JPS63224489A - Special playback system for vtr - Google Patents

Abstract

PURPOSE:To prevent a noise from appearing on a screen even when a tape speed is increased by making the rotating speed of a head drum faster than a normal rotating speed at the time of high-speed reproduction, and extending the time base of a video signal of a field selected correspondingly to the rotating speed of the head drum and obtaining a video signal of normal frequency. CONSTITUTION:The rotating speed of the head drum 1 at the time of cue reproduction and review reproduction is set double as fast as the normal speed. Thus, the rotating speed of the head drum is made double, and then modulated video signal outputted from rotary heads 2 and 2' through preamplifiers 18 and 18' are double in frequency and their time bases are shortened to 1/2. A video signal processing circuit 20 demodulates the modulated video signal as a luminance signal Y and a color signal C separately and extends the time base by twice to obtain a continuous signal of normal frequency. Consequently, even when the playback speed of a helical scan VTR at the time of special reproduction such as cue or review reproduction is increased, there is neither a noise band nor skew generated or at least reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a Hercal Scan VT using a one-rotation head.
The present invention relates to a special playback method for R, and in particular to a playback method for reducing noise during high-speed playback of cues, reviews, etc.

[Summary of the invention]

This invention is a Hercal Scan VT using a rotating head.
In R, the rotational speed of the head drum is made higher than the normal rotational speed during high-speed playback, and a field selected according to the rotational speed of the head drum is selected from among the video signals obtained from the head provided on the head drum. By extending the time axis of the video signal to obtain a video signal with a regular frequency, noise does not appear on the screen even when the tape speed is increased.

[Conventional technology]

The fifth Hercal Scan VTR uses a rotating head.
As shown in the figure, one rotation (NT
In SC, two rotary heads 2 and 2' are provided at symmetrical positions on the outer circumference of a head drum 1 that rotates at 300 revolutions per second, and a magnetic tape (hereinafter simply referred to as "tape") 3 is placed on a guide 7.8 with respect to the head drum 1. Accordingly, it travels in the direction of arrow A with an inclination that winds in a helical shape, maintaining contact for more than half the circumference.

The rotating heads 2 and 2' each scan and record one field's worth of signals on one track, and one set of heads 2 and 2' scans and records one field's worth of signals on one track.
Record the signal for one frame.

In such a VTR, the head drum 1 rotates in the direction of arrow B as the tape 3 runs during recording and playback.
The relative speed between the tape 3 and the heads 2, 2' is much greater than the running speed of the tape 3 itself, making it possible to record and reproduce wideband video signals.

In addition, in order to prevent interference from adjacent tracks during reproduction, the two heads 2 and 2' are arranged at fixed angles (for example, ±6
°) Since both heads are tilted (azimuthal recording), the signals recorded by the other head will not be reproduced.

When viewed from the base surface of the tape 3, the video track on the tape 3 recorded with such a VTR has a gap between the audio track 4 and the control track 5 for tracking, as shown in FIG. +Azimuth and -
Tracks of +azimuth and one azimuth (hereinafter referred to as "ten tracks" and "-
(referred to as "track") consists of 6.8'.

The running direction of the heads 2, 2' relative to the tape 3 is from the lower left to the upper right, as shown by arrows in FIG.

In such a VTR, during normal playback, both the running speed of the tape and the rotational speed of the head drum 1 are maintained at the same normal speeds as during recording. - heads 2' trace ten tracks each, - track correctly;

However, in the case of forward high-speed playback (hereinafter referred to as "queue") or reverse direction playback (hereinafter referred to as "review"),
In the conventional technique, only the tape running speed or running direction was changed while the rotational speed of the head drum 1 was kept constant.

Therefore, each head is unable to correctly trace the tracks on the tape and ends up tracing a plurality of tracks diagonally, and the effective track width changes, causing fluctuations in the playback output.

In particular, when the other head (with a different azimuth) crosses over the recorded track, the playback output becomes 0.

So-called noise bands occur within the screen.

For example, as shown in Figure 7, in the case of triple-speed cueing, the head traces at least three tracks (the trace locus is shown surrounded by thick lines, and the areas where video signals can be played are shown with diagonal lines). As shown in the figure, the noise band can be traced without crossing tracks with different azimuths, so the noise band becomes a substantially vertical blanking period and does not appear on the monitor screen.

However, in the case of 6x speed cue, each head traces at least six tracks across tracks with different azimuths, so as is clear from the figure, at least two tracks per field are displayed on the monitor screen. It is unavoidable that noise bands (4 lines per frame) appear in which the video signal is not reproduced.

That is, in the case of a cue, noise bandless playback is possible at 3x speed or lower, but noise bands appear at 4x speed or higher.

Because the tape runs in the opposite direction at the time of review.

As shown in Figure 8, in the case of 1x speed review, each spatula bottom traces at least 3 tracks, but since it does not straddle tracks with different azimuths, the screen is similar to the case of 3x speed cueing. No noise band appears.

However, in the case of double-speed review, each head traces at least four tracks across tracks with different azimuths, so at least one video signal per field (two per frame) is not played within one screen. A noise band appears.

That is, in the case of review, noise bandless playback is possible if the review is at a constant speed, but noise bands will appear if the speed is 2x or higher.

To solve this problem, we used a so-called double azimuth 4 head, in which heads with different azimuths were placed adjacent to each other on the head drum, and the heads were switched according to the azimuth of the track to be traced during high-speed playback, so that playback was always possible. A method of controlling the output so as to obtain the output is also known.

However, this method not only increases costs but also has the disadvantage that some skew (noise) occurs at the time of head switching.

[Problem that the invention seeks to solve]

As mentioned above, the special playback method of conventional VTRs has the problem that noise bands or skews occur when a cue speed exceeds 3 times the speed or a review speed exceeds a constant speed, which limits the playback speed.

The purpose of the present invention is to solve this problem and enable faster queue or review than before on a noise-free screen.

[Means for solving problems]

This invention is a helical scan VT using a rotating head.
In order to solve the above problems, in R, the rotational speed of the head drum is made higher than the normal rotational speed during high-speed playback, and the video signal obtained from the head installed on the head drum is The time axis of the video signal of the selected field is extended in accordance with the rotation speed of the video signal, thereby obtaining a video signal of a regular frequency.

[For production]

By doing this, even if the tape speed during cue playback is increased to more than 3 times the speed, or the tape speed during review playback is increased to more than constant speed, the relative speed between the tape and the head can be increased to 3 times the speed. It can be made equivalent to the time of , or the time of constant velocity.

However, in this case, the frequency of the video signal reproduced from the head will increase as the rotation speed of the head drum increases. By obtaining a video signal of a regular frequency, a noise-free video signal can be obtained, and noiseless high-speed playback becomes possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram showing the main part of a VTR embodying the present invention, and FIG. 2 is a block circuit diagram showing an example of its video signal processing circuit.

In FIG. 1, parts corresponding to those in FIG. 5 are given the same reference numerals. The tape 3 is sent in the direction of the arrow by a capstan 10 rotated by a capstan motor 9 and a pinch roller 11.

Capstan motor 9 is capstan motor driver 1
A drum motor 13, which is driven by a drum motor 2 and rotates a head drum 1, is driven by a drum motor driver 14.

The operation of the capstan motor driver 12 is switched by a changeover switch 15 controlled by a mode changeover control circuit 17, and when the changeover switch 15 is in the normal position (N) shown in the figure, it causes the capstan motor 9 to rotate forward at a normal speed; At the cue position, it rotates forward at six times the normal speed, and at the review position, it rotates backward at twice the normal speed.

On the other hand, the operation of the drum motor driver 14 is also switched by a changeover switch 16 controlled by a mode changeover control circuit 17, and when the changeover switch 16 is in the normal position (N) shown in the figure, the drum motor 13 is rotated at a normal speed, and the drum motor 13 is rotated at a high speed. In position (H) it is rotated twice as fast.

In the normal mode, the mode switching control circuit 17 includes a changeover switch 15.18 and a changeover switch 22.18 in the video signal processing circuit 20, which will be described later. .

23 are set to the normal position (N) as shown in the figure, but when the operator enters the cue mode or review mode, the selector switch 15 is switched to the cue position or the review position. Changeover switches 1B and 22.23 are both set to high speed position (H).

On the other hand, the output signals of the rotating heads 2 and 2' are taken out to the main body side via a rotary transformer (not shown), amplified and equalized by preamplifiers 18 and 18', respectively, and then alternately sent to the video signal via a head selector switch 19. The signal is input to the signal processing circuit 20.

The head changeover switch 19 is switched by a head changeover control circuit 21, which is controlled by a control head (not shown) to switch the control track 5 (
By inputting the control signal read out from Fig. 6),
It can be switched for each field.

This control signal is also input to the capstan motor driver 12 and used for tracking control, and is also input to the memory switching control circuit 24 in the video signal processing circuit 20, which will be described later.
It is also used to control field memory switching timing.

According to this embodiment, the rotation speed of the head drum 1 is twice the normal speed during cue playback and review playback, so the tracing state of the rotary heads 2 and 2' with respect to the video track recorded on the tape 3 is Even in the case of a 6x speed cue, it is relatively the same as in the case of a 3x speed cue shown in Figure 7, and in the case of a 2x speed review, it is relatively the same as in the case of a constant speed review shown in Figure 8. Become.

Therefore, by adjusting the tracking timing, a screen without noise bands can be obtained.

However, if the rotational speed of the head drum is doubled in this way, the preamplifier 18.18'
The modulated video signal outputted through the filter has twice the frequency and the time axis has been shortened to 172.

Therefore, the video signal processing circuit 20 demodulates this modulated video signal by dividing it into a luminance signal Y and a color signal C, and also extends the time axis by twice to obtain a continuous video signal with a regular frequency. There is.

This video signal processing circuit 20 is configured as shown in FIG. 2, and in the normal mode, a selector switch 22.
23 is on the N side as shown in the figure, the modulated luminance signal Y that is FM modulated among the modulated video signals input through the head changeover switch 1 in FIG. The demodulated color signal C is demodulated by a color processing circuit 45, and then the demodulated luminance signal and color signal are combined and output as a regular video signal.

In the cue mode or review mode, the changeover switches 22 and 23 are switched to the H side, so the input modulated luminance signal Y is demodulated by the high-speed Y demodulation circuit 26 and then
Write clock oscillator 28 by A/D converter 27
The data is digitized in synchronization with the write clock from On the other hand, the modulated color signal C is directly digitized by the A/D converter 29.

Here, 30 is a frequency divider that divides the write clock output from the write clock oscillator 28 by 172 and outputs a read clock with twice the cycle, and 31 to 34 each have data for one field. The field memories 35 to 42, which have a capacity to store , are changeover switches that are switched by the memory changeover control circuit 24 in conjunction with every two fields of the input signal.

Now, when the changeover switches 35 to 42 are switched as shown, the brightness data from the A/D converter 27 is stored in the field memory 31, and the color data from the A/D converter 29 is stored in the field memory 33. Written by the write clock from write clock oscillator 28.

During this time, the luminance data and color data stored in the field memories 52 and 34 are respectively read out by the read clock from the frequency divider 30, and the D/A converter 4''
! 1.44, respectively.

Here, the period of the read clock is 2 times the period of the write clock.
Since the signal is doubled, a luminance signal and a modulated color signal that are extended along the regular time axis can be obtained.

Therefore, the modulated color signal is demodulated by the color processing circuit 45, combined with the luminance signal, and output as a regular video signal.

By the way, while the data of one field of the field memories 32 and 54 is being read, the field memories 31 and 5
The data of the second field is written to the ES, and the data of the previous field is erased.

Then, just before the next field signal is input, all of the changeover switches 35 to 42 are switched to the side opposite to that shown in the figure.
New data is now written into the field memories 32, 34, and data stored therein is read from the field memories 31, 33.

That is, by extending the time axis of the video signal of the selected field every other field, a continuous video signal of a regular frequency can be obtained.

FIG. 3 shows the relationship between the write and read cycles of each field memory 31 to 34 (A to D) and the input signal and output signal fields in this case. Note that the numbers in the figure indicate field numbers.

The above description has been made of the case where n=2, where n is the ratio of the rotational speed of the head drum in the high speed mode and the normal mode, but it is also possible to take a larger value if n is used.

For example, if n=3, noiseless high-speed playback of 9x speed cue and 3x speed review becomes possible. In that case, the relationship between the write and read cycles of each field memory and the input signal and output signal fields is as shown in Figure 4, and the time axis of the video signal of every second selected field is tripled. It is then output as a continuous video signal at the regular frequency.

Increasing n increases the write clock frequency,
A/D converters 27, 29 and field memory 31~
There is a risk that the write processing speed of 34 will increase and the cost will increase, but except for special uses, the higher the speed for queue and review purposes, the lower the resolution will be less of a concern, so the number of pixels will increase depending on n. By reducing the write clock frequency, there is no need to increase the write clock frequency to the extent that it causes high costs.

Further, according to the present invention, even when switching heads in a two-head system or a double azimuth four-head system,
Even if n is not set too large compared to the tape running speed, it is possible to reduce the number of noise bands or reduce the number of head changes, thereby reducing skew.

Therefore, if the same noise band or skew is allowed, the queue is n times faster than the conventional one.

High-speed reviews are possible.

〔Effect of the invention〕

As explained above, according to the present invention, noise bands and skews do not occur, or at least are reduced, even if the playback speed during special playback such as cue or review is increased in a helical scan VTR using a rotating head. Therefore, the image quality during high-speed playback can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of a VTR showing an embodiment of the present invention, FIG. 2 is a block circuit diagram showing an example of the video signal processing circuit 20 in FIG. 1, and FIGS. FIG. 5 is an explanatory diagram showing the relationship between the write and read cycles of each field memory and the fields of input signals and output signals when the rotational speed of the drum is twice and three times the normal speed. FIG. 6 is an explanatory diagram showing the state of each track recorded on the tape as seen from the base surface of the tape; FIGS. 7 and 8 2 is an explanatory diagram showing how a rotating head traces a track on a tape during cue and review, respectively. FIG. 1... Head drum 2, 2'... Rotating head 3
...Magnetic tape 9...Capstan motor 1
0... Capstan 11... Pinch roller 12
... Capstan motor driver 13 ... Drum motor 14 ... Drum motor driver 15.18 ... Changeover switch 17 ... Mode changeover control circuit 1 day ... Head changeover switch 20 ... Video signal Processing circuit 22.23.3; 5-42...Selector switch 25...
・Normal Y demodulation circuit 2 days...High speed Y demodulation circuit 28...Write clock oscillator 3o...Frequency divider 31
~34...Field memory 45...Color processing circuit Figure 3 Figure 4 Output signal Figure 5 Figure 6 Procedure correction band (voluntary) April 17, 1985 Commissioner of the Japan Patent Office Black 1) Mr. Yu Akira 1. Indication of the case Japanese Patent Application No. 62-56496 2. Title of the invention Special reproduction method for VTR 3. Person making the amendment Relationship with the case Patent applicant: Akai, 2-12-14 Higashikojiya, Ota-ku, Tokyo (002) Denki Co., Ltd. 4, Agent (Telephone 986-2380) 1-20-5 Higashiikebukuro, Toshima-ku, Tokyo 6 Contents of amendment (1) “Hercal Scan V” on page 2, lines 3-4 of the specification
Correct TRJ to r helical scan VTRj. (2) R Hercal Scan VTR in the same book, same page, lines 8-9
Correct J to r helical scan VTR. 3) “Helcal Scan VTR” on the 18th line of the same page in the same book
Correct it to "helical scan VTR". (4) In the same book, page 3, line 4, ``(hercal)'' is corrected to ``Ir (helical)''. (5) "Special regeneration method" on page 7, line 15 of the same book is corrected to "special regeneration method." (6) "Modulated color signal C" in the same book, page 13, lines 15-16.
" is corrected to "modulated color signal C." (7) “Helcal Scan VT” on page 17, line 12 of the same book.
Correct RJ to ``helical scan VTII.'' (8) Correct ``on tape'' to ``on tape'' in line 12 of page 18 of the same book. (9) "Figure 7" of the drawing is corrected as shown in the attached corrected drawing.

Claims (1)

[Claims] 1. In a helical scan VTR using a rotating head, the rotational speed of the head drum is made higher than the normal rotational speed during high-speed playback, and the video signal obtained from the head provided on the head drum is A special reproduction method for a VTR, characterized in that the time axis of a video signal of a selected field is extended in accordance with the rotational speed of the head drum to obtain a video signal of a regular frequency. 2. The time axis is extended by writing the video signal of the selected field into the field memory using a write clock of a predetermined frequency, and then reading it using a read clock of a lower frequency than the write clock. A special playback system for a VTR according to claim 1, characterized in that: