JPH07101935B2 - Field discriminating circuit of magnetic recording / reproducing apparatus - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus for video signals, and more particularly to a first field (or odd field) and a second field (or even field) during reproduction. ) For determining the circuit.

[Conventional technology]

Conventionally, as a field identification circuit, Japanese Patent Laid-Open No. 59-90463
As described in Japanese Patent Laid-Open Publication No. 2004-187, the phase of the vertical sync signal and the horizontal sync signal in the composite sync signal is different between the first field (or odd field) and the second field (or even field). .

Therefore, in order to reduce the recording signal band, etc., if the composite sync signal is not recorded, the first field (or odd field) and the second field (or even field) are discriminated during reproduction. It is not possible.

[Problems to be solved by the invention]

In order to record a wideband video signal, a segment recording method is used in which the relative speed of the head and the drum is increased and the video signal of one field is divided into a plurality of tracks to be recorded, or the video signal is time-axis expanded to a plurality of channels. The recording signal band is reduced by using a channel division recording method in which the recording is divided into two. To reproduce the signal thus recorded and return it to the original signal, the first (or odd number),
It is necessary to discriminate the second (or even) field, but in the prior art, it was impossible to discriminate unless the data was recorded in the form of a composite sync signal.

An object of the present invention is to ensure that in a magnetic recording / reproducing apparatus using the above-mentioned segment recording system or channel division recording system, the first (or odd number),
It is to determine the second (or even) field.

[Means for solving problems]

The above object is achieved as follows. The video signal of one field is divided into M segments of N channels (M, N
Is a positive integer), a magnetic recording / reproducing apparatus that records the vertical synchronizing signal VD at the beginning of each field, depending on the polarity of the drum servo reference signal when the vertical synchronizing signal is separated from the reproduced video signal during reproduction. , Field discrimination is performed.

[Work]

The playback vertical sync signal indicates the beginning of each field,
On the other hand, since the reference signal of the drum servo is the frame frequency, it is always the first (or odd number) or the second (or even number) regardless of the N channel division or the M segment division.
There are differences in polarity in the field. Therefore, by comparing the polarities of the reproduction VD and the reference signal of the drum servo while the CTL servo control using the conventionally used control signal is performed, the field can be surely discriminated.

〔Example〕

An embodiment of the present invention in the case of recording and reproducing a high definition television signal on a helical scan type VTR will be described below.

As an example, a high-definition television signal is composed of 30 frames per second and 1125 scanning lines per frame. Also, 1 frame consists of 2 fields, and 2: 1
It shall be interlaced scanned. It is assumed that one set of magnetic heads, which are opposed to each other, is used in total, a magnetic tape is wound around a drum by 180 ° or more, and a video signal is recorded over 180 °. And
Since it is necessary to increase the relative speed of the head in order to record a wideband video signal, as an example, by rotating the drum three times faster than the conventional VTR (5,400 rpm), the signal of one field becomes three as shown in FIG. Three-segment recording is performed over one track. This is N = 1, M = 3
Corresponds to the case of.

Further, at the time of recording, the vertical synchronizing signal is recorded at the beginning of each field in the form of a composite synchronizing signal or a form suitable for the system.

In FIG. 1, 1 is a magnetic tape, 2 and 3 are magnetic heads,
4 is a rotary drum, 10 and 11 are reproduction amplifiers, 12 is a switching circuit, 13 is an FM demodulation circuit, 20 is a sync information division circuit for separating sync information such as sync signals and bass signals added at the time of recording, and 21 is a drum. , A tack head for detecting a tack pulse indicating the rotation phase of the head, 22 is a head switching signal generating circuit for generating a head switching signal (hereinafter abbreviated as SW90) from the detected tack pulse, 30 is a first (or an odd number), Two
A discriminating circuit for discriminating (or an even number) field and generating a field discriminating pulse (hereinafter abbreviated as FP), 40 is a reproduced video signal processing circuit for processing the reproduced signal and outputting it in the form of the original high definition television signal, 50 is a crystal oscillator circuit to obtain a stable frequency reference clock, 51 is a crystal oscillator circuit 50
Sync generator circuit that generates horizontal sync signal (HD), vertical sync signal (VD), and drum servo reference signal (hereinafter referred to as REF30) from the reference clock of 60, 62 to 62 are reproduced three primary color signals, red (R) , Green (G), blue (B) output terminal, 63
Is an output terminal of the horizontal synchronizing signal HD, and 64 is an output terminal of the vertical synchronizing signal VD.

The recording pattern on the tape in this embodiment is shown in FIG. As described above, in this example, since the recording is 3 segments, the signal of 1 field is recorded over 3 tracks. At this time, each track is segment 1 (seg.
1), segment 2 (seg.2), segment 3 (seg.3)
And

At the time of reproduction, based on the reference clock obtained from the crystal oscillation circuit 50, the reference signal REF30 for the drum servo shown in FIG. 3 (a) is output from the synchronization generation circuit 51, and the drum servo control device (not shown) outputs the reference signal REF30. Head switching signal SW
For example, CTL servo control using a conventionally used control signal is performed so that 90 is phase-locked with REF30. Here, the REF 30 is, for example, a signal having a frame frequency and a duty of 50%.

The tack head 21 detects a tack pulse indicating the actual rotation phase of the servo-controlled drum. Based on the detected tack pulse shown in FIG. 3 (b), the SW90 generation circuit 22 outputs the head switching signal SW shown in FIG. 3 (c).
90 is output.

The SW90 is a head switching signal at the time of reproduction, and as shown in FIG. 3 (c), the polarity is alternately inverted to a high level "H" and a low level "L" every 180 ° rotation of the drum. is there.

On the other hand, the video signals reproduced from the magnetic tape 1 by the magnetic heads 2 and 3 are amplified by the reproduction amplifiers 10 and 11, respectively, and then input to the switching circuit 12. The magnetic heads 2 and 3 are arranged to face each other by 180 °. Therefore, every time the drum rotates 180 °, the video signal is alternately reproduced, and the output of the heads 2 and 3 is alternately switched and output by the switching circuit. The output of the switching circuit 12 is input to the FM demodulation circuit 13 and subjected to FM demodulation, and then the synchronization information separation circuit 20 and the reproduced video signal processing circuit 40.
Entered in. The synchronization information separation circuit 20 is shown in FIG.
The vertical synchronizing signal is separated from the reproduced video signal shown in (3) and the reproduced VD as shown in FIG. 3 (e) is output.

The discriminating circuit 30 can discriminate between the first field (or odd field) and the second field (or even field) using the REF 30 and the reproduction VD. The principle will be described below.

With the playback VD separated and output by the synchronization information separation circuit 20,
The beginning of each field is shown. On the other hand, since the REF 30 is a signal having a frame frequency and a duty of 50%, the polarity is inverted to a high level "H" and a low level "L" for each field. Therefore, if the high level is “H” in the first (or odd number) field, the low level is “L” in the second (or even number) field, or conversely, the first level (or odd number).
Second (or even) if low level "L" in field
It becomes a high level "H" in the field. Therefore, the third
If the discrimination circuit 30 is constituted by an AND circuit as shown in FIG. 4 with respect to the signal example shown in the figure, a field identification pulse FP as shown in FIG. 3 (f) can be obtained. In this example,
The discriminating circuit 30 composed of an AND circuit can be easily realized by a NAND, NOR, OR circuit or a combination thereof, if necessary, such as the polarities of the REF 30, the reproduction VD, and the FP.

In addition, although channel division is not performed in this embodiment, in general, when recording is performed by dividing it into N channels (N is a positive integer), when recording is performed in M segments (M is a positive integer), The present invention is also effective in the case of N channel M segment recording.

Further, in this embodiment, a signal having a frame frequency of 50% duty is used as the reference signal of the drum servo.
This discriminating circuit discriminates based on the difference in the polarity of REF30 when the playback VD is detected.
Does not have to be.

Next, another embodiment of the present invention will be described with reference to the block diagram of the discrimination circuit of FIG. 5 and the timing chart of FIG.

The discriminator circuit shown in FIG.
This is an example using the head switching signal SW90. REF30 is 1
Assuming a duty of 50% at the frame frequency as an example, as shown in the timing chart of FIG. 6, if the logical sum (AND in this case) with SW90 is taken, only the first field (or odd field) will be SW90. The same signal GOUT is obtained. Logical sum of GOUT and playback VD (in this case, AND)
By taking, the FP can be obtained. In this example,
Although it is composed of an AND circuit, it can be easily realized by a NAND, NOR, OR circuit or a combination thereof, if necessary, such as the polarities of the REF 30, the reproduction VD, the SW 90, and the FP.

Also in this example, it can be applied to the case of N channel M segment recording, and REF30 does not need to have a duty of 50%.

〔The invention's effect〕

According to the present invention, since the field discrimination is performed by using the polarity difference of the reference signal of the drum servo when the vertical synchronizing signal is separated from the reproduction signal, the N-channel M segment recording (M and N are positive integers) is performed. Even in this case, the field can be surely discriminated.

[Brief description of drawings]

FIG. 1 is a block diagram of a reproducing system of a VTR showing an embodiment of the present invention, FIG. 2 is a diagram showing a recording pattern on a tape at the time of segment recording, and FIG. 3 is each signal in reproducing at the time of three segment recording. FIG. 4, FIG. 4 is a block diagram of a field discriminating circuit using a gate circuit, FIG. 5 is a block diagram of a field discriminating circuit showing another embodiment, and FIG. 6 is each signal in the embodiment of FIG. FIG. 20 …… Synchronous separation circuit, 50 …… Crystal oscillator circuit, 51 …… Synchronous generation circuit, 30 …… Field discrimination circuit, 40 …… Reproduction video signal processing circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Furihata, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Home Appliances Research Laboratory, Hitachi, Ltd. (56) Reference JP 62-141869 (JP, A) JP 59-205880 (JP, A) JP 60-264175 (JP, A) JP 64-5273 (JP, A) JP 51-26767 (JP, B2)

Claims (2)

[Claims] 1. An N-channel division M segment recording method in which one field of a video signal is divided into N channels M segments (M and N are positive integers) by a rotary head and recording is performed on different recording tracks. In the magnetic recording / reproducing apparatus, of the M segments forming each field,
A means for recording the vertical synchronizing signal in the first area of the first segment, a means for separating and outputting the vertical synchronizing signal from the reproduced signal at the time of reproduction, and a frame in which the polarity is reversed at a substantially field cycle which is a reference of the drum servo. A means for generating a frequency reference signal is provided, and in the state where the CTL servo control using the drum servo reference signal and the playback control signal is applied, the vertical synchronizing signal separated from the playback signal and the drum servo reference signal are generated. By the gate circuit that responds,
A field discriminating circuit of a magnetic recording / reproducing apparatus, which outputs a field discriminating pulse indicating the polarity of the reference signal of the drum servo when the vertical synchronizing signal is detected. 2. An N-channel division M segment recording system in which one field of a video signal is divided into N channels and M segments (M and N are positive integers) by a rotary head, and each segment is recorded on different recording tracks. In the magnetic recording / reproducing apparatus, of the M segments forming each field,
A means for recording the vertical synchronizing signal in the first area of the first segment, a means for separating and outputting the vertical synchronizing signal from the reproduced signal at the time of reproduction, and a frame in which the polarity is reversed at a substantially field cycle which is a reference of the drum servo. Means for generating a reference signal of frequency, means for outputting a head switching signal whose polarity is inverted every 180 ° rotation of the drum synchronized with the reference signal for the drum servo, reference signal for the drum servo and head switching A first gate circuit which responds to the signal, and a second gate circuit which responds to the output of the first gate circuit and a vertical synchronizing signal separated from the reproduction signal. The drum servo at the time when the vertical synchronizing signal is detected by the first and second gate circuits under the condition that CTL servo control using Field determination circuit of the magnetic recording and reproducing apparatus and outputs a field identification pulse indicating the polarity of the reference signal and the head switching signal.