally across a magnetic tape, and various control signals including servo information, audio signals, etc. are recorded on tracks formed in the longitudinal direction of the magnetic tape.

Then, this recorded control signal is the fixed spatula F (C
This control signal is read by the VTR head (TL head) and used for the servo of the VTR, and some high-end models also use this control signal to detect the frame number.

However, since the running speed of the magnetic tape varies from 0 to high speed depending on the control mode of the VTR, it is not possible to read out control signals using a fixed helad, especially during still playback, slow playback, and high speed playback. It becomes difficult.

Therefore, as shown in Japanese Patent Publication No. 51-22807, for example, the winding angle of the magnetic tape around the rotating drum is set to 1.
It has been proposed to set the angle at 80 degrees or more so that tracks formed in the longitudinal direction can also be scanned by a rotary head, and to read signals recorded on these tracks.

According to this method, as shown in the tape format of Fig. 5, data recorded in a longitudinal track (hereinafter referred to as a CTL rack) that is an extension of a track T recorded in an oblique direction is rotated. Since it can be read by the head, the control data AI, A2 . A3 can be read, and this control data AI, A2 . There is an advantage that the CTL signal for tracking is also read out from the gap A3.

[Problems to be Solved by the Invention] However, in the recording and reproducing apparatus of the present invention, when one rotary head finishes scanning the track for one field,
The control data includes AI, A2. Since A3 is detected, there is a problem in that the circuit for reading only the control data A2 necessary for this frame becomes complicated.

Further, although the type of read data is unknown, it is difficult to accurately detect the position of the recording track being reproduced from the data.

This invention was made in view of the above points, and includes:
The color frame signal of the video track being played back is detected using the control signal obtained when the rotating head crosses the CTL rack, and the position of the recording track in the diagonal direction currently being played can be detected using a simple circuit. This relates to a magnetic recording and reproducing device that enables accurate detection.
Since the recording track position during playback can be accurately detected, recording modes such as still playback and variable speed playback are possible at a specific recording track position.

[Means for solving problems]

The magnetic recording/reproducing device of the present invention calculates the phase difference between a recording track position signal recorded in the longitudinal direction of a tape read by a rotary head and a reference signal, for example, by using a clock signal as a count value of a counting circuit. , and the position of the recording track currently being reproduced is detected based on the counted value.

[Effect]

Since at least three read recording track position signals are detected by the rotary head, the tape speed can be adjusted by detecting the phase difference between a specific position of the plurality of recording track position signals and the reference position of the one-rotation drum. Color frame signals or tracking information can be detected regardless.

〔Example〕

FIG. 6 is a diagram showing the relationship between a rotating drum D and a magnetic tape T showing an embodiment of the present invention.
The sub-head SH is provided at an angle of about 30' and with a step. Then, the video track and sync track of the magnetic tape T wound in Ω around the rotating drum D are scanned.

This type of recording method is generally well known as the 1.5 head helical scan method, and although detailed explanation thereof will be omitted, C
TL) Rack and audio track U I + U
A fixed head for 2 is located on the inlet side of the tape.

Figure 7 shows the tape format using this recording method) (
The A zone is mainly a video track in which one field's worth of video signal read out by the main head MH is recorded.
The B zone indicates a sync track in which a vertical synchronizing signal read out by the sub head SH is recorded.

Between this A zone and B zone, there is a so-called C
A CTL rack (width 0.6 mm) extending in the longitudinal direction on which TL signals are recorded is formed, and three audio tracks Ul and U are located at both the top and bottom ends of the tape.
2. U3 is formed.

Fig. 8 is an enlarged view of a part of the tape format shown in Fig. 7. Generally, in the C format for broadcasting stations, the inclination angle of the video track and the sync track is formed at 2°34', and the CTL The width of the track is 0.6m
m is set.

Therefore, the longitudinal dimension when the sub head SH crosses the CTL track is 0.6/5in2°34'#1
However, considering the width of the sync track of 130 mm, the sub head SH scans a length of about 16.3 mm.

By the way, since the length of the L field in the longitudinal direction of the tape is approximately 4 mm, when the sub head SH passes through the CTL rack, it crosses at least three CTL signals.

An NTSC composite video signal consists of an odd field and an even field, with 2 fields equaling 1
A screen is formed. In the case of a color video signal,
Furthermore, the color subcarriers are formed to have different phases for each field, and the pattern of the video signal is repeated at a period of four fields.

Therefore, a CTL signal is typically repeated every four fields to indicate a color frame, and at the beginning of the first field a CF signal is formed to identify the color frame, as shown in FIG. Then, the CF signal is superimposed on the CTL signal every 'F'4 fields.

By the way, according to the recording/reproducing device of this invention.

As mentioned above, when the sub head SH passes through the CTL rack, it is possible to detect at least three fields worth of CTL signals. By analyzing the playback signal, it is possible to detect the position of the field that the VTR is playing.

FIG. 1 is a block diagram showing an embodiment of the present invention.
This method is suitable for detecting the color field number of the video track currently being played from MH, SH).

In this figure, reference numeral 1 indicates a switch for switching and outputting reproduction signals of the main head MH and sub-head SH, and reference numeral 2 indicates a demodulation circuit, and the output of this demodulation circuit 2 is input to a video signal processing circuit.

On the other hand, the signal reproduced by the sub head SH is sent to the shaping amplifier 3.
The CTL detection circuit 4 extracts only the signal when the signal is input to the CTL and crosses the rack (CTL). The signal is then input to a gate signal generation circuit 5 that outputs a signal with a constant pulse width.

Reference numeral 6 denotes a gate circuit that extracts a signal by the gate signal generation circuit 5, and 7 a counter that stops counting when the signal passes through the gate circuit and starts counting the clock signal φ according to the reference signal output from the timing signal generator 8. , 9 is a determination circuit.

The operation of the CF signal detection block diagram shown in this figure will be explained below with reference to the waveform diagram in FIG. 2.

When playing the C format tape shown in Figure 7,
As described above, from the sub head SH, the signal H from the sync track, the CTL signal, and the video signal Sv when scanning the video track are obtained as shown in waveform A.

The CTL signal portion of the signal output from the shaping amplifier 3 is extracted by the CTL detection circuit 4 (waveform B).
, are input to the gate signal generation circuit 5. Since the gate signal generation circuit 5 is constituted by, for example, a monostable multivibrator that is triggered at the falling point of the CTL signal, its output is a signal having a pulse width t as shown in waveform C.

Therefore, when the gate circuit 6 is opened or closed by this signal, the CF signal contained in the reproduced CTL signal is extracted as shown in the waveform.

The counter 7 counts the clock signal φ every field using the reference pulse P (waveform E) output from the timing circuit 8 as a start signal, and when the CF signal is input to the counter 7, the count is started. Stop. As a result, the count value of the counter 7 becomes a count value NO which is proportional to the phase difference between the reference pulse P and the CF signal, as shown by waveform F, and from this count value No. It can indicate the track position that the MH is playing.

The reference pulse P is, for example, V, which indicates the reference position of the drum that rotates once.
Since it is formed by a synchronization signal or the like, when the position of the CF signal is determined by the count value N, the color field number of the video track currently being played is determined by the determination circuit 9.

That is, since at least three CTL position signals are included in the signal reproduced from the sub-head SH as shown in waveforms B, Bl, and B2 in FIG. 2, for example, a CF signal as shown in waveform B is output. If time is the first field, then
It can be determined that when a CTL reproduction signal of the Bl waveform is obtained, the second field is used, and when there is no CF marker as shown in the B2 waveform, the reproduction signal is the fourth field.

Therefore, even when variable speed playback or still playback is being performed, the determination circuit 9 can easily search for a recording track that has a predetermined color field number.

FIG. 3 is a block diagram for tracking detection showing another embodiment of the present invention, in which, like in FIG. 1, 1 is a switch for switching between main and sub heads, 2 is a demodulation circuit, and 3 is a shaping amplifier. . 10 is a gate circuit that detects the CTL signal part, that is, the signal of the part where the sub head SH crosses the CTL rack; 11 is a plurality of detected CTL position signals, for example, the second CTL obtained during just roughking; 12 is a CTL detection circuit that extracts the signal position as the center, and the number of the extracted CTL position signals is h -/
7' L・t゛j % c7) # * (if b<
5-/+II u 13”-@.

The counter 14 to be sent is a timing circuit that outputs various timing signals from a reference signal obtained at a predetermined position of the rotary head.

FIG. 4 shows waveforms (a-g) of the main parts of FIG. 3.

In this embodiment, similarly to the detection of the color frame position, a plurality of CTL position signals reproduced from the sub-head SH pass through the gate circuit 10, and a second CTL, for example, generated centering on the just roughing position by the reference signal VD is detected. The signal is extracted in the second CTL signal product TL detection circuit 11 using a gate pulse d (Pe) for signal production.

The counter 12 is configured to fail to count the clock signal φ by the reference pulse f (p) at the rising point of the gate pulse P6, and to stop counting when the second CTL signal is multiplied.

Therefore, if this count value is a predetermined value N, it indicates that the second CTL position signal is being tracked, and the main head MH is scanning the center of the recording track.

Further, when the position is at a position where a count value different from the second CTL position signal count value N is output, it indicates that the tracking is out of alignment.

Note that the third CTL position signal to be compared with the reference pulse f(p) may be used;
This is not preferable because the level of the CTL position signal varies depending on the position of the second CTL position signal.

According to this method, tracking information is output regardless of the tape speed, so if you configure a servo circuit that controls the pinch roller using this tracking information, the main head will be at the just roughing position in still playback, ultra-low speed playback mode, etc. It can be controlled so that the image quality is improved.

〔Effect of the invention〕

As explained above, the magnetic recording/reproducing device of the present invention has the following features:
A rotating head detects the position signal of the recording track formed in the longitudinal direction of the tape.

The system is configured to detect the color frame position and tracking information of the video signal to be reproduced by detecting the phase difference between the detected position signal (CTL position signal) and the reference signal. Accurate recording track positions can be known regardless of the reproduction mode of the magnetic recording/reproducing device.

Further, there is an advantage that the recording track detection circuit is simpler than the conventional one.

[Brief explanation of drawings]

FIG. 1 is a color frame position detection block diagram showing one embodiment of this invention, FIG. 2 is a main waveform diagram of FIG. 1, and FIG. 3 is tracking information detection showing another embodiment of this invention. A block diagram, FIG. 4 is an operating waveform diagram of FIG. 3, FIG. 5 is a tape pattern diagram for detecting known control data, and FIG. 6 is a diagram showing the relationship between the rotating drum and tape of the 1.5 head helical force scan system. Outline diagram, Figures 7, 8, and 9 are C
FIG. 3 is a signal waveform diagram showing the relationship between recording tracks and CTL signals in a format. In the figure, 1 is a switch, 3 is a shaping amplifier, 4 is a CTL detection circuit, 5 is a gate signal generation circuit, 6 is a gate circuit, and 7 is a counter. Figure 2 '3 Figure 4 (9): Figure 5 Figure 6

Claims (1)

[Claims] In a magnetic recording and reproducing device configured to reproduce information on recording tracks formed diagonally on a tape by a rotating head, a signal for identifying at least the position of the recording track in the longitudinal direction of the tape is provided. a detection circuit that includes a recorded control track, detects a track position signal output when the rotary head crosses the control track; and a predetermined position of the rotary drum and the track position signal output from the detection circuit; and a phase difference detection circuit for detecting a phase difference with a reference signal output in connection with the magnetic recording, and the position of a recording track being reproduced is detected from the output signal of the phase difference detection circuit. playback device.