Color recorder having means for reducing luminance crosstalk in displayed image

A method of and apparatus for recording a video signal in successive parallel tracks on a record medium, and for reproducing the recorded signal. The video signal, which may be the luminance component of a composite color television signal, frequency modulates a carrier to produce a frequency modulated video signal. The phase of the frequency modulated video signal is selectively shifted in selected line intervals and is recorded in parallel tracks such that the phase difference between frequency modulated video signals in at least some adjacently recorded line intervals of successive tracks is an odd multiple of .pi.. In one embodiment, the difference between the phase of alternate line intervals which are recorded in one track and the phase of alternate line intervals which are recorded in the next adjacent track is equal to an odd multiple of .pi.. In accordance with another embodiment, the difference between the phases of successive line intervals which are recorded in the same track is equal to an odd multiple of .pi.. The phase shift is attained by inserting a pulse signal into selected line intervals of the video signal in advance of the frequency modulation. During reproducing, the successive tracks are scanned and the frequency modulated signals recorded therein are reproduced together with a crosstalk component which is picked up by the transducer from an adjacent track, the crosstalk components being out of phase with each other. The reproduced frequency modulated signal is demodulated so as to recover the original video signal and the inserted pulse signal, the latter being eliminated from the recovered video signal.

BACKGROUND OF THE INVENTION 
This invention relates to a method of and apparatus for recording and/or 
reproducing video signals on a record medium and, more particularly, to a 
method and apparatus for recording video signals with a high recording 
density and for reproducing such signals with minimal interference in the 
displayed video picture due to crosstalk picked up from adjacent tracks 
when a particular track is reproduced. 
In a typical video recording system, such as a video tape recorder (VTR), a 
video signal is recorded on a magnetic medium, such as magnetic tape, in 
successive, parallel, skewed tracks, each track generally having a field 
interval recorded therein and being formed of successive areas which 
correspond to respective line intervals of the video signal. If the video 
signal is a composite color television signal, recording is carried out by 
separating the chrominance and luminance components, frequency modulating 
the luminance component to a relatively higher band of frequencies, 
frequency converting the chrominance component to a band of frequencies 
which is lower than that contained in the frequency-modulated luminance 
signal, combining the frequency-modulated luminance signal and 
frequency-converted chrominance signal and recording the combined signal 
in the same track. In order to avoid interference due to crosstalk during 
a signal reproduction operation that is, to avoid interference due to 
signals which are picked up by a scanning transducer from an adjacent 
track when a given track is scanned, it has been the practice heretofore 
of providing guard bands to separate successive parallel tracks on the 
record medium. Such guard bands essentially are "empty" of information so 
as to avoid crosstalk pickup from such adjacent guard bands when a 
particular track is scanned. 
However, the use of guard bands to separate successive tracks is a 
relatively inefficient usage of the record medium. That is, if the guard 
bands themselves could be provided with useful information, the overall 
recording density would be improved. Such improvement can be attained to 
some degree by providing two transducers for recording the combined 
luminance and chrominance signals, the two transducers having different 
azimuth angles. Hence, information is recorded in one track at one azimuth 
angle and information is recorded in the next adjacent track with a 
different azimuth angle. When the information in such tracks is reproduced 
by the same, respective transducers, the information recorded in the 
scanned track is reproduced with minimal attenuation, but because of 
azimuth loss, the crosstalk which is picked up from the next adjacent 
track is substantially attenuated. Since azimuth loss is proportional to 
the frequency of the recorded signals, it may be appreciated that the 
crosstalk due to the frequency-modulated luminance signals included in the 
recorded color television signals is far more attenuated than the 
crosstalk due to the frequency-converted chrominance signals. Also, since 
crosstalk attenuation due to azimuth loss is less effective as the width 
of the parallel tracks is reduced, it is not sufficient to rely solely on 
the use of transducers having different azimuth angles in order to reduce 
crosstalk noise when video signals are recorded in very narrow or 
overlapped tracks. If the crosstalk picked up from an adjacent track is 
not attenuated adequately, an interference or beat signal, having a 
frequency different from either the information signals which are recorded 
in the scanned track or the picked up signals which are recorded in an 
adjacent track, will appear as a beat or moire pattern in the video 
picture which ultimately is displayed. 
Since reliance upon azimuth loss is not completely adequate for minimizing 
crosstalk interference caused by the frequency-converted chrominance 
signals which are picked up from an adjacent track, it has been proposed 
that such cross-talk can be reduced substantially by recording the 
frequency-converted chrominance signals in adjacent tracks with different 
carriers. For example, the phase of the frequency-converted chrominance 
carrier can be constant throughout successive line intervals in one track 
but will shift by 180.degree. from line-to-line in the next adjacent 
track. As another example, the phase of the frequency-converted 
chrominance carrier in alternate line intervals in one track will differ 
by 180.degree. (or .pi.) from the phase of the frequency-converted 
chrominance carrier in adjacent alternate line intervals in an adjacent 
track, while all of the remaining line intervals in adjacent tracks will 
have frequency-converted chrominance carriers which are in phase with each 
other. Because of these phase characteristics in both examples, the 
crosstalk interference due to the frequency-converted chrominance signals 
which are picked up from an adjacent track will exhibit a frequency 
interleaved relationship with respect to the frequency-converted 
chrominance signals which are reproduced from the scanned track. Suitable 
filtering techniques can be used to eliminate those frequency components 
which correspond to the crosstalk interference. 
While the use of different frequency-converted chrominance carriers is an 
effective technique for minimizing crosstalk interference attributed to 
the chrominance signals, there still will be crosstalk interference due to 
the frequency-modulated luminance signals, particularly if the record 
tracks exhibit minimal width. One proposed solution to this problem is 
disclosed and claimed in copending application Ser. No. 770,315, filed 
Feb. 18, 1977, wherein different carriers for the frequency-modulated 
luminance signal are recorded in adjacent tracks. This is carried out by 
using two different bias voltages superposed onto the luminance signal 
prior to frequency modulation thereof, which bias voltages effectively 
determine the frequency of a frequency-modulated carrier. As one example 
of this proposed solution, the frequencies of the carriers differ from 
each other by an odd multiple of one-half the horizontal synchronizing 
frequency. In a signal reproduction operation, the reproduced 
frequency-modulated luminance signal is demodulated, and the bias voltages 
which had been added to the original luminance signal are removed 
therefrom, as by subtracting locally-generated bias voltages from the 
recovered luminance signal. When the reproduced signals are displayed, as 
on a cathode ray tube, crosstalk interference will be present in 
successive lines, but such interference will be phase-inverted from 
line-to-line. Hence, this crosstalk interference will cancel visually and 
will not be perceived by a viewer. 
Another proposed solution is described in application Ser. No. 815,012, 
filed on even date herewith, wherein the phase of the frequency modulated 
luminance signal is selectively shifted by an odd multiple of .pi. during 
selected line and field intervals. For example, the phase of the frequency 
modulated luminance signal may be shifted in successive line intervals 
which are recorded in alternate tracks, while such phase remains constant 
in the remaining tracks. As another example, the phase of the frequency 
modulated luminance signal varies by an odd multiple of .pi. between 
alternate line intervals in one track and adjacent alternate line 
intervals in the next adjacent track. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide an improved phase 
shifting technique for carrying out the proposed solution disclosed in 
application Ser. No. 815,012. 
Another object of this invention is to determine the phase shift of a 
frequency modulated video signal for a recording operation by selectively 
inserting a pulse of predetermined amplitude and phase into the video 
signal in advance of the frequency modulation thereof. 
A further object of this invention is to provide a method of and apparatus 
for determining selective phase shifts of a frequency modulated video 
signal by selectively superimposing a pulse signal thereon, such as during 
the horizontal synchronizing interval, such that when the phase shifted 
frequency modulated video signal is recorded and then reproduced, 
crosstalk noise is not present in a video picture derived therefrom, and 
the reproduced superimposed pulse signal is readily cancelled for the 
video signal. 
A further object of this invention is to provide an improved method of and 
apparatus for recording a composite color television signal in relatively 
narrow, successive parallel tracks on a record medium wherein crosstalk 
interference due to both luminance and chrominance components which are 
picked up during a signal reproducing operation is minimized. 
Various other objects, advantages and features of this invention will 
become readily apparent from the ensuing detailed description, and the 
novel features will be particularly pointed out in the appended claims. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an information signal component, 
such as a video signal component, is recorded in successive parallel 
tracks on a record medium, the information signal component occurring in 
successive first time intervals, such as line intervals, which are 
included in repetitive second time intervals, such as field intervals, 
each track being formed of successive areas corresponding to the first 
time intervals. The information signal component is frequency modulated 
and selectively phase shifted so that the phase of the frequency-modulated 
information signal recorded in a predetermined area differs from the phase 
of the frequency-modulated information signal recorded in an adjacent area 
by an odd multiple of .pi.. These adjacent areas are, in one embodiment, 
successive areas in a given track; and in another embodiment, are in 
adjacent tracks. The phase shifting of the frequency-modulated information 
signal is obtained by selectively inserting a pulse signal of 
predetermined amplitude and duration into selected first time intervals of 
the information signal component in advance of the frequency modulation 
thereof. In a signal reproducing operation, the recorded signals are 
reproduced such that the frequency-modulated information signal recorded 
in each track together with a cross-talk component picked up from an 
adjacent track are recovered, the crosstalk components being out of phase 
with each other. The frequency-modulated information signal is demodulated 
to recover the original information signal component and the previously 
inserted pulse signals, the latter then being eliminated from the 
recovered information signal component.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS 
Referring now to the drawings, wherein like reference numerals are used 
throughout, and initially to FIG. 1, a rotary head assembly 10 is used to 
record video signals on and reproduce such signals from a magnetic tape T, 
the assembly including a guide drum 11 having a circumferential slot, and 
a pair of diametrically opposed rotary transducers or heads 12A and 12B 
mounted at opposite ends of a suitable support so as to move in a circular 
path along the circumferential slot of drum 11. The magnetic tape T is 
suitably guided, as by guide rollers 14A and 14B, in a helical path 
extending about a substantial portion of the periphery of drum 11. Thus, 
when the heads are rotated in the direction of the arrow 15 and, 
simultaneously, tape T is suitably driven in the longitudinal direction 
indicated by the arrow 16, heads 12A and 12B alternately scan successive 
parallel tracks 17 extending across tape T at an angle to the longitudinal 
direction of the tape (FIG. 3). As shown in FIG. 3, head 12A scans 
alternating tracks, for example, tracks 17A.sub.1, 17A.sub.2, 17A.sub.3, 
17A.sub.4, . . . while head 12B scans the remaining alternating tracks 
17B.sub.1, 17B.sub.2, 17B.sub.3, 17B.sub.4, . . . Thus, adjacent tracks, 
such as tracks 17A.sub.1 and 17B.sub.1, are respectively scanned by the 
heads 12A and 12B. 
Usually, but not necessarily, each of tracks 17 has recorded therein the 
signal information corresponding to a respective field interval of the 
video signals, and each track is divided into successive areas or 
increments each having recorded therein the signal information 
corresponding to a line interval of the respective field of the video 
signals. Each line interval and each field interval of the video signals 
contains a blanking and synchronizing portion and, in accordance with 
accepted practice, the relative movements of head and tape in the 
directions 15 and 16 preferably are regulated in accordance with the 
synchronizing signals of the video signals to be recorded so as to obtain 
so-called H-alignment of the areas in which line intervals are recorded in 
each track in alignment with the areas in which line intervals are 
recorded in the next adjacent tracks. In other words, as shown 
schematically in FIG. 3, the ends of the margins between the areas in 
which the line intervals are recorded in each of tracks 17 preferably are 
aligned, in the direction transverse to the lengths of the tracks, with 
the adjacent ends of such margins in the next adjacent tracks. However, 
this H-alignment configuration is not absolutely necessary for recording 
or reproducing video information on tape T. 
As shown in FIG. 2, heads 12A and 12B have air gaps 18A and 18B, 
respectively, arranged at substantially different azimuth angles 
.theta..sub.1 and .theta..sub.2 in respect to the plane of rotation of 
heads 12A and 12B. Because of these different azimuth angles, each of 
heads 12A and 12B, when recording video signals in the respective tracks 
on tape T, effects magnetization of magnetic domains in the magnetic 
coating on tape T in what would appear to be, if such domains were 
visible, a series of parallel lines or stripes extending across the 
respective track and each having an orientation that corresponds to the 
azimuth angle .theta..sub.1 or .theta..sub.2 of the gap of the respective 
head 12A or 12B. When reproducing video signals which have been recorded 
with these different azimuth angles, each of tracks 17A.sub.1 -17A.sub.4 
is scanned by head 12A and each of tracks 17B.sub.1 -17B.sub.4 is scanned 
by head 12B, so that gap 18A extends at an angle with respect to the 
domains in tracks 17B.sub.1 -17B.sub.4 but is aligned with the domains in 
tracks 17A.sub.1 -17A.sub.4 and, similarly, gap 18B extends at an angle 
with respect to the domains in tracks 17A.sub.1 -17A.sub.4 but is aligned 
with the domains in tracks 17B.sub.1 -17B.sub.4. Hence, if one head, such 
as head 12A, while scanning one track, such as track 17A.sub.1, overlaps 
an adjacent track, such as track 17B.sub.1, to reproduce as crosstalk the 
signals recorded in such adjacent track, the well-known azimuth loss 
causes attenuation of the crosstalk signals picked up from such adjacent 
track. 
Turning now to FIG. 4, there is illustrated a block diagram of one 
embodiment of apparatus in accordance with the teachings of the present 
invention. For the purpose of simplification, the illustrated apparatus is 
directed to that portion of a color television signal recorder which is 
capable of recording the luminance component included in the color 
television signal. That is, the remainder of the recording circuitry which 
is used for recording the chrominance component is omitted from FIG. 4. As 
may be appreciated, if the video signal which is to be recorded comprises 
merely a monochrome (black-and-white) signal, then the apparatus 
illustrated in FIG. 4 is, essentially, complete for the recording of such 
a monochrome video signal. 
The recording apparatus includes an input terminal 21 to which the 
luminance component of a composite color television signal or the 
monochrome video signal (both hereinafter being referred to as a video 
signal) is applied, this input terminal being coupled to a channel wherein 
the video signal is frequency modulated prior to recording on a record 
medium. The channel is comprised of an amplifier 22, which may be an 
automatic gain control amplifier, a pre-emphasis circuit 23 in which the 
high frequency response of the video signal is enhanced, a clipping 
circuit 24 wherein overshooting and undershooting portions of the enhanced 
video signal, as well as undesired amplitude modulations thereof, are 
eliminated or clipped, a frequency modulator 26 in which a carrier of 
relatively high frequency is frequency modulated by the enhanced, clipped 
video signal, and a recording amplifier 27. As shown, these circuits are 
connected in cascade. The output of recording amplifier 27 is coupled 
through suitable switching circuitry (not shown) to the rotary head 
assembly previously described with respect to FIG. 1 wherein heads 12A and 
12B record successive tracks 17A and 17B across tape T. 
As is conventional, the video signals applied to input terminal 21 also 
include synchronizing signals comprised of horizontal synchronizing 
signals and vertical synchronizing signals. The horizontal synchronizing 
signals separate successive line intervals of video information, and the 
vertical synchronizing signals define successive field intervals in which 
the line intervals are provided. A vertical synchronizing signal separator 
31 is coupled to input terminal 21 and is adapted to separate the vertical 
synchronizing signals from the received video signal. Vertical 
synchronizing signal separator circuits are well known to those of 
ordinary skill in the art and need not be further described herein. A 
bistate device 32, such as a flip-flop circuit, is coupled to the output 
of the vertical synchronizing signal separator and is adapted to change 
its state, or condition, in response to each separated vertical 
synchronizing signal. As may be appreciated, the vertical synchronizing 
frequency of the separated vertical synchronizing signals is divided by 
flip-flop circuit 32, this flip-flop circuit producing an alternating 
signal whose half-cycle duration is equal to a field interval. 
The output of flip-flop circuit 32 is coupled to a servo control circuit 30 
which is adapted to control the operation of a drive motor 37 mechanically 
coupled to the rotary transducer assembly to insure that the respective 
heads 12A and 12B commence their scanning of a record track 17A and 17B at 
the beginning of a field interval. Servo control circuit 30 is comprised 
of a comparator 33 which is capable of comparing the phase of the 
alternating signal produced by flip-flop circuit 32 to the phase of heads 
12A and 12B. The phase, or relative positions, of the heads is represented 
by a pulse signal generated by a pulse generator 34. In a typical 
embodiment, drive motor 37 is mechanically coupled to the rotary 
transducer assembly by a drive shaft, this shaft including an element, 
such as a magnet, aligned with one of heads 12A and 12B. A magnetic 
pick-up coil is positioned to sense the magnet and to generate an output 
pulse in response thereto; that is, to generate an output pulse when, for 
example, head 12A first comes into contact with tape T. The output of 
pulse generator 34 is coupled via a wave-shaping amplifier 35 to another 
input of comparator 33. An error signal proportional to the difference 
between the phase of the alternating signal produced by flip-flop circuit 
32 and the phase of the pulse signals generated by pulse generator 34 is 
supplied as an adjusting signal to motor 37 via an amplifier 36. Hence, it 
is seen that servo control circuit 30 functions to bring heads 12A and 12B 
into contact with tape T at the beginning of a field interval such that a 
complete field interval is recorded in a given track across the tape. In 
an alternative embodiment, if more than one field interval is to be 
recorded in a track, servo control circuit 30 would be substantially the 
same as shown in FIG. 4, and flip-flop circuit 32 would be replaced by an 
appropriate divider circuit, whereby the alternating signal produced by 
such a divider circuit would be formed of half-cycle intervals which are 
substantially equal to the duration of each track. 
The output of flip-flop circuit 32 also is used as a control signal which 
is recorded along a longitudinal edge of tape T for a purpose soon to be 
described. To this effect, the output of flip-flop circuit 32 is coupled 
through an amplifier 38 to a fixed transducer or head 39, whereby control 
signals 56 (FIG. 3) are recorded in alignment with particular tracks. 
As mentioned previously, if the tracks in which the video signals are 
recorded are free of guard bands, and if such tracks exhibit minimal 
width, a crosstalk component will be picked up during a signal reproducing 
operation when a particular track is scanned, the crosstalk component 
being attributed to the video signals recorded in an adjacent track. 
Furthermore, even if the tracks are recorded by use of transducers having 
different azimuth angles, such as by use of heads 12A and 12B, the normal 
attenutation of crosstalk components due to azimuth loss is not effective 
to minimize such crosstalk components. Hence, it is necessary to process 
the video signals in a manner whereby crosstalk interference will be 
substantially reduced during a signal reproducing operation, and 
particularly when the reproduced video signal is displayed on a cathode 
ray tube. This crosstalk reduction is attained by varying the phase of the 
frequency-modulated video signals recorded in one track relative to the 
phase of the frequency-modulated video signals recorded in an adjacent 
track. In one embodiment of this invention, and with reference to FIG. 3, 
the phase of the frequency-modulated video signal is changed by an odd 
multiple of .pi. in successive line intervals of, for example, track 
17A.sub.1, but remains constant from one to the next line interval in 
adjacent track 17B.sub.1. This phase shift in successive line intervals is 
repeated in track 17A.sub.2, 17A.sub.3, . . .; and the phase in successive 
line intervals of tracks 17B.sub.2, 17B.sub.3, . . . remains constant. In 
another embodiment, the phase of the video signals recorded in alternate 
line intervals of, for example, trac, 17A.sub.1 differs from the phase of 
the video signals recorded in alternate line intervals in adjacent track 
17B.sub.1 for an odd multiple of .pi., such alternate line intervals in 
track 17A.sub.1 being adjacent the aforementioned alternate line intervals 
in track 17B.sub.1. A similar phase relation holds for the remaining 
tracks. A mathematical explanation as to how this selective phase shifting 
of the frequency-modulated video signals minimizes perceptible cross-talk 
interference in a video picture derived from a reproduction of such 
frequency-modulated video signals, is set out in detail in copending 
application Ser. No. 815,012. 
The manner in which the phase of the recorded video signals is controlled 
in accordance with the foregoing embodiments is shown by the phase control 
circuitry of FIG. 4. This phase control circuitry is comprised of a 
horizontal synchronizing signal separator 41, a pulse forming or shaping 
circuit 42, a switching circuit 43 and an adding or combining circuit 25. 
Horizontal synchronizing signal separator 41 may be of conventional 
construction and is coupled to input terminal 21 so as to separate the 
horizontal synchronizing signal from the received video signal. The 
separated horizontal synchronizing signals produced by horizontal 
synchronizing signal separator 41 are supplied to pulse forming circuit 42 
which is adapted to generate a pulse of predetermined amplitude and 
duration in response to each separated horizontal synchronizing pulse, as 
will be described below with respect to FIGS. 6C and 6D. 
Switching circuit 43 is shown diagramatically as having a movable contact 
selectively switched to connect its input to its output. Switching circuit 
43 may be comprised of transistor switching devices, a diode switching 
array, or the like. The input of the illustrated switching circuit is 
supplied with the pulse signals generated by pulse forming circuit 42. 
Switching circuit 43 is controlled so as to selectively couple the pulse 
signals applied thereto to its output. Appropriate control over the 
switching circuit is achieved by flip-flop circuit 32 which produces a 
signal that alternates between two levels and which is used to selectively 
energize, or close, switching circuit 43. When the switching circuit is 
closed, pulses produced by pulse forming circuit 42 are adapted to be 
added to the enhanced, clipped video signal in an adding circuit 25, the 
resultant signal being applied to frequency modulator 26. 
The operation of the apparatus illustrated in FIG. 4 will best be 
understood by referring first to the waveforms shown in FIGS. 5A-5J. Let 
it be assumed that the received video signal S.sub.y at input terminal 21 
is as shown in FIG. 5A, constituted by successive line intervals of video 
information separated by horizontal synchronizing intervals each 
containing a horizontal synchronizing pulse P.sub.h, the line intervals 
being included in successive field intervals T.sub.a, T.sub.b. Video 
signal S.sub.y is applied to preemphasis circuit 23, resulting in the 
waveform shown in FIG. 5B wherein the transitions of the horizontal 
synchronizing pulses P.sub.h are subjected to undershoots and overshoots. 
Video signal S.sub.y also is applied to horizontal synchronizing signal 
separator 41, from which separated horizontal synchronizing pulses P.sub.b 
(FIG. 5C) are transmitted to pulse forming circuit 42. The pulse forming 
circuit may include delay, inverting and amplifying circuits so as to 
produce pulse signals P.sub.s (FIG. 5D) from the received horizontal 
synchronizing pulses P.sub.b. Pulse signals P.sub.s are of predetermined 
amplitude and predetermined duration, for a purpose soon to be explained. 
For the purpose of the present discussion, the pulse "amplitude" is 
intended to mean both magnitude and polarity of the pulse signal. Hence, 
in some embodiments, pulse signals P.sub.s may appear as negative pulses. 
In the illustrated waveforms, pulse signals P.sub.s are delayed, or timed, 
to coincide with the back porch of the horizontal synchronizing pulses. It 
will become apparent that pulse signals P.sub.s may coincide with any 
portion of the horizontal synchronizing interval, or with the line 
interval, as desired. 
Video signal S.sub.y also is applied from input terminal 21 to vertical 
synchronizing signal separator 31 so as to derive the vertical 
synchronizing signals therefrom. These vertical synchronizing signals 
occur at the field rate between successive fields T.sub.a, T.sub.b, 
T.sub.a, . . . The separated vertical synchronizing signals are supplied 
to flip-flop circuit 32 so as to produce the alternating signal S.sub.v 
shown in FIG. 5E. This alternating signal preferably is a rectangular wave 
signal formed of successive half-cycles of field durations T.sub.a, 
T.sub.b, respectively. Signal S.sub.v is applied as a control signal to 
switching circuit 43, thereby selectively energizing the switching circuit 
during one or the other of its halfcycles. It will be assumed that 
switching circuit 43 is energized (i.e., closed) during the positive 
half-cycles of signal S.sub.v. 
When switching circuit 43 is energized, the pulse signals P.sub.s applied 
thereto are transmitted to a-ding circuit 25 whereat they are added, or 
superimposed onto the video signal S.sub.y, thereby forming the signal 
S.sub.y shown in FIG. 5G. Of course, when switching circuit 43 is 
de-energized, the transmission path between pulse forming circuit 42 and 
adding circuit 25 is interrupted. The resultant signal S.sub.y (FIG. 5G) 
having pulse signals P.sub.p selectively superimposed thereon is applied 
to frequency modulator 26 whereat it modulates a carrier. This 
frequency-modulated video signal then is recorded in successive, narrow 
tracks, as shown in FIG. 3. As will be discussed with reference to FIGS. 
6A-6D, superimposed pulse signals P.sub.p are present in successive line 
intervals, then the phase of the frequency modulated video signal will 
shift successively, that is, from line-to-line. If the pulse signal 
P.sub.p is omitted from a line interval, the phase of the frequency 
modulated video signal will remain as during the preceding line interval. 
While various examples of phase shift are described below, let it be 
assumed that, as shown in FIG. 5G, the phase of the frequency-modulated 
video signal is shifted in successive line intervals during alternate 
field intervals, and that this phase shift is equal to an odd multiple of 
.pi., or 180.degree.. 
When the selectively shifted phase of the frequency-modulated video signal 
is recorded in successive tracks on tape T by heads 12A and 12B, the phase 
in successive line intervals in the track corresponding to field interval 
T.sub.a is constant throughout. However, the phase of the 
frequency-modulated video signal which is recorded in the next adjacent 
track corresponding to field interval T.sub.b varies by 180.degree. in 
successive line intervals. That is, the phase in this track will appear 
as, for example, 0.degree. in one line interval and will be shifted by 
180.degree. in the next line interval, and will be shifted by 180.degree. 
in the following line interval, and so on. As is explained in copending 
application Ser. No. 815,012, when the frequency-modulated video signals 
are recorded in accordance with this phase relationship, crosstalk 
interference is effectively eliminated from the video picture which 
ultimately is reproduced. Insofar as elimination of this crosstalk 
component is concerned, the phase of the frequency-modulated video signal 
recorded in alternate line intervals during field interval T.sub.b differs 
from the phase of the frequency-modulated video signal recorded in 
alternate line intervals during field interval T.sub.a by 180.degree.. 
That is, the phase of the first line interval in field interval T.sub.b 
differs from the phase of the first line interval in field interval 
T.sub.a by 180.degree.. Also, the phase in the third line interval in 
field interval T.sub.b differs from the phase in the third line interval 
in field interval T.sub.a also by 180.degree.. The remaining alternate 
line intervals in the respective field intervals exhibit this phase 
relationship. The remaining line intervals in field interval T.sub.b are 
in phase with the remaining line intervals in field interval T.sub.a. 
Control signals 56 recorded by transducer 39 along the longitudinal edge of 
tape T may be only the positive transitions in signal S.sub.v, produced by 
flip-flop circuits 32, or only the negative transitions in this signal. 
Hence, these control signals serve to identify which tracks contain the 
aforedescribed phase-shifted frequency-modulated video signals. This 
identifying information is useful during a signal reproducing operation. 
Signal S.sub.v also is applied as a control signal to servo control circuit 
30. It is believed that one of ordinary skill in the art will fully 
understand how servo control circuit 50 operates; and in the interest of 
brevity, further description of this circuit is not provided. 
When the frequency-modulated video signal, recorded with the phase relation 
described hereinabove, is reproduced, the primary signal which is 
recovered from the track being scanned is accompanied by a crosstalk 
signal picked up from an adjacent track. The frequency of this crosstalk 
signal is an odd multiple of one-half the horizontal synchronizing 
frequency f.sub.H. That is, the crosstalk signals picked up during the 
scanning of successive tracks have the frequency (m + 1/2)f.sub.H, with 
this crosstalk signal being phase-inverted in successive horizontal line 
intervals. Consequently, if an interfering crosstalk signal is reproduced 
in one line interval and is inverted in phase during the following line 
interval, this phase relationship in the interfering signals results in 
visual cancellation of the crosstalk signals when a corresponding video 
picture is reproduced on a cathode ray tube. 
The manner in which pulse signals P.sub.p (FIG. 5G) determine the phase 
shift of the frequency modulated video signal now will be described, with 
reference to FIGS. 6A-6D. Let it first be assumed that a signal of 
constant level is applied to frequency modulator 26. Since this signal 
level does not charge, the output frequency f of the modulator remains 
constant. As is known, frequency can be expressed as a rate of change of 
phase, so that f = d.theta./dt where .theta. represents the phase of the 
frequency modulated signal. With the assumption that the frequency t is 
constant, the rate of change of phase .theta. is constant, and can be 
represented as a straight line of, for example, positive slope. However, 
if a signal level is applied to frequency modulator 26 so as to change the 
output frequency of the modulator, this frequency change can be 
represented as a corresponding change in the rate of phase change. That 
is, d.theta./dt will exhibit a change due to this applied signal level and 
will not be coincident with its afore-mentioned constant slope. 
Turning now to FIG. 6A, the illustrated waveform represents a video signal 
S.sub.y wherein the horizontal synchronizing interval is greatly 
exaggerated. When the illustrated video signal is applied to frequency 
modulator 26, the modulated frequency will have a range from that 
corresponding to the white level (f.sub.w) to that corresponding to the 
sync tip, or synchronizing pulse P.sub.h. As is shown, when the back porch 
(at the pedestal level) is applied to the modulator, the corresponding 
output frequency is f.sub.p. Since the back porch is at a constant level, 
frequency f.sub.p is constant, and the change in phase d.theta./dt occurs 
at a constant rate. This is represented by the solid line shown in FIG. 
6C, and designated .theta..sub.o. 
The modulated frequency output from frequency modulator 26 varies as a 
function of the video information signal and also as a function of the 
synchronizing pulse P.sub.h. Therefore, the phase change d.theta./dt will 
not coincide with curve .theta..sub.o (FIG. 6C) during most of the 
horizontal line interval, but will exhibit a more complex waveform. This 
is represented by the broken line shown in FIG. 6C. Hence, when the video 
signal shown in FIG. 6A is applied to frequency modulator 26, the phase of 
the frequency modulated signal will be represented by the lower curve in 
FIG. 6C, and will change at a generally constant rate from line-to-line. 
Let it now be assumed that pulse signals P.sub.p are inserted onto the back 
porch of video signal S.sub.y, the duration of these pulse signals being 
equal to .DELTA.t. Frequency modulator 26 is responsive to this pulse 
signal to produce an abrupt change in the modulating frequency. 
Consequently the rate of change of the phase of the frequency modulated 
signal d.theta./dt also changes abruptly. This is represented by the 
change .DELTA..theta. in FIG. 6C. As may be appreciated, pulse signal 
P.sub.p is both preceded and followed by the pedestal level. Accordingly, 
the frequency f.sub.p corresponding to the pedestal level is constant, and 
the phase changes at a constant rate d.theta./dt. FIG. 6C represents the 
constant slope in the phase .theta. during the beginning portion of the 
back porch, followed by the abrupt change .DELTA..theta. due to the pulse 
P.sub.p, and then followed by the same constant slope for the remainder of 
the back porch, shown as curve .theta..sub.b. Therefore, the phase of the 
frequency modulated video signal is changed from one line interval to the 
next by .DELTA. .theta. when a pulse signal P.sub.p is inserted into that 
line interval. A comparison between the substantially constant phase of 
the frequency-modulated video signal in the absence of pulse signals (FIG. 
6A) and the phase-shifted frequency modulated video signal due to such 
pulse signals (FIG. 6B) is shown by curves .theta..sub.a and .theta..sub.b 
in FIG. 6C. 
If the axis of FIG. 6C is rotated so as to coincide with the constant phase 
curve .theta..sub.o, the result would appear as in FIG. 6D. As shown 
therein, the phase of the frequency modulated video signal increases due 
to the pulse signal P.sub.p by an amount .DELTA..theta., but then remains 
constant for the remainder of the line interval, and until the next pulse 
signal P.sub.p is received to cause a further phase change .DELTA..theta.. 
In FIG. 6D, it is assumed that each pulse signal P.sub.p has an amplitude 
sufficient to cause a change in phase .DELTA..theta.=.pi., and that the 
pulse signals are inserted into the horizontal synchronizing interval in 
successive lines (t.sub.1, t.sub.2, . . . ) of alternate fields (T.sub.b 
only). Other examples of phase changes .DELTA..theta. in selected line 
intervals are discussed below. 
As a numerical example of the amplitude and duration of pulse signal 
P.sub.p, let it be assumed that the pulse signal extends from the pedestal 
level to the white level (FIG. 6B). The frequencies produced by frequency 
modulator 26 corresponding to these levels are f.sub.p and f.sub.w, 
respectively, which may be, for example, 4.04MHz and 4.4MHz, respectively. 
The change in angular frequency (W.sub.w -W.sub.p) during the time 
interval .DELTA.t is to produce a phase shift of .pi.. Accordingly, (2.pi. 
f.sub.w -2.pi.f.sub.p).DELTA.t=.pi.. A reasonable approximation for the 
duration of pulse signal P.sub.p is one microsecond. 
The apparatus shown in FIG. 4 is adapted to be incorporated into apparatus 
for recording and/or reproducing a composite color television signal onto 
tape T. One embodiment of such apparatus is illustrated in FIG. 7 which 
includes a recording section 100 and a reproducing section 200. The 
recording section is provided with an input terminal 21 for receiving 
composite color television signals which include luminance and chrominance 
components and are composed of line, field and frame intervals with 
blanking and synchronizing portions in each of those intervals. The 
composite color signals are applied from input terminal 21 to a low pass 
filter 121 which transmits substantially only the luminance signal S.sub.y 
to automatic gain control amplifier 22, the latter applying an amplified 
luminance component to a clamp circuit 122 for clamping the luminance 
component to a fixed reference level, as is typical in such recording 
apparatus. The clamped luminance component is applied to pre-emphasis 
circuit 23 and then to adding circuit 25, as described previously with 
respect to FIG. 4. The output S'.sub.y of adding circuit 25 is supplied 
through clipping circuit 24 to frequency modulator 26 wherein it modulates 
an FM carrier. A comparison of FIGS. 4 and 7 indicates that clipping 
circuit 24 may be provided either before or after adding circuit 25. The 
frequency modulated luminance component Y.sub.FM from modulator 38 is 
passed through a high pass filter 126 to a mixing or adding circuit 58. 
In accordance with this invention, and as previously described with 
reference to FIG. 4, the frequency modulated luminance component Y.sub.FM 
is selectively phase-shifted by an odd multiple of .pi. between adjacent 
line intervals. As will be recalled, this is achieved by inserting a pulse 
signal into selected line intervals of the frequency-modulated luminance 
component, the pulse signal being derived by pulse forming circuit 42 from 
a horizontal synchronizing pulse separated from the received luminance 
component by horizontal synchronizing signal separator 41, and being 
selectively inserted by the combination of switching circuit 43 and adding 
circuit 25. 
In the FIG. 7 embodiment, switching circuit 43 is controlled by control 
signals S.sub.v ', which are similar to signals S.sub.v of FIG. 4 (shown 
in FIG. 5E) to selectively energize switch 43, thereby selectively 
applying pulse signals P.sub.p to adding circuit 25. 
The composite color television signals applied to input terminal 21 also 
are coupled to a band pass filter 54 which separates the chrominance 
component S.sub.i from the composite color signals and passes the 
chrominance component through an automatic color control circuit 55 to a 
frequency converter 57 in which the chrominance component and its carrier 
is converted from an original frequency f.sub.i to a frequency band lower 
than that of the frequency modulated luminance component Y.sub.FM supplied 
to mixing circuit 58. The frequency converted chrominance component 
S.sub.j also is supplied to mixing circuit 58 whereat it is combined with 
the frequency modulated luminance component Y.sub.FM for providing a 
composite signal S.sub.c which is supplied through a recording amplifier 
59 and a record terminal R of a record/playback switch 159 to the rotary 
heads 12A and 12B. 
The luminance component S.sub.y from automatic gain control circuit 22 also 
is supplied to vertical synchronizing signal separator 31, as in the FIG. 
4 embodiment. The separated vertical synchronizing signals P.sub.v are 
applied from separator 31 to flip-flop divider 32 which is operative to 
provide control signals at a repetition rate which is a predetermined 
fraction (1/2 .times. n) of the repetition rate of the separated vertical 
synchronizing signals, in which n is the number of field intervals to be 
recorded in each of the tracks and is equal to one in the illustrated 
embodiment. The control signals produced by flip-flop circuit 32 occur in 
correspondence with the recording of color video signals in alternating, 
or every other one of the tracks so as to identify or distinguish between 
the tracks in which the chrominance component is recorded with first and 
second carriers, as hereinafter described in detail. Accordingly, the 
control signals are applied through an amplifier 38 and a record terminal 
R of a record/playback switch 138 to fixed transducer 39, as in the FIG. 4 
embodiment. 
The control signals from flip-flop circuit 32 also are supplied to servo 
control circuit 30 via the record terminal R of a record/playback switch 
60. This servo control circuit has been discussed with respect to the 
embodiment of FIG. 4 and is seen to provide a brake control or servo 
signal which is passed through a servo amplifier 36 for either suitably 
decreasing or increasing the speed at which heads 12A and 12B are driven 
by motor 37, to that heads 12A and 12B will commence to move along 
respective tracks on tape T at the commencement of alternating field 
intervals of the color video signals being recorded. 
The separated horizontal synchronizing signals P.sub.h are applied from 
separator 41 to flip-flop circuit 45 which produces control signal S.sub.h 
(FIG. 5H) for application to one input of an AND gate 64. The output of 
wave forming circuit 35 is also applied to a signal forming circuit 65 
which produces the previously mentioned control S'.sub.v applied to a 
second input of AND gate 64. Control signal S.sub.h is a rectangular wave 
having high and low intervals, each equal to one line interval H, and 
control signal S'.sub.v is a rectangular wave having high and low 
intervals, each equal to one field interval T, so that control AND gate 64 
produces a control signal S.sub.x which remains low during one entire 
field interval and goes high only during alternate line intervals of the 
alternate field interval. 
In the embodiment shown in FIG. 7, control signal S.sub.x controls the 
establishment of different carriers for the frequency converted 
chrominance component S.sub.j to be recorded in tracks that are next 
adjacent to each other, with such carriers differing from each other in 
their phase characteristics. 
The apparatus for providing different carriers with which to frequency 
convert the chrominance component included in the composite color signal 
includes a voltage controlled oscillator 66 for providing an output 
oscillation with a center frequency of, for example, 44f.sub.H. The output 
of oscillator 66 is applied to a frequency divider 67 to be 
frequency-divided by a factor of 44, and the output of divider 67 is 
applied to a comparator 68 wherein the frequency of the output oscillation 
is compared to the frequency of the separated horizontal synchronizing 
signals P.sub.h which are supplied from separator 41. Upon any frequency 
deviation between the signals applied to comparator 68, a suitable control 
voltage is supplied thereby to voltage controlled oscillator 66 so that 
the frequency of the oscillation output is automatically controlled or 
maintained at 44f.sub.H. 
The oscillation output from oscillator 66 is applied to a frequency 
converter 69, which may be in the form of a balanced modulator, to 
frequency convert the oscillation output by a frequency converting signal 
S.sub.p produced by a voltage controlled oscillator 70 having a center 
frequency of f.sub.i -1/4f.sub.H, in which f.sub.i is the original or 
standard carrier frequency of the chrominance component S.sub.i of the 
received color video signals. Balanced modulator 69 has two outputs (+ and 
-) of opposite polarity for providing frequency converting signals 
+S.sub.q and -S.sub.q, respectively. Such frequency converting signals 
+S.sub.q and -S.sub.q are of opposite phase or polarity, but each has the 
frequency (f.sub.i +44f.sub.H -1/4f.sub.H). 
The frequency converting signals +S.sub.q and -S.sub.q are applied 
selectively to frequency converter 57 through a switching circuit 71, 
shown schematically as having fixed contacts a and b respectively 
connected to the + and - outputs of balanced modulator 69 and a movable 
contact c which is switchable between contacts a and b and is connected to 
frequency converter 57. Switching circuit 71 is controlled by control 
signal S.sub.x produced by AND gate 64 so that the switching circuit 
applies frequency converting signal +S.sub.q to converter 57 whenever 
control signal S.sub.x has a low value, and the switching circuit applies 
frequency converting signal -S.sub.q to the converter whenever control 
signal S.sub.x has a high value. By alternately applying frequency 
converting signals +S.sub.q and -S.sub.q to frequency converter 57, the 
carrier of the chrominance component is converted from its original 
carrier frequency f.sub.i to a relatively lower carrier frequency f.sub.c 
=44f.sub.H -1/4f.sub.H, the converter carrier frequency f.sub.c being 
below the frequency band of the frequency modulated luminance component 
Y.sub.FM, and the phase or polarity of the frequency converted chrominance 
component S.sub.j is alternately reversed in response to the alternately 
applied frequency converting signals. 
The converted carrier frequency f.sub.c of the frequency converted 
chrominance component S.sub.j satisfies the equation 
EQU f.sub.c = 1/4f.sub.H (2m-1) 
in which m is a positive integer. Of course, in the present case, in which 
f.sub.c =44f.sub.H -1/4f.sub.H, the value for m is 88. As a result of this 
converted carrier frequency f.sub.c, the second harmonic of the converted 
carrier is interleaved with the luminance component so as to avoid beat 
interference therebetween. By avoiding such beat interference, the 
frequency converted chrominance component can be recorded with a 
relatively high amplitude in respect to the amplitude of the frequency 
modulated luminance component, thereby obtaining a good signal-to-noise 
ratio of the chrominance component. 
When the frequency converted chrominance component S.sub.j and the 
frequency modulated luminance component Y.sub.FM are combined in mixing 
circuit 40, the frequency converted chrominance component S.sub.j 
amplitude modulates the frequency modulated luminance component Y.sub.FM 
to supply a composite signal S.sub.c through amplifier 59 and 
record/playback switch 159 to heads 12A and 12B for recording in the 
successive parallel tracks on tape T. 
Switches 60, 87, 122, 138 and 159 are ganged, or interconnected, for 
simultaneous change-over from their recording positions, shown in FIG. 7, 
to their reproducing or playback positions in which the movable contact of 
each switch engages its playback terminal or contact P. In the reproducing 
section 200, a reproducing amplifier 72 is coupled to heads 12A and 12B 
via the playback terminal P of switch 159 for receiving the signals 
alternately reproduced by the heads from the successive parallel tracks on 
tape P. The output of reproducing amplifier 72 is connected in common to a 
band pass filter 73 and a low pass filter 74 which respectively separate 
the reproduced frequency modulated luminance component Y.sub.FM and 
frequency converted chrominance component S'.sub.j. The frequency 
modulated luminance component Y'.sub.FM, separated from the reproduced 
signals, is passed through a limiter 75 to a frequency demodulator 76 so 
as to obtain a demodulated luminance component S'.sub.Y. It will be noted 
that the demodulated luminance component S'.sub.Y obtained from 
demodulator 76 will have the pulse signals P.sub.p selectively 
superimposed thereon, corresponding to the pulse signals which had been 
superimposed onto the luminance component S.sub.Y in adding circuit 25 in 
recording section 100. In order to eliminate the recovered pulse signals 
P.sub.p from the demodulated luminance component S'.sub.Y, the demodulated 
component is applied to a subtracting circuit 77 which is also connected 
to the output of switching circuit 43 so as to supply pulse signals 
P.sub.p to the subtracting circuit during signal reproduction. As will be 
explained below, the pulse signals P.sub.p produced by switching circuit 
43 during a reproducing operation are substantially equal to the pulse 
signals that had been reproduced thereby during a recording operation. 
Hence, this pulse signal P.sub.p is removed from the luminance component 
S.sub.Y ' to result in luminance component S.sub.Y which is applied 
through a de-emphasis circuit 78 to a mixing or adding circuit 79 having 
its output connected to an output terminal 80. 
The frequency converted chrominance component S'.sub.j, separated from the 
reproduced signals by filter 74, is applied through an automatic color 
control circuit 81 to a frequency reconverter 82 which alternately 
receives the frequency converting signals +S.sub.q and -S.sub.q from 
switching circuit 71, and by which the carrier of the reproduced 
chrominance component S'.sub.j is reconverted to the original carrier 
frequency f.sub.i. The resulting frequency reconverted chrominance 
component S'.sub.i is passed through a comb filter 83 in which, as 
hereinafter described in detail, chrominance components of crosstalk 
signals are cancelled or suppressed so that only the chrominance component 
C.sub.s of the video signals being reproduced from a particular track is 
passed to mixing circuit 79 whereat it is combined with the luminance 
component S.sub.Y from de-emphasis circuit 78. Hence, the desired 
reproduced video signals are applied by mixing circuit 79 to output 
terminal 80. 
The chrominance component C.sub.S from comb filter 83 also is applied to a 
burst gate 84 adapted to extract burst signals from the reconverted 
chrominance signal component. The extracted burst signals are applied to 
one input of a phase comparator 85, and an oscillator 86 applies an output 
at the standard or original chrominance carrier frequency f.sub.i to a 
second input of the phase comparator. The output of phase comparator 85 is 
connected through playback terminal P of switch 87 to voltage controlled 
oscillator 70. It will be apparent that, in the reproducing mode of 
operation, any phase difference between the burst signals extracted by 
gate 84 from the reconverted chrominance component and the output of 
oscillator 86 causes comparator 85 to apply a suitable control voltage to 
voltage controlled oscillator 70 for effecting a required change in the 
phase of the converting signals +S.sub.q and -S.sub.q whereby to achieve 
an automatic phase control function for eliminating so-called jitter from 
a picture or image produced on a cathode ray tube in response to video 
signals obtained at output terminal 80. 
In the reproducing mode of operation, control signal S.sub.x for operating 
switching circuit 71 again is obtained from AND gate 64 in response to 
control signals S.sub.v ' and S.sub.h from signal forming circuit 65 and 
flip-flop 45, respectively. As before, the signal forming circuit 65 
responds to the output of wave forming circuit 35 which, in turn, is 
responsive to the pulse signals from pulse generating means 34. However, 
in the reproducing mode, fixed head 39 reproduces the recorded control 
signals 56 which are applied through playback terminal P of switch 138 and 
through an amplifier 88 to comparator 33 via playback terminal P of switch 
60. Thus, comparator 33 compares the phase of the reproduced control 
signals 56 with the output of wave forming circuit 35 so as to provide a 
suitable servo control signal which is applied through servo amplifier 36 
for controlling the rotation of heads 12A and 12B by motor 37. Hence, the 
servo control arrangement is effective, in the reproducing mode, to ensure 
that each of the tracks on tape T will be scanned by the same head 12A or 
12B which was employed for recording video signals in such track, and 
further to ensure that the control signal S'.sub.v applied to AND gate 64 
will have the same relationship to the reproduced video signals as it had 
to the recorded video signals. In other words, if control signal S'.sub.v 
has its low and high values during the recording of video signals by heads 
12A and 12B, respectively, control signal S'.sub.v will similarly have its 
low and high values during the reproducing of the signals by heads 12A and 
12B, respectively. Further, the output of de-emphasis circuit 78 is 
connected through the playback terminal of switch 122 to horizontal sync 
separator 41, whereby the separator separates horizontal synchronizing 
signals from the reproduced luminance component S.sub.Y in order to 
control pulse forming circuit 42 and flip-flop circuit 45 in the 
reproducing mode similar to the control obtained in the recording mode. 
During recording, the operation of switching circuit 43 is as described 
above with respect ro FIG. 4. The chrominance component S.sub.i, having an 
original carrier frequency f.sub.i, is separated from the received color 
video signals and is frequency converted in frequency converter 57 by the 
frequency converting signal +S.sub.q or -S.sub.q so as to provide the 
frequency converted chrominance component S.sub.j with the reduced carrier 
frequency f.sub.c =44f.sub.H -1/4f.sub.H. Thus, the frequency band of the 
frequency converted chrominance component S.sub.j is lower than that of 
the frequency modulated luminance component Y.sub.FM with which it is 
combined in mixing circuit 58 to form the composite or combined signal 
S.sub.c which is recorded by heads 12A and 12B in successive tracks on 
tape T. Switching circuit 71, which is controlled by the control signal 
S.sub.x (FIG. 5I) from AND gate 64, selectively determines which frequency 
converting signal +S.sub.q or -S.sub.q is applied to frequency converter 
57. Since frequency converting signals +S.sub.q and -S.sub. q are of 
opposite phase or polarity, the resulting frequency converted chrominance 
component S.sub.j is provided with respective carriers C.sub.a and 
-C.sub.a which are similarly of opposed phase or polarity. It is 
appreciated that control signal S.sub.x remains low during one entire 
field interval recorded by, for example, head 12A, and goes high only 
during alternate line intervals of the next field interval, for example, 
the field interval recorded by head 12B. Thus, during each field interval 
recorded by head 12A, frequency converting signal +S.sub.q is continuously 
applied to frequency converter 57 with the result that the successive line 
intervals of each field interval recorded by head 12A are provided with a 
carrier of the same polarity. During successive line intervals of each 
field interval recorded by head 12B, frequency converting signals +A.sub.q 
and -S.sub.q are alternately applied to frequency converter 57 so that the 
successive line intervals of each field interval recorded by head 12B are 
alternately recorded with the carriers C.sub.a and -C.sub.a of opposed 
polarity. As one example of the foregoing, head 12A will scan tape T 
during intervals T.sub.a and head 123 will scan tape T during intervals 
T.sub.b, as represented in FIG. 5J. 
During reprodution, the rotation of heads 12A and 12B is servo-controlled 
by comparing the control signals 56 reproduced from tape T by fixed head 
39 with the pulses from pulse generating means 34, so that those signals 
which had been recorded in respective tracks by heads 12A and 12B will be 
reproduced by the same heads. Because of this servo control of the 
rotation of heads 12A and 12B, the control signals S'.sub.v from signal 
forming circuit 65, and thus the control signal S.sub.x from AND gate 64, 
have the same relationships to the operative positioning of the heads 12A 
and 12B during the reproducing operation as during the recording 
operation. Thus, switching circuits 43 and 71 are controlled in the same 
manner during both recording and reproduction. 
The frequency modulated luminance component Y'.sub.FM separated from the 
reproduced signals is demodulated in frequency demodulator 76 so as to 
obtain the demodulated luminance component S'.sub.Y which, as previously 
noted, will have selected pulse signals P.sub.p superimposed thereon. 
Since switching circuit 43 is controlled in synchronism with the recorded 
frequency modulated luminance signal (because of synchronized control 
signal S'.sub.v), the selective transmission of a pulse signal from pulse 
forming circuit 42 through switching circuit 43 corresponds to the 
selective phase shifting of the reproduced frequency modulated luminance 
component, and thus coincides with the pulse signal P.sub.p which is 
inserted into the recovered luminance component S.sub.Y '. By subtracting 
this generated pulse signal from the luminance component S.sub.Y ' in 
subtracting circuit 77, the recovered luminance component S.sub.Y is 
substantially equal to the original luminance component. 
During reproduction, crosstalk interference in the reproduced luminance 
component is eliminated partly because of the different azimuth angles of 
heads 12A and 12B, and also by reason of the fact that the frequency 
modulated luminance component is recorded with different phases in 
adjacent tracks, as described above. Thus, in the event that each of the 
tracks on tape T has a small width so as to increase the recording 
density, in which case the azimuth loss is not sufficient to prevent 
crosstalk in respect to the frequency modulated luminance component, the 
reproducing head 12A, for example, when scanning track 17A.sub.2, for 
example, when scanning track 17A.sub.2, will pick up the signals recorded 
in that track and also, to some extent, the signals recorded in the next 
adjacent track 17B.sub.1. However, the crosstalk component in each line 
interval reproduced by head 12A from track 17B.sub.1 will differ in phase 
from the crosstalk component in the next adjacent line interval by an odd 
multiple of .pi.. Similarly, the crosstalk component in each line interval 
reproduced by head 12B from track 17A.sub.2 when this head scans track 
17B.sub.2 will differ in phase from the crosstalk component in the next 
adjacent line interval by an odd multiple of .pi.. Accordingly, the 
interfering or noise signal due to crosstalk will be inverted in phase in 
successive horizontal line intervals of the video signals. Thus, when the 
reproduced video signals obtained at output terminal 80 are applied to a 
cathode ray tube, the interfering or noise signal due to luminance 
component crosstalk will visually cancel itself on the screen of the 
cathode ray tube, and will not appear as a conspicuous noise or beat in 
the displayed image. 
Considering the frequency converted chrominance component, the effect of 
providing this component with carriers C.sub.a, -C.sub.a of reversed phase 
or polarity in successive line intervals or areas of each track recorded 
by head 12B results in a new carrier C.sub.b having frequency components 
offset by 1/2f.sub.H with respect to the frequency components of the 
carrier C.sub.a with which the frequency converted chrominance component 
is recorded in the next adjacent tracks by head 12A so as to interleave 
therewith. Accordingly, when, for example, head 12A wcans track 17A.sub.2 
on tape T for reproducing the frequency converted chrominance component 
recorded therein with the carrier C.sub.a, the undesired or crosstalk 
signal simultaneously reproduced by head 12A from the next adjacent track 
17B.sub.1 has its frequency converted chrominance component provided with 
a carrier (C.sub.b) in frequency interleaving relation to the carrier 
C.sub.a. Similarly, when, for example, head 12B scans tracks 17B.sub.1 for 
reproducing the frequency converted chrominance component recorded therein 
with the carrier C.sub.b, the undesired or crosstalk signal simultaneously 
reproduced by head 12B from the next adjacent track 17A.sub.2 has its 
frequency converted chrominance component provided with a carrier 
(C.sub.a) in frequency interleaving relation to the carrier C.sub.b. 
Since switching circuit 71 is controlled by control signal S.sub.x in the 
same manner during both recording and reproduction, frequency reconverter 
82 in the reproducing section 200 continuously receives the frequency 
converting signal +S.sub.q during the scanning of a track by head 12A, and 
frequency converting signals +S.sub.q and -S.sub.q are alternately applied 
to frequency reconverter 82 for successive line intervals during the 
scanning of a track by head 12B, as represented in FIG. 5J. Hence, during 
the scanning of a track by head 12A, frequency reconverter 82 reconverts 
the carriers C.sub.a of the chrominance component then being reproduced to 
a carrier C.sub.sa having the original carrier frequency f.sub.i, while 
the carrier C.sub.b of the crosstalk chrominance component has its 
frequency similarly converted so as to be spaced midway between the 
principal side bands of the desired carrier C.sub.sa. Similarly, during 
the scanning of a track by head 12B, frequency reconverter 82 frequency 
reconverts the carrier C.sub.b of the chrominance component then being 
reproduced to a carrier C.sub.sb also having the original frequency 
f.sub.i, while the carrier C.sub.a of the crosstalk chrominance component 
has its frequency converted so as to be spaced midway between the 
principal side bands of the desired carrier C.sub.sb. Thus, the 
reconverted carriers C.sub.sa and C.sub.sb of the chrominance component 
reproduced during alternate field intervals both have the same carrier 
frequency f.sub.i, while the chrominance component of the undesired or 
crosstalk signal is, in each case, spaced midway between the principal 
side bands of the desired carrier and can be eliminated by comb filter 83 
to yield the desired reconverted chrominance component C.sub.s which is 
free of any crosstalk chrominance component. 
It will be apparent from the above that, in the described recording and/or 
reproducing apparatus according to this invention, the resultant video 
picture which is displayed in response to the reproduced color video 
signals obtained at output terminal 80 will be free of crosstalk 
interference even though the video signals have been recorded without 
guard bands between successive parallel tracks on tape T and even though 
such tracks have been provided with a very small width so as to attain a 
high recording density. 
In the embodiment described with respect to FIGS. 4 and 7, it was assumed 
that the pulse signal P.sub.p selectively inserted into a line interval, 
such as onto the back porch of the horizontal synchronizing pulse, was 
formed of a single pulse whose amplitude was sufficient to produce a phase 
shift of .theta. (=.pi.). However, in an alternative embodiment, pulse 
signal P.sub.p is formed of a plurality (for example, n) of pulses, each 
having an amplitude less than the amount necessary for causing a phase 
shift .theta., as shown in FIG. 8. If the amplitude of each of these n 
pulses is P.sub.n, then the sum of the pulse amplitudes (nP.sub.n) is the 
amount necessary for causing a phase shift .theta. (such as .theta.=.pi.). 
When the single pulse signal P.sub.p is replaced by n smaller pulses (as 
shown in FIG. 8), subtracting circuit 77 in the reproducing section can be 
omitted. This is because, in one type of video record/playback systemj a 
control pulse is added to the reproduced video signal for the purpose of 
an automatic gain control operation. If the single pulse P.sub.p is not 
removed from the recovered video signal, this pulse could falsely 
interfere with the automatic gain control operation. However, since the n 
pulses of FIG. 8 are of relatively low amplitude, this problem of 
interfering with the automatic gain control operation is not present; and 
subtracting circuit 77 can be omitted. 
In another embodiment shown in FIG. 9, the pulse signal P.sub.p is 
superimposed onto the horizontal synchronizing pulse P.sub.h. Also, the 
amplitude of the pulse signal P.sub.p is negative so as to impart a 
negative phase shift to the frequency modulated video signal. That is, the 
phase change .DELTA..theta. in FIGS. 6C and 6D will be negative. 
It may be recognized that, theoretically, the pulse signal P.sub.p can be 
inserted into any desired portion of a line interval, provided this 
inserted pulse signal is removed during a reproducing operation. However, 
it is preferred to insert the pulse signal into the horizontal 
synchronizing interval, as described above. 
In yet another embodiment, the pulse signals need not be inserted only in 
successive line intervals of alternate tracks (or fields), and need not 
have an amplitude for causing a phase shift of .pi.. For example, and as 
represented in FIG. 10, in one line interval the inserted pulse signal has 
an amplitude that causes a phase shift of .alpha., and in the next 
successive line interval the inserted pulse signal has an amplitude that 
causes a phase shift of .alpha.-.pi.. Hence, the phase shift between 
successive line intervals in a given track is .alpha.-(.alpha.-.pi.)=.pi.. 
Also, the frequency modulated video signal recorded in successive line 
intervals in the next adjacent track may have a constant phase .alpha., 
thereby providing a phase shift of .pi. between alternate line intervals 
in one track and alternate line intervals in the next adjacent track. 
As a still further embodiment, the phase of the frequency modulated video 
signal may change by .alpha. from line-to-line in one track, and the phase 
of the frequency modulated video signal may change by -.beta. from 
line-to-line in the next adjacent track, wherein .alpha.+.beta.=.pi., as 
shown in FIG. 11. 
In another embodiment, a pulse signal of amplitude for causing a phase 
shift of .pi. is inserted into alternate line intervals (for example, line 
intervals t.sub.a) in one track, and the same pulse signal is inserted 
into different alternate line intervals (for example, line lintervals 
t.sub.b) in the next adjacent track. 
The foregoing alternate embodiments can be implemented by providing, for 
example, two pulse forming circuits in place of pulse forming circuit 42, 
each adapted to generate a pulse signal of amplitude corresponding to a 
phase shift .alpha. and .beta., respectively. Also, switching circuit 43 
may be provided with two input terminals and may be controlled as a 
function of pulses S.sub.h (FIG. 5H) or pulses S.sub.x (FIG. 5I). 
Although illustrative embodiments of the invention have been described in 
detail herein with reference to the accompanying drawings, it is to be 
understood that the invention is not limited to those precise embodiments, 
and that various changes and modifications can be effected therein by one 
skilled in the art without departing from the scope or spirit of the 
invention as defined in the appended claims. For example, the record 
medium need not be limited solely to a magnetic tape; but may comprise a 
magnetic sheet, a magnetic disc, a photo-optical medium, or the like, 
having successive adjacent tracks recorded thereon. Other changes and 
modifications have been suggested at various portions of the foregoing 
specification; and it is intended that the appended claims be interpreted 
as including such changes and modifications.