CA1088197A - Color video signal recording and/or reproducing apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A color video signal recording and/or reproducing apparatus which comprises a circuit for generating a first signal having a field frequency of the color video signal and circuit for generating a second signal which indicates a field interval having a predetermined phase relationship between a horizontal synchronizing signal and a color subcarrier signal. In NTSC signal, the second signal is generated every four field. The first and second signals thus obtained are synthesized to form a composite control signal, and the latter is recorded on a control track of a magnetic tape in the conventional manner. The apparatus further comprises a circuit for comparing the composite control signal reproduced from the tape with a reference control signal. The reference control signal is composed of a third signal having a field frequency and a fourth signal indicating a field interval, in which a phase relationship between a reference horizontal synchronizing signal and a reference color subcarrier signal is equal to said predetermined phase relationship. Thus, in reproducing, a travelling of the magnetic tape is controlled in response to the output of the comparing circuit so that the phase of the composite control signal reproduced from the tape coincides with that of the reference control signal.

Description

Background of the Invention Field of the Invention This invention relates to a color video signal recording and/or reproducing apparatus and, more particulary, to an apparatus for providing precise color frame lock of color television signals, even if a splicing of a magnetic tape con-taining the color television signals, like NTSC signal, will be done electrically or physically.
Description of the Prior Art ~ . . . =. . _ . . . .
As is well known, in the NTSC color television signal, there is an exact frequency relationship between the horizontal synchronizing frequency fh and the color subcarrier frequency f , namely fSC=455!2fh, and consequently four television fields must occur before the color subcarrier signal e~actly repeats itself in phase with respect to the horizontal synchronizing signal. In other words, the periods of the color frame is four fields. This is explained with reference to Fig. 1 in more detail. Assuming now that the color sub-carrier signal Sc has its positive peak value at the front edge o~ the horizontal synchronizing signal Ph ~which is indicated by an arrow ~ in Fig. 1~, the signal Sc has its negative peak value at the front edge of the subsequent horizontal synchronizing signal Ph [which is indicated by an arrow ~-in Fig. 1]. This means that the ph~se of the subcarrier signal Sc is reversed at every horizontal interval. As a result of the reversal, as shown in Fig. 3A, it is apparent that, if the sub-carrier signal Sc has its negative peak valua at the front edge of the first equalizing pulse Pe included in the first field of frame 1, the signal Sc has its positive peak value at the front edge of the irst equalizing pulse Pe included in the first ield of frame 2 which is immediately adjacent in time to frame 1. In that sense, the frames 1 and 2 are different, and it will ., .

he evident that if a continuous signal is to be reproduced, splices must join the succeeding frames in correct sequence;
i.e., the frame 1 must be joined to the frame 2. If the frame 1 is joined to another frame 1, there will be a sudden 180 phase shift in the burst or color subcarrier signals at the splicing point.
In the conventional color television receiver, the color subcarrier signal Sc being used for synchronous detector is formed on the basis of the burst signals, and further the subcarrier signal forming circuit has a fly-wheel effect to some extent, so that even if the phase of the burst signal is suddenly reversed, the phase of the subcarrier signal Sc cannot follow the sudden change of the phase of the burst signal. As a result, there are existing some phase differences between the chrominance signal and the color subcarrier signal, and hence the hue on a reproducing picture will be disturbed transiently.
This is an obviously unacceptable condition, and the normal VTR is provided with means for recognizing the improper phase and shifting the phase of the whole television signal by half a cycle of the subcarrier signal to bring it back into ~he proper phase. In order to perform the above -~
operation, the VTR has a delay line, to which the color ;~
television signal is applied. The burst signal separated from the signal is compared in phase with a reference subcarrier signal in a comparator, and if the phase of the color subcarrier signal is reversed at the editing point, an error voltage will be obtained from the comparatox. The error voltage is supplied to the delay line to shift the phase of the whole signal, and ~
thus the latter will be moved 180 (140 nano seconds) ahead or -behind the proper timing position~ In other words, the phase correction places the color subcarrier signal in proper phase, but it introduces a 140 nano second error in the horizontal

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timing. Thus, the insertion or removal of 140 nsec. of delay at the editing point causes the picture on the screen to jump sideways.
In order to avoid the above-described disadvantage, there are proposed several approaches and methods. One method is to use the 15 H frame pulses instead of the 30 H pulses used on the control track. This refers to use of frame pulses at one-fourth the basic field repetition rate of NTSC signals.
This means that a servo operation is performed once every four field. Accordingly, the lock-up time of the servo operation will be increased by approximately 20 percent in comparison with ~he 30 Hz servo operation. Also, it is difficult to splice the tape at the exact field or frame.
Another method is to use the servo control circuit, in whicht if the error voltage from the burst phase comparator indicates lock-up to the wrong frame, an electrical signal is generated which causes the tape drive motor momentarily to speed up thereby to physically move the magnetic tape ahead by a distance corresponding to approximately one frame. However, in -- -this method, the servo circuit must be unlocked once the error voltage is detecked, and thereafter the servo circuit is operated to lock in the new frame again. This means that the total lock-up time of the VTR is increased extraordinarily, as well ; -as the above-described method.
Summary of the Invention Therefore, an essential object of this invention is to provide an improved color video signal recording and/or reproducing apparatus which can lock up to the proper color frame in a short time.
In accordance with the invention, the color video signal recording and/or reproducing apparatus comprises a circuit for generating a first signal having a field frequency '' "' ~ _3_ - . . ............................................... .
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of the color video signal and circui-t for yenerating a second signal which indicates a field interval having a predetermined phase relationship between a horizontal synchronizing signal and a color subcarrier signal. In NTSC signal, the second signal is generated every four field. The first and second signals thus obtained are synthesized to form a composite control signal, and the latter is recorded on a control track of a magnetic tape in the conventional manner. The apparatus further comprises a circuit for comparing the composite control signal reproduced from the tape with a reference control signal. The reference control signal is composed of a third signal having a field frequency and a fourth signal indicating a field interval, in which a phase relationship between a reference horizontal syn- .
chronizing signal and a reference color subcarrier signal is equal to said predetermined phase relationship. Thus, in re-producing, a travelling of the magnetic tape is controlled in response to the output of the comparing circuit so that the phase . :
o:E the composite control signal reproduced from the tape coin-cides with that of the reference control signal. .;
More particularly, there is provided: :
a color video signal recording and/or reproducing ::~
apparatus comprising;
means for generating a first signal having a field :
frequency of said color video signal;
means for generating a second signal indicating a field interval which has a predetermined phase relationship between a synchronizing signal and a color subcarrier signal;
: means for inserting said second signal into said first signal and the.reby a composite control signal is produced; ;
~30 means for recording said composite control signal on a recording medium and reproducing the former therefrom;

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means for comparing said composite control siynal reproduced therefrom with a reference control siynal, said reference control siynal comprisiny a third siynal haviny a field frequency and a fourth siynal indicatiny a field interval in which a phase relationship between a reference synchronizing signal and a reference color subcarrier siynal is substantially equal to said predetermined phase relationship, and, means for controlliny a travelling of said recordiny medium in response to a control output of said comparing means so that the phase of said reproduced control signal coincides with that of said reference signal.
Brief Description of-the Drawinys . _ ~ . ... _ .. _ .. _ .. . . _ Other objects, features and advantayes of the invention - -will become apparent, and its construction and operation better understood, from the following detailed description taken in conjunction with the accompanyiny drawings, in which;
Fig. 1 is waveforms of the horizontal synchronizing signal and the color subcarrier signal, to which reference has already been made in discussing the background of the invention;
Fig. 2 is a block diagram of a field discriminating signal generator which is used in the system of this invention;

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Figs. 3 and 4 are timing waveEorms which are used for explaining the operation of the generator of Fig. 2;
Fig. S is a schematic block diagram of the video signal processing apparatus of this invention;
Fig. 6 is a timing waveform which is used ~or explaining the operation of the apparatus of Fig. 5.
Description of the_Preferred Embodiment An example o~ the present invention will be herein described with reference to the drawings.
Firstly, a field discriminating signal generator used in the system o~ the present invention will now be -described.
Fig. 2 shows a ~ield discriminating signal generator 30 as a whole, in which a numeral 10 designates an ; external synchronizing signal generator producing a color sub-carrier signal Sc and a composite synchronizing signal Pc. The color subcarrier signal Sc is fed to a slicing circuit 11 to be wave-formed as a rectangular-shaped signal which is then fed to à D-input terminal o a D-flip-~lop circuit 12. The com-posite synchronizing signal Pc~from the generator 10 is applied to a slicing circuit 13 to be wave-formed as a signal Pc shown in Fig. 3A and then applied to a T-input o~ the fli~-flop ~
circuit 12. Thus, the flip-flop circuit 12 is triggered by ~ ;
the going-down edges of the synchronizing signal Pc and hence produces at its Q-terminal a raGtangular waveform signal Sb, the level of which is varied to take "1" or "0" in response to the levels of the subcarrier signal Sc at the going-down edges of the horizontal synchronizing signal Ph in the signal Pc as shown in Fig. 3B.
However, it should be noted that, during the vertical interval, the signal Sb can not be alternatively changed at every horizontal interval, as shown in Fig. 3B. The ~ 5~
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reason is that the flip-~lop circui-t 12 is triggered by an equalizing pulse Pe (refer to Fig. 3A). That is, the equalizing pulse Pe, which is positioned at every one H
duration with respect the horizontal synchronizing pulse Ph, is equivalent to the horizontal synchronizing pulse Ph, so that the signal Sb is made "0" or "1" alternatively in response to the levels of the subcarrier signal Sc at the position (refer to the arrows ~ in Fig. 3A), as shown in Fig. 3B by the solid lineO While, the half-H pulse P is positioned at odd multiple of 0.5 H with respect to the pulse Ph, so that the subcarrier signal Sc at the position also becomes a nodal point tchanging point). As a result, the level of the signal Sb becomes vague or ambiguous during the interval from the half-H pulse Pe to the next pulse Pe as shown in Fig. 3B by a dotted line.
Further, it is noted that the level of the signal Sb is opposite with each other a-t the starts of the first and third ~ields. Thus, the output signal Sb ~rom the flip-flop circuit 12 is ~ed to a D-terminal of a D-flip-flop circuit 14, which is triggered by the going-up edges of the signal ~upplied to a T-terminal of the D-fllp-flop circuit 14.
On the other hand, the composite synchronizing signal P ~rom the slicing circuit 13 is supplied also to a serrated signal forming circuit 17, in which a capacitor 17C
is charged through a resistor 17R from a voltage source +Vcc during the level of the signal Pc being "0", that is, a transistor 17T being OFF. As a result of the charglng of the capacitor 17c, a serrated signal Sa as shown in Fig. 3C is generated from the circuit 17. Herein , it is of importance that the serra~ed signal Sa has larger amplitude during the vertical synchronizing interval than that during the other interval. The serrated signal Sa is supplied to a mono-. . .

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multivibrator 18, which is triggered by the going-down edge of the first serrated signal Sa in the vertical synchroniziny interval, and which generates a rectangular signal Sd having a pulse width more than the vertical synchronizing interval as shown in Fig. 3D. The rectangular signal Sd is supplied to the T-terminal of the flip-flop circuit 14 as set forth above.
As above-described, the signal Sb is supplied to the D-terminal of the flip-flop circuit 14, so that the flip-flop 14 produces at its Q-terminal a signal S as shown in Fig.
3E. The signal Se is produced in the manner that, since the level of the signal Sb is "1" at the going-up edge of the signal Sd in the first field, the level of the signal Se becomes "1"
and since the level of the signal Sb is "0" at the going-up ~
of the signal Sd in the third field, the level of the signal -Se becomes "0". Further, in the second and fourth fields the .
level of the signal Sb is ambiguous at the going-up of the signal Sd, so that the level of the signal Se also becomes ambiguo.us also.
The signal Sd from the mono-multivibrator 18 is further supplied to a mono-multivibrator 21 which is triggered by the going-up edge of the signal Sd and produces a pulse Pn which rises up at the going-up edge of the signal Sd and goes down at the time after about lH duration passing from the starting point Pv as shown in Fig. 4D. The pulse Pn is supplied to a mono-multivibrator 22 which is triggered by the going-down edge of the pulse Pn and produces a pulse Pp of narrow ' width which is substantially equal to the horizontal ~, synchronizing pulse width, as shown in Fig. 4E. In this : case,it is noted that the pulse Pp is produced at every one field and located at a position passing about lH durationafter the starting point of the vertical synchronizing signal.
The pulse Pp is supplied to one input termi.nal of an AND-circuit :

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23.
The composite synchronizing pulse Pc from the generator 10 is further supplied to a mono-multivibrator 25 which is triggered by the going-down edge of the pulse Pc and produces a rectangular waveform signal Sq which has a pulse width more than the half-H duration as shown in Fig. 4F. This signal Sq is fed to a mono-multivibrator 26 which is triggered by the going-up edge of the pulse Sq and produces a pulse Pr which is synchronized with the horizontal synchronizing pulse Ph. This pulse Pr is fed to the other input terminal of the AND-circuit 23.
Accordingly, the pulse signals Pp and Pr are fed to the AND-circuit 23, so that the AND~circuit 23 produces a pulse signal Ps shown in Fig. 4H at every odd field or first and third fie:Lds. This is because the pulse Pp is shifted from the horizontal synchronizing Ph by 0.5 H in the second and fourth fields. That is, appearance of the pulse Ps shows that the field is first and third field.
The pulse Pp of the field period from the mono-multivibrator 22 is fed to a reset terminal of a flip-flOp circuit 27 , while the pulse Ps from the AND-circuit 23 is supplied to a set te~minal thereof. The flip-flop circuit 27 thus produces a signal Sf which is reversed at every pulse Pp. That is, the signal Sf becomes "0" in the first and ;
third fields and becomes "1" in the second and fourth fields as shown in Fig. 4I and Fig. 3F, respectively. The signal Sf is supplied first to a D-terminal of a D-flip-flop circuit 28, which is trigg~red by the going-down edges of a signal applied to its T-terminal, and second to a mono-multivibrator 29, which is triggered by the going-up and going-down edges of the signal ;
Sf and produces at a rectangular wave signal Sg having the pulse width of approximately half-field duration as shown in .,~::., : :

q Fig. 3G. This signal Sg is applied to the flip-flop circuit 28 at its T-terminal as set forth above, so that -the flip-flop circuit 28 produces its Q-terminal a rectangular wave signal Sh which is reversed at about the center of each field and has a high level in the former halves of the first and third fields and in the latter halves of the second and four-th fields as shown in Fig. 3H.
The signal Sh is then fed to a mono-multivibrator 31 which is triggered by the going-down edge of the signal Sh and produces a pulse Pi having a pulse width of about 3H as shown in Fig. 3I. This pulse Pi is then fed to a mono-multivibrator 32 which is triggered by the going-down edge o~
the pulse Pi and produces a pulse Pj having a pulse width of about 3H as shown in Fig. 3J. As apparent from the above description, the pulse signal P] is located at the position after 3H from the going-down edge of the signal Sh.
The pulse Pj is supplied to one input terminal of an AND-circuit 33 while the signal Sè from the circuit 14 is supplied to its other input terminal thereof. Accordingly, the AND-circuit 33 delivers therefrom the pulse Pj in only the first field as an index pulse signal Pk as shown in Fig. 3K.
The pulse Pk and the signal Sh from the flip-flop circuit 28 are supplied to an OR-circuit 34, which then produces a rectangular wave signal Sm which is reversed in level at -every one field and contains the pulse Pk in the first field as shown in Fig. 3L. Thus, it is noted that this signal Sm is varied with a four-field period and contains the index pulse Pk in the first field. As will be described later, the pulse signal Sm, which is obtained from OR-circuit 34 and delivered to an output terminal 35, is used as a field discriminating signal in color framing.

The video signal processing apparatus according to ~, _g_ .h ~ t this invention is to provide a color framing system usiny the field discriminating signal Sm. The one embodiment of the apparatus will be explained hereinafter in reference to Fig. 5.
In Fig. 5, a pair of rotary magnetic heads 1 and 2 are provided with the angular distance of 180 and are rotated by a motor 41 at the speed of frame frequency. A
magnetic tape 3 is obliquely in contact with the rotary peripheral sur~ace of the heads 1 and 2 with the angular range of about 180 and is transported by the cooperation of a capstan 51 and a pinch roller 52 at a predetermined speed.
During recox~ing, a color video signal, which is applied to a video input terminal 4, is supplied to a recording circuit 5, in which the color video signal is processed in the conventional manner. The video signal thus obtained is supplied through an R-terminal of a switch 6 to the magnetic heads 1 and 2 to be recorded as a slanted track on the magnetic tape 3. On ; the other hand, during reproducing, the color video signal reproduced from the magnetic tape 3 by means of the heads 1 and 2 is supplied through a P-terminal of the switch 6 to a reproducing circuit 7, from which the processed video signal is obtained and supplied to a video output terminal 8.
The video signal processing apparatus is provided with a drum servo circuit 40 controlling the phase of the rotary magnetic heads 1 and 2, and which has a pulse generator 43 ` mounted on a rotary shat 42 of the heads 1 and 2. The pulse generator 43 produces a pulse indicating the rotary phase of the heads 1 and 2 at every one rotation thereof. The pulse from the generator 43 and the composite synchronizing pulse Pc from the synchronizing signal generator 10 are supplied to a comparator circuit 44, in which the former is phase-comparated -~
with the vertical synchronizing signal Pv in the pulse Pc. The output signal from the comparator 44 is fed through an amplifier :

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45 to the motor ~1. Thus, the rotary phase of the heads 1 and 2 are synchronized with the vertical sy~chroniziny pulse Pv in the pulse P from the generator 10.
The video signal processing apparatus is also provided with a capstan servo circuit 60 controlling the rotating speed of the capstan 51, and which has a reference voltage source 61 producing a reference voltage. During recording the reference voltage is supplied through an R-terminal of a switch 62 to a voltage controlled or variable frequency oscillator 63 to control the frequency of the oscillating signal therefrom, and thereby a constant frequency signal will be obtained from the oscillator 63. The oscillating signal from the oscillator 63 is fed to a phase modulator circuit 64 as a carrier signal.
On the other hand, a frequency generator 65 is provided on a rotary shaft 54 of a motor 53 driving the capstan 51. This generator 65 produces an alternating signal which is then fed to a frequency discriminator 66, in which the alternating signal is converted to a DC voltage proportional to the rotating speed of the capstan 51. Since this DC voltage from the frequency discriminator 66 is supplied to the phase modulator 64 as a modulating input signal, the carrier signal from the oscillator 63 is modulated with the DC voltage. The modulated signal from the modulator 6~ is supplied through an amplifier 67 to the motor 53. Thus, the motor 53 is rotated at a constant speed with the reference voltage from the voltage supply source 61, and hence the tape 3 is transported at a constant speed.
In Fig. 5, numeral 30 represents the generator circuit forming the discriminating signal Sm, which was already ~ -described in connection with Fig. 2. During recording, the ~ -signal Sm from the circuit 30 is supplied through an amplifier 30 71 and an R-terminal of a switch 72 to a control head 73.
Thus, the signal Sm is recorded by the control head 73 on the ' ~ -11-

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longitudinal track formed along the edge of the tape. This means that on the tape 3 there is recorded the siynal Sm which indicates the phase of the color subcarrier siynal in the color video signal relative to the horizontal synchroniziny signal Ph.
On the other hand, during reproducing the field discriminatiny signal Sm from the circuit 30 and the signal Pm repxoduced by the control head 73 and passed through an amplifier 74 are supplied to a phase detecting circuit 100, in which the signal Pm is compared in phase with the signal Sm, and the phase detecting circuit 100 produces a control voltage so as to synchronize the signal Pm with the signal Sm during the color framing operation. The control voltage from the circuit 100 is supplied through a P-terminal of the switch 62 to the oscillator 63, and thereby the rotating speed of the capstan 51 is controlled in response to the control voltage in the above-described manner.
The phase detecting circuit 100 is provided with a framing switch 101, the movable arm of which is connected to an A-terminal thereof in color framing operation, to a B~terminal thereof in VH framing operation and to a C-terminal thereof in field lock OperatiOn~ respectively.
The reference field discriminating signal Sm from the circuit 30, shown in Fig. 6A is supplied first to a mono-multivibrator 131 of a reference signal forming circuit 130 which is triggered b~ the going-down edge of the signal Sm and produces a pulse signal P31 having a pulse width somewhat -narrower than one field duration F, for example, 0.8F shown in Fig. 6C, and second to another mono-multivibrator 132 which is triggered by the going-up edge of the signal Sm and produces a pulse signal P32 having the same pulse width as that of the pulse P31, as shown in Fig. 6D. In Fig. 6, for simplicity ~ . . ~ . , .

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of the explanation, the phase of the sign~l Sm is delay~d by 1/2 field. The pulses P31 and P32 are supplied to both input terminals of an AND-circuit 133, so that the AND-circuit 133 produces a pulse signal P33 only in the first field as shown in Fig. 6E. The pulse signal P33 is then fed to a mono-multi-vibrator 134 which produces a pulse signal P34 rising up at every going-up edge of the pulse P33 and having the somewhat narrower pulse width than 2F, for example, 1.8F as shown in Fig. 6F. Thus, the pulse signal P34 appearing at every four field is used as a reference signal for color framing.
A differentiated pulse signal Pm of the signal Sm, shown in Fig. 6B, is reproduced by the control head 73 from the control track on the tape 3, and then fed through a P-terminal of the switch 72 and the amplifier 74 to mono-multi-vibrato~s l~l and 142 of a comparing signal forming circuit 140, respectively. The mono~multivibrators 141 and 142 are so designed to have the same time constants as those of the multivibrators 131 and 132, respectively, that pulse signals P41 and P42 corresponding to the pulse signals P31 and P32 are 20 generated from the multivibrators 1~1 and 142, as shown in Fi~s. 6C' and 6D', respectively. The pulse signals P41 and P42 are supplied to both input terminals of an AND-circuit 143, which then generates a pulse signal P43 having the same pulse width as that of the pulse signal P33 shown in Fig. 6E'. ;-~s apparent from Figs. 6A to 6E', it shollld be noted that since there is a phase difference between the pulse signal Sm from the circuit 30 and the pulse signal Pm from the head 73 there is also existing a phase difference between the pulse signal P33 and the pulse signal P43.
Upon color framing, the movable arm of the switch 101 is in contact with the A-terminal thereof, so that the supply voltage ~cc is supplied to input terminal of an AND
circuit 1020 Accordingly, the AND circuit 102 produces an - - , ..... , . : :

an output signal of "1" which is then applied to a transistor 112. While, the pulse signals P33 and P43 from the AND-circuits 133 and 143 are supplied to both input terminals of a NAND-circuit 111. However, the phase of the signal P33 is different from that of the signal 43, but the signals P33 and P43 are shifted in phase as shown in Figs. 6E and 6E'. Thus, the NAND-circuit 111 produces an output signal of "1" which is also supplied to the transistor 112. Since both the output signals ~rom the NAND-circuit 111 and the AND-circuit 102 are "1" in level, the transistor 112 becomes ON, and thereby its -collector potential becomes "0". The "0" voltage of the transistor 112 is supplied to one input terminal of an AND-circuit 151 of a switching circuit 150 and to one input terminal ~-of another AND-circuit 152 thereof after being inversed hy an - - -inverter 153. As a result, the pulse signal P34 (refer to Fig. 6F) ~rom the multivibrator 134 is derived through the AND-circuit 152 and an OR-circuit 154 to a serrated or -trapezoidal wave signal generator circuit 771 which generates a serrated wave signal S71 shown in Fig. 6G. This signal S71 -is supplied to a sampling circuit 172 as an input signal to be sampled.
On the other hand, the signal of the "0" level from the collector of the transistor 112 is also supplied to one input terminal of~an AND-circuit 161 and after being inversed by an inverter 163 to one input terminal of an AND-circuit 162, so that the pulse signal P43 (reer to Fig. 6E') is derived through the AND-circuit 162 fxom an OR-circuit 164 to a mono-multivibrator 175 which produces a pulse signal P75 rising up at the going-up edge of the pulse P43 as shown in Fig. 6H.
The pulse P75 is fed to a mono-multivibrator 176 which produces a pulse signal P76 having a relatively narrow pulse width, as shown in Fig. 6I. This pulse signal P76 is supplied to the .

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sampling circuit 172 as a sampliny pulse.
Thus, the serrated wave signal S71 from the serrated wave signal generator 171 is sampled in the sampling circuit 172 by the pulse signal P76 from the multivibrator 176, so that a DC voltage with the level corresponding to the phase difference between the signals S71 and the pulse signal P76, that is, the phase difference between the signal Sm from the circuit 30 and the pulse signal Pm from the control head 73 can be derived from the sampling circuit 172. The DC voltage from the sampling circuit 172 is supplied through the P-terminal of the switch 62 to the variable frequency oscillator 63 as its control signal, and, accordingly the transporting speed of the tape 3 is -controlled in response to the DC voltage.
As shown in Fig. 6, however, when the phase of the pulse signal Pm in the reproducing system is different from the phase of the signal Sm in the reference system to a great extent/ the sampling pulse signal P76 samples the low level portion of the serrated wave signal S7L. This means that since the reference DC voltage supplied to the capstan servo syste~ 60 becomes low, the transporting speed of the tape 3 is lower than a predetermined speed. Accordingly, the phase of the reproduced pulse-signal Pm to the sig~al Sm becomes to be delayed gradually, and hence the reproduced signal Pm shown in Fig. 6B
is moving to the right side in the drawing. As a result, the pulse signal P43 and the sampling pulse signal P76 are moving to the right side gradually. Herein, it should be noted that in such a state the sa;mpling operation is carried out once every four field as shown in Figs. 6G and 6I.
Thus, ~s the phase of the pulse Pm becomes close to 30 that o~ the signal Sm, the pulse P43 overlaps partially with the pulse P33 as shown in Figs. 6E and 6J. As a result, the level of the output signal fro]m the NAND-circuit 111 becomes "0" at .

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the overlapping, and thereby the transistor 112 keeps OFF over the four fie].ds interval because o~ the large time constant of a capacitor charging circuit 110T, and its collector potential becomes "1" regardless of the level o~ the output signal from and AND-circuit 102. Accordingly, since the output signals from the inverters 153 and 163 become "0", respectively, the pulse signals P34 and P43 which are derived through the AND-circuits 152 and 162, respectively, are not supplied to the serrated i-signal generator 171 and multivibrator 175. While, the output signal of "1" from the collector of the transistor 112 is supplied to the AND-circuits 151 and 161, respectively.
At this time, the pulse signals P31 and P41 which have the same phase as the pulse signals P33 and P43 are supplied to input terminals of a NAND-circuit 121 of a frame phase comparator 120, respectively. Thus, when the pulse signals P31 ~
and P41are in the phase relation as shown in Figs. 6E and 6J, ~:
the output signal o~ the NAND-circuit 121 becomes "0" partially.
However, the time constant of a capacitor charging circuit 120T --. in the frame phase comparator 120 is selected smaller than that .
o~ a capacitor charging circuit 110T in a color frame phase comparator 110, so that the capacitor of the capacitor charging : circuit 120T is charged ~uickly after the output of the NAND
~; circuit 121 returning to "1". Therefore, even if the transistor ..
112 is in OFF-state, a transistor 112 of the frame phase comparator 120 is still in ON-state and its collector potential remains "0".
~ pon color framing operation, since the input signal to a buffer amplifier 103 i9 ~ , its output level becomes "1"
which has no afect on the operation of the transistor 122. The collector potential "0" of the transistor 122 is supplied to AN~-circuits 135 and 145 to close their AND-gates, respectively, but the pulse signals P31 and P~l are supplied to the AND-circuits ~ -: :
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151 and 161 through OR-circuits 136 and 146, respectively. At this time, since the collector potential of the transistor 112 is "1", the pulse signals P31 and P41 supplied to the AND-circuits 151 and 161 are applied through the OR-circuits 154 and 164 to the generator 171 and multivibrator 175, respectively. Thus, the generator 171 produces the serrated wave signal S71 in response to the pulse signal P31 through OR-circuit 154 at every two field or at the first and third field as shown in Fig. 6K. Similarly, the multivibrator 175 produces the pulse signal P75 in response to the pulse signal P41 through the OR-circuit 164 at the first and third fields as shown in Fig. 6L.
Thereby, the pulse signal P76 is generated from the multivibrator 176 at every two field or at the first and third field as shown in in Fig. 6M. This means that the sampling operation is carried out in the sampling circuit 172 at every two field and hence the transportation speed of the tape 3 is controlled at every two field. As a result, the phase of the pulse Pm approaches -to that o the signal Sm rapidly.
As the phase of the pulse. Pm further approaches to that of the signal Sm, the pulse 31 becomes to sufficiently overlap with the pulse 41. As a result, the level of the output signal from the NAND-circuit 121, to which the pulses P31 and P41 is supplied, becomes "0" at the overlapping portion and thereby the transistor 122 becomes OFF over at least two field interval irrespective o the level of the buffer amplifier 103 being "1". Thus, collector potential of the transistor 122 becomes the high level of "1", which is supplied to the AND-circuits 135 and 145, respectively.
Accordingly, the pulses P32 and P42 from the multi-vibrators 132 and 142 are supplied through the AND-circuits 135 and 145 to the OR-circuits 136 and 146, respectively, so that the latter deliver pulse signals P36 and P46, which are ,- .
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.

q equivalent to the sum of the puls69 P31 and P32 and the sum of the pulses P~l and P42, respectively, as shown in Figs. 6N
and 6P. The pulses P36 and P46 are fed through the AND-circwits 151, 161 and the OR-circuits 154, 164 to the circuits 171 and 175, respectively. Accordingly, it is noted that the signal S71 is obtained from the yenerator 171 at every field as shown in Fig. 60 and the pulses P75, P76 are obtained from the multivibrators 175, 176 at every field as shown in Figs. 6Q
and 6R, respectively.
Thus, the servo control for the transporting speed of the tape 3 is performed at every field, and hence the phase of the pulse P rapidl~ coincides with that of the signal Sm.
In this case, it is apparent that the pulse Pm from the control head 73 and the signal from the circuit 30 are coincident with each other in phase and the phase relation between the subcarrier signal Sc and horizontal synchronizing pulse Ph in the reproduced color video signal is the same as that bet~een th~ reference subcarrier signal Sc and the reference horizontal synchronizing pulse Ph from the generator 10.
Therefore, if two VTR apparatus, which are synchroni~ed by the same external synchronizing signal generator, are connected to achieve an electronic edition, the color framing can be perfectly carried out or there occurs no problem that a reproduced picture is disturbed at the editing points.
When the VH framing is carried out, the movable arm of the switch 101 is in contact with the B-terminal thereo~.
Then, the level of the output signal from the AND-cricuit 102 becomes "O" with the result that the transistor 112 becomes OFF
and hence its collector potential becomes the high level. Thus, the pulse signals from the OR-circuits 136 and 146 are supplied through the AND-circuits 151, 161 and further through the OR-. . .

-: . . . .. . . .

~ ~3~

circuits 154, 164 to the circuits 171, 175, respectively.
Accordingly, in this case it is apparent that the operation described in connection with and af~er Fig. 6K is carried out, in other words the servo control is achieved first at every two field or at the first and third fields and then at every field. This means that the phase relation between the odd and even fields in the reproduced color video signal is synchronized with that in the composite synchronizing pulse P from the generator 10.
Thus, if an electronic edition is carried out under the condition that the movable arm of the switch 101 is in contact with the B-terminal thereof, the VH framing is performed.
In a field lock operation, the movable arm of the switch 101 is made in contact with the C-terminal thereof. Then, the level of the output signal from the AND-circuit 102 becomes "0", so that the collector level of the transistor 112 becomes "1", and further the level of the output signal from the amplifier 103 becomes "0" so that the collector level of the transistor 122 becomes "1". Accordingly, the pulses P32 and P42 are derived through the AND- circuits 135 and 145 and fed to the OR-circuits 136 and 146, so that the pulses P36 and P46 are derived from the OR-circuits 136 and 146 and then fed through the AND-circuits 151, 161 and the OR-circuit 154, 16~
to the circuits 171 and 175, respectively. Thus, in this case as described in connection with and after Fig. 6N, the servo control for the transporting speed of the tape is carried out at every field, so that the reproduced color video signal is in synchronism with the composite synchronizing signal P from the generator 10 at every one field. Therefore, if an electronic edition is achieved under such a state, an edition per a field unit only can be performed.

--19- . :

Further, though the app~ratus according to this invention has been applied to the NTSC signal in the embodiment, the apparatus will be also applied to PAL and SECAM signals.
In case of PAL signal, the phase of the color subcarrier is reversed every horizontal intervals with respect to the (B-Y) axis, so that the periods of the color frame is four fields, in that sense, as well as the NTSC signal. Exactly speaking, in the PAL color signal, there is existing the frequency relationship fsc = (n + l)fh between the horizontal synchronizing frequency fh and the color subcarrier signal fsc, and consequently eight fields must occur before the color sub-carrier signal exactly repeat itself in phase. However, if four fields lo~k-up of the PAL signal is performed in the apparatus of this invention, it is possible to at least correct the inversion of the color subcarrier signal. As a matter of fact, the four field lock-up is a sufficient correction to the PAL signal. In order to determine the first field of the PAL
signal, it is detected whether the burst signal exists in sixth horizontal interval of the odd field. The detected output is supplied to the input of the AND circuit 33 instead of the signal Se.
In case of SECAM signal, the (R-Y) and (B-Y) color signals are transferred line-sequentially and frequency-modulated with different carrier signals to each other, so that the periods of the SECAM color frame is also four fields. The .. .
carrier frequency in the seventh horizontal interval of the odd field is detected in order to determine the first field of the ~` SECAM signal. Thus, the detected output is supplied to the input of the AND circuit 33 inst.ead of the signal, like the PAL
signal.
`' , :

':

~ 20-,

Claims (6)

What is claimed is:

1. A color video signal recording and/or reproducing apparatus comprising;
means for generating a first signal having a field frequency of said color video signal;
means for generating a second signal indicating a field interval which has a predetermined phase relationship between a synchronizing signal and a color subcarrier signal;
means for inserting said second signal into said first signal and thereby a composite control signal is produced;
means for recording said composite control signal on a recording midium and reproducing the former therefrom;
means for comparing said composite control signal reproduced therefrom with a reference control signal, said refer-ence control signal comprising a third signal having a field frequency and a fourth signal indicating a field interval in which a phase relationship between a reference synchronizing signal and a reference color subcarrier signal is substantially equal to said predetermined phase relationship, and, means for controlling a travelling of said recording midium in response to a control output of said comparing means so that the phase of said reproduced control signal coincides with that of said reference signal.

2. A color video signal recording and/or reproducing apparatus according to claim 1, in which said first signal generating means includes a flop-flop circuit (27) triggered by a vertical synchronizing signal for producing said first signal which is reversed at every field.

3. An apparatus according to claim 1, in which said second signal generating means comprises means for obtaining a field discriminating signal which is reversed at every odd field by comparing said synchronizing signal with said color subcarrier signal, means for obtaining a field pulse signal which is generated at every odd field by comparing the horizontal synchronizing signal with the vertical synchronizing signal, and means for comparing said field discriminating signal with said field pulse signal to produce said second signal at every four fields.

4. An apparatus according to claim 1, in which said comparing means includes means (141, 142, 143) for generating a color frame signal which is produced every four fields in basis of said second signal reproduced from said recording medium, means (131, 132, 133) for generating a reference color frame signal which is produced every four fields in basis of said fourth signal, a first means (110) for detecting a first phase difference between said color frame signal and said reference color frame signal, and means (152, 162) for gating said color frame signal and said reference color frame signal to compare the former with the letter during said first phase difference being beyond a first predetermined value.

5. An apparatus according to claim 4, in which said comparing means further includes means (141) for generating a frame signal which is produced every odd fields in basis of said first signal reproduced from said recording medium, means (131) for generating a reference frame signal which is produced every odd fields in basis of said third signal, and means (151, 161) for gating said frame signal and said reference frame signal to compare the former with the latter during said first phase difference being within said first predetermined value.

6. An apparatus according to claim 5, in which said comparing means further includes means (141, 142, 145, 146) for generating a field signal which is produced every field in basis of said composite control signal reproduced from said recording medium, means (131, 132, 135, 136) for generating a reference field signal which is produced every field in basis of said reference control signal, a second means (120) for detecting a second phase difference between said frame signal and said reference frame signal, and means (135, 151, 145,.161) for gating signal to compare the former with the latter during said second phase difference being within a second predetermined value.