JPS63110881A - Recording and reproducing device for video signal - Google Patents

Abstract

PURPOSE:To reproduce a satisfactory varying by controlling the travel speed of a tape at the time of reproducing the varying speed to prescribed-multiplied at the time of recording. CONSTITUTION:If a multichannel and multisegment recording system is introduced and the output level of a reproduced signal from a recorded magnetic tape 1 exceeds a prescribed level at the time of reproducing the varying speed, the reproduced signal is written in a field memory 6 the written contents is read asynchronously with the synchronizing signal of the reproduced signal. In such a case, memory control circuits 9a and 9b control the writing and reading into the memory 6 based on the synchronizing signal outputted from a video signal processing circuit 5 and outputs from comparators 8a and 8b. The travel speed of the tape 1 at the time of reproduction is controlled to (N+m/M)-multiplied (N is integer: m and M are mutually prime positive integers, and m<M). Consequently, a high speed reproduction without the deterioration of an S/N and a fixed noise band is attainable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to variable speed playback of a video signal recording and playback device (hereinafter referred to as VTR) that employs a multi-channel, multi-segment recording method. [Technology] Conventionally, the high image quality of variable speed playback of VTRs, which have adopted a recording method in which one field of video signal is recorded on one track on magnetic tape (one channel, one segment recording method), has been achieved by high precision tape running control. This has been realized through the use of advanced technology and special playback heads. In addition, with the recent trend toward lower prices and higher speeds and higher densities of semiconductor products such as memories, some VTRs have been equipped with field memories to perform variable speed playback better.

Variable speed playback using field memory will be explained below. Figure 3 shows a VTR variable speed playback system using field memory, (1) is a recorded magnetic tape, (2a
)#(21)) are rotating heads with different azimuths,
(3a) and (3b) are respectively rotating heads (2a).

A head amplifier amplifies the output of (2b), (4) a switching circuit that selects the output of either head amplifier (3a) or (3b), and (5) performs FM demodulation to obtain a video signal. (6) is a field memory; (7) is an envelope detection circuit that extracts the envelope of the reproduced FM signal; (8) is a video signal processing circuit that also detects a synchronization signal.
) is a comparator that compares the output of the envelope detection circuit (7) with a predetermined level, and (9) is a comparator (7) that compares the output of the envelope detection circuit (7) with the synchronization signal output from the video signal processing circuit (5).
A memory control circuit that performs write control of the field memory (6) based on the output of the field memory (6) and performs read control asynchronously with the above synchronizing signal,
is the control head, ση is the OF motor, (2) is O
Motor Drino (, (To) is a travel control circuit that controls the motor driver @, which troubles the P motor (B).) Next, the operation will be explained.
．． ±6... 0+ indicates the direction in which the archer is traveling (the same direction as in normal playback), - indicates the opposite direction. ) will be played back at high speed. If M=6, the relationship between the recording track and the head travel trajectory is w! 0 as shown in J4 diagram (a)
In the figure, 9R and L are marked on the track and are heads (2a
), (2b) or a head having the same azimuth as that.

Due to the azimuth effect, what is reproduced by each head is
The signal is indicated by the diagonal line on the track. The comparator circuit (8) compares the output of the envelope detection circuit (7) with a predetermined level and outputs a signal representing the magnitude relationship to the memory control circuit (9). The memory control circuit (9) operates to write the output of the video signal processing circuit (5) into the field memory (6) when the output of the envelope detection circuit (7) is above a predetermined level. Therefore, in the field memory (6), 1
If the video signal for one field is recorded in the pattern shown in FIG.

On the other hand, there is a high-definition TV system that has recently been developed as a next-generation TV system and is being put into practical use. The video signal band of the high-definition TV system is approximately 2
It has a wide band of 0.2. As a means for recording such wideband signals, there is a method that employs a multi-channel multi-segment recording method. In other words, by increasing the number of channels, the signal bandwidth per channel can be reduced, and by increasing the relative speed between the multi-rotation head and the magnetic tape by increasing the recording wavelength by increasing the number of segments, the conventional magnetic This is an attempt to record and reproduce broadband signals using recording technology.

A case using the two-channel three-segment recording method will be described below. The input video signal (one channel composite signal) is divided into two channels (OH and A, respectively) in one horizontal scanning period (hereinafter abbreviated as 1H).
, CH, B) The K shift extends the time axis by twice. As a result, the signal bandwidth of each channel is halved.

FIG. 5(a) shows the arrangement of the rotating head.

(A) is a rotating drum, (20a), (zob)
is a rotary head for recording and reproducing signals of CH and A (21a
), (211)) are rotary heads for recording and reproducing the OR and B signals.

Rotating heads (20a), (21a), (20b), and (
211++) are arranged adjacently. Further, during recording and reproduction, the magnetic tape is wound around the rotating drum (A) with a strong xsCP. The rotating drum (A) rotates 1.5 times during one field period. Therefore, one field of video signal is recorded by being divided into three segments (3 segments) for OH, A, OR, and B. FIG. 5(b) shows a conceptual diagram of the two-channel three-segment recording system, and FIG. 5(0) shows a recording track pattern formed on the magnetic tape (1). Al, A2, and A3 shown on the tracks indicate the video information of the gl and #le third segments recorded by the heads (2a) and b) for channel A, respectively.

Here, consider high-speed playback in which the tape running speed is increased by an integer multiple as in the past. When M=2, the relationship between the recording track and the scanning trajectory of the head is as shown in FIG. 6(a).
lb) have the same azimuth.

Since there is no azimuth effect, it is possible to reproduce the video signals of all tracks that the head crosses.

On the other hand, the head (2
0a), (20b) and the head (21a)
).

There is a section where what was recorded at (211:+) is read at the same time. In this part, the video signals overlap, making it impossible to obtain a good output.

Considering the above, the first segment C! The output envelopes of H and A are shown in (0) of the same figure. In the shaded areas, overlapping occurs and a good screen cannot be obtained. The same figure (d
) shows the actual screen. The shaded area shows that the video information in the field memory is not rewritten and a fixed nozzle band occurs. When such a fixed noise band occurs, a problem arises in that a visually good screen cannot be obtained.

[Problem that the invention seeks to solve]

Therefore, even though field measurement is used, VTs that adopt a multi-channel multi-segment recording method
In the case of R, there was a problem in that a dropout occurred in the video signal during variable speed reproduction, making it impossible to obtain a visually good video.

This invention was made to solve the above-mentioned problems, and an object thereof is to realize good variable speed reproduction using a field mechanism.

[Means for solving problems]

The V'I'R according to the present invention is configured so that the running speed during variable speed reproduction is (N+m/M) times that during recording. Here, N, M, and m are integers, and N=0. ±1.
±2...M==2.3,4...m=+l, 2.3 - one bitee However, M>m. Furthermore, M and m are relatively prime. 0 [Operation] According to the above structure, in variable speed playback of a multi-channel multi-segment recording VTR, by appropriately selecting the running speed of the tape, the fi S/N can be improved. A good variable speed playback screen without any drop or fixed noise band can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) and (II-(to)) are the same as in Figure 3, so explanations are omitted. (2a), (2b) and (3)
a) and (3b) are rotary heads with different channels, (41!L) and (41)) are head amplifiers,
The video signal processing circuits (5a) and (5b) perform FM demodulation to obtain a video signal, detect a synchronizing signal, and perform time correction and the like. (6) is field memory% (7
8), (ma b) to -cy 0-near' test i times iL (
8a), Q! lb) is a comparator, (9a)-(9b
) performs write control of the field memory (6) based on the synchronization signal output from the video signal processing circuit (5) and the outputs of the comparators (8a) and (8b), and read control is asynchronous with the above synchronization signal. It is a memory control circuit that performs. (30a) and (30t+) are each O
The field memory (6) is a memory for storing what is recorded in H, A and CH, B, and is composed of these two memories (30a) and #(30b).

Next, the operation will be explained. As an example, consider a case where the tape running speed is (3+1/4) times that of recording and a two-channel three-segment recording method is adopted. Head (z
It is assumed that a), (2b) and (3a)t (31)) have the same azimuth.

As in the conventional example, the relationship between the recording track and the head scanning locus is as shown in FIG. 2(a). Since the same azimuth is used, as in the conventional example, the reproduced video signal has overlap of the reproduced signals from adjacent tracks, as shown by the hatched area in FIG. 2(1)). The widths of the comparators (8a), (8b) and the guard band are appropriately adjusted so that no overlapping parts occur. Considering that the relationship between the track pattern and the head trajectory is repeated with four field periods being synchronized, C! The output envelope of the first segment of H and A is shown in FIG.

Reading from the field memory (6) is performed asynchronously to the writing operation. As shown in FIG. 2(c), the output level of the reproduced video signal stored in the field memory (6) is relatively high, and the S/N of the read video signal does not deteriorate to the extent that the screen becomes unsightly. Also, 4
Since all data is rewritten twice for each field, there are no fixed noise bands and extremely high-speed playback can be achieved.

In this case, focus on the video signal output from one of the heads (0! (, A or CH, B). For example, consider only the output of CH, A. The track pattern in Figure 2 (,) From the relationship of the head scanning locus, the envelope diagram of CH,A during the 4-field period is shown in the same figure (Q).The shaded area is the output envelope of the first segment of OH,A. (e) is obtained.It can be seen that the same performance as above can be obtained by using only one channel.

This has the effect that signal processing written into the field memory (6) can be relatively simple.

Nao, in the above embodiment, (3+x/4) times the speed was shown as an example when the 2-channel 3-segment recording method was adopted, but even when the multi-channel multi-segment recording method was adopted, the tape running speed could be changed at the time of recording. of the speed of (N+m
/M) A similar effect can be achieved by appropriately selecting the double speed.

Further, in the above embodiment, azimuth recording was performed, but the same effect can be obtained even when each channel has a different azimuth head.

However, N, M, and m are integers, and N22. ±1
．． ±2. ±3...M=2.3,4...fist・m=1,2,3・Q...M)m M and m are relatively prime. Furthermore, when determining the tape running speed, if the number of segments is S, in the range S≧2, (N→)XMXk=rXS N: integer M: 2, 3.4...m: 1, pt, s- Fist skewer-M) mk: 1,
It is determined that there is no integer r that satisfies the relationship 2, 5---8-1.

In addition, when each channel has the same azimuth, other than the above conditions (the following condition must be satisfied. Letting the number of channels be L, determine an integer M that satisfies the relationship L to M.

The above-mentioned restrictions on determining the tape running speed are due to the following reasons. VTRs that generally use the S segment recording method
In the variable speed playback at (N+m7M) times, the contents in the field memory are rewritten in M field cycles. However, before the above conditions are met, the process returns to the beginning and a fixed noise band is generated, making it impossible to obtain a good variable speed playback screen. Furthermore, if all the heads have the same azimuth, as described above, the video signals will overlap, resulting in an output envelope as shown in FIG. 6(C) in one scanning period. Here, if M is determined so that L=M, the position where a good envelope is output will be at the same position as the next one scanning period, the next one scanning period, etc., so the shaded part The video signal is dropped, causing a fixed noise band as described above, making it impossible to obtain a good variable speed playback screen.

The proof is omitted here, but in the above embodiment, as an example of a case where a 2-channel 3-segment recording method is adopted (3
+1/4) double speed, but in high-speed playback when a multi-channel multi-segment recording method in which each channel has the same azimuth, the tape running speed satisfies the above conditions, M = 2XjXL (L is number of channels,
j=l.

2...), the same effect as described above is achieved in that high-speed playback can be performed just by using one channel.

〔Effect of the invention〕

As described above, according to the present invention, during high-speed playback, the tape running speed is multiplied by (N + m7M) (N is an integer, m is a positive integer, M is a positive integer) and a field memory is used. Since the image is reproduced at high speed, the S/N
This has the effect of making it possible to perform good high-speed playback without excessive deterioration or fixed noise bands.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram of a video recording and reproducing device according to an embodiment of the present invention, Figs. 2 (a) to (e) are explanatory diagrams of the operation of the inventive device, and Fig. 3 is a conventional one-channel, one-segment method. A block diagram of a video recording and playback device that employs
Figures 4 (a) and (b) are explanatory diagrams of the operation of a conventional video recording and sickle playback device, Figure 5 is a conceptual diagram of a 2-channel 3-segment recording system, and Figure 6 is a diagram using a 2-channel 3-segment recording system. This is an explanatory diagram of the operation in this case. In the figure, 1...magnetic tape, 2a, 2b...rotary head (OH, A), 3a, 3b = rotary head (
OH, B), 5a, 5b... Video signal processing circuit, 6... Field memory, 7a, Ma b... Envelope detection circuit, aa, sb °°° comparator, 9
a, 9b...Memory control circuit, 13...Travel control circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A multi-channel multi-segment recording method is adopted, and when the output level of the playback signal from the recorded magnetic tape is higher than a predetermined level during variable speed playback, the playback signal is written to the field memory, and the written content is used as the playback signal. In a video signal recording and reproducing device that reads a video signal asynchronously with a synchronization signal, the running speed of the magnetic tape during variable speed playback is multiplied by (N+m/M) during recording (N is an integer: m, M is a relatively prime positive number). 1. A video signal recording and reproducing device comprising a travel control circuit that controls an integer so that m<M. (2) The video signal recording and reproducing apparatus according to claim 1, wherein M≠L, where L is the number of channels.