JPH0316486A - Skew correction system - Google Patents

Abstract

PURPOSE:To always obtain an excellent variable speed reproducing picture in each variable speed reproduction mode by providing a 1st switch means switching and selecting an input reproduction video signal and an output video signal from a 1st minute delay means at each production of a 1/2H skew detection pulse and a 2nd switch means selecting an output video signal of the 2nd minute delay means and the output video signal of the 1st switch means. CONSTITUTION:A mode discrimination circuit 7 generates a mode decision signal (d) representing a set variable speed mode and a switch circuit 3 is controlled by using the mode decision signal (d) as a control signal and an output of a minute delay circuit 2 with a minute delay corresponding to the set variable speed reproduction mode is selected. Then a reproduction video signal (f) from a switch circuit 4 subjected to 1/2H correction is fed to a switch circuit 11 and also to a 1H delay circuit 8. The video signal (g) delayed by nearly 1H by the 1H delay circuit 8 is fed to a minute delay circuit 9 with several kinds of minute delays and respective outputs retarded by respective delays are fed to the switch circuit 10.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a skew correction method for a magnetic recording/reproducing device, and is particularly applicable to variable speed playback in which the tape is played back at a different speed from that used during normal playback. The present invention relates to a suitable skew correction method.

[Jubei technology]

Helical scan type magnetic recording and reproducing device R (hereinafter referred to as VT
An azimuth recording method has been adopted in which the azimuth angles of a pair of video heads that alternately scan the magnetic tape are made different, so that the azimuth angles are different between adjacent tracks on the magnetic tape. During normal reproduction, servo is applied to the running of the magnetic tape and the rotation of the video heads so that each video head reproduces and scans tracks with matching azimuth angles. This allows you to transfer the video from the magnetic tape! The signal is reproduced well.

During variable speed playback such as slow, still, fast forward search, and rewind search, the video head scans diagonally across multiple tracks on the magnetic tape in order to make the running speed of the magnetic tape different from that during recording. Specifically, 9, this causes the video signal to be reproduced only from the track that matches the azimuth angle of the video head.

By the way, depending on the outer diameter of the cylinder in which the video head is mounted and the running speed of the magnetic tape during recording, the tracks formed on the magnetic tape are separated by 3/4 in the longitudinal direction between adjacent tracks. It is shifted by H (however, H is one horizontal period). For this reason, the next track (adjacent tracks) having the same azimuth angle is shifted by 1/2H in the track longitudinal direction.

Therefore, when variable-speed playback is performed on a magnetic tape with the track pattern described above, the video head scans a certain track with the same azimuth angle for playback, and the video signal obtained by scanning the track and the video signal adjacent to this track. There is a deviation of K 1/2 }1 0 from the video signal obtained when the track with the same azimuth angle is scanned next time. For this reason, when an image is reproduced using a video signal reproduced in this way, when the phase of the video signal shifts by 1/2 H, that is, the video head starts reproducing scanning the track that matches the azimuth angle. Every time you do this, a skew occurs on the playback screen and distortion appears in the image.

One method for correcting this skew was published in Japanese Patent Application Laid-Open No. 55-55.
It is disclosed in Japanese Patent No. 2688. This method will be briefly explained below using the gs diagram. However, in the same figure, 3
0, 31 Ifi input terminals, 32, 35 are 1/2 H delay circuits, 34, 35 are switch circuits, 36 are 172 H skew detection circuits, 37 are inverting circuits, 38 are switch circuits, 59 are phase error detection circuits, 40 is an adder circuit, and 41 is an output terminal.

In FIG. 3, a reproduced luminance signal a reproduced from a magnetic tape (not shown) is supplied to a 1/2 H delay circuit 52 and also supplied to a switch circuit 34. The switch circuit 54 uses the 172H skew detection pulse 0 generated by the 1/2H skew detection circuit 36 as a control signal,
The reproduced luminance signal a and the luminance signal b delayed by the 172H delay circuit 32 are alternately switched. This is fi, 1/2
} A luminance signal d with 1 skew corrected is obtained. In addition, the reproduced chroma signal e is supplied to the 1/2 H delay circuit 1i%33 and also to the switch circuit wr35, and the switch circuit 35 outputs the same 1/2 H detection pulse O as the luminance system.
Accordingly, the reproduced chroma signal e and the chroma signal f delayed by the 1/2 H delay circuit 33 are alternately switched. As a result, a chroma signal g with p, 1/2}1 skew corrected is obtained.

However, in a PAL video signal, the burst phase of the chroma signal is inverted every 1H, so the continuity of the chroma phase is lost by performing 1/2H skew correction. In order to correct this, in this conventional example, 1/2H
The skinny-corrected chroma signal g is supplied to the switch circuit 5B and also to the inversion circuit W&67, and is inverted from the non-inverted chroma signal g by the phase error detection pulse 1 generated by the phase error detection circuit S9. The chroma signal h is switched alternately. As a result, a chroma signal j with continuous chroma phases is obtained.

Similarly to the reproduced luminance signal d after 1AH skew correction, the chroma signal j after chroma skew correction is added in an adding circuit 40, and outputted from an output terminal 41 as a composite video signal k.

Among these, although this conventional technique is compatible with PAL video signals, it cannot be applied to SECAM video signals in which the frequency of the chroma burst signal changes for each IH. On the other hand, one of the conventional examples in which chroma skew correction is possible for both PAL and SECAM systems is described in Japanese Patent Application Laid-Open No. 59-54396. This will be briefly explained with reference to FIG. However, in the same figure,
42 is an input terminal, 43 is a P1H:M extension circuit, 44 is a switch circuit, 45 is an output terminal, 46 is a 1/2H skew detection circuit, 47 is a chroma skew detection circuit, and 48 is a mode discrimination circuit.

In this conventional example, a 1H delay circuit is used for chroma skew correction. However, the correction of the 1/2H skew between the reproduced luminance signal and the chroma signal may be the same as the method described above.

Click the button in Fig. 6 and select the reproduced chroma signal t (after 1/2H correction).
(corresponding to the chroma signal j in FIG. 3) is supplied to the P1H delay circuit 43 and also to the switch circuit 44. 1/2H generated by the 1/2H skew detection circuit 46
A skew detection pulse O is supplied to the chroma skew detection circuit 47, and according to the mode discrimination signal q generated by the mode discrimination circuit 4B, variable speed reproduction is performed in the same direction as in normal reproduction and variable speed in the opposite direction. In the case of reproduction, the timings of the rise, 6> and fall of the chroma skew detection pulse P are changed to ftf. The switch circuit 44 uses the chroma skew detection pulse P as a control signal of 1/! The chroma signal t after H skew correction and the chroma signal m delayed by the 1H delay circuit wr43 are alternately switched. In addition, the output terminal 45 has PAL. According to the SgCAM system, a chroma signal n whose 1/2H skew button and chroma phase sequentiality are corrected is obtained.

[Invention tries to solve! ! Title]

The above-mentioned prior art corrects the 1/2H gap by switching between the reproduced signal and the fixed 1/2H period delay output. 1. Chroma skew detection pulse 1
/2 The rise and fall of the chroma skew detection pulse is different depending on whether the chroma skew detection pulse is reproduced at the same variable speed in all directions as during normal playback or when it is played back at variable speed in the opposite direction. The chroma skew is corrected by changing the timing of the signal and alternately switching between the reproduced signal and the fixed 1H period delay output.

However, in each variable speed playback mode, such as fast forward search, rewind search, still, slow, etc., the relative speeds of the magnetic tape and the video head are different from each other, so the playback horizontal synchronization The signal frequencies are different. Normally, during variable speed playback, drum servo is applied so that the frequency of the playback horizontal synchronization signal is constant, but in home VTRs, errors may occur in the correction. Therefore, if the interval of the reproduced horizontal synchronization signal is no longer constant and the output is switched to a fixed 1/2H period or 1H period delay output, a phase shift or frequency shift will occur, resulting in chroma flicker, hue fluctuation, or color fading. There was a problem that occurred.

An object of the present invention is to solve such problems, and to always obtain good variable speed reproduction images in each variable speed reproduction mode.
The purpose of the present invention is to provide a complete skew correction method that is compatible with both PAL and SRCAM systems.

[Means to solve the problem]

In order to achieve the above object, the skew correction method of the present invention includes a first means for detecting a 1/2H skew, and an IA
1 {Second means for delaying the reproduced signal by about 1/2 H period using a delay circuit; and a plurality of devices having mutually different minute delays f to which signals delayed by about 1/2 H are supplied by the second means; a fourth means for selecting the delay circuit having a set delay amount applied to the third means; and a third means for selecting the delay circuit having a set delay amount applied to the third means; and a sixth means for generating a chroma skew detection pulse corresponding to each variable speed playback mode, and a 1H delay circuit to control the output signal of the third means for approximately 1H period. a seventh means for delaying; an eighth means comprising a plurality of delay circuits to which the output signal of the seventh means is supplied and having mutually different minute delays t; Ninth means for selecting the delay circuit having a delay amount corresponding to the tape feed speed in the variable speed reproduction mode; and a ninth means for switching between the output signal of the third means and the output signal of the ninth means. It is composed of ten means.

[Effect]

When a 1/2H skew occurs in the reproduced video signal,
With the first means, the reproduced video signal is 1/! The phase of the reproduced video signal that is delayed by 1AH and immediately before the occurrence of the 1AH skew is significantly different from that of the reproduced video signal, and further, the frequency fluctuation of the horizontal synchronization signal due to variable speed reproduction is corrected by the third means, and the phase of the reproduced video signal is 1/1H.
The phases of the reproduced video signal will match with high accuracy before and after the 2H skew occurs. Therefore, the video signal obtained from the third means has a continuous phase even when the 1/2H skew occurs, and does not include the 1/2H skew.

Similarly, even if the frequency of the horizontal synchronizing signal changes due to variable speed playback, as with the seventh means button, the eighth means button, and the ninth means button, even if the frequency of the horizontal synchronizing signal changes due to variable speed playback, the distortion due to the 1/2 H skew correction will be suppressed. Accurate line sequentiality of the matrix can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the skew correction method according to the present invention, in which 1 is a 172H delay circuit, 2 is a minute delay circuit, 3.4 is a switch circuit, and 5 is a 1/2H skew detection circuit. , 6 is a chroma skew detection circuit, 7 is a mode discrimination circuit, 8 is a 1H delay circuit, 9 is a minute delay image circuit,
10 and 11 are switch circuits, 12 is an input terminal, and 15 is an output terminal.

In the figure, the reproduced video signal a is, for example, C C
D (Charge Coupled Devioe
) consisting of 1/! The signal is supplied to the H delay circuit 1 and also to the switch circuit 4. The video signal b delayed by approximately 1AH by the 1/2H delay circuit 1 is further supplied to a micro delay circuit 2 having several types of micro delay amounts, and the respective outputs delayed by the respective delay amounts are sent to the switch circuit. 5. The mode discrimination circuit 7 generates a mode discrimination signal dt representing the set variable speed mode, and the switch circuit 5 is controlled using this mode discrimination signal d as a control signal to generate a minute signal corresponding to the set variable speed playback mode. The output of the minute delay circuit 2 having a delay amount is selected. The switch circuit 4 is controlled by the 1/2H skew detection pulse e generated by the 1/2H skew detection circuit 5, and corresponds to the variable speed playback mode set with the playback video signal a. Delayed video signal 0 from switch time wr3 is 1/2
It is switched every H skew detection pulse e.

This corrects the 1/2 H skew of the luminance signal and chroma signal of the reproduced video signal.

Next, the 1/2H corrected reproduced video signal f from the switch (own) path 4 is supplied to the switch circuit 11 and also to the 1H delay circuit 8. The video signal 8 delayed for approximately 1H period by the 1H delay circuit 8 is further supplied to a microdelay circuit 9 having several types of microdelay amounts, and the respective outputs delayed by the respective delay amounts are sent to the switch circuit 10.
supplied to

This switch circuit 10 is also controlled by the mode discrimination signal d from the mode discrimination circuit 7, and the output of the minute delay circuit 9 having a minute delay amount corresponding to the set variable speed playback mode is selected. As a result, from the switch circuit 10,
Delay output h corresponding to the set variable speed playback mode
is obtained.

In the chroma skew detection circuit 6, the chroma skew detection circuit 6 has a chroma skew detection pulse set by the mode discrimination signal d outputted from the mode discrimination circuit 7 and the 1/2H skew detection pulse e outputted from the 1/2H skew detection circuit #&5. A chroma skew detection pulse 1 corresponding to the variable speed playback mode is generated.

The switch circuit 11 is connected to this chroma skew detection pulse 1.
Each time the chroma skew detection pulse i is supplied, the output signal f of the switch circuit 4 and the output signal h6 of the switch circuit 1ro corresponding to the set variable speed playback mode are switched. As a result, a reproduced video signal j whose chroma line sequentiality has been corrected is obtained at the output terminal 13.

In such a configuration, in principle, every time a 1/2H skew is detected, the reproduced video signal a and the 1AH delay circuit 1
(In the case of the PAL system, this delay time can be determined by switching between the output signal b and the output signal b of 52 μseo.

However, in a home VTR, the video head scans the track a, which is recorded diagonally with respect to the longitudinal direction of the tape, during variable speed playback, as shown in Figure 2, so that the tape travels in the same way as during normal playback. If the tape runs in the 10,000 direction, the slope changes as shown in b, and if the tape runs in the opposite direction, the slope changes as shown in 0. That is, the number of horizontal synchronization signals reproduced during one revolution of the cylinder differs from that during normal reproduction, and also differs depending on each variable speed reproduction mode. Therefore, the frequency of the horizontal synchronization signal changes accordingly. Change.

Generally, the reproduced horizontal synchronization signal is corrected by a drum servo so that it has the standard frequency at the time of recording.
There may be some errors even after correction. For that purpose, 1
When a /2H skew detection pulse is generated, if the output is switched to a fixed 1H period M delay output, a phase shift and a frequency shift occur, resulting in chroma flicker, hue fluctuation, color fading, etc.

In order to prevent this, in this embodiment, the output signal b of the 1AH delay circuit 1 is further supplied to the minute delay circuit 2 having a plurality of minute delay amounts, and the output signal b of the 1AH delay circuit 1 is further supplied to the minute delay circuit 2 having a plurality of minute delay amounts. This corrects the frequency deviation of the horizontal synchronization signal by delaying it by the amount of delay. Therefore, the phase shift and frequency shift when switching between the output signal 0 of the switch circuit 3 and the reproduced video signal a are lost.

As the minute delay circuit 2, for example, an LC7 filter or a delay line constructed of a coil (L) and a capacitor (C) can be used. For example, when a VTR has fast forward search, rewind search, and still functions, the frequency of the horizontal synchronizing signal applied to each mode changes three times, so the minute delay circuit 2 has three different delay times.
The micro-delay circuit can be configured with two micro-delay circuits, and the micro-delay circuit can be switched for each mode. For example, regarding these minute delay times, the element values of the respective LC filters are determined so that the delay time becomes longer in the order of fast forward search, still search, and rewind search. According to all the laws explained above,
Accurate 1/2 H skew correction can be performed in each variable speed playback mode.

The chroma phase of the 1/2 H corrected video signal g#i is not line sequential. In order to correct this, in principle, for example, a 1H delay circuit (PAL
In the case of this method, the delay time is 64 μs●0), and the output signal g of the switch circuit 4 can be switched between the output signal g and the output signal f of the switch circuit 4.
For the same reason as above, a minute delay circuit 9 and a switch circuit jkl}10 are provided at the next stage of the 1H delay circuit 8, and the output signal h of this switch circuit 10 and the output signal f of the switch circuit 4 are sent to the switch circuit 11. I try to switch it with υ.

As a special case, during field still or field throw, the chroma line sequence is disrupted every time the video head is switched, so the switch circuit 1 is switched in synchronization with the field head switching signal.
1, chroma skew is corrected.

FIG. 3 is a block diagram showing an example of the 1/2H skew detection circuit 5 in FIG.
15 is a frequency oscillator, 16 is a frequency divider circuit, 17 is an AND gate, and 18 is an output terminal.

In the same figure, a horizontal synchronizing signal Is of a reproduced video signal a is inputted from an input terminal 14, and is supplied to a frequency oscillator 15 that oscillates at twice the frequency of the horizontal synchronizing signal HS. A signal k that is phase-synchronized with is output. Furthermore, the oscillation output kp2 frequency divider circuit 16
supplied to

The reproduced horizontal synchronizing signal HS and the output signal t of the divide-by-2 circuit 16 are phase-compared by an AND gate 17, and FIG. 4 is a block diagram showing a specific example of the chroma skew detection circuit 6 shown in FIG. 19 is an input terminal, 20 is an inversion circuit, 21 is a switch circuit, 22 is an input terminal, 25 is a frequency divider circuit, and 24 is an output terminal.

In the same figure, a 1/2H skew detection pulse e is connected to the input terminal 19 from 1/2H skew detection pulse # & 5 (Fig. 1).
is input, and is supplied to the switch circuit 21, and is also supplied to the inversion circuit 20, and is input to the input terminal 22 from the mode discrimination circuit 7 (FIG. 1) by the mode discrimination signal d. The gap 11 detection pulse e and the pulse inverted by the inversion circuit 2o are switched.

The output pulse of this switch circuit 21 is divided by a frequency divider circuit 23, and the chroma skew detection pulse 1 is output to an output terminal 24.
is prayed for.

The above embodiment has been described with respect to a composite TV set in which the reproduced luminance signal and the reproduced chroma signal are added, but by performing the gap correction independently for the reproduced luminance signal and the reproduced chroma signal, It is also possible to separate and output the luminance signal and chroma signal. In this case, the luminance system has at least one 1/2H delay circuit, and the chroma system has at least 1/! H, 1} {Delay circuit The configuration has two delay circuits.

That is, the processing system for the reproduced chroma signal is the same as that shown in FIG. 1, and the processing system for the reproduced luminance signal is 1/2.
This is equivalent to a structure consisting of an H delay circuit 1, a delay circuit 2, and switch circuits 3 and 4. Furthermore, in order to eliminate the 1H time difference between the skew-corrected reproduced chroma signal and the reproduced luminance signal, the reproduced luminance signal processing system may be configured as shown in FIG. Of course, it goes without saying that the 1/2 H skew detection circuit 5, the chroma skew detection circuit 6, and the mode discrimination circuit 7 are common to the reproduction chroma signal processing system and the reproduction luminance signal processing system.

〔Effect of the invention〕

As described above, according to the present invention, a good variable speed reproduction image can be obtained in any variable speed reproduction mode, and skew correction applicable to both PAL and SECAM systems can be realized. Furthermore, since the skew correction of the luminance signal and the chroma number signal can be configured independently, it is possible to easily support a high-quality VTR in which there is no interference between the luminance signal and the chroma signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the skew correction method according to the present invention, FIG. 2 is a diagram showing a scanning locus during variable speed playback on a magnetic tape, and FIG. 3 is a 1/2H FIG. 4 is a block diagram showing a specific example of the chroma skew detection circuit shown in FIG. 1, and FIGS. 3D and 6 each show a conventional skew correction method. It is a block diagram. 1...1/2H delay single circuit, 2...minor delay circuit, 3
．． 4...Switch circuit, 5...1/2H skew detection circuit, 6...Chroma skew detection circuit, 7...Mode discrimination circuit, 8...1H delay circuit, 9...Minute delay Circuit, 10, Fig. 1 Fig. 2L￥1 Fig. 4 Fig. 5 Fig. 6 Fig. 6 48...71 Tori゛▼Riji・LC3 road

Claims (1)

[Claims] 1. On a magnetic tape, adjacent tracks have different azimuth angles, and between adjacent tracks with the same azimuth angle, the recording position of the horizontal synchronization signal is 1/2H in the longitudinal direction of the track (however, In a magnetic recording and reproducing apparatus in which video signals are recorded so as to be shifted by 1H (1H = 1 horizontal period), and each variable speed reproduction mode can be set for reproducing the magnetic tape at a tape feed speed different from that during normal reproduction. , a first delay means for delaying the input playback video signal by 1/2H in the set variable speed playback mode; and a first delay means for delaying the input playback video signal by 1/2H in the set variable speed playback mode; a first minute delay means for time delaying; a first detection means for detecting a 1/2H skew in the input reproduction video signal and generating a 1/2H skew detection pulse; a first switch means for switching and selecting the input reproduction video signal and the output video signal of the first minute delay means; and a second delay means for delaying the output video signal of the first switch means by 1H. , second minute delay means for delaying the output video signal of the second delay means by a minute time corresponding to the set variable speed playback mode; a second detection means for detecting chroma skew and generating a chroma skew detection pulse; and switching between an output video signal of the first switch means and an output video signal of the second minute delay means each time the chroma skew detection pulse is generated. A skew correction method characterized in that a second switch means for selecting is provided. 2. In claim 1, a third delay means for making the reproduced video signal a reproduced chroma signal and delaying the input reproduced luminance signal by 1/2H in the set variable speed reproduction mode; and the third delay means. a third minute delay means for delaying the output luminance signal by a minute time according to the set variable speed reproduction mode; A skew correction method characterized by comprising: third switch means for switching and selecting the output luminance signal of the delay means.