CA1045710A - Apparatus for reproducing color video signals - Google Patents
Apparatus for reproducing color video signalsInfo
- Publication number
- CA1045710A CA1045710A CA219,438A CA219438A CA1045710A CA 1045710 A CA1045710 A CA 1045710A CA 219438 A CA219438 A CA 219438A CA 1045710 A CA1045710 A CA 1045710A
- Authority
- CA
- Canada
- Prior art keywords
- phase
- signal
- signal components
- frequency
- signals
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/79—Processing of colour television signals in connection with recording
- H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
- H04N9/82—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only
- H04N9/83—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only the recorded chrominance signal occupying a frequency band under the frequency band of the recorded brightness signal
- H04N9/84—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback the individual colour picture signal components being recorded simultaneously only the recorded chrominance signal occupying a frequency band under the frequency band of the recorded brightness signal the recorded signal showing a feature, which is different in adjacent track parts, e.g. different phase or frequency
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Television Signal Processing For Recording (AREA)
- Signal Processing Not Specific To The Method Of Recording And Reproducing (AREA)
- Processing Of Color Television Signals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In reproducing chrominance signal components of com-posite color video signals recorded on a record medium in a form of parallel tracks with different carrier frequencies having interleaving relations therebetween, there are disposed a switch circuit and a comb-filter for cancelling the cross-talk components of chrominance signals reproduced from adjacent tracks. The switching actions of the switch circuit are con-trolled by phases of the resultant chrominance signals for phase alignment during entire reproduction of the chrominance signals.
In reproducing chrominance signal components of com-posite color video signals recorded on a record medium in a form of parallel tracks with different carrier frequencies having interleaving relations therebetween, there are disposed a switch circuit and a comb-filter for cancelling the cross-talk components of chrominance signals reproduced from adjacent tracks. The switching actions of the switch circuit are con-trolled by phases of the resultant chrominance signals for phase alignment during entire reproduction of the chrominance signals.
Description
BACKGROUMD OF T~IE INVENTION
Field of the ~nvention This invention relates to a recording and/or reproduc-ing system to be applied to a video signal, and particularly to such system that cross-talk components of adjacent tracks can be cancelled in spite of no guard-bands among them.
Description of ~the Prior Art As well known, a chrominance signal of composite color video signal is preferably frequency-converted to lower frequency than that of frequency modulated luminance signal upon recording. There are disposed guard-bands between adja-cent recording tracks on a recording medium for cross-talk eli-mination. Recently, there have been proposed many technics of guard-ban~-less recording on a recording medium in order to achieve a reduction of tape consumption, in other words, high recording density. One approach is that the adjacent tracks on the recording medium such as magnetic video tape are scanned or recorded by at least two magnetic heads having different azimuth angles. The azimuth loss of a recorded signal upon reproduction is proportional to the frequency of recorded signal, so that the deterioration due to cross-talk still exists in the chrominance signal which lies in lower "J
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frequency range on the entire recording frequency.
In this view point, introduction of interleaving tech-nic to the chrominance signal carriers of adjacent tracks on the recording medium has been proposed in a pending application assigned to the same assignee of this application.
That is, there is an interleaving relation between reproduced true chrominance signal and cross-talk components of chrominance signal of adjacent tracks so that the cross-talk components of chrominance signal can be eliminated through a comb-filter.
When applying this technic, the applicants found that the phase of chrominance signal carriers of succeeding tracks become discontinuous with certain possibilities, so that the initial part of one scanning track yields deteriorated color phase in the reproduced picture until an automatic phase con-trol circuit stabilizes the phase in proper order.
S~MMARY OF THIS INVENTION
It is therefore a general object of this invention to provide a new recording and/or reproducing system.
It is another object of this invention to p~ovide a novel recording and/or reproducing system to be applied to a color composite video signal having a chrominance signal and a luminance signal.
It is still another object of this invention to provide an improved recording and/or reproducing system in which chromi-nance signal is frequency-converted to lower frequency than that of luminance signal.
It is further object of this invention to provide an improved recording and/or reproducing system in which no guard ban-~ is required between adjacent recording tracks.
More particularly there is provided an apparatus for reproducing video signals having luminance and chrominance ~0~57~
signal components and comprised of field intervals and line in-tervals which are recorded in respective areas of successive parallel tracks on a record medlum with said chrominance signal components of video signals recorded in next adjacent tracks having different first and second carriers; the com-bination of rotational transducer means for scanning along said tracks one at a time so as to reproduce the video sig-nals recorded in each of said tracks along with cross-talk signals from the tracks next adjacent thereto, pulse signal generating means for producing pulse signals indicating the rotational positioning of said transducer means, means for separating said chrominance signal components from the lumi-nance signal components in the reproduced signals, means for extracting horizontal synchronizing signals from said reproduced signals, signal processing means for providing the separated chrominance signal components of video signals reproduced from each of said tracks with a common carrier and for elimi-nating from the resultant chrominance signal components the chrominance signal components of the cross-talk signals on the basis of said different first and second carriers with which the chrominance signal components are recorded in the tracks which are next adjacent to each other, phase detecting means for detecting phase reversals of said common carrier of said resultant chrominance signal components, and means for controlling said signal processing means in response to said pulse signals, said horizontal synchronizing signals and said phase detecting means so as to maintain continuity of the phase of said common carrier of the resultant chrominance signal components.
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Other objects and aspects of this invention will become apparent from the illustrati~e embodiments about to be described or will be ~nd~cated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.
BRIEF DESCRIPTION OF ~'HE DRAWINGS
Figure '1 is a block diagram showing one embodiment of a reproducing apparatus according to the invention, -3a-57~
Figure 2 is a schematic plan view showing the dis-position of rotary magnetic heads and a magnetic tape, Figure 3 is a cross-sectional view showing the rela-tion between two magnetic heads used in the invention, Figure 4 is a schematic view showing a recording pattern on a magnetic tape used in the invention, Figure 5 is a block diagram showing one embodiment of a recording apparatus used for providing the recording pattern necessary for performing the invention, Figures 6A and 6B are waveform diagrams showing switching signals used in the invention, Figures 7A to 7G are views showing frequ~ncy spectra used for explaining the operati.on of this invention, Figures 8A and 8B are respectively a structural :
view of a comb-filter used in the invention and its character~
istic diagram, Figures 9A and 9E are waveform diagrams used for explaining the effect of this invention, Figures 10A to 10G are waveform diagrams used for explaining the operation of this invention, ..
Figures llA to llC are waveform diagrams used for explaining the effect of this invention, Figures 12A and 12B are views used for explaining `.:
another embodiment of this invention, ..
Figure 13 is a block diagram showing another embodi-ment of a reproducing apparatus according to this .invention, Figures 14A to 14H are waveform diagrams used for explaining the operation of the embodiment of Figure 13, and Figure 15 is a block diagram showing the main part .
of a further embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows one embodiment of reproducing .:
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apparatus according to the present invention, wherein refer-ence characters HA and HB indicate rotary magnetic heads which are secured on a rotary disc 1 as shown in Figure 2. One of these magnetic heads HA and H~ has an air gap GA with one azimuth angle, and the other an air gap GB with different azi-muth angle as shown in Figure 3. A magnetic tape 2 is run on a rotary locus of two magnetic heads HA and HB. The disc 1 rotates at 30 r.p.s., so that one pair of recording tracks TA
and TB is scanned with respective magnetic heads HA and HB at every rotation af the rotary disc 1 as shown in Figure 4.
That is to say, one pair of tracks TA and TB corresponds to one frame interval of a video signal. Each line interval and each field interval contains a blanking and synchronizing portions, and in accordance with accepted practice, the tracks TA and TB
are arranged in a pattern referred to as H-alignment. This is achieved by regulating the relative movements along directions 3 and 4 in accordance with the synchronizing portions of the video signal to be recorded so that one line interval section on which the blanking and synchronizing signals are recorded in the tradk TA is aligned with the adjacent section on which the blanking and synchronizing signals for that line interval are recorded in the track TB.
The magnetic tape 2 is recorded by a recording appa-ratus shown in Figure 5 wherein the magnetic heads HA and HB
are constructed completely in the same manner as those installed in the reproducing apparatus.
In Figure 5, a composite color video signal supplied to an input terminal 5 is fed to a low pass filter 6 to derive therefrom a luminance signal. The luminance signal thus derived is applied to a frequency modulator 7 to produce a frequency-modulated luminance signal occupying the higher frequency region of recordable and reproducible frequency band, ~ 5 -S7~
which is then applied to an adder 8. The composite colorvideo signal is also supplied to a ba~pass filter 9, which passes a chrominance signal Cs of carrier frequency fS to a frequency converter 10. A carrier signal of frequency fS + fA
from an oscillator 11 is also fed to the frequency converter 10, so that the chrominance signal Cs is converted to lower fre-quency region as a frequency-converted chrominance signal CA
of carrier frequency fA which is fed to a phase splitter 12.
Then, the signal CA from the positive (+) output terminal of the phase splitter 12 is fed to one input terminal of a switch - :
circuit 13, while a signal CA from the negative (-) output terminal of the phase splitter 12 is fed to -the other input terminal of the switch circuit 13. The switch circuit 13 is changed-over to the illustrated state by a switching signal .
SC as depicted in Figure 6A during an interval wherein the magnetic head HA scans along the track TA, for example, in an off field, and changed-over alternately to the illustrated ..
state and to the reverse state thereto at every horizontal line ~:~
interval H during a period wherein the magnetic head HB scans along the track TB, for example, in an even field. Thus, an output of the switch circuit 13 is fed to the adder 8 to be added with the frequency-modulated luminance signal and the ; resultant output therefrom is supplied through a recording amplifier 14 to the magnetic heads HA and HB, respectively. .
With such an arrangement, the frequency-converted chrominance signal CA of carrier frequency fA and of constant phase is recorded on the track TA. Meanwhile, the frequency-converted chrominance signal CA of carrier frequency fA and the :
signal CA, which is out of phase with respect to the former, are ~ :
alternately derived from the switch circuit 13 at every hori-zontal line interval H. The above mentioned alternate deriva-tion of the signals CA and CA is equivalent to that rectangular - : . . -:
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wave signals capable of being represented by "+l" and "-1"
alternately at every horizontal interval are multiplied to the signal CA. This is also equivalent to that the signal CA is balance-modulated with a rectangular wave signal having fre-quency of 1/2 the horizontal frequency fH. Accordingly, the track TB is recorded thereon with a fre~uency-converted chromi-nance signal CB of carrier frequency fB which is shifted 1/2 fH
relative to fA.
In other words, the adjacent tracks TA and TB are recorded there~n with the frequency-converted chrominance signals CA and CBwhich are in a fre~uency interleaving relation with each other as shown in Figures 7A and 7B.
~pon recording, a pulse generator (not shown) pro-vided at the rotary shaft of the rotary disc 1 generates a pulse of frequency 30Hz to control the rotation of the rotary disc. Accordingly, in this case, as shown in Figure 6A the switching signal Sc supplied to an input terminal 15 of the switch circuit 13 is arranged to be constant during a period where the magnetic head HA scans on the magnetic tape 2, while to be converted alternately at every horizontal line interval H during a period where the magnetic head HB scans on the tape 2.
A color video signal recorded on the magnetic tape 2 as described above is reproduced by the reproducing apparatus shown in Figure 1. In other words, a reproduced output signal from the magnetic heads HA and HB is applied through a repro-ducing amplicier 16 to a low pass filter 17 and a high pass filter 18 respectively. The frequency-modulated luminance signal derived from the high pass filter 18 is further applied through a limiter 19 to a demodulator 20 and the demodulated output therefrom is fed to an adder 21 as the luminance signal.
In this case, two magnetic heads HA and HB have ~s~
di~ferent azimuth angles as described before and the frequency-modulated luminance signal occupies higher frequency region relative to the frequency-converted chrominance signal,`so that ~:
even though the magnetic head HA scans along one part of the track TB when the same scans along the track TA and also the magnetic head HB scans along one part of the track TA when the same scans along track TB ~ the adder 21 is supplied with the luminance signal having no cross-talk. ;~
The reproduced output signal from the magnetic heads HA and HB is also supplied to the low pass fîlter 17 as des-cribed above to derive therefrom a reproduced frequency-converted chrominance signal. Upon recording, if the magnetic head HA
scans along a part of the track TB when the same scans along the track TA, the filter 17 has passed therethrough a signal :
composed of the signal CA and the signal CB, the latter being in a frequency interleaving relation with the former and mixed therewith as a crosstalk component as shown in Figure 7C.
Further, if the magnetic head ~IB scans along a part of the track TA when the same scans along the track TB ~ the filter 17 has passed therethrough a signal composed of the signal CB and the signal CA, the latter being in a frequency interleaving rela-tion with the former and mixed therewith as a crosstalk com-ponent as shown in Figure 7D. The output signal from the filter 17 is applied to a phase splitter 22. A signal obtained at a positive (+) output terminal of the phase splitter 22 is supplied to one input terminal of a switch circuit 23 and a signal obtained at a negative (-) output terminal thereof is supplied to the other input terminal of the switch circuit 23.
Simllarly as in the switch circuit 13 at recording, a switching - 30 signal Sc shown in Figure 6B iS used to change-over the switch circuit 23 to the illustrated state during a period where the magnetic head HA scans along the track TA and to change-over -: ' . ~ ' ' '-~57~
the same alternately to the illustrated state and the state re-verse to the former at every horizontal line interval H during a period where the magnetic head HB scans along the track TB.
Accordingly, during the period where the magnetic head HA scans along the track TA, the switch circuit 23 derives therefrom the aforesaid signal composed of the signal CA and the signal CB mixed therewith as the cross-talk component through the positive (+) output terminal of the phase splitter 22. On the other hand, during the period where the magnetic head HB scans along the track TB, the filter 17 supplies the aforesaid signal composed of the signal CB and the signal CA mixed there-with as the cross-talk component to the switch circuit~23. How-ever, since the signal CB ~s ~o~med ~ a~ alternate repetition of the signals CA and CA at every horizontal line interval, during the period where the magnetic head HB scans along the track TB, a signal composed of the signal CA mixed with a signal CA
of a cross-talk component through the (~) output terminal of the phase splitter 22 is obtained from the switch circuit 23 at .-every some other horizontal line interval, while a signal com-posed of the signal CA mixed with the signal CA of a cross-talk component through the (-) output terminal of the phase splitter 22 is obtained from the switch circuit 23 at every next other horizontal line interval. As a result, even during the period where the magnetic head HB scans along the track TB, the switch circuit 23 has derived therefrom the signal composed of the signal CA mixed with the signal CB as the cross-talk com-ponent. Accordingly, if the output signal of the switch cir-cuit 23 is supplied to a frequency converter 24 to be frequency-converted by a carrier signal of carrier frequency fS + fA' signals composed of true chrominance signals CsA and CsB of carrier frequency fS from the predetermined tracks mixed with cross-talk components respectively in a frequency interleaving g _ ~ L57~1LO
relation therewith are obtained from~the frequency converter 24 as shown in Figures 7E and 7F. Therefore, if the output signals of the frequency converter 24 are applied to a comb-filter ..
25, the cross-talk components are eliminated, and the original chrominance signal Cs as shown in Figure 7G is obtained. The chrominance signal Cs is fed to the adder 21 to be mixed with the luminance signal.
Thus, a reproduced color composite video signal with no cross-talk component is obtained at an output terminal 26.
As shown in Figure 8A, the comb-filter 25 used in this embodiment comprises an input terminal 27 connected to a delay line 28 that delays signals passing through it by one horizontal line interval H, which in the case of the NTSC
signal is approximately l/15,750th of a second. Both the input terminal 27 and the output of the lH delay line 28 are connected to input terminals of a combining circuit 29 that has an output terminal 30.
The response characteristic of the comb-filter 25 of Figure 8A is illustrated in Figure 8B. Further, as de-picted in Figure 1, a standard carrier signal of frequency fSfrom a fixed frequency oscillator 31 and a carrier signal of frequency fA from a variable frequency oscillator 32 are supplied to a frequency converter 33 to obtain the carrier signal of frequency fS + fA which is supplied to the fre-quency converter 24. Further, the reproduced chrominance signal from the frequency converter 24 is supplied to a burst gate circuit 34 to derive therefrom a burst signal which is applied to a phase detector circuit 35. Meanwhile, the standard carrier signal from the fixed frequency oscillator 31 is also fed to the circuit 35 and the detected output signal of the circuit 35 is fed to the variable frequency oscillator 32 to control the oscillation frequency thereof, namely, the frequency of the frequency conversion signal supplied to the frequency converter 24~
Thus, an automatic phase control circuit 36 is con-structed. With this invention, in addition to the phase de-tector circuit 35 used in the automatic phase control circuit 36 there is provided another phase detector circuit 37 and the burst signal from the burst gate circuit 34 is supplied to the phase detector circuit 37, while the standard carrier signal from the fixed frequency oscillator 31 is supplied to the circuit 37 through a phase shifter 38 with a proper shi~ting amount. Then, the phase-detected output from this circuit 37 is delivered to a flip-flop circuit 39 to control its revers-ing operation, that is, the switching state of the switch circuit 23.
In this case, when the signal CA is derived from the switch circuit 23 and hence the signal Cs is obtained from the frequency converter 24, the burst signal and standard carrier signal both supplied to the phase detector circuit 37 are coincident in phase with each other to make the phase-detected output therefrom negative. On the contrary, when the signal CA is derived from the switch circuit 23 and hence a signal CS of a carrier converted in a phase relative to the signal CS is ob-tained from the frequency converter 24, the burst signal and standard carrier signal both supplied to the phase detector circuit 37 are opposite in phase to each other to make the phase-detected output therefrom positive. When the posi-tive detected output is obtained, the flip-flop circuit 39 will be reversed thereby.
In addition, a pulse SpG for detecting the rotational angular positions of the magnetic heads HA and HB shown in Figure 9A is supplied from a pulse generator 40 to, for example, a monostable multivibrator 41 to obtain a rectangular wave .
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signal Sv shown in Figure 9B which is "O" during the period where the magnetic head HA scans on the magnetic tape 2, for example, in the odd field VO and "1" during the period where the magnetic head HB scans on the tape 2~ for example, in the even field VE. Meanwhile, a horizontal synchronizing signal PH is supplied to the flip-flop circuit 39 to obtain a signal SH reversed at every horizontal line interval H. These sig-nals Sv and SH are fed to an AND gate circuit 42. Though not . shown, the horizontal synchronizing signal PH is obtained, for example, by separating it from the demodulated luminance signal.
Accordingly, when the magnetic head HB reproduces a signal in the even field VE from the track TB, the filter 17 has sequentially derived therefrom chrominance signals CA, CA, CA, ........ as depicted in Figure 10~ and at this time the flip-flop circuit 39 will be reversed as shown in Figure lOC.
When the switch circuit 23 is changed-over to the state reverse to the illustrated one during a horizontal line interval where the signal CA is obtained from the filter 17 and to the ; illustrated state during another horizontal line interval where the signal CA is obtained from the filter 17, the signal :
CA will be continuously obtained from the switch circuit 23 as shown in Fig. lOD. In this case, however, at a time tl where the first burst signal in the field VE is obtained, as described above the phase detector circuit 37 has yielded thereErom a positive detected output D+ as shown in Figure lOE
and hence the flip-flop circuit 39 is thereby reversed at the time tl as shown in Figure lOF, thus the reversing condition of the flip-flop circuit 39 being changed. For this reason, the switch circuit 23 is thereafter changed-over to the illustrated condition during the horizontal line interval where the signal CA is obtained from the filter 17 and to the condition reverse to the illustrated one during the horiz~ntal - , , ............. , . :
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line interval where the signal CA is obtained from the filter 17. Thus, the signal C~ will be successively obtained from the switch circuit 23 as shown in Fig. 10~ . With this con-dition, as described above the negative detected output D_ is obtained from the phase detector circuit 37 as shown in Fi-gure lOE, so that the flip-flop circuit 39 is not reversed by the output from the phase detector circuit 37. The same opera-tion is observed also in the case when the reversing condition of the flip-flop circuit 39 and hence the switching condition of the switch circuit 23 is reversed by some reason in the middle of the field ~E.
As a result, the switch circuit 23 has derived therefrom the chrominance signal CA whose carrier phase is always co~stant and hence the chrominan~e signal Cs having a predetermined color phase or hue is obtained from the comb-~ filter 25. Even in the case that the hue is shifted, the shift ; is caused only during one horizontal line interval and hence there is no problem. ~ -The effect of this invention will be described with the assumption such that the flip-flop circuit 39 is not triggered by the output of the phase detector circuit 37. In this case, during the period where the magnetic head HB scans on the magnetic tape 2, the flip-flop circuit 39 is sometimes reversed as shown in Figure 9C or reversed at a condition opposite to the former. In the case that upon reproducing the flip-flop circuit 39 is reversed as shown in Figure 9C to obtain the switching signal Sc as shown in Figure 9D during the period where the magnetic head HB scans on the tape 2 and the switch circuit 23 is changed over according thereto, as the . 30 output of the filter 17 the signals CA and CA are produced - alternately at every horizontal line interval as shown in Figure llA and hence as the putput of the switch circuit 23 the .
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signals CA are successively produced as shown in Figure llB.
In this case, if the flip-flop circuit 39 is reversed at a condition opposite to the condition of Figure 9C to yield the switching signal Sc as shown in Figure 9E and the switchocircuit 23 is changed-over according thereto, as the output of the switch circuit 23 the signals CA are successively produced as shown in Figure llC. That is, in this case, as apparent from Figure llC the chrominance signals derived from the switch circui~ 23 will be reversed in phase every time when the repro-~ duced outputs from the magnetic heads HA and HB are changed-over, that is, at every field. The automatic phase control operation is once~carried out by the automatic phase control circuit 36 so as to obtain the reproduced chrominance signal whose car-rier phase is constant with a predetermined value. In this " ~ ~ - :, .
case, however, when the reproduced outpu-ts from the magnetic heads HA and HB are changed-over and the carrier phase of the reproduced chrominance signal from t~e switch circuit 23 is o . .
reversed, the phase control operation according toO the automatic phase control circuit 36 is not ~mmediately followed thereto and hence the chrominance signal supplied to the a ~ r 21 o will have the hue which is deteriorated immediately af~er the reproduced outputs from the magnetic heads HA and HB have been changed-over or at the beginning of the field.
In ~e present invention, as is previously described .
the burst signal in the chromin~nce signal obtained from the frequency converter circuit is phase-detected and the detected output signal is used to control the switching condition of the switch circuit forming the frequency converter circuit, so that the above described hue disturbance can be avoided.
, In the above described case, the cross-talk com-ponent is considered negligible. In a practical case, however, the output of the switch circuit 23 and accordingly the output ~ ,:
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of the frequency converter 24 is mixed with the cross-talk component as described in the beginning. If a burst signal in O the chrominance signal from a predetermined track and a burst signal in the chrominance signal rom the adjacent track as the cross-talk component are obtained at the same time, the level of the former signal is quite higher than that of the latter's signal. Therefore, even though the phases of the both are reversed, the burst signal obtained from the burst gate circuit 34 is coincident in phase with the burst gate signal in the chrominance signal from the predetermined track result-ing in no problem. However, if the recording positions TH f the horizontal synchronizing signals PH are slightly shifted each other as shown in Figure 12A, and hence the burst signal in the chrominance signal from the predetermined track and the burst signal in the chrominance signal from the adjacent track as the cross-talk component are obtained at different times, there occurs a problem.
In this case, when the magnetic head HB reproduces a signal from the track TB, the burst signals in the chromi-nance signal CB from the track TB are obtained from the filter 17 in a form of being alternately reversed in phase as shown ; by B, B, B, B,.. ....in Figure 12A. However, the outputs of the switch circuit 23 and accordingly those of the burst gate circuit 34 are constant in phase and hence negative detected outputs D_ as shown in Figure 12B are obtained from the ; phase detector circuit 37 as described above. Meanwhile, the burst signals in the chrominance signal C~ from the adjacent track TA as the cross-talk component are obtained from the filter 17 in a form of being constant in phase as shown by B, B, B, ....... in Figure 12A. However, the outputs of the switch circuit 23 and accordingly those of the burst gate circuit 34 are alternately reversed in phase and hence a ~04~
negative detected output E_ and a positive detected output E+ as shown in Figure 12B are alternately obtained, for ex-ample, at the rear of the aforesaid negative detected output D_ from the phase detector circuit 37. In this case, if the level of the cross-talk component is quite low, there is no problem. However, if the level of the cross-talk component becomes relatively high and the positive detected output E~
is increased more than a voltage enough for triggering the flip-flop circuit 39, which is shown by hatched lines in ;~ 10 Figure 12B, the flip-flop circuit 39 is reversed and the .switching condition of the switch circuit 23 becomes opposite :
to the initial condition. As a result, the chrominance signal derived from the f~ilter 25 will not be normal in phase until the switching condition of the switch circuit 23 is next cor-;' rected by the aforesaid control operation.
Another embodiment of this invention is designed to . eliminate the above described defect in such a manner that a burst signal in the chrominance signal derived from the comb-filter 25 is phase-detected and the detected output therefrom is used to control the switching condition of the switch cir-cuit 23.
In other words, as shown in Figure 13, the output signal of the comb-filter 25 is supplied to the burst gate circuit 34. The other circuit arrangement is the same as .
the example of Figure 1 with the same reference numerals being used.
; With such an arrangement, the chrominance signal : from the adjacent track as the cross-talk component is not : obtained from the comb-filter 25 as mentioned initially, ~ 30 so that no burst signal as the cross-talk component is deri-: ved from the burst gate circuit 34. Accordingly, the phase detector circuit 37 has derived therefrom only a phase ~ - 16 -.~
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1~45i7~Lal detected output signal o~ the burst signal in the chromi-nance signal from the track and there occurs no trouble as des-cribed with reference to Figure 12.
In this case, however, when the switching condition of the switch circuit 23 becomes improper, the condition of the chrominance signal derived from the filter 25 is a little different from the embodiment of Figure 1.
In other words, when the magnetic head HB reproduces signals in the even field VE from the track TB, if the revers-; 10 ing condition of the flip-flop circuit 39 and hence the switch-ing condition of the switch circuit 23 is not proper, a positive detected output D+ as shown in Figure 14G is obtained from the phase detector circuit 37 at a time tl where the first burst signal in the field VE is obtained from the switch circuit 23 and accordingly the comb-filter 25 thereby to reverse the flip-flop circuit 39 as shown in Figure 14H, thus the switching condition of the switch circuit 23 is made proper in the same manner as the example of Figure 1. Accordingly, the switch circuit 23 has continuously derived therefrom the signals CA having constant carrier phase excepting the first burst signal as shown in Figure 14D and the frequency conver-ter 24 has derived therefrom the similar signals Cs. However, in the comb-filter 25 the above signals and signals delayed one horizontal interval relative to the former as shown in Figure 14E are mixed with each other. After all, the filter 25 has passed therethrough chrominance signals such that the hue is changed in the horizontal line interval where the first burst signal is obtained and a signal disappears in the next hori-zontal line interval but the normal hue is obtained in the other line intervals as shown in Figure 14F. In the case that the re~ersing state of the flip-flop circuit 39 and hence the switching state of the switch circuit 23 is reversed to the ~)457~ ~
initial state by some reason in the middle of the ~ield VE, the same phenomenon car3 also be observed.
Instead of the anove described embodiment wherein the chrominance signal is supplied to the phase splitter to change-over lts output, the phase of a frequency-converting signal is reversed to effect the recording and reproducing operation as mentioned above. The present invention is applicable also to the above caseO In other words, upon recording the output of the filter 9 in Figure 5 is supplied to the frequency converter 10 and the output therefrom is supplied to the adder 8, while upon reproducing the output of the filter 17 is directly supplied to the frequency converter 24 and the output therefrom is supplied through the comb-filter 25 to the adder 21. With the above arrangement, as depicted in Figure 15, a carrier signal of frequency fS + fA~ which is obtained from, for example, the oscillator 11 at recording and from the aforesaid frequency converter 33 at reproducing, - .
is supplied to a phase splitter 43 and the resultant output therefrom is changed-over by the switch circuit 44. Upon re-producing, a burst signal in the chrominance signal obtained from the frequency converter 24 or the comb-filter 25 is phase~
detected and the detected output therefrom is used to control the switching condition of the switch circuit 44 similarly as mentioned above.
In a case of PAL system composite color video signals, - the switch circuit 23 or 44 may be changed-over at every two horizontal intervals during a period where the magnetic head HB scans along the track TB. The present invention can also ; be applied to the above case.
It will be apparent that many modifications and - variations may be effected without departing from the scope of the novel concepts of this invention.
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Field of the ~nvention This invention relates to a recording and/or reproduc-ing system to be applied to a video signal, and particularly to such system that cross-talk components of adjacent tracks can be cancelled in spite of no guard-bands among them.
Description of ~the Prior Art As well known, a chrominance signal of composite color video signal is preferably frequency-converted to lower frequency than that of frequency modulated luminance signal upon recording. There are disposed guard-bands between adja-cent recording tracks on a recording medium for cross-talk eli-mination. Recently, there have been proposed many technics of guard-ban~-less recording on a recording medium in order to achieve a reduction of tape consumption, in other words, high recording density. One approach is that the adjacent tracks on the recording medium such as magnetic video tape are scanned or recorded by at least two magnetic heads having different azimuth angles. The azimuth loss of a recorded signal upon reproduction is proportional to the frequency of recorded signal, so that the deterioration due to cross-talk still exists in the chrominance signal which lies in lower "J
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frequency range on the entire recording frequency.
In this view point, introduction of interleaving tech-nic to the chrominance signal carriers of adjacent tracks on the recording medium has been proposed in a pending application assigned to the same assignee of this application.
That is, there is an interleaving relation between reproduced true chrominance signal and cross-talk components of chrominance signal of adjacent tracks so that the cross-talk components of chrominance signal can be eliminated through a comb-filter.
When applying this technic, the applicants found that the phase of chrominance signal carriers of succeeding tracks become discontinuous with certain possibilities, so that the initial part of one scanning track yields deteriorated color phase in the reproduced picture until an automatic phase con-trol circuit stabilizes the phase in proper order.
S~MMARY OF THIS INVENTION
It is therefore a general object of this invention to provide a new recording and/or reproducing system.
It is another object of this invention to p~ovide a novel recording and/or reproducing system to be applied to a color composite video signal having a chrominance signal and a luminance signal.
It is still another object of this invention to provide an improved recording and/or reproducing system in which chromi-nance signal is frequency-converted to lower frequency than that of luminance signal.
It is further object of this invention to provide an improved recording and/or reproducing system in which no guard ban-~ is required between adjacent recording tracks.
More particularly there is provided an apparatus for reproducing video signals having luminance and chrominance ~0~57~
signal components and comprised of field intervals and line in-tervals which are recorded in respective areas of successive parallel tracks on a record medlum with said chrominance signal components of video signals recorded in next adjacent tracks having different first and second carriers; the com-bination of rotational transducer means for scanning along said tracks one at a time so as to reproduce the video sig-nals recorded in each of said tracks along with cross-talk signals from the tracks next adjacent thereto, pulse signal generating means for producing pulse signals indicating the rotational positioning of said transducer means, means for separating said chrominance signal components from the lumi-nance signal components in the reproduced signals, means for extracting horizontal synchronizing signals from said reproduced signals, signal processing means for providing the separated chrominance signal components of video signals reproduced from each of said tracks with a common carrier and for elimi-nating from the resultant chrominance signal components the chrominance signal components of the cross-talk signals on the basis of said different first and second carriers with which the chrominance signal components are recorded in the tracks which are next adjacent to each other, phase detecting means for detecting phase reversals of said common carrier of said resultant chrominance signal components, and means for controlling said signal processing means in response to said pulse signals, said horizontal synchronizing signals and said phase detecting means so as to maintain continuity of the phase of said common carrier of the resultant chrominance signal components.
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Other objects and aspects of this invention will become apparent from the illustrati~e embodiments about to be described or will be ~nd~cated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.
BRIEF DESCRIPTION OF ~'HE DRAWINGS
Figure '1 is a block diagram showing one embodiment of a reproducing apparatus according to the invention, -3a-57~
Figure 2 is a schematic plan view showing the dis-position of rotary magnetic heads and a magnetic tape, Figure 3 is a cross-sectional view showing the rela-tion between two magnetic heads used in the invention, Figure 4 is a schematic view showing a recording pattern on a magnetic tape used in the invention, Figure 5 is a block diagram showing one embodiment of a recording apparatus used for providing the recording pattern necessary for performing the invention, Figures 6A and 6B are waveform diagrams showing switching signals used in the invention, Figures 7A to 7G are views showing frequ~ncy spectra used for explaining the operati.on of this invention, Figures 8A and 8B are respectively a structural :
view of a comb-filter used in the invention and its character~
istic diagram, Figures 9A and 9E are waveform diagrams used for explaining the effect of this invention, Figures 10A to 10G are waveform diagrams used for explaining the operation of this invention, ..
Figures llA to llC are waveform diagrams used for explaining the effect of this invention, Figures 12A and 12B are views used for explaining `.:
another embodiment of this invention, ..
Figure 13 is a block diagram showing another embodi-ment of a reproducing apparatus according to this .invention, Figures 14A to 14H are waveform diagrams used for explaining the operation of the embodiment of Figure 13, and Figure 15 is a block diagram showing the main part .
of a further embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows one embodiment of reproducing .:
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apparatus according to the present invention, wherein refer-ence characters HA and HB indicate rotary magnetic heads which are secured on a rotary disc 1 as shown in Figure 2. One of these magnetic heads HA and H~ has an air gap GA with one azimuth angle, and the other an air gap GB with different azi-muth angle as shown in Figure 3. A magnetic tape 2 is run on a rotary locus of two magnetic heads HA and HB. The disc 1 rotates at 30 r.p.s., so that one pair of recording tracks TA
and TB is scanned with respective magnetic heads HA and HB at every rotation af the rotary disc 1 as shown in Figure 4.
That is to say, one pair of tracks TA and TB corresponds to one frame interval of a video signal. Each line interval and each field interval contains a blanking and synchronizing portions, and in accordance with accepted practice, the tracks TA and TB
are arranged in a pattern referred to as H-alignment. This is achieved by regulating the relative movements along directions 3 and 4 in accordance with the synchronizing portions of the video signal to be recorded so that one line interval section on which the blanking and synchronizing signals are recorded in the tradk TA is aligned with the adjacent section on which the blanking and synchronizing signals for that line interval are recorded in the track TB.
The magnetic tape 2 is recorded by a recording appa-ratus shown in Figure 5 wherein the magnetic heads HA and HB
are constructed completely in the same manner as those installed in the reproducing apparatus.
In Figure 5, a composite color video signal supplied to an input terminal 5 is fed to a low pass filter 6 to derive therefrom a luminance signal. The luminance signal thus derived is applied to a frequency modulator 7 to produce a frequency-modulated luminance signal occupying the higher frequency region of recordable and reproducible frequency band, ~ 5 -S7~
which is then applied to an adder 8. The composite colorvideo signal is also supplied to a ba~pass filter 9, which passes a chrominance signal Cs of carrier frequency fS to a frequency converter 10. A carrier signal of frequency fS + fA
from an oscillator 11 is also fed to the frequency converter 10, so that the chrominance signal Cs is converted to lower fre-quency region as a frequency-converted chrominance signal CA
of carrier frequency fA which is fed to a phase splitter 12.
Then, the signal CA from the positive (+) output terminal of the phase splitter 12 is fed to one input terminal of a switch - :
circuit 13, while a signal CA from the negative (-) output terminal of the phase splitter 12 is fed to -the other input terminal of the switch circuit 13. The switch circuit 13 is changed-over to the illustrated state by a switching signal .
SC as depicted in Figure 6A during an interval wherein the magnetic head HA scans along the track TA, for example, in an off field, and changed-over alternately to the illustrated ..
state and to the reverse state thereto at every horizontal line ~:~
interval H during a period wherein the magnetic head HB scans along the track TB, for example, in an even field. Thus, an output of the switch circuit 13 is fed to the adder 8 to be added with the frequency-modulated luminance signal and the ; resultant output therefrom is supplied through a recording amplifier 14 to the magnetic heads HA and HB, respectively. .
With such an arrangement, the frequency-converted chrominance signal CA of carrier frequency fA and of constant phase is recorded on the track TA. Meanwhile, the frequency-converted chrominance signal CA of carrier frequency fA and the :
signal CA, which is out of phase with respect to the former, are ~ :
alternately derived from the switch circuit 13 at every hori-zontal line interval H. The above mentioned alternate deriva-tion of the signals CA and CA is equivalent to that rectangular - : . . -:
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wave signals capable of being represented by "+l" and "-1"
alternately at every horizontal interval are multiplied to the signal CA. This is also equivalent to that the signal CA is balance-modulated with a rectangular wave signal having fre-quency of 1/2 the horizontal frequency fH. Accordingly, the track TB is recorded thereon with a fre~uency-converted chromi-nance signal CB of carrier frequency fB which is shifted 1/2 fH
relative to fA.
In other words, the adjacent tracks TA and TB are recorded there~n with the frequency-converted chrominance signals CA and CBwhich are in a fre~uency interleaving relation with each other as shown in Figures 7A and 7B.
~pon recording, a pulse generator (not shown) pro-vided at the rotary shaft of the rotary disc 1 generates a pulse of frequency 30Hz to control the rotation of the rotary disc. Accordingly, in this case, as shown in Figure 6A the switching signal Sc supplied to an input terminal 15 of the switch circuit 13 is arranged to be constant during a period where the magnetic head HA scans on the magnetic tape 2, while to be converted alternately at every horizontal line interval H during a period where the magnetic head HB scans on the tape 2.
A color video signal recorded on the magnetic tape 2 as described above is reproduced by the reproducing apparatus shown in Figure 1. In other words, a reproduced output signal from the magnetic heads HA and HB is applied through a repro-ducing amplicier 16 to a low pass filter 17 and a high pass filter 18 respectively. The frequency-modulated luminance signal derived from the high pass filter 18 is further applied through a limiter 19 to a demodulator 20 and the demodulated output therefrom is fed to an adder 21 as the luminance signal.
In this case, two magnetic heads HA and HB have ~s~
di~ferent azimuth angles as described before and the frequency-modulated luminance signal occupies higher frequency region relative to the frequency-converted chrominance signal,`so that ~:
even though the magnetic head HA scans along one part of the track TB when the same scans along the track TA and also the magnetic head HB scans along one part of the track TA when the same scans along track TB ~ the adder 21 is supplied with the luminance signal having no cross-talk. ;~
The reproduced output signal from the magnetic heads HA and HB is also supplied to the low pass fîlter 17 as des-cribed above to derive therefrom a reproduced frequency-converted chrominance signal. Upon recording, if the magnetic head HA
scans along a part of the track TB when the same scans along the track TA, the filter 17 has passed therethrough a signal :
composed of the signal CA and the signal CB, the latter being in a frequency interleaving relation with the former and mixed therewith as a crosstalk component as shown in Figure 7C.
Further, if the magnetic head ~IB scans along a part of the track TA when the same scans along the track TB ~ the filter 17 has passed therethrough a signal composed of the signal CB and the signal CA, the latter being in a frequency interleaving rela-tion with the former and mixed therewith as a crosstalk com-ponent as shown in Figure 7D. The output signal from the filter 17 is applied to a phase splitter 22. A signal obtained at a positive (+) output terminal of the phase splitter 22 is supplied to one input terminal of a switch circuit 23 and a signal obtained at a negative (-) output terminal thereof is supplied to the other input terminal of the switch circuit 23.
Simllarly as in the switch circuit 13 at recording, a switching - 30 signal Sc shown in Figure 6B iS used to change-over the switch circuit 23 to the illustrated state during a period where the magnetic head HA scans along the track TA and to change-over -: ' . ~ ' ' '-~57~
the same alternately to the illustrated state and the state re-verse to the former at every horizontal line interval H during a period where the magnetic head HB scans along the track TB.
Accordingly, during the period where the magnetic head HA scans along the track TA, the switch circuit 23 derives therefrom the aforesaid signal composed of the signal CA and the signal CB mixed therewith as the cross-talk component through the positive (+) output terminal of the phase splitter 22. On the other hand, during the period where the magnetic head HB scans along the track TB, the filter 17 supplies the aforesaid signal composed of the signal CB and the signal CA mixed there-with as the cross-talk component to the switch circuit~23. How-ever, since the signal CB ~s ~o~med ~ a~ alternate repetition of the signals CA and CA at every horizontal line interval, during the period where the magnetic head HB scans along the track TB, a signal composed of the signal CA mixed with a signal CA
of a cross-talk component through the (~) output terminal of the phase splitter 22 is obtained from the switch circuit 23 at .-every some other horizontal line interval, while a signal com-posed of the signal CA mixed with the signal CA of a cross-talk component through the (-) output terminal of the phase splitter 22 is obtained from the switch circuit 23 at every next other horizontal line interval. As a result, even during the period where the magnetic head HB scans along the track TB, the switch circuit 23 has derived therefrom the signal composed of the signal CA mixed with the signal CB as the cross-talk com-ponent. Accordingly, if the output signal of the switch cir-cuit 23 is supplied to a frequency converter 24 to be frequency-converted by a carrier signal of carrier frequency fS + fA' signals composed of true chrominance signals CsA and CsB of carrier frequency fS from the predetermined tracks mixed with cross-talk components respectively in a frequency interleaving g _ ~ L57~1LO
relation therewith are obtained from~the frequency converter 24 as shown in Figures 7E and 7F. Therefore, if the output signals of the frequency converter 24 are applied to a comb-filter ..
25, the cross-talk components are eliminated, and the original chrominance signal Cs as shown in Figure 7G is obtained. The chrominance signal Cs is fed to the adder 21 to be mixed with the luminance signal.
Thus, a reproduced color composite video signal with no cross-talk component is obtained at an output terminal 26.
As shown in Figure 8A, the comb-filter 25 used in this embodiment comprises an input terminal 27 connected to a delay line 28 that delays signals passing through it by one horizontal line interval H, which in the case of the NTSC
signal is approximately l/15,750th of a second. Both the input terminal 27 and the output of the lH delay line 28 are connected to input terminals of a combining circuit 29 that has an output terminal 30.
The response characteristic of the comb-filter 25 of Figure 8A is illustrated in Figure 8B. Further, as de-picted in Figure 1, a standard carrier signal of frequency fSfrom a fixed frequency oscillator 31 and a carrier signal of frequency fA from a variable frequency oscillator 32 are supplied to a frequency converter 33 to obtain the carrier signal of frequency fS + fA which is supplied to the fre-quency converter 24. Further, the reproduced chrominance signal from the frequency converter 24 is supplied to a burst gate circuit 34 to derive therefrom a burst signal which is applied to a phase detector circuit 35. Meanwhile, the standard carrier signal from the fixed frequency oscillator 31 is also fed to the circuit 35 and the detected output signal of the circuit 35 is fed to the variable frequency oscillator 32 to control the oscillation frequency thereof, namely, the frequency of the frequency conversion signal supplied to the frequency converter 24~
Thus, an automatic phase control circuit 36 is con-structed. With this invention, in addition to the phase de-tector circuit 35 used in the automatic phase control circuit 36 there is provided another phase detector circuit 37 and the burst signal from the burst gate circuit 34 is supplied to the phase detector circuit 37, while the standard carrier signal from the fixed frequency oscillator 31 is supplied to the circuit 37 through a phase shifter 38 with a proper shi~ting amount. Then, the phase-detected output from this circuit 37 is delivered to a flip-flop circuit 39 to control its revers-ing operation, that is, the switching state of the switch circuit 23.
In this case, when the signal CA is derived from the switch circuit 23 and hence the signal Cs is obtained from the frequency converter 24, the burst signal and standard carrier signal both supplied to the phase detector circuit 37 are coincident in phase with each other to make the phase-detected output therefrom negative. On the contrary, when the signal CA is derived from the switch circuit 23 and hence a signal CS of a carrier converted in a phase relative to the signal CS is ob-tained from the frequency converter 24, the burst signal and standard carrier signal both supplied to the phase detector circuit 37 are opposite in phase to each other to make the phase-detected output therefrom positive. When the posi-tive detected output is obtained, the flip-flop circuit 39 will be reversed thereby.
In addition, a pulse SpG for detecting the rotational angular positions of the magnetic heads HA and HB shown in Figure 9A is supplied from a pulse generator 40 to, for example, a monostable multivibrator 41 to obtain a rectangular wave .
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signal Sv shown in Figure 9B which is "O" during the period where the magnetic head HA scans on the magnetic tape 2, for example, in the odd field VO and "1" during the period where the magnetic head HB scans on the tape 2~ for example, in the even field VE. Meanwhile, a horizontal synchronizing signal PH is supplied to the flip-flop circuit 39 to obtain a signal SH reversed at every horizontal line interval H. These sig-nals Sv and SH are fed to an AND gate circuit 42. Though not . shown, the horizontal synchronizing signal PH is obtained, for example, by separating it from the demodulated luminance signal.
Accordingly, when the magnetic head HB reproduces a signal in the even field VE from the track TB, the filter 17 has sequentially derived therefrom chrominance signals CA, CA, CA, ........ as depicted in Figure 10~ and at this time the flip-flop circuit 39 will be reversed as shown in Figure lOC.
When the switch circuit 23 is changed-over to the state reverse to the illustrated one during a horizontal line interval where the signal CA is obtained from the filter 17 and to the ; illustrated state during another horizontal line interval where the signal CA is obtained from the filter 17, the signal :
CA will be continuously obtained from the switch circuit 23 as shown in Fig. lOD. In this case, however, at a time tl where the first burst signal in the field VE is obtained, as described above the phase detector circuit 37 has yielded thereErom a positive detected output D+ as shown in Figure lOE
and hence the flip-flop circuit 39 is thereby reversed at the time tl as shown in Figure lOF, thus the reversing condition of the flip-flop circuit 39 being changed. For this reason, the switch circuit 23 is thereafter changed-over to the illustrated condition during the horizontal line interval where the signal CA is obtained from the filter 17 and to the condition reverse to the illustrated one during the horiz~ntal - , , ............. , . :
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~LC3457 ~
line interval where the signal CA is obtained from the filter 17. Thus, the signal C~ will be successively obtained from the switch circuit 23 as shown in Fig. 10~ . With this con-dition, as described above the negative detected output D_ is obtained from the phase detector circuit 37 as shown in Fi-gure lOE, so that the flip-flop circuit 39 is not reversed by the output from the phase detector circuit 37. The same opera-tion is observed also in the case when the reversing condition of the flip-flop circuit 39 and hence the switching condition of the switch circuit 23 is reversed by some reason in the middle of the field ~E.
As a result, the switch circuit 23 has derived therefrom the chrominance signal CA whose carrier phase is always co~stant and hence the chrominan~e signal Cs having a predetermined color phase or hue is obtained from the comb-~ filter 25. Even in the case that the hue is shifted, the shift ; is caused only during one horizontal line interval and hence there is no problem. ~ -The effect of this invention will be described with the assumption such that the flip-flop circuit 39 is not triggered by the output of the phase detector circuit 37. In this case, during the period where the magnetic head HB scans on the magnetic tape 2, the flip-flop circuit 39 is sometimes reversed as shown in Figure 9C or reversed at a condition opposite to the former. In the case that upon reproducing the flip-flop circuit 39 is reversed as shown in Figure 9C to obtain the switching signal Sc as shown in Figure 9D during the period where the magnetic head HB scans on the tape 2 and the switch circuit 23 is changed over according thereto, as the . 30 output of the filter 17 the signals CA and CA are produced - alternately at every horizontal line interval as shown in Figure llA and hence as the putput of the switch circuit 23 the .
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signals CA are successively produced as shown in Figure llB.
In this case, if the flip-flop circuit 39 is reversed at a condition opposite to the condition of Figure 9C to yield the switching signal Sc as shown in Figure 9E and the switchocircuit 23 is changed-over according thereto, as the output of the switch circuit 23 the signals CA are successively produced as shown in Figure llC. That is, in this case, as apparent from Figure llC the chrominance signals derived from the switch circui~ 23 will be reversed in phase every time when the repro-~ duced outputs from the magnetic heads HA and HB are changed-over, that is, at every field. The automatic phase control operation is once~carried out by the automatic phase control circuit 36 so as to obtain the reproduced chrominance signal whose car-rier phase is constant with a predetermined value. In this " ~ ~ - :, .
case, however, when the reproduced outpu-ts from the magnetic heads HA and HB are changed-over and the carrier phase of the reproduced chrominance signal from t~e switch circuit 23 is o . .
reversed, the phase control operation according toO the automatic phase control circuit 36 is not ~mmediately followed thereto and hence the chrominance signal supplied to the a ~ r 21 o will have the hue which is deteriorated immediately af~er the reproduced outputs from the magnetic heads HA and HB have been changed-over or at the beginning of the field.
In ~e present invention, as is previously described .
the burst signal in the chromin~nce signal obtained from the frequency converter circuit is phase-detected and the detected output signal is used to control the switching condition of the switch circuit forming the frequency converter circuit, so that the above described hue disturbance can be avoided.
, In the above described case, the cross-talk com-ponent is considered negligible. In a practical case, however, the output of the switch circuit 23 and accordingly the output ~ ,:
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of the frequency converter 24 is mixed with the cross-talk component as described in the beginning. If a burst signal in O the chrominance signal from a predetermined track and a burst signal in the chrominance signal rom the adjacent track as the cross-talk component are obtained at the same time, the level of the former signal is quite higher than that of the latter's signal. Therefore, even though the phases of the both are reversed, the burst signal obtained from the burst gate circuit 34 is coincident in phase with the burst gate signal in the chrominance signal from the predetermined track result-ing in no problem. However, if the recording positions TH f the horizontal synchronizing signals PH are slightly shifted each other as shown in Figure 12A, and hence the burst signal in the chrominance signal from the predetermined track and the burst signal in the chrominance signal from the adjacent track as the cross-talk component are obtained at different times, there occurs a problem.
In this case, when the magnetic head HB reproduces a signal from the track TB, the burst signals in the chromi-nance signal CB from the track TB are obtained from the filter 17 in a form of being alternately reversed in phase as shown ; by B, B, B, B,.. ....in Figure 12A. However, the outputs of the switch circuit 23 and accordingly those of the burst gate circuit 34 are constant in phase and hence negative detected outputs D_ as shown in Figure 12B are obtained from the ; phase detector circuit 37 as described above. Meanwhile, the burst signals in the chrominance signal C~ from the adjacent track TA as the cross-talk component are obtained from the filter 17 in a form of being constant in phase as shown by B, B, B, ....... in Figure 12A. However, the outputs of the switch circuit 23 and accordingly those of the burst gate circuit 34 are alternately reversed in phase and hence a ~04~
negative detected output E_ and a positive detected output E+ as shown in Figure 12B are alternately obtained, for ex-ample, at the rear of the aforesaid negative detected output D_ from the phase detector circuit 37. In this case, if the level of the cross-talk component is quite low, there is no problem. However, if the level of the cross-talk component becomes relatively high and the positive detected output E~
is increased more than a voltage enough for triggering the flip-flop circuit 39, which is shown by hatched lines in ;~ 10 Figure 12B, the flip-flop circuit 39 is reversed and the .switching condition of the switch circuit 23 becomes opposite :
to the initial condition. As a result, the chrominance signal derived from the f~ilter 25 will not be normal in phase until the switching condition of the switch circuit 23 is next cor-;' rected by the aforesaid control operation.
Another embodiment of this invention is designed to . eliminate the above described defect in such a manner that a burst signal in the chrominance signal derived from the comb-filter 25 is phase-detected and the detected output therefrom is used to control the switching condition of the switch cir-cuit 23.
In other words, as shown in Figure 13, the output signal of the comb-filter 25 is supplied to the burst gate circuit 34. The other circuit arrangement is the same as .
the example of Figure 1 with the same reference numerals being used.
; With such an arrangement, the chrominance signal : from the adjacent track as the cross-talk component is not : obtained from the comb-filter 25 as mentioned initially, ~ 30 so that no burst signal as the cross-talk component is deri-: ved from the burst gate circuit 34. Accordingly, the phase detector circuit 37 has derived therefrom only a phase ~ - 16 -.~
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1~45i7~Lal detected output signal o~ the burst signal in the chromi-nance signal from the track and there occurs no trouble as des-cribed with reference to Figure 12.
In this case, however, when the switching condition of the switch circuit 23 becomes improper, the condition of the chrominance signal derived from the filter 25 is a little different from the embodiment of Figure 1.
In other words, when the magnetic head HB reproduces signals in the even field VE from the track TB, if the revers-; 10 ing condition of the flip-flop circuit 39 and hence the switch-ing condition of the switch circuit 23 is not proper, a positive detected output D+ as shown in Figure 14G is obtained from the phase detector circuit 37 at a time tl where the first burst signal in the field VE is obtained from the switch circuit 23 and accordingly the comb-filter 25 thereby to reverse the flip-flop circuit 39 as shown in Figure 14H, thus the switching condition of the switch circuit 23 is made proper in the same manner as the example of Figure 1. Accordingly, the switch circuit 23 has continuously derived therefrom the signals CA having constant carrier phase excepting the first burst signal as shown in Figure 14D and the frequency conver-ter 24 has derived therefrom the similar signals Cs. However, in the comb-filter 25 the above signals and signals delayed one horizontal interval relative to the former as shown in Figure 14E are mixed with each other. After all, the filter 25 has passed therethrough chrominance signals such that the hue is changed in the horizontal line interval where the first burst signal is obtained and a signal disappears in the next hori-zontal line interval but the normal hue is obtained in the other line intervals as shown in Figure 14F. In the case that the re~ersing state of the flip-flop circuit 39 and hence the switching state of the switch circuit 23 is reversed to the ~)457~ ~
initial state by some reason in the middle of the ~ield VE, the same phenomenon car3 also be observed.
Instead of the anove described embodiment wherein the chrominance signal is supplied to the phase splitter to change-over lts output, the phase of a frequency-converting signal is reversed to effect the recording and reproducing operation as mentioned above. The present invention is applicable also to the above caseO In other words, upon recording the output of the filter 9 in Figure 5 is supplied to the frequency converter 10 and the output therefrom is supplied to the adder 8, while upon reproducing the output of the filter 17 is directly supplied to the frequency converter 24 and the output therefrom is supplied through the comb-filter 25 to the adder 21. With the above arrangement, as depicted in Figure 15, a carrier signal of frequency fS + fA~ which is obtained from, for example, the oscillator 11 at recording and from the aforesaid frequency converter 33 at reproducing, - .
is supplied to a phase splitter 43 and the resultant output therefrom is changed-over by the switch circuit 44. Upon re-producing, a burst signal in the chrominance signal obtained from the frequency converter 24 or the comb-filter 25 is phase~
detected and the detected output therefrom is used to control the switching condition of the switch circuit 44 similarly as mentioned above.
In a case of PAL system composite color video signals, - the switch circuit 23 or 44 may be changed-over at every two horizontal intervals during a period where the magnetic head HB scans along the track TB. The present invention can also ; be applied to the above case.
It will be apparent that many modifications and - variations may be effected without departing from the scope of the novel concepts of this invention.
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Claims (15)
1. In an apparatus for reproducing video signals having luminance and chrominance signal components and comprised of field intervals and line intervals which are recorded in respective areas of successive parallel tracks on a record medium with said chrominance signal components of video signals recorded in next adjacent tracks having different first and second carriers; the combination of rotational transducer means for scanning along said tracks one at a time so as to reproduce the video signals recorded in each of said tracks along with cross-talk signals from the tracks next adjacent thereto, pulse signal generating means for producing pulse signals indicating the rotational positioning of said transducer means, means for separating said chrominance signal components from the luminance signal components in the reproduced signals, means for extracting horizontal synchronizing signals from said reproduced signals, signal processing means for providing the separated chrominance signal components of video signals reproduced from each of said tracks with a common carrier and for eliminating from the resultant chrominance signal components the chrominance signal components of the cross-talk signals on the basis of said different first and second carriers with which the chrominance signal components are recorded in the tracks which are next adjacent to each other, phase detecting means for detecting phase reversals of said common carrier of said resultant chrominance signal components, and means for controlling said signal processing means in response to said pulse signals, said horizontal synchronizing signals and said phase detecting means so as to maintain continuity of the phase of said common carrier of the resultant chrominance signal components.
2. An apparatus according to Claim 1; in which said signal processing means includes frequency-converting means receiving said separated chrominance signal components and providing said common carrier therefor, and comb-filter means receiving the output of said frequency converting means for eliminating therefrom said chrominance signal components of the cross-talk signals; and in which said phase detecting means includes means for extracting burst signals from said resultant chrominance signal components and which are representative of the phase of said common carrier, and means for comparing the phase of said burst signals with the phase of a standard frequency signal.
3. An apparatus according to Claim 2; in which the video signals are recorded in said next adjacent tracks with different azimuth angles, said transducer means includes first and second reproducing heads having gaps with said different azimuth angles, respectively, and reproducing the video signals recorded in the tracks with the respective azimuth angles, and said luminance signal components of the recorded video signals are in a relatively high frequency band so that azimuth loss is effective to minimize said luminance signal components in said cross-talk signals.
4. An apparatus according to Claim 2; further comprising fixed oscillator means for producing said standard frequency signal of constant phase, and automatic phase control means for maintaining the phase of said common carrier of the resultant chrominance signal components substantially constant in respect to said phase of the standard frequency signal.
5. An apparatus according to Claim 1; in which said signal processing means includes switching means changeable be-tween first and second conditions for reversing the phase of said common carrier of the resultant chrominance signal components, and said means for controlling the signal processing means includes means for producing a switching control signal for said switching means and which changes the condition of the latter in response to the detection by said phase detecting means of a phase reversal of said common carrier of the resultant chrominance signal components.
6. An apparatus according to Claim 5; in which said first carrier is of constant phase and said second carrier has its phase reversed at every predetermined number of said line intervals; and in which said means for producing said switching control signal includes means responsive to said pulse signals and said horizontal synchronizing signals for maintaining said switching control signal at a first level corresponding to said first condition of said switching means during reproducing of video signals recorded with said first carrier and for changing said switching control signal between said first level and a second level corresponding to said second condition of the switching means at each said predetermined number of the line intervals, and means for changing the switching control signal between said first and second levels thereof in response to said detection by the phase detecting means of a phase reversal of said common carrier of the resultant chrominance signal components.
7. An apparatus according to Claim 6; in which said signal processing means includes fixed oscillator means for producing a standard frequency signal, and said phase detecting means compares the phase of said common carrier of the resultant chrominance signal components with the phase of said standard frequency signal.
8. An apparatus according to Claim 7; further comprising phase shifting means for shifting the phase of said standard frequency signal to be compared with the phase of said common carrier.
9. An apparatus according to Claim 6; in which said signal processing means includes phase splitting means receiving the separated chrominance signal components of video signals reproduced from each of said tracks and having positive and negative output terminals connected with said switching means and at which said separated chrominance signal components are derived with the phases of said carrier of the latter reversed in respect to each other.
10. An apparatus according to Claim 9; in which said first and second carriers with which the chrominance signal components are recorded in said adjacent tracks, respectively, have frequencies substantially below a standard carrier frequency for said chrominance signal components; and in which said signal processing means further includes a frequency converter receiving the output of said switching means, and means for applying a frequency-converting signal to said frequency converter so as to cause the latter to provide said common carrier with said standard carrier frequency.
11. An apparatus according to Claim 10, in which said signal processing means further includes comb filter means receiving the output of said frequency converter and eliminating therefrom said chrominance signal components of the cross-talk signals.
12. An apparatus according to Claim 6; in which said first and second carriers with which the chrominance signal components are recorded in said adjacent tracks, respectively, have frequencies substantially below a standard carrier frequency for said chrominance signal components; and in which said signal processing means includes a frequency converter receiving said separated chrominance signal components of the video signals reproduced from each of said tracks, means for producing a frequency-converting signal, and phase splitting means receiving said frequency-converting signal and having positive and negative output terminals at which said frequency-converting signal is obtained with its phase relatively reversed, and said switching means is connected between said phase splitting means and said frequency converter for selectively applying said frequency converting signal to said frequency converter from said positive and negative output terminals so as to cause said frequency converter to provide said common carrier with said standard carrier frequency.
13. An apparatus according to Claim 12; in which said signal processing means further includes comb filter means receiving the output of said frequency converter for removing therefrom said chrominance signal components of the cross-talk signals.
14. An apparatus according to Claim 1; further comprising adding means for combining said resultant chrominance signal components, from which the cross-talk signals have been eliminated, with the separated luminance signal components.
15. An apparatus according to Claim 1; in which the ends of the margins between successive areas in which said second intervals are recorded in each of said tracks are aligned, in the direction transverse to the length of the tracks, with the adjacent ends of the margins between the successive areas in which said second intervals are recorded in the next adjacent tracks.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1474674A JPS5422376B2 (en) | 1974-02-05 | 1974-02-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1045710A true CA1045710A (en) | 1979-01-02 |
Family
ID=11869665
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA219,438A Expired CA1045710A (en) | 1974-02-05 | 1975-02-05 | Apparatus for reproducing color video signals |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS5422376B2 (en) |
| AT (1) | AT339971B (en) |
| BR (1) | BR7500715A (en) |
| CA (1) | CA1045710A (en) |
| CH (1) | CH589989A5 (en) |
| DE (2) | DE2560585C2 (en) |
| ES (1) | ES434483A1 (en) |
| FR (1) | FR2260245B1 (en) |
| GB (1) | GB1490423A (en) |
| IT (1) | IT1031475B (en) |
| NL (1) | NL177458C (en) |
| SE (1) | SE402396B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS586437B2 (en) * | 1975-09-25 | 1983-02-04 | 松下電器産業株式会社 | Kirokusai Seihoshiki |
| US4079412A (en) * | 1976-01-30 | 1978-03-14 | Victor Company Of Japan, Limited | Signal processing circuit in a color video signal recording and/or reproducing apparatus |
| JPS5927515B2 (en) * | 1976-07-14 | 1984-07-06 | ソニー株式会社 | Color video signal recording/playback method and recording device |
| DE3731767C2 (en) * | 1987-09-22 | 1993-10-21 | Thomson Brandt Gmbh | VCR for the recording of PAL television signals |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4860520A (en) * | 1971-11-26 | 1973-08-24 | ||
| GB1497865A (en) | 1973-12-28 | 1978-01-12 | Sony Corp | Magnetic recording and/or reproducing apparatus |
| JPS531171B2 (en) | 1974-01-21 | 1978-01-17 |
-
1974
- 1974-02-05 JP JP1474674A patent/JPS5422376B2/ja not_active Expired
-
1975
- 1975-01-30 GB GB413275A patent/GB1490423A/en not_active Expired
- 1975-02-03 AT AT78075A patent/AT339971B/en not_active IP Right Cessation
- 1975-02-04 DE DE19752560585 patent/DE2560585C2/en not_active Expired
- 1975-02-04 DE DE19752504608 patent/DE2504608C2/en not_active Expired
- 1975-02-04 BR BR7500715A patent/BR7500715A/en unknown
- 1975-02-04 CH CH134775A patent/CH589989A5/xx not_active IP Right Cessation
- 1975-02-05 CA CA219,438A patent/CA1045710A/en not_active Expired
- 1975-02-05 SE SE7501241A patent/SE402396B/en not_active IP Right Cessation
- 1975-02-05 NL NL7501403A patent/NL177458C/en not_active IP Right Cessation
- 1975-02-05 FR FR7503615A patent/FR2260245B1/fr not_active Expired
- 1975-02-05 ES ES434483A patent/ES434483A1/en not_active Expired
- 1975-02-05 IT IT1996575A patent/IT1031475B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| SE402396B (en) | 1978-06-26 |
| IT1031475B (en) | 1979-04-30 |
| DE2560585C2 (en) | 1985-03-21 |
| BR7500715A (en) | 1975-11-11 |
| FR2260245A1 (en) | 1975-08-29 |
| AT339971B (en) | 1977-11-25 |
| ES434483A1 (en) | 1976-12-16 |
| ATA78075A (en) | 1977-03-15 |
| JPS5422376B2 (en) | 1979-08-06 |
| NL7501403A (en) | 1975-08-07 |
| FR2260245B1 (en) | 1978-02-03 |
| AU7773875A (en) | 1976-08-05 |
| NL177458C (en) | 1985-09-16 |
| CH589989A5 (en) | 1977-07-29 |
| DE2504608C2 (en) | 1984-11-29 |
| JPS50110222A (en) | 1975-08-30 |
| SE7501241L (en) | 1975-08-06 |
| GB1490423A (en) | 1977-11-02 |
| DE2504608A1 (en) | 1975-08-14 |
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