GB1566612A - Colour videy signal recording and/or reproducing apparatus - Google Patents

Description

(54) COLOUR VIDEO SIGNAL RECORDING AND/OR REPRODUCING APPARATUS (71) We, SONY CORPORATION, a Japanese Body Corporate of 7-35 Kitashinagawa 6-Chome, Shinagawa-ku, Tokyo, 141 Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a colour video signal recording and/or reproducing apparatus and, more particularly, to an apparatus for providing precise colour frame lock of colour television signals, even if splicing of a magnetic tape containing the colour television signals, like NTSC signal, is done electrically or physically.

As is well known, in the NTSC colour television signal, there is an exact frequency relationship between the horizontal synchronizing frequency f, and the colour subcarrier frequency fec, namely f,c=455/2 fh, and consequently four television fields must occur before the colour subcarrier signal exactly repeates itself in phase with respect to the horizontal synchronizing signal. In other words, the period of the colour frame is four fields. This is explained with reference to Figure 1 of the accompanying drawings which shows waveforms of the horizontal synchronizing signal and the colour subcarrier. Referring to Figure 1, assuming now that the colour subcarrier signal Sc has a positive peak value at the front edge of the horizontal synchronizing signal Ph, the front edge being indicated by an upwardly pointing arrow in Figure 1, and the signal Sc has a negative peak value at the front edge of the subsequent horizontal synchronizing signal P,, which front edge is indicated by downwardly pointing arrow in Figure 1. This means that the phase of the subcarrier signal Se is reversed at every horizontal interval. As a result of the reversal, as shown in Figure 3A of the accompanying drawings, it is apparent that, if the subcarrier signal Sc has its negative peak value at the front edge of a first equalizing pulse Pc included in a first field of frame 1, the signal Se has its positive peak value at the front edge of the first equalizing pulse P included in the first field 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 be 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 1800 phase shift in the burst or colour subcarrier signals at the splicing point.

In a conventional colour television receiver, the colour subcarrier signal Se used for synchronous detection is formed on the basis of the burst signals, and 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 Se cannot follow the sudden change of the phase of the burst signal. As a result, there exist some phase differences between the chrominance signal and the colour subcarrier signal, and hence the hue on a reproducing picture will be momentarily disturbed.

This is an obviously unacceptable condition, and normally a VTR is provided with means for recognizing improper phase and shifting the phase of the whole television signal by half a cycle of the subcarrier signal to bring it back into the proper phase. In order to perform the above operation, the VTR has a delay line, to which the colour 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 colour subcarrier signal is reversed at the editing point, an error voltage will be obtained from the comparator.

The error voltage is supplied to the delay line to shift the phase of the whole signal, and thus the latter will be moved 1800 (140 nano seconds) ahead or behind the proper timing position. In other words, the phase correction places the colour subcarrier signal in proper phase, but it introduces a 140 nano second (n sec.) error in the horizontal 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, several approaches and methods have been proposed. One method is to use 15 Hz frame pulses instead of the 30 Hz pulses used on the control track.

This refers to use of frame pulses at onefourth the basic field repetition rate of NTSC signals. This means that a servo operation is performed once every four fields. Accordingly, the lock-up time of the servo operation will be increased by approximately 20 percent in comparison with 30 Hz servo operation. Also, it is difficult to splice the tape at the exact beginning of a field or frame.

Another method is to use a servo control circuit, in which, if the error voltage from the burst phase comparator indicates lockup to the wrong frame, an electrical signal is generated which causes the tape drive motor momentarily to speed up thereby physically to 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 detected, 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 inordinately increased as is the case with the above-described method.

According to the present invention there is provided a colour video signal reproducing apparatus for reproducing a colour video signal recorded on a tape, the video signal comprising chrominance components and field and line synchronising signals, the fields being in a colour frame format so that the chrominance sub-carrier has a predetermined phase relationship with respect to the field and line synchronising signals, the apparatus comprising means for reproducing the recorded video signal, means for reproducing a composite control signal recorded on the tape, the composite signal including a first signal component having a frequency commensurate with the field frequency of the video signal and a second signal component indicative of specific fields in the colour frames of the recorded video signal in which the chrominance sub-carrier signal has a predetermined phase relationship with respect to the field and line synchronising signals, the composite signal reproducing means comprising a generator for producing a reference control signal including a first signal component having a frequency commensurate with saicl field frequency and a second signal component designating fields of reference colour frames corresponding to said specific fields; and a comparison circuit for comparing the reproduced composite control signal with said reference control signal; and a control circuit connected to said comparison circuit for controlling the movement of the tape in response to a control output signal of the comparison circuit.

The present invention will now be de.- scribed, by way of example, with reference to Figures 2 to 6 of the accompanying drawings, wherein: Figure 2 is a block diagram of a field discriminating signal generator which is used in the recording and reproducing apparatus of Figure 5; Figures 3 and 4 are timing waveforms which are used for explaining the operation of the generator of Figure 2; Figure 5 is a schematic block diagram of part of an embodiment of video signal recording and apparatus in accordance with this invention; and Figure 6 is a timing waveform which is used for explaining the operation of the apparatus of Figure 5.

Figure 2 shows a field discriminating signal generator 30 as a whole, in whirl an external synchronizing signal generator 10 produces a colour subcarrier signal Se and a composite synchronizing signal P,.

The colour subcarrier signal Sc is fed to a slicing circuit 11 to be wave-shaped as a rectangular-shaped signal which is then fed to a D-input terminal of a D-type flip-flop circuit 12. The composite synchronizing signal Pc from the generator 10 is applied to a slicing circuit 13 to be wave-shaped as a signal Pc shown in Figure 3A and then applied to a T-input of the flip-flop circuit 12. Thus, the flip-flop circuit 12 is triggered by the downwardly going edges of the synchronizing signal Pc and hence produces at its Q-terminal a rectangular waveform signal Sb, Figure 3B, the level of which is varied to take "1" or "O" in response to the levels of the subcarrier signal Se at the downwardly going edges of the horizontal synchronizing signal P, in the signal Pr.

However, it should be noted that, during the vertical interval, the signal Sb cannot be alternately changed at every horizontal interval, as shown in Figure 3B. The reason is that the flip-flop circuit 12 will be triggered by the equalizing pulses Pr (refer to Figure 3A). That is, the equalizing pulse Pea which is positioned at every one H duration with respect the horizontal synchronizing pulse P,, is equivalent to the horizontal synchronizing pulse P,, so that the signal Sb is made "0 " or " 1 " alternately in response to the levels of the subcarrier signal Sr at the position (refer to the arrows 1t in Figure 3A), as shown in Figure 3B by the solid line. The half-H pulse Pr, is positioned at odd multiples of 0.5H with respect to the pulse P,, so that the suhcarrier signal Se at the position also becomes a nodal point (changing point). As a result, the level of the signal Sb becomes vague or ambiguous during the interval from the half-H pulse Pc to the next pulse Pr as shown in Figure 3B by a dotted line.

Further, it is noted that the levels of the signal Sb are opposite to each other at the starts of the first and third fields. Thus, the output signal Sb from the flip-flop circuit 12 is fed to a D-terminal of a D-type flipflop circuit 14, which is triggered by the upwardly going edges of the signal supplied to a T-terminal of the D-type flip-flop circuit 14.

On the other hand, the composite synchronizing signal Pr from the slicing circuit 13 is supplied also to a serrated or sawtooth signal forming circuit 17, in which a capacitor 17C is charged through a resistor 17B from a voltage supply source +Vec during the level of the signal P,.

being "0", that is, a transistor 17T being OFF. As a result of the charging of the capacitor 17C, a serrated signal 5a as shown in Figure 3C is generated from the circuit 17. Herein, it is of importance that the serrated signal S has larger amplitude during the vertical synchronizing interval than that during the other interval. The serrated signal S, is supplied to a monostable multivibrator 18, which is triggered by the downwardly going edge of the first serrated signal S, in the vertical synchronizing interval, and which generates a rectangular signal S, having a pulse width more than the vertical synchronizing interval as shown in Figure 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 S, is supplied to the D-terminal of the flip-flop circuit 14, so that the flipflop produces at its Q-terminal a signal Se as shown in Figure 3E. The signal Se is produced in a manner such that, since the level of the signal Sb is "1" at the upwardly going edge of the signal Sd in the first field, the level of the signal 5e becomes " 1" and since the level of the signal Sb is "0" at the upwardly going edge of the signal Sa in the third field, the level of the signal Sr becomes "0". Further, in the second and fourth fields the level of the signal Sb is ambiguous at the upwardly going edge of the signal Sd, so that the level of the signal Se also becomes ambiguous.

The signal Sd from the monostable multivibrator 18 is further supplied to a monostable multivibrator 21 which is triggered by the upwardly going edge of the signal Sd and produces a pulse P which rises at the upwardly going edge of the signal S, and falls after an interval of substantially 1H duration passing from the starting point of the vertical synchronizing pulse Pr as shown in Figure 4D. The pulse Pr. is supplied to a monostable multivibrator 22 which is triggered by the downwardly going edge of the pulse P, and produces a pulse Pp of narrow width, which is substantially equal to the horizontal pulse width as shown in Figure 4E. In this case, it is noted that the pulse Pp is produced once every field and is located at a position delayed by about 1H duration after the starting point of the vertical synchronizing signal.

The pulse Pp is supplied to one input terminal of an AND-circuit 23.

The composite synchronizing pulse P,.

from the generator 10 is further supplied to a monostable multivibrator 25 which is triggered by the downwardly going edge of the pulse Pc and produces a rectangular waveform signal Sa which has a pulse width more than the half-H duration as shown in Figure 4F. This signal Sq is fed to a monostable multivibrator 26 which is triggered by the upwardly going edge of the pulse Sq and produces a pulse Pr which is synchronized with the horizontal synchronizing pulse Pb. This pulse Pr is fed to the other input terminal of the AND-circuit 23.

Accordingly, the pulse signals Pp and P,.

are fed to the AND-circuit 23, so that the AND-circuit 23 produces a pulse signal Pb shown in Figure 4H at every odd field, that is, the first and third fields. This is because the pulse Pp is shifted from the horizontal synchronizing P, by 0.5H in the second and fourth fields. In other words, the appearance of the pulse P, shows that the fields are the first or third field.

The pulse Pp of the field period from the monostable multivibrator 22 is fed to a reset terminal of a flip-flop circuit 27, while the pulse P, from the AND-circuit 23 is supplied to the set terminal thereof. The flipflop 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 Figure 41 and Figure 3F, respectively. The signal Sf is supplied first to a D-terminal of a D type flip-flop circuit 28, which is triggered by the downwardly going edges of a signal applied to its T-terminal, and second to a monostable multivibrator 29, which is triggered by the upwardly going and downwardly going edges of the signal St and produces a rectangular wave signal S9 having the pulse width of approximately halffield duration as shown in Figure 3G. This signal So is applied to the flip-flop circuit 28 at its T-terminal as set forth above, so that the flip-flop circuit 28 produces at its Qterminal a rectangular wave signal Sh which has a frequency commensurate with field frequency, is reversed at about the centre of each field and has a high level in the first halves of the first and third fields and in the latter halves of the second and fourth fields as shown in Figure 3H.

The signal Sh is then fed to a monostable multivibrator 31 which is triggered by the downwardly going edge of the signal S,l and produces a pulse Pi having a pulse width of about 3H as shown in Figure 31. This pulse Pi is then fed to a monostable multivibrator 32 which is triggered by the downwardly going edge of the pulse Pi and produces a pulse Pj having a pulse width of about 3H as shown in Figure 3J. As apparent from the above description, the pulse signal Pj is located at a position 3H after the falling edge of the signal Sh.

The pulse Pi is supplied to one input terminal of an AND-circuit 33 while the signal S, from the circuit 14 is supplied to the 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 Figure 3K. The pulse Pl thus indicates the field in each colour frame in which the chrominance sub-carrier has a predetermined phase relationship with the field and line synchronising signals. 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 field and contains the pulse Pk in the first field as shown in Figure 3L. Thus, it is noted that this signal Sm is varied with a four-field period and contains the index pulse Pb. 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 colour framing.

The pulse signal 5m can thus be considered as a composite signal comprising a first component, the signal Sh, having a frequency commensurate with field frequency and a second component, the pulse signal Pk indicating the field in each colour frame in which the chrominance sub-carrier has a predetermined phase relationship with the field and line synchronising signals.

In the present apparatus a colour framing system is employed which uses the field discriminating signal Sm. An embodiment of the apparatus in accordance with the present invention will be explained hereinafter in reference to Figure 5.

In Figure 5, a pair of rotary magnetic heads 1 and 2 are angularly spaced apart 1800 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 surface of the heads 1 and 2 in an angular range of about 1800 and is transported by the cooperation of a capstan 51 and a pinch roller 52 at a predetermined speed. During recording, a colour video signal, which is applied to a video input terminal 4, is supplied to a recording circuit 5, in which the colour 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 reproduction, the colour 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 shaft 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 compared with the vertical synchronizing signal PU in the pulse Pc. The output signal from the comparator 44 is fed through an amplifier 45 to the motor 41. Thus, the rotary phase of the heads 1 and 2 are synchronized with the vertical synchronizing- pulse P0 in the pulse Pc 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 opened 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 rotational 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 64 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 reference voltage supply source 61, and hence the tape 3 is transported at a constant speed.

In Figure 5, numeral 30 represents the generator circuit forming the discriminating signal Srn, which was already described in connection with Figure 2. During recording, the signal S,n from the circuit 30 is supplied through an amplifier 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 longitudinal track formed along the edge of the tape. This means that on the tape 3 there is recorded the signal Sm which indicates the phase of the colour sub-carrier signal relative to the horizontal synchronising signal lPk.

On the other hand, during reproduction the field discriminating signal Srn continues to be generated and is used as a reference control signal comprising a first component, the signal 5h of a frequency commensurate with field frequency, and a second component, the signal Pk. The signal S, thus defines a reference colour frame, with the signal Pk, designating one field of the rereference colour frame corresponding to the field of the colour frame indicated by the signal Pk during recording. The signal Sm from the circuit 30 and the composite control signal P1n reproduced by the control head 73 and passed through an amplifier 74 are supplied to a phase detecting circuit 100, in which the signal Prn is compared in phase with the signal Sm, and the phase detecting circuit 100 produces a control voltage so as to synchronize the signal P,n with the signal Sm during the colour 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 rotational 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 colour framing operation, to a B-terminal thereof during the VH framing operation and to a C-terminal thereof during the field lock operation, respectively.

The reference field discriminating signal Srn from the circuit 30, shown in Figure 6A is supplied first to a monostable multivibrator 131 of a reference signal forming circuit 130 which is triggered by the downwardly going 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 Figure 6C, and second to another monostable multivibrator 132 which is triggered by the upwardly going edge of the signal 5m and produces a pulse signal PM having the same pulse width as that of the pulse PM as shown in Figure 6D. (In Fig. 6, for simplicity of exception, the phase of the signal Sm is delayed by a field). The pulses P31 and PM 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 Figure 6E. The pulse signal is then fed to a monostable multivibrator 134 which produces a pulse signal PM rising at every upwardly going edge of the pulseP,, and having the somewhat narrower the pulse width than 2F, for example, 1.8 F as shown in Figure 6F. Thus, the pulse signal PM appearing at every fourth field is used as a reference signal for colour framing.

A differentiated pulse signal Pm of the signal S", 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 monostable multivibrators 141 and 142 of a comparing signal forming circuit 140, respectively. The monostable multivibrators 141 and 142 are so designed to have the same time constants as those of the multivibrators 131 and 132, respectively, so that pulse signals P41 and P.7 corresponding to the pulse signals PM and P1 are generated from the multivibrators 141 and 142, as shown in Figs. 6C' and 6D', respectively. The pulse signals P41 and P1 are supplied to both input terminals of an AND-circuit 143, which then generates a pulse signal P, having the same pulse width as that of the pulse signal P33 shown in Fig. 6E'.

As apparent from Figs. 6A and 6E', it should be noted that since there is a phase difference between the pulse signal S" from the circuit 30 and the pulse signal Pm from the head 73 there is also existing a phase difference between the pulse signal P3; and the pulse signal P < .

Upon colour framing, the movable arm of the switch 101 is in contact with the A-terminal thereof, so that the supply voltage Vic is supplied to an input terminal of an AND circuit 102. Accordingly, the AND circuit 102 produces 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 P43 and 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 from 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 ANDcircuit 152 thereof after being inverted by an inverter 153. As a result, the pulse signal P, (refer to Fig. 6F) from the multivibrator 134 is derived through the AND-circuit 152 and an OR-circuit 154. The pulse P34 is supplied to a serrated or trapezoidal wave signal generator circuit 171 which generates a serrated wave signal S73 shown input signal to a buffer amplifier 103 is 1 1 ", its output level becomes " 1 " which has no effect on the operation of the transistor 122. The collector potential "0" of the transistor 122 is supplied to ANDcircuits 135 and 145 to close their ANDgates, respectively, but the pulse signals P31 and P41 are supplied to the AND-circuits 151 and 161 through OR-circuits 136 and 146, respectively. At this time, since the collector potential of the transistor 112 is 1 1 ", the pulse signals P31 and P4, 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 P3, through OR-circuit 154 at every two fiields or at the first and third fields as shown in Fig. 6K. Similarly, the multivibrator 175 produces the pulse signal P75 in response to the pulse signal P" 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 fields or at the first and third fields as shown in Fig.

6M. This means that the sampling operation is carried out in the sampling circuit 172 at every two fields and hence the transportation speed of the tape 3 is controlled at every two fields. As a result, the phase of the pulse Pin approaches to that of the signal Sm rapidly.

As the phase of the pulse Pin further approaches to that of the signal Sm, the pulse P3, overlaps the pulse P41 sufficiently.

As a result, the level of the output signal from the NAND-circuit 121, to which the pulses P31 and P4, are supplied becomes "0" at the overlapping portion and thereby the transistor 122 becomes OFF over at least two field interval irrespective of the level of the buffer amplifier 103 being " 1 ". Thus, the collector potential of the transistor 122 becomes the high "1" level, which is supplied to the AND-circuits 135 and 145, respectively.

Accordingly, the pulses P32 and P, from the multivibrators 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 P11 and P,6, which are equivalent to the sum of the pulses P3, and P32 and the sum of the pulses P4, and P42, respectively, as shown in Figs. 6N and 6P. The pulses P36 and P, are fed through the AND-circuits 151, 161, and the OR-circuits 154, 164 to the circuits 171 and 175, respectively. Accordingly, it is noted that the signal Sn is obtained from the generator 171 at every field as shown in Fig. 60 and the pulses P7s, 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 Pm rapidly coincides with that of the signal S,.

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 Sr and horizontal synchronizing pulse P in the reproduced colour video signal is the same as that between the reference subearrier signal Sr and the reference horizontal synchronizing pulse P, from the generator 10.

Therefore, if two VTR apparatus, are synchronized by the same external synchronizing signal generator are connected to achieve an electronic edition, the colour 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 thereof. Then, the level of the output signal from the AND-circuit 102 becomes "0" 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 ANDcircuit 151, 161, and further through the OR-circuits 154, 164 to the circuits 171, 175 respectively. Accordingly, in this case it is apparent that the operation described in connection with and after Fig. 6K is carried out, or the servo control is achieved first at every two fields in other words 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 colour video signal is synchronized with that in the composite synchronizing pulse Pr 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 112 be comes " 1 ". Accordingly, the pulses Pz2 and P42 are derived through the AND- circuits 135 and 145 and fed to the OR-circuits 136 and 146, so that the pulses Psg and P16 are derived from the OR-circuits 136 and 146 and then fed through the AND-circuits 151, 161 and the OR-circuit 154, 164, to the circuits 171 and 175, respectively. Thus, in this case as described in connection with and after Figure 6N the servo control for the transporting speed of the tape is carried out at every field, so that the reproduced colour video signal is in synchronism with the composite synchronizing signal Pr 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.

Further, though the apparatus in accordance with this invention has been described with reference to the processing NTSC signals, the apparatus may be also applied to PAL and SECAM (Registered Trade Mark) signals. In case of PAL signal, the phase of the colour subcarrier signal is reversed every horizontal interval with respect to the (B-Y) axis, so that the periods of the colour frame is four fields, as well as the NTSC signal. More precisely, in the PAL colour signal, there is existing the frequency relationship f,p=(n+alf between the horizontal synchronizing frequency flt and the colour subcarrier signal Ar, and consequently eight fields must occur before the colour subcarrier signal exactly repeats itself in phase. However, if four fields lock-up of the PAL signal is performed in the apparatus in accordance with this invention, it is possible to at least correct the inversion of the colour 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 the sixth horizontal interval of the odd field. The detected output is supplied to the input of the AND circuit 33 (Fig. 2) instead of the signal Sr.

In case of the SECAM (Registered Trade Mark) signal, the (R-Y) and (B-Y) colour signals are transferred line-sequentially and frequency-modulated with different carrier signals to each other, so that the period of the SECAM colour 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 instead of the signal Sc, like the PAL signal.

WHAT WE CLAIM IS:- 1. A colour video signal reproducing apparatus for reproducing a colour video signal recorded on a tape, the video signal comprising chrominance components and field and line synchronising signals, the fields being in a colour frame format so that the chrominance sub-carrier has a predetermined phase relationship with respect to the field and line synchronising signals, the apparatus comprising means for reproducing the recorded video signal, means for reproducing a composite control signal recorded on the tape the composite signal including a first signal component having a frequency commensurate with the field frequency of the video signal and a second signal component indicative of specific fields in the colour frames of the recorded video signal in which the chrominance subcarrier signal has a predetermined phase relationship with respect to the field and line synchronising signals, the composite signal reproducing means comprising a generator for producing a reference control signal including a first signal component having a frequency commensurate with said field frequency and a second signal component designating fields of reference colour frames corresponding to said specific fields; and a comparison circuit for comparing the reproduced composite control signal with said reference control signal; and a control circuit connected to said comparison circuit for controlling the movement of the tape in response to a control output signal of the comparison circuit.

2. Apparatus according to Claim 1 in which said comparison circuit comprises: a first circuit arranged to receive said composite control signal for generating a colour frame signal once every four fields; a second circuit connected to said generator for generating a reference colour -frame signal, gate circuits connected to said first and second circuits, respectively; a phase comparing circuit for producing said control output signal in response to the phase difference between said signals generated by said first and second circuits; and a phase detecting circuit to respond to the phase difference between said colour frame signal and said reference colour frame signal, an output of said phase detecting circuit being connected to said gate circuits to transmit said colour frame signal and said reference colour frame signal to said phase comparing circuit when the phase difference therebetween is greater than a predetermined value.

3. Apparatus according to Claim 2 in which said first and second circuits are arranged to generate a frame signal and a reference frame signal during alternate fields, respectively, and said gate circuits transmit said frame signal and said reference colour frame signal is less than said predetermined value.

4. Apparatus according to Claim 3 in which said first and second circuits are arranged to generate a field signal and a reference field signal, respectively, and the apparatus further comprises a second phase detecting circuit connected to said first and second circuits to respond to the certain of the signals generated thereby and connected to said gate circuit to control the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. circuits 171 and 175, respectively. Thus, in this case as described in connection with and after Figure 6N the servo control for the transporting speed of the tape is carried out at every field, so that the reproduced colour video signal is in synchronism with the composite synchronizing signal Pr 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. Further, though the apparatus in accordance with this invention has been described with reference to the processing NTSC signals, the apparatus may be also applied to PAL and SECAM (Registered Trade Mark) signals. In case of PAL signal, the phase of the colour subcarrier signal is reversed every horizontal interval with respect to the (B-Y) axis, so that the periods of the colour frame is four fields, as well as the NTSC signal. More precisely, in the PAL colour signal, there is existing the frequency relationship f,p=(n+alf between the horizontal synchronizing frequency flt and the colour subcarrier signal Ar, and consequently eight fields must occur before the colour subcarrier signal exactly repeats itself in phase. However, if four fields lock-up of the PAL signal is performed in the apparatus in accordance with this invention, it is possible to at least correct the inversion of the colour 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 the sixth horizontal interval of the odd field. The detected output is supplied to the input of the AND circuit 33 (Fig. 2) instead of the signal Sr. In case of the SECAM (Registered Trade Mark) signal, the (R-Y) and (B-Y) colour signals are transferred line-sequentially and frequency-modulated with different carrier signals to each other, so that the period of the SECAM colour 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 instead of the signal Sc, like the PAL signal. WHAT WE CLAIM IS:-

1. A colour video signal reproducing apparatus for reproducing a colour video signal recorded on a tape, the video signal comprising chrominance components and field and line synchronising signals, the fields being in a colour frame format so that the chrominance sub-carrier has a predetermined phase relationship with respect to the field and line synchronising signals, the apparatus comprising means for reproducing the recorded video signal, means for reproducing a composite control signal recorded on the tape the composite signal including a first signal component having a frequency commensurate with the field frequency of the video signal and a second signal component indicative of specific fields in the colour frames of the recorded video signal in which the chrominance subcarrier signal has a predetermined phase relationship with respect to the field and line synchronising signals, the composite signal reproducing means comprising a generator for producing a reference control signal including a first signal component having a frequency commensurate with said field frequency and a second signal component designating fields of reference colour frames corresponding to said specific fields; and a comparison circuit for comparing the reproduced composite control signal with said reference control signal; and a control circuit connected to said comparison circuit for controlling the movement of the tape in response to a control output signal of the comparison circuit.

2. Apparatus according to Claim 1 in which said comparison circuit comprises: a first circuit arranged to receive said composite control signal for generating a colour frame signal once every four fields; a second circuit connected to said generator for generating a reference colour -frame signal, gate circuits connected to said first and second circuits, respectively; a phase comparing circuit for producing said control output signal in response to the phase difference between said signals generated by said first and second circuits; and a phase detecting circuit to respond to the phase difference between said colour frame signal and said reference colour frame signal, an output of said phase detecting circuit being connected to said gate circuits to transmit said colour frame signal and said reference colour frame signal to said phase comparing circuit when the phase difference therebetween is greater than a predetermined value.

3. Apparatus according to Claim 2 in which said first and second circuits are arranged to generate a frame signal and a reference frame signal during alternate fields, respectively, and said gate circuits transmit said frame signal and said reference colour frame signal is less than said predetermined value.

4. Apparatus according to Claim 3 in which said first and second circuits are arranged to generate a field signal and a reference field signal, respectively, and the apparatus further comprises a second phase detecting circuit connected to said first and second circuits to respond to the certain of the signals generated thereby and connected to said gate circuit to control the

operation thereof to transmit said frame and reference frame signals through said gate circuit when the phase difference between said certain of said signals is greater than a predetermined value and to transmit said field and reference field signals through said gate circuit when the phase difference between said certain of said signals is less than said predetermined value.

5. Apparatus according to Claim 4 in which said comparison circuit further com pris s a switch connected to said first and second phase detecting circuits, the first phase electing circuit being disabled in a first state of said switch in which said frame and reference frame signals are supp:ied through said gate circuits to said phase comparing circuit and the first and second phase detecting circuit being dis abied it a second state of said switch in which said field and reference field signals are supplied through said gate circuits to said phase comparing circuit.

6. A colour video signal recording and/ or reproducing apparatus constructed and arranged to operate substantially as hereinbefore described with reference to and as shown by Figures 2 to 6R of the accompanying drawings.