JPS5937786A - Reproducing device for video signal - Google Patents

Abstract

PURPOSE:To eliminate the generation of a guide noise band, by extracting a reproduction output when a tape is run at a different speed from that during recording and its delay output selectively, and compensating the reproduction output. CONSTITUTION:Heads 1A-1D reproduce signals Sfa and Sfb, field by field, from tracks alternately and signals Sa and Sc, and Se and Sf are generated from those signals. A switch circuit 28 selects the signals SC and Se alternately at every horizontal period to extract a signal Sd. In this case, the signals Sfa and Sfb are supplied to a detecting circuit 29 to detect the guide band noise, and since there is constant time difference between the guard-band-noise period of the signals Sfa and Sfb and that of the signals Sc and Se, its detection output is supplied as a control signal to the circuit 28 to select the signals Sf and Sa instead while guard band noises are generated in the signals Sc and Se, leading the signal Sd out of the circuit 28. This signal Sd has a guard band noise compensated by the signals Sa and Sf and the line number increases monotonously.

Description

DETAILED DESCRIPTION OF THE INVENTION In general, a VTR is constructed of a helical scan type, and one field P of a video signal is recorded as one diagonal magnetic track. In this case, the longer the track, the longer the recording wavelength, and the better the S/N of the reproduced signal. However, in order to increase the track length, it is necessary to increase the rotation radius of the rotary head, which has its limits, and is particularly problematic in 4-tuple VTRs.

Therefore, methods are being considered in which the time axis of the video signal is expanded and recorded.

Figure 1 shows an example of the recording system, in which the video signal Sy
is supplied from the input terminal (11) to the A/D converter Q31 through the low frequency filter 0, and is sampled at a frequency that is, for example, four times the color subcarrier frequency fC.
As shown in Figure A, it is converted into an 8-bit digital signal Sd (numbers 1 to 525 indicate line numbers).

Then, as shown in FIG. 4B, this signal Sd is applied to the memories IJ (14A) to (14) having a capacity for one horizontal period.
C), each horizontal period is sequentially written at a frequency of 4fc, and read at a frequency of 2fc, that is, 1/2 the writing speed. Therefore, the time axis of this read signal is expanded twice as compared to the original signal Sd.

Furthermore, this read signal is transmitted to the switch circuit (+5
), and from the switch circuit (15), as shown in FIG.
, 8db is extracted. And this signal 8da
, Sdb is D/A controller (16A), (1
6B) and are converted into analog signals Saa and 8ab, and these signals Saa and Sab are supplied to the FM modulation circuit (1
7A) and (17B) and are converted into FM signals 8fa and Sfb as shown in FIG.
8C) and (lsB), (xsn) through the rotating magnetic head (IA), (IC) and (lB), (ID
).

The heads (IA) to (ID) are connected between the heads (IA) and (IB), for example, as shown in FIG.
A predetermined angular interval θ is between C) and (11)), and an angular interval of 1800 is between heads (IA) and (IC) and between heads (IB) and (ID). At the same time, as shown in FIG. 3, the heads (IA) and (IB),
(IC) and (11)) have a predetermined level difference.

The heads (IA) to (ID) are rotated at a frame frequency, and the magnetic tape (2) is tilted over an angular range of just over 1,800 degrees with respect to the rotating circumferential surface.
Moreover, the heads (IA) to (ID) are caused to run in a direction opposite to the rotational direction of the heads (IA) to (ID).

Therefore, tracks (3) are formed on the tape (2) in the format shown in FIG. 5, for example. That is,
Odd field period signal 8fa, Sfb is the head (IA), (IB) is the signal track (3A),
(3B), and the signals 8fa and Sfb in the even field period are the head (IC) and (ID
) are simultaneously formed as tracks (3C) and (31)). , the tape speed and head (
By selecting the rotation radius etc. of IA) to (ID), the recording position of horizontal synchronization and Lus ph is set to track (3).
) are lined up in the width direction, and in the example shown in Figure 5, tracks (3A) and (3C)
The distance between tracks (3B) and (3D) is 1.2.
5H is shifted and H arrangement is performed, and the track (3A
) and (3B), (3C) and (3D), H arrangement is performed so that the line numbers are shifted by -1. In addition, IH
is a track length corresponding to one horizontal period of the signals Sfa and Sfb, which corresponds to two horizontal periods of the original signal Sy.

- At the time of reproduction, the original video signal Sy is reproduced by signal processing opposite to that described above.

In this way, in the VTR shown in Fig. 1, the time axis of the video signal Sy is expanded twice and recorded on the tape (2), so the recording wavelength is long, and therefore recording and reproduction with good S/N ratio is achieved. I can do it.

By the way, in a general helical scan type VTR, if the running speed of the tape during playback is different from that during recording, variable-speed playback such as still playback, slow playback, and high-speed search playback can be performed depending on the tape running speed. It can be carried out. This variable-speed playback is similar to the above-mentioned VTR, but during this variable-speed playback, the head (IA
) to (ID) diagonally scan tracks (3A) to (31)) and cross Guard Nokund, signal 8fa,
Since 8fb is not reproduced, guard band noise occurs (this also applies to general VTRs).

This invention attempts to solve these problems.

Let's explain one example below.

In Figure 6, during normal playback, the head (IA)
, (IB), (IC), and (ID), signals 8fa and Sfb are alternately reproduced from track (3) for one field at a time, and these signals 8fa and Sfb are input to a reproduction amplifier (21A).

The signals are supplied to switch circuits (22A) and (22B) through (21B), (21C), and (21D), respectively, to form continuous signals Sfa and Sfb. In this case, the heads (IA), (IB), (IC)
The angular interval θ between and (ID) is selected and the track (3A)
(3B), (3C), and (31)) are scanned simultaneously with a shift of 3 horizontal intervals, and therefore, as shown in the fourth diagram, signals Sfa and 8fb are reproduced with a shift of 3 horizontal intervals. .

These signals 8fa and Sfb are connected to a limiter (23
A).

(23B) through the FM demodulation circuit (24A), (2
4B) and the signals 8aa and Sab are demodulated, and this signal Saa+8ab is supplied to the A/D:yy part (2
5A) and (25B), and as shown in Figure 4, the same digital signal Sda and 8 db as during recording is generated.

Furthermore, the signals Sda and Sdb are transmitted to the memories (26A), (26C) and the input 2 as shown in FIG. 4E.
6B) and (26D) are alternately omitted by one horizontal period, and then read out at twice the writing frequency, and this read signal is sent to the switch circuits (27A) and (27f3). Figure 4 E
As shown in FIG. 3, the digital signals 8a and 8b have the same length as the original time axis and are arranged every other horizontal period.

This signal Sa is then supplied to the switch circuit (21O and also to the delay circuit 01) to become a signal Sc delayed by one horizontal period as shown in FIG. 4G. ). Further, the signal sb is supplied to the delay circuit 33 to become a signal Se delayed by four horizontal periods as shown in FIG.
The signal Sf is further delayed by one horizontal period as shown in FIG. 4G, and this signal Sf is supplied to the switch circuit (281).

Then, in the switch circuit (281), the signals 8c and 8e are alternately selected every horizontal period as shown by the arrows in FIG. A digital signal Sd with consecutive numbers is taken out, and this signal Sd is supplied to the 1)/A converter c34) and converted into the original video signal Sy.
y is taken out to terminal G.

On the other hand, during variable speed playback, for example during double speed playback, the scanning loci of heads (IA) and (IB) with respect to track (3) are as shown by the broken lines in FIG.
), (IB) reproduced signals Sfa and Sfb are the eighth
The line numbers are ordered as shown in Figure A. In addition, the 8th
In the figure, the broken line portion indicates guard band noise caused by the head (IA), (], B) crossing the guard band.

By the way, on a television screen, the lines (line numbers) of odd fields and the lines (line numbers) of even fields have a positional relationship as shown in FIG.
As shown in parentheses in the figure, the even field line can be considered to be at a position 262.5 smaller than the original line number.

Then, the signals 8fa and Sfb in FIG. 8A can be rewritten as shown in FIG. 8B. Then, from these signals Sfa, 8fb, signals Sa, 8c, S
e, Sf are formed, so the signal Sa
-&f becomes as shown in FIG. 8C.

In the switch circuit (c), as described above, the signals Sc and Se are alternately selected every horizontal period, and the signal Sd is taken out. However, in the case of, for example, the signals Sfa and 8fb are supplied to the detection circuit to detect guard band noise, and at this time, the signals Sfa and 8fb are supplied to the detection circuit to detect the guard band noise.
a, period of 8fb guardband noise and signal 8
Since there is a fixed time difference between the guardband noise period of signals Sc and 8e, this detection output is supplied as a control signal to the switch circuit (281), and during the period when guardband noise is occurring in the signals Sc and Se, the 8th As shown by the arrow in Figure C, the signal Sf replaces the signals Sc and Se.
, 8a is selected, and therefore, the signal 8d is taken out from the switch circuit (2 hammers) in the order of line numbers as shown in Figure 8. In this case, in the signal Sd, guard band noise is added to the signal Sa, 8f. In addition to being well compensated, the line numbers also increase monotonically.

Then, this signal Sd is converted into a signal sy])/A and taken out from terminal 0.

Thus, according to the present invention, variable speed regeneration is performed;
In this case, in particular, according to the present invention, no guard band noise is generated in the reproduced signal Sy even if the heads (IA) to (ID) cross the guard band during variable speed reproduction. Since the line numbers of the reproduced signal Sy are still monotonically increasing, when this signal sy is reproduced as a television screen, the vertical positions of the lines are not reversed.

Furthermore, it is also possible to compensate for idle lag out.

In the above description, the track format is a main turn as shown in FIG. Select the radius, angular interval θ, step, etc., and tape (2
) track format as follows.

In other words, ■ The traveling direction of the chip f(2) and the head (IA) to (1
1) If the scanning direction of (1) odd field track (3A), (
3B) and the next even field track (3C),
(3D) means that H is arranged with a shift of C2n+ 0.75 )H.

(11) Signal Sfa tracks (3A), (3C)
And the tracks (3B) and (3D) of the signal Sfb mean that the line number (L+2n+1) of the track (3B) and (3D) is adjacent to the horizontal section of the line number of the track (3A) and (3C). H-arrangement is performed so that the horizontal sections of are located respectively.

Note that the values n in terms (i) and (ii) are equal to each other and are 0 or a positive integer. Further, IH is one horizontal section in track (3), as in the case of FIG. Furthermore, even field track (3C)
, (31)) ,! : The same applies to the next odd field tracks (3A) and (3B).

■ The running direction of the tape (2) and the head (IA) to (I
If the scanning direction of D) is opposite 610 Odd field track (3A), (
3B) and the next even field track 4:! ? L-
”) and (3])) are shifted by ((2n-1)+0.25)H and arranged in H order.

(IV) Track (3A) of signal Sfa, (3
C) and signal 8fb track (3B), (3D)
This means that tracks (3B) and (3D) are located next to the horizontal sections with line numbers of tracks (3A) and (3C).
The horizontal sections of the line numbers (L-(2n-1)) are arranged in 1* order.

Note that the values n in the terms (iiD and (iV)) are positive integers that are equal to each other.Others are the same as in the first term.

Note that in the example shown in FIG. 5, n = l in term (■).

In addition, in the above, like a U standard VTR, the head (IA), (113) and (IC), (11)
) and the multi-signal sy is recorded alternately one field at a time.
Like TR, the heads (1 person) to (ID) are rotated at the field frequency, and the heads (IA) and (tB) record the horizontal scanning period of the signal sy of one field, and then the head (IC) records the horizontal scanning period of the signal sy of one field. ), (ID) may be used to record the remaining vertical synchronization pulse (vertical retrace period).

In addition to the angular spacing θ and steps of the heads (IA) to (ll)), the memo 'IJ (14A) to (14c) and the timing of reading them may be modified to create a format as shown in Figure 5, for example. It is also possible to do this.

[Brief explanation of the drawing]

Figures 1 to 5 and Figures 7 to 9 are diagrams for explaining the present invention, and Figure 6 is a system diagram of an example of the present invention. (I+) ~(18D) is the recording system, (21A) ~r3
! e is a carrier silk.

Claims (1)

[Claims] The video signal is recorded by running the tape obliquely over a predetermined angular range with respect to the rotating peripheral surface of the recording head, and one field of the video signal is divided into a plurality of adjacent tracks and recorded. To reproduce the video signal from the tape that has been recorded, the tape is run diagonally over a predetermined angular range with respect to the rotating circumferential surface of the playback head at a speed different from that at the time of recording. A video signal reproducing device which delays the reproduced output of a head and selectively extracts the delayed output and the reproduced output to compensate for the reproduced output.