Method and apparatus for recording and reproducing a color-aligned line-sequential color video signal

A method and apparatus for recording in successive parallel tracks on a record medium a periodic information signal, such as a video signal having information contained in successive line intervals, a predetermined number of line intervals being included in a field interval and a predetermined number of field intervals being included in a frame interval. Alternate ones of the frame intervals are delayed by a time delay equal to an odd multiple (2n-1) of a line interval. The delayed and undelayed frame intervals are supplied, in sequence, to a recording transducer for recording in successive parallel tracks on the record medium. If the video signal is a SECAM color video signal, then the effect of delaying alternate frame intervals, such as the odd (or even) frame intervals is to align line intervals in adjacent tracks with information representing the same color. Also disclosed are a method and apparatus for reproducing the periodic information signal which had been recorded in the aforementioned manner. These recorded signals are reproduced from the successive parallel tracks to recover the delayed and undelayed frame intervals alternately. The undelayed frame intervals are delayed, during reproduction, by a time delay equal to the aforesaid odd multiple (2n-1) of a line interval, thereby recovering the periodic information signal which appears in successive frame intervals as being undelayed relative to each other. Thus, if, during recording, the odd frame intervals are delayed, then during reproduction, the even frame intervals are delayed so as to equalize the reproduced odd and even frames.

BACKGROUND OF THE INVENTION 
This invention relates to a method and apparatus for recording and 
reproducing periodic information signals, such as composite color video 
signals, and more particularly, is directed to a method and apparatus for 
recording and reproducing color video signals wherein information relating 
to different colors is arranged in line-sequence, and wherein such a 
line-sequential color information signal is recorded in color alignment. 
In a typical video recording system, such as a video tape recorder (VTR) 
which is capable of recording composite color video signals with high 
recording density, the color signals are recorded in successive, adjacent 
record tracks which are provided without guard bands therebetween. In this 
format, the record medium is utilized efficiently because "blank" portions 
thereof need not be provided between adjacent record tracks. To minimize 
crosstalk interference when video signals which are recorded in this 
format are reproduced, the incoming video signal is processed prior to the 
recording thereof. Typically, the luminance and chrominance components of 
the composite color video signal are separated from each other, the 
luminance component is frequency-modulated to a relatively higher 
frequency band and the chrominance component is frequency-converted down 
to a relatively lower frequency band. Then, the processed luminance and 
chrominance components are combined for recording in successive parallel 
tracks. Usually, a single field of the video signal is recorded in each 
track, thereby resulting in the recording of a frame in two successive 
tracks. In one type of VTR, a pair of magnetic transducers, or recording 
heads, rotatably scan the magnetic tape, each head being supplied with a 
single field so as to record that field of video signals in the track 
which is scanned thereby. In order to reduce crosstalk interference, the 
air gaps of the two heads are provided with different azimuth angles. 
Thus, one field, such as the odd field, in each track is recorded with one 
azimuth angle while the other field is recorded with a different azimuth 
angle. 
During reproduction, the transducers, or playback heads, which are used to 
reproduce the recorded video signals are provided with the same azimuth 
angles as were used during recording. Since there are no guard bands to 
separate adjacent tracks, it is likely that, when one playback head scans 
its appropriate track to reproduce the video signals recorded therein, it 
also will pick up a crosstalk component from the adjacent track. However, 
because of the phenomenon of azimuth loss, since the picked up crosstalk 
component had been recorded with a different azimuth angle, the picked up 
crosstalk component will be reproduced with substantial attenuation. 
Azimuth loss is directly related to the frequency of the recorded signal, 
so that the reproduced luminance crosstalk component, which had been 
frequency modulated to a relatively higher frequency band, will be 
seriously attenuated. 
The aforementioned phenomenon of azimuth loss is not as effective in 
minimizing chrominance crosstalk components. This is because the 
chrominance components had been frequency-converted down to a relatively 
lower frequency band during recording. Accordingly, in order to reduce 
crosstalk interference, adjacent tracks are recorded in so-called 
H-alignment; that is, the horizontal synchronizing intervals in each track 
are aligned transversely across the tracks. This H-alignment occurs if the 
distance that the tape moves during the recording of one field interval is 
equal to a whole number of lines plus half a line so as to account for the 
phase at the start of the next field. 
Although the foregoing technique generally is used to record color video 
signals which are present in various formats, such as the NTSC, and 
SECAM formats, a particular problem may arise if the color video signal is 
in a line-sequential format, such as the SECAM format. As referred to 
herein, a line sequential color video signal is of the type wherein 
successive line intervals are provided with color information signals 
which relate to different colors. For example, odd line intervals may 
include blue color information while even line intervals may include red 
color information. In the SECAM format, this line sequential color 
information is provided by frequency-modulating a blue subcarrier of about 
4.25 MHz with blue color difference signals (B-Y) followed by 
frequency-modulating a red subcarrier of about 4.41 MHz with red color 
difference signals (R-Y). Thus, the blue and red color information signals 
appear alternately. Furthermore, since the SECAM color video signal is 
provided with 625 line intervals in each frame, the color information 
which is recorded in the first line interval also is recorded in the last 
line interval of that frame. This means that, in odd frames, the blue 
color information may be provided in odd line intervals while the red 
color information may be provided in the even line intervals, while in the 
even frames, the blue color information may be provided in the even line 
intervals while the red color information may be provided in the odd line 
intervals. Of course, the converse of this also may occur. 
When a SECAM color video signal of the aforementioned type is recorded in 
accordance with the technique discussed above, then, because the first 
field of one frame generally is shifted by 1.5H (H is the length or delay 
of a horizontal line interval) from the start of the last field of a 
preceding frame, successive frames are recorded in the absence of color 
alignment. That is, in one frame, constituted by two tracks each 
containing a single field, adjacent line intervals are provided with 
information relating to the same color. Hence, blue color information is 
aligned transversely of the record tracks, followed by aligned red color 
information, aligned blue color information, and so on. However, when the 
next frame is recorded, the blue color information which is present in the 
preceding frame is aligned with the red color information in the next 
following frame. A representation of this type of recording is illustrated 
in FIG. 1 of the accompanying drawings wherein the subscript 1 represents 
frame 1, or odd frames, and subscript 2 represents frame 2, or even 
frames. Furthermore, subscript a represents the first field in each frame 
while subscript b represents the second field in each frame. In FIG. 1, 
those line intervals which contain blue color information are illustrated 
without cross-hatching, and those line intervals which contain red color 
information are illustrated with cross-hatching. 
From FIG. 1, it is seen that, in a frame, the beginning of the first field 
in that frame is displaced from the beginning of the following field by a 
distance equal to one-half a horizontal line interval, this displacement 
being in the direction of the track. Thus, the beginning of the track 
T.sub.a1 in which the first field is recorded is displaced from the 
beginning of track T.sub.b1 in which the following field is recorded by 
0.5H. Also, the beginning of the first field in one frame is displaced 
from the beginning of the second field in the immediately preceding frame 
by one and one-half horizontal line intervals. That is, the beginning of 
track T.sub.a2 in which the first field of, for example, the second frame 
is recorded, is displaced from the beginning of track T.sub.b1 in which 
the second field of the first frame is recorded by 1.5H. Furthermore, in 
one frame, such as the frame recorded in tracks T.sub.a1 and T.sub.b1, the 
horizontal line intervals in these respective tracks are in 
color-alignment with each other. That is, red color information signals 
are recorded in adjacent line intervals, and blue color information 
signals are recorded in adjacent line intervals. However, although tracks 
T.sub.a1 and T.sub.b1 are recorded in color-alignment, and tracks T.sub.a2 
and T.sub.b2 are recorded in color alignment, track T.sub.b1 is not in 
color-alignment with tracks T.sub.a2. That is, although the first and 
second fields of a given frame are recorded in color-alignment, adjacent 
frames are not recorded in such color-alignment. 
The SECAM color video signal is formed of 625 line intervals. Each frame is 
constituted by 312.5 line intervals. For proper alignment of the 
horizontal synchronizing intervals, track T.sub.b1 is displaced by 0.5H 
from track T.sub.a1. If it is assumed that two rotary transducers are used 
to record the successive tracks, and if it is further assumed that these 
two heads, referred to for the purpose of the present discussion as heads 
A and B, are separated from each other by 180.degree., and if the tape is 
transported a distance equal to 1H for each pass of a head thereacross, 
then successive tracks will be displaced by an amount equal to 1H. In 
order to record the tracks in the format shown in FIG. 1, heads A and B 
must be separated from each other by an angle of 180.degree.-.alpha.. The 
angle .alpha. is such that the tape is transported by 0.5H from the time 
that head A scans the tape until head B reaches the tape; and the tape is 
transported by an amount equal to 1.5H from the time that head B scans the 
tape until head A reaches the tape. 
When the SECAM color video signal is recorded in the format shown in FIG. 
1, that is, wherein information relating to a particular color is recorded 
in odd line intervals in odd-numbered frames and in even line intervals in 
even-numbered frames, there is no difficulty in reproducing the original 
video signal during a normal playback operation. This is because the 
respective playback heads scan the same tracks during a reproducing 
operation as were scanned by such heads (or the equivalent thereof) during 
recording. That is, the scanning traces of the heads during a reproducing 
operation are substantially coincident with the scanning traces of the 
heads during a recording operation. However, there is a problem when the 
recorded SECAM color video signal is reproduced during a slow-motion or 
still-motion mode. In such modes, the speed at which the tape is 
transported is less than the normal recording/reproducing tape speed. As a 
consequence thereof, the playback heads do not scan the same traces during 
a slow-motion or still-motion reproducing operation as were scanned during 
a normal recording operation. As an example of the scanning trace of each 
playback head during such slow-motion or still-motion reproducing 
operations, reference is made to FIG. 1 wherein the trace of the playback 
head is illustrated by the broken line A. It is seen that this scanning 
trace crosses over a number of tracks. Furthermore, since the SECAM color 
video signal is not recorded in color alignment from one frame to the 
next, scanning trace A does not cross over alternate color information 
signals. Rather, when this scanning trace traverses adjacent tracks which 
are associated with different frames, for example, tracks T.sub.a2 and 
T.sub.b1, color signals relating to the same color are reproduced in 
successive line intervals. More particularly, as scanning trace A 
traverses tracks T.sub.b2, T.sub.a2, T.sub.b1 and T.sub.a1, in sequence, 
the color difference signals which are reproduced by the playback head are 
seen to be (B-Y), (R-Y), (R-Y) and (B-Y), respectively. 
As a result of the scanning of two successive line intervals having color 
information signals therein relating to the same color, the 
line-sequential format of the SECAM video signal is disturbed. 
Consequently, if the video signals which are reproduced during the 
slow-motion or still-motion mode are supplied to a television monitor, the 
displayed video signal will exhibit substantial color noise, or 
interference. This is because, since the line-sequential arrangement is 
distorted, a (B-Y) color difference signal will be misinterpreted as a 
(R-Y) color difference signal in some line intervals and will be supplied 
to the red color demodulator. Similarly, in other line intervals, the 
reproduced (R-Y) color difference signal will be misinterpreted as the 
(B-Y) color difference signal and will be supplied to the blue color 
demodulator. Consequently, the respective color demodulators will not be 
capable of demodulating the particular color difference signals which are 
supplied thereto. Since color discrimination cannot be attained properly, 
the usual color killer circuit which is provided to avoid erroneous 
display of a color picture will be operated. Although the usual color 
discriminating signals are provided in each vertical blanking interval of 
the recorded SECAM color video signal, these discriminating signals, when 
reproduced, will establish a particular switching condition for switching 
the reproduced line intervals alternately to different ones of the color 
demodulators. But since the reproduced color information signals do not 
alternate properly, incorrect color difference signals will be supplied to 
the respective red and blue color demodulators. Consequently, the 
aforenoted problem of displayed color noise or of color killer operation 
is present. 
In order to avoid this mis-operation of the color demodulators in a SECAM 
television receiver, the color information signals in all frames should be 
recorded in color-alignment. That is, in addition to the normal 
color-alignment of both fields in a given frame, there also should be 
color-alignment between frames. A type of color alignment is described in 
U.S. Pat. No. 3,852,520. However, as described therein, a given color 
information signal is recorded in, for example, odd line intervals in both 
odd and even frames. This means that if, for example, the (R-Y) color 
difference signal is recorded in the last, or 625th, line interval of one 
frame, it also is recorded in the first line interval of the next 
following frame. However, in a conventional SECAM color video signal, if 
the (R-Y) color difference signal is provided in the 625th line interval 
of one frame, then the (B-Y) color difference signal should be provided in 
the first line interval of the next-following frame. Consistent with this 
normal convention, a typical SECAM television receiver is adapted to 
respond to the first line interval of the next following frame as 
containing color information which is different from the last line 
interval of the immediately preceding frame. But, since the same color 
information signal is recorded in the last and first line intervals of all 
frames, in accordance with the technique described in U.S. Pat. No. 
3,852,520, the video signals which are reproduced are not in proper 
line-sequence from one frame to the next. Thus, the aforementioned 
difficulty in color noise and color killer operation will be present when 
the technique described in this patent is used for the recording and 
reproducing of SECAM color video signals in color-alignment. 
OBJECTS OF THE INVENTION 
Therefore, it is an object of the present invention to provide an improved 
method and apparatus for recording and reproducing video signals, 
particularly SECAM color video signals, which avoid the aforenoted 
difficulties. 
Another object of this invention is to provide a method and apparatus for 
recording SECAM color video signals in successive parallel tracks in 
color-alignment for all tracks. 
A further object of this invention is to provide an improved method and 
apparatus for reproducing SECAM color video signals which are recorded in 
parallel tracks in color-alignment for all tracks. 
An additional object of this invention is to provide an improved method and 
apparatus for recording and reproducing SECAM color video signals in 
parallel record tracks in color-alignment wherein, during reproduction, a 
proper line sequence of color information signals is obtained from one 
frame to the next. 
Various other objects, advantages and features of the present invention 
will be 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 this invention, a method and apparatus for recording a 
periodic information signal, such as a video signal, in successive 
parallel tracks on a record medium are provided. In a preferred use of 
this invention, the periodic information signal is a SECAM color video 
signal. Alternate ones of the frame intervals of the video signal are 
delayed by a time delay equal to an odd multiple (2n-1) of a line 
interval. The delayed and undelayed frame intervals are supplied to a 
recording transducer for recording in successive parallel tracks on the 
record medium. 
In accordance with another aspect of this invention, a method and apparatus 
for reproducing the aforementioned recorded signals also are provided. In 
reproducing such signals, the delayed and undelayed frame intervals are 
reproduced alternately, and the reproduced undelayed frame intervals are 
subjected to a time delay which is equal to the time delay used during 
recording. 
Thus, in accordance with this invention, video signals are recorded in 
successive frames in color-alignment by delaying, for example, each 
odd-numbered frame by one line interval during recording. The proper 
line-sequence of color information signals is recovered during reproducing 
by delaying only the even-numbered frames. Hence, there is no delay 
between the reproduced odd-numbered and even-numbered frames.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
For convenience in describing the various aspects of the present invention, 
it is assumed that the signals which are recorded and reproduced are color 
video signals. This invention finds ready application with the SECAM color 
video signal which is comprised of alternate line intervals formed of red 
and blue subcarriers which are frequency-modulated with red and blue color 
difference signals, respectively. In one frame, for example, all of the 
odd line intervals may be constituted by red color information, and all 
even line intervals may be constituted by blue color information. Then, in 
the next frame interval, all odd line intervals are constituted by blue 
color information and all even line intervals are constituted by red color 
information. It will, of course, be appreciated that the apparatus which 
is disclosed herein can be readily adapted to record and reproduce other 
types of periodic information signals other than color video signals, and 
other than SECAM color video signals. Such other periodic information 
signals, nevertheless, should be formed of periodic sub-intervals, 
corresponding to the horizontal line intervals of a video signal, a 
predetermined number of such sub-intervals constituting a field interval, 
or its equivalent, and a predetermined number of field intervals 
constituting a frame interval, or its equivalent. In this type of periodic 
information signal, the alternate line intervals may contain multiplexed 
information such that, in one frame, information relating to one 
characteristic, or to one source, may be provided in the odd line 
intervals while information relating to another characteristic or to 
another source may be provided in the even line intervals. This is 
analogous to the alternating red and blue color information contained in 
alternating line intervals in the SECAM color video signal. 
Turning now to the drawings, FIG. 1 has been described hereinabove. It is 
recalled that this figure represents the parallel tracks which are 
recorded on a record medium 10, such as a magnetic tape, each track 
containing a field interval, and two adjacent tracks comprising a frame 
interval. Thus, tracks T.sub.a1 and T.sub.b1 constitute the first and 
second fields of a first frame; and tracks T.sub.a2 and T.sub.b2 
constitute the first and second fields in the next adjacent frame. In 
accordance with standard recording techniques, the starting edge of the 
first field in the second frame, that is, track T.sub.a2, is displaced 
from the starting edge of the second field in the preceding frame, that 
is, track T.sub.b1, by a distance corresponding to 1.5 horizontal line 
intervals (1.5H). However, the adjacent tracks which constitute a single 
frame are displaced from each other by 0.5H. Thus, tracks T.sub.a1 and 
T.sub.b1 are displaced from each other by 0.5H, as are tracks T.sub.a2 and 
T.sub.b2. The cross-hatched areas in FIG. 1 represent those line intervals 
in which the red color difference signals are recorded, and the unhatched 
areas represent those line intervals in which the blue color difference 
signals are recorded. As mentioned above, during a slow-motion or 
still-motion mode of reproduction, the reproducing transducer, or playback 
head, scans across the respective tracks along scanning trace A. It is 
seen that when the playback head follows scanning trace A, it traverses 
two successive line intervals containing information signals relating to 
the same color. Specifically, as the head traverses one track in which the 
first field of a frame interval is recorded and then traverses the next 
adjacent track in which the second field interval of the preceding frame 
is recorded, information signals relating to the same color are reproduced 
in sequential line intervals. This disrupts the normal alternate color 
information which is reproduced from sequential lines in a SECAM color 
video signal. Thus, when the tracks shown in FIG. 1 are scanned for 
slow-motion or still-motion reproduction, the color difference signals 
which are reproduced appear as (B-Y), (R-Y), (R-Y), (B-Y), (B-Y), and so 
on, rather than the proper sequence of (B-Y), (R-Y), (B-Y), (R-Y), and so 
on. 
The purpose of the present invention is to shift, or displace, the relative 
positions of the line intervals which are included in alternate frames, 
such as the even frames, recorded in parallel tracks T.sub.a and T.sub.b. 
More particularly, by this invention, the line intervals which are 
recorded in tracks T.sub.a2 and T.sub.b2 are shifted, relative to the line 
intervals recorded in tracks T.sub.a1 and T.sub.b1, such that all of the 
line intervals are in coloralignment, as shown in FIG. 2. Thus, while the 
first line interval recorded in track T.sub.a1 and the last line interval 
recorded in track T.sub.b1 contain color information relating to the same 
color, the first line interval recorded in track T.sub.a2 and the last 
line interval recorded in track T.sub.b2 likewise include color 
information signals relating to that very same color. As will be explained 
below, this format is attained by delaying the chrominance component of 
the SECAM color video signal in alternate frame intervals by one 
horizontal line interval. With this delay, the first line interval which 
is recorded in track T.sub.a2, the track in which the first field of the 
delayed frame is recorded, is the same line interval as was recorded as 
the last line interval in immediately preceding track T.sub.b1. Since only 
alternate frame intervals are delayed, the first and last line intervals 
in each track for all of the recorded frames contain color information 
signals relating to the same color, resulting in color-alignment. 
When the recorded signals on record medium 10 are reproduced in a 
slow-motion or still-motion mode, the trace of the playback heads across 
the surface of the record medium appears as shown by the broken line B. 
Since the recorded tracks are in color-alignment, the playback head scans 
alternating color information signals as it proceeds across trace B. Thus, 
and as shown, in the slow-motion and still-motion modes, the color 
information signals which are reproduced appears as (B-Y) (R-Y) (B-Y) 
(R-Y), and so on. Consequently, by reason of this color-alignment which is 
achieved by the present invention, the proper line-sequence of alternating 
color information signals are reproduced even during slow-motion and 
still-motion operation. A SECAM television monitor responds properly to 
this reproduced color information; and the video picture which is 
displayed on this monitor is substantially free of color noise. Moreover, 
the color killer operation will not be carried out erroneously. 
Turning now to FIG. 3, there is illustrated apparatus including a recording 
section and a reproducing section, in accordnce with one embodiment of the 
present invention. To facilitate a ready understanding of this invention, 
it is assumed that the record medium upon which the signals are recorded 
in successive parallel tracks is a magnetic tape. Furthermore, it is 
assumed that the signals are color video signals and, specifically, they 
are SECAM color video signals wherein color information signals relating 
to different colors are present alternately in sequential line intervals. 
Of course, and as will be apparent, other periodic information signals can 
be recorded on the magnetic tape, such periodic information signals being 
constituted by a predetermined number of sub-intervals included in a field 
interval, and a predetermined number of field intervals included in a 
frame interval. 
The video signals are recorded on magnetic tape 10 by a pair of rotary 
transducers, or record heads 12a and 12b. These record heads are rotatably 
driven by a drive shaft mechanically coupled to a drive motor 13. Tape 10 
is deployed about at least 180.degree. of the periphery of a guide drum 
and is longitudinally transported by conventional tape-drive apparatus, 
such as the combination of a capstan and a pinch roller. Motor 13, which 
is driven by a servo-control circuit (not shown), rotates record heads 12a 
and 12b at the frame repetition rate of the SECAM color video signal, e.g. 
25 rotations per second. As each frame includes two field intervals, each 
of record heads 12a and 12b functions to record a field in a respective 
track across tape 10. 
The recording section of the illustrated apparatus includes a luminance 
channel, for separating and processing the luminance component included in 
the color video signal, and a chrominance channel for separating and 
processing the chrominance component included in the video signal. The 
luminance channel is comprised of a low pass filter 15, a gain-controlled 
amplifier 16, a clamp circuit 17, a pre-emphasis circuit 18, a 
dark-and-white clipper 19, and a frequency modulator 20. The luminance 
channel is connected to an input terminal 14 for receiving the composite 
color video signal. Low pass filter 15 is connected to this input terminal 
for separating the luminance component, which is contained in a relatively 
lower frequency band, from the chrominance component. The output of low 
pass filter 15 is connected to gain-controlled amplifier 16, which 
comprise an automatic gain control (AGC) amplifier. AGC amplifier 16 is 
connected to clamp circuit 17, the latter serving to compensate for level 
changes in the luminance component by clamping the DC level thereof to a 
reference level, such as the pedestal level. 
The output of clamp circuit 17 is supplied through pre-emphasis circuit 18, 
which may be a conventional pre-emphasis circuit, to dark-and-white 
clipper 19. This clipper serves to prevent the dark and white levels of 
the luminance component from exceeding predetermined values. The luminance 
component provided at the output of clipper 19, which is a properly 
compensated and prepared luminance component, is supplied to frequency 
modulator 20 wherein the luminance component frequency-modulates a carrier 
of relatively higher frequency, resulting in a frequency-modulated (FM) 
luminance component. This higher frequency FM luminance component is 
supplied through a high pass filter 21 to a combining circuit 22, shown 
herein as a summing circuit. This combining circuit is adapted to combine 
the chrominance component processed by the chrominance channel with the FM 
luminance component, and then to supply the combined signal through a 
recording amplifier 30 and the record contact R of a change-over switch 
SW.sub.1 to heads 12a and 12b. 
Preferably, in order to exploit the aforementioned phenomenon of azimuth 
loss for eliminating cross-talk interference due to the higher frequency 
luminance component which may be picked up from an adjacent record track 
during the reproducing operation, heads 12a and 12b are provided with air 
gaps of different azimuth angles. Hence, if the higher frequency FM 
luminance component which is recorded in a record track by head 12a is, 
subsequently, reproduced by head 12b, this reproduced FM luminance 
component will be substantially attenuated because of azimuth loss. 
The chrominance channel included in the recording section of the 
illustrated apparatus includes a high pass filter 23, a reverse bell 
filter 24, an automatic chrominance control (ACC) circuit 25, a selective 
delay circuit comprised of a delay circuit 26 and a change-over switch 27, 
and a frequency converter 28. High pass filter 23 is connected to input 
terminal 14 to receive the composite color video signal and to separate 
the chrominance component, which is included in a relatively higher 
frequency band, from the luminance component. The output of this high pass 
filter is connected to reverse bell filter 24, the latter having a 
frequency characteristic which resembles the inverse of a bell-shaped 
curve. Hence, reverse-bell filter 24 serves, in part, to provide some 
frequency compensation to the filtered chrominance component, resulting in 
a chrominance component exhibiting a relatively flat frequency 
characteristic. The output of the reverse bell filter is supplied through 
ACC circuit 25 to the selective delay circuit. The ACC circuit is adapted 
to control the level of the filtered chrominance component so as to 
eliminate undesired amplitude fluctuations therein. As an example, ACC 
circuit 33 may include a gate circuit operative to transmit a 
discriminating signal which is present during the back porch portion of 
each horizontal synchronizing signal, and which is constituted by an 
unmodulated chrominance subcarrier which is equal to the subcarrier that 
is frequency-modulated in the remainder of the line interval. The 
amplitude of this transmitted discriminating signal is detected and used 
to adjust the amplitude of the chrominance component accordingly. As an 
alternative, since the chrominance component is comprised of 
frequency-modulated blue and red subcarriers, and since color information 
is not represented by amplitude fluctuations, such amplitude fluctuations 
can be removed by ACC circuit 33 if this ACC circuit is a limiter. 
The output of ACC circuit 25 is supplied through the selective delay 
circuit to frequency converter 28. In this selective delay circuit, delay 
circuit 26 is adapted to impart a delay equal to one horizontal line 
interval (referred to herein as a 1H delay) to the signals which are 
supplied thereto. As shown, the output of ACC circuit 25 is connected to 
the input of 1H delay circuit 26. Change-over switch 27, sometimes 
referred to herein as a switching circuit, is provided with fixed input 
contacts a and b, and a movable output contact c selectively controlled so 
as to engage either of its input contacts. A switch control circuit, 
described below, supplies a switch control signal to the control input of 
change-over switch 27, this switch control signal being determinative of 
the particular input contact to which the output contact is connected. As 
shown, input contact a is connected directly to the output of ACC circuit 
25 so as to receive an undelayed signal therefrom; and input contact b is 
connected to the output of 1H delay circuit 26 so as to receive a delayed 
signal. Output contact c is connected to frequency converter 28. 
The frequency converter is adapted to frequency-convert the chrominance 
components supplied thereto to a frequency band which is substantially 
below the frequency band of the FM luminance component produced by 
frequency modulator 20. In this regard, frequency divider 28 may include a 
modulating or heterodyning circuit which is supplied with the chrominance 
component from change-over switch 27 and a frequency-converting signal 
from a suitable source. These respective signals are heterodyned, and 
preferably, the lower sideband, or difference frequency, is derived from 
the output of the frequency converter. Such frequency converters are known 
to the prior art. In another embodiment, frequency converter 28 may be of 
the type described in copending application Ser. No. 960,839, filed Nov. 
15, 1978. In either embodiment, the output of frequency converter 28 is 
supplied through a summing circuit 29 to combining circuit 22 whereat the 
frequency-converted chrominance component and FM luminance component are 
combined into a composite signal. This composite signal is supplied 
through recording amplifier 30 and through change-over switch SW.sub.1 to 
record heads 12a and 12b. 
The switch control circuit which determines the operating condition, or 
state, of change-over switch 27 is comprised of a flip-flop circuit 47, a 
frequency divider 48 and a change-over switch SW.sub.2. Flip-flop circuit 
47 is of the so-called RS type including a set input S and a reset input 
R. The state of flip-flop circuit 47 is determined by the signals which 
are supplied to the set and reset inputs thereof, respectively. More 
particularly, this flip-flop circuit is set in response to a binary "1" 
applied to its S input and is reset in response to a binary "1" applied to 
its R input. Flip-flop circuit 47 is included in a sensing circuit which 
is adapted to sense the rotary positions of heads 12a and 12b. In this 
regard, the drive shaft which extends from motor 13 and is used to 
rotatably drive heads 12a and 12b is provided with magnetic elements 
spaced thereon. These magnetic elements rotate with the drive shaft and 
are detected by fixedly disposed magnetic detectors 45a and 45b. One 
magnetic element is particularly disposed so as to be detected by magnetic 
detector 45a when head 12a rotates into position so as to commence 
scanning a record track across tape 10. The other magnetic element is 
particularly disposed on the drive shaft so as to be detected by magnetic 
detector 45b when head 12b rotates into position to commence scanning a 
record track across the tape. Magnetic detectors 45a and 45b are adapted 
to produce detecting pulses when the respective magnetic elements are 
detected thereby, these detecting pulses being supplied to the S and R 
inputs of flip-flop circuit 47 by amplifiers 46a and 46b, respectively. 
The output of flip-flop circuit 47, which may comprise a rectangular pulse 
signal representing the state of the flip-flop circuit, is coupled through 
frequency divider 48 to the control input of change-over switch 47. 
Frequency divider 48 may comprise a conventional frequency-dividing 
circuit, such as a triggerable flip-flop circuit, adapted to divide the 
frequency of the rectangular pulse signal supplied thereto from flip-flop 
circuit 47 by a factor of 2. The output of frequency divider 48 also is 
coupled to the record contact R of change-over switch SW.sub.2 to a 
monostable multivibrator 49, the output of which being coupled to another 
monostable multivibrator 15. 
Monostable multivibrators 49 and 50 are adapted to respond to the output of 
frequency divider 48 for producing a gate pulse P.sub.g of predetermined 
duration at a predetermined time. This gate pulse is used during the 
recording operation to control the insertion of a discriminating signal 
into the frequency-converted chrominance component. As will be described 
below, the presence of this discriminating signal is used as an indication 
of the particular frames of video signals which are shifted in the 
recording thereof, as shown in FIG. 2. The circuit for producing and 
inserting this discriminating signal is comprised of a reference 
oscillator 51, a switching circuit 52, such as a gating circuit, and 
change-over switches SW.sub.3 and SW.sub.4. Reference oscillator 51 is 
adapted to produce an oscillating signal of substantially constant 
frequency. This oscillating signal is used as the discriminating signal 
and is supplied to switching circuit 52 via the record contact R of 
change-over switch SW.sub.3. A control signal, that is, the gating signal 
P.sub.g, is applied to switching circuit 52 by monostable multivibrator 
50. The output of this switching circuit is coupled via the record contact 
R of change-over switch SW.sub.4 to summing circuit 29 whereat the 
discriminating signal is combined with, or inserted into, the 
frequency-converted chrominance component. The output of summing circuit 
29 is connected to combining circuit 22. 
The manner in which the recording section illustrated in FIG. 3 operates 
now will be described with reference to the waveform diagrams of FIGS. 
4A-4D and 5A-5E. The luminance component is processed to an FM luminance 
component by a luminance channel in a manner which is known to those of 
ordinary skill in the art. Hence, in the interest of simplification, 
further description of this known operation is not provided herein. 
As motor 13 rotatably drives heads 12a and 12b, magnetic detectors 45a and 
45b produce detecting pulses when the respective magnetic elements which 
are disposed on the drive shaft rotate therepast. It is appreciated that 
each magnetic detector produces detecting pulses at a rate corresponding 
to the frame rate, that is, the rate at which each head is rotated. Thus, 
flip-flop circuit 47 is set when head 12a scans tape 10 to record a field 
of video signals, and this flip-flop circuit is reset when head 12b scans 
the tape to record the next field of video signals. This operation of 
flip-flop circuit 47 results in the rectangular pulse signal P.sub.25 
produced thereby, as shown in FIG. 4A. Thus, the flip-flop circuit is set 
for the duration of field interval t.sub.a1 in the first frame, then is 
reset for the duration of field interval t.sub.b1 in the first frame, then 
is set for the duration of field interval t.sub.a2 in the second frame, 
then is reset for the duration of field interval t.sub.b2 in the second 
frame, and so on. The frequency of the rectangular pulse signal P.sub.25 
is divided by frequency divider 48, resulting in the divided rectangular 
pulse signal P.sub.f, shown in FIG. 4. It is appreciated that this divided 
pulse signal is at its relatively higher binary "1" level for the duration 
of one frame and then is at its relatively lower binary "0" level for the 
duration of the immediately following frame. For convenience in describing 
the operation of the illustrated apparatus, it is assumed that the 
frequency-divided pulse signal P.sub.f, which is seen to be the switch 
control signal, is a binary "1" for odd frames and is a binary "0" for 
even frames. Of course, if desired, this relationship can be reversed 
wherein the switch control signal is a binary "1" for even frames and is a 
binary "0" for odd frames. 
Switching circuit 27 is operated such that output contact c engages input 
contact a when the switch control signal applied thereto is a binary "1". 
When the state of the switch control signal reverses to a binary "0", 
switching circuit 27 is operated so as to connect output contact c to 
input contact b. Thus, for each odd frame, the undelayed frame of the 
chrominance component provided at the output of ACC circuit 25 is coupled 
via switching circuit 27 to frequency converter 28. However, for each even 
frame, the delayed chrominance component provided at the output of 1H 
delay circuit 26 is supplied to frequency converter 28 by switching 
circuit 27. This means that each even frame interval is delayed by one 
horizontal line interval. The frequency converter supplies the 
frequency-converted chrominance component, having alternating delayed and 
undelayed frames, to combining circuit 22 via summing circuit 29, for 
combining with the FM luminance component, and for recording in successive 
parallel tracks on tape 10 by heads 12a and 12b. It is appreciated that, 
by delaying alternate frames of the chrominance component by one 
horizontal line interval, successive frames are recorded in the format 
shown in FIG. 2, whereby all of the record tracks are disposed in 
color-alignment. 
Monostable multivibrator 49 is responsive to the positive transition in 
switch control signal P.sub.f (FIG. 4B) to produce a timing pulse of 
predetermined duration .tau..sub.1. At the negative transition of this 
timing pulse, monostable multivibrator 50 is triggered to produce gating 
pulse P.sub.g having the predetermined duration .tau..sub.2, as shown in 
FIG. 4C. Hence, this gating pulse is provided at a repetition frequency 
equal to one-half the frame repetition rate. Stated otherwise, gating 
pulse P.sub.g is provided at a predetermined location in each odd frame. 
This gating pulse is supplied to gate circuit 52 for opening this gate so 
as to couple the discriminating signal produced by oscillator 51 through 
change-over switch SW.sub.4. FIG. 4D represents this discriminating signal 
S.sub.f which is applied to summing circuit 29 whereat it is inserted into 
the frequency-converted chrominance component S.sub.s. The combined 
frequency-converted chrominance component and inserted discriminating 
signal (S.sub.s +S.sub.f) is combined with the FM luminance component in 
combining circuit 22, the resultant composite video signal being recorded 
in successive tracks by heads 12a and 12b. It is recognized that the 
discriminating signal S.sub.f is inserted only for predetermined durations 
at predetermined locations of the frequency-converted chrominance 
component S.sub.s. 
The location of the chrominance component in which discriminating signal 
S.sub.f is inserted now will be described with reference to the waveform 
diagrams of FIGS. 5A-5E. Let it be assumed that a portion of the incoming 
video signal, including the vertical synchronizing interval, appears as 
shown in FIG. 5A, wherein each horizontal line interval is defined by the 
periodic horizontal synchronizing pulses HD, and wherein the video 
information signals, including both the luminance and chrominance 
components, are represented as amplitude-varying signals between 
successive horizontal synchronizing pulses. The vertical blanking interval 
is represented as VBLK, and the vertical synchronizing pulse is 
represented as VD. As is conventional, a plurality of equalizing pulses 
are provided before and after the vertical synchronizing pulse interval, 
and a plurality of vertical synchronizing pulses are present during the 
vertical synchronizing pulse interval. Furthermore, and in accordance with 
the SECAM convention, line discriminating signals are provided in 
successive line intervals following the equalizing pulses in the vertical 
blanking interval VBLK. These line discriminating signals are formed of 
unmodulated blue and red subcarriers which are present in alternate line 
intervals. Thus, if the blue line discriminating signal is represented as 
DB and the red line discriminating signal is represented as DR, then the 
line discriminating signals are present in the sequence DB, DR, DB, DR, 
etc., for a given number of line intervals during the vertical blanking 
interval for odd-numbered frames; and these line discriminating signals 
are present in the sequence DR, DB, DR, DB, etc. for the given (e.g. 9) 
number of line intervals for the even-numbered frames. The purpose of 
these line discriminating signals is to condition switching circuitry 
included in a conventional SECAM television receiver to supply the 
chrominance components which are received during successive line intervals 
to the proper demodulators. 
The switch control signal P.sub.f, produced by frequency divider 48, and 
discussed previously with respect to FIG. 4B, is illustrated in FIG. 5B 
relative to the vertical blanking interval provided at the beginning (or 
end) of each frame. It is recalled that the generation of this switch 
control pulse P.sub.f is dependent upon the detection of the magnetic 
elements provided on the drive shaft for record heads 12a and 12b by 
magnetic detectors 45a and 45b. Thus, the commencement of switch control 
pulse P.sub.f is dependent upon the particular positioning of these 
magnetic elements. FIG. 5C represents the gate pulse P.sub.g which is 
produced for a duration .tau..sub.2 at a delayed time .tau..sub.1 
following the beginning of the switch control signal P.sub.f. FIG. 5D 
represents the output of gate circuit 52, wherein the discriminating 
signal S.sub.f is provided during the duration of the gate pulse P.sub.g. 
These signals have, of course, been described previously with respect to 
FIGS. 4C and 4D, respectively. 
FIG. 5E represents the combination of the frequency-converted chrominance 
component and the inserted discriminating signal (S.sub.s +S.sub.f) which 
is combined with the FM luminance component in combining circuit 22. The 
line intervals which precede the inserted discriminating signal S.sub.f 
are seen to contain the frequency-converted chrominance component, these 
chrominance components being constituted by alternate blue and red 
frequency-converted subcarriers which are frequency-modulated with the 
blue and red difference signals, respectively. Following the inserted 
discriminating signal S.sub.f are the alternating line discriminating 
signals DB, DR, DB, DR, etc., as shown. Preferably, the inserted 
discriminating signal S.sub.f should be present for a duration which is as 
long as possible, but does not interfere with or overlap any of the line 
discriminating signals DB, DR. Thus, the time constant of monostable 
multivibrator 50 should be selected accordingly. 
In a numerical example, the average frequency of the frequency-converted 
blue and red subcarriers is about 680 KHz. The frequency of the 
oscillating signal produced by reference oscillator 51 is about twice this 
average frequency, or about 1.3 MHz. Hence, the frequency of the 
discriminating signal is at the upper limit, yet is within the frequency 
band of the frequency-converted chrominance component S.sub.s and, 
therefore, is below the frequency band of the FM luminance component. 
In view of the foregoing discussion of the illustrated apparatus, it is 
appreciated that record head 12a is adapted to record the first field, for 
example, in each frame and record head 12b is adapted to record the second 
field in each frame. Thus, field t.sub.a1 is recorded by head 12a in track 
T.sub.a1, and field t.sub.b1 is recorded by head 12b in track T.sub.b1. 
Then, in the next frame, field t.sub.a2 is recorded by head 12a in track 
T.sub.a2, and field t.sub.b2 is recorded in track T.sub.b2 by head 12b. 
Alternate ones of the frames are delayed by one horizontal line interval. 
In the embodiment discussed herein, the chrominance component in the 
even-numbered frames, which are present when switch control signal P.sub.f 
is a binary "0", are delayed by one horizontal line interval, are 
frequency-converted and then are recorded. The chrominance component 
included in the odd-numbered frames, that is, those frames which are 
present when switch control signal P.sub.f is a binary "1", are 
frequency-converted and then recorded in undelayed fashion. Although FIG. 
4D represents that the discriminating signal S.sub.f, which will be 
described below as being used as a frame discriminating signal, is 
inserted into the vertical blanking interval of the first field of the 
odd-numbered frames, that is, the first field of those frames which are 
not delayed, it will be apparent that, if desired, this discriminating 
signal S.sub.f can be inserted into the vertical blanking interval of the 
first field in each of the even-numbered frames. 
As shown in FIG. 3, heads 12a and 12b are angularly displaced from each 
other by an amount equal to 180.degree.-.alpha.. If the angular separation 
of these heads is equal to 180.degree., then the beginning of the tracks 
T.sub.b recorded by head 12b will be displaced, or shifted, from the 
beginning of the tracks T.sub.a recorded by head 12a by an amount equal to 
one horizontal line interval in the direction of the track. However, in 
the SECAM convention, each field is comprised of 312.5 line intervals. 
Thus, if the horizontal synchronizing intervals in adjacent tracks are to 
be aligned, the track containing the second field in a frame should be 
shifted from the track containing the first field in that frame by an 
amount equal to 0.5 line intervals. This shift is attained by displacing 
head 12b by the angular amount .alpha. from a 180.degree. displacement 
relative to head 12a. That is, if the heads are angularly displaced from 
each other by an amount equal to 180.degree.-.alpha., then, in the 
recording of each frame, track T.sub.b will be shifted by an amount equal 
to 0.5 line intervals relative to track T.sub.a. Furthermore, and as is 
preferred for the recording of successive tracks in H-alignment (i.e., 
with their horizontal synchronizing intervals in alignment), the first 
track in which the next following frame is recorded is shifted from the 
preceding track in which the preceding frame is recorded by an amount 
equal to 1.5 line intervals. 
The apparatus illustrated in FIG. 3 also includes a reproducing section 
which is comprised of a luminance channel for separating and processing 
the reproduced luminance component, and a chrominance channel which is 
provided to separate and process the reproduced chrominance component. The 
luminance channel is comprised of a high pass filter 32, a limiter 34, a 
frequency demodulator 35 and a de-emphasis circuit 36. High pass filter 32 
is connected via a playback amplifier 31 and playback contact P of 
change-over switch SW.sub.1 to heads 12a and 12b. The high pass filter is 
adapted to pass the higher frequency band of the FM luminance component 
and to attenuate the lower frequency band of the frequency-converted 
chrominance component. Thus, of the reproduced video signals, only the 
luminance component is supplied through the high pass filter. Limiter 34 
is connected to the output of high pass filter 32 and serves to eliminate 
amplitude fluctuations of the FM luminance component. The output of the 
limiter is coupled to frequency demodulator 35 which serves to demodulate 
the FM luminance component back to its original frequency band, and to 
produce an amplitude-varying luminance signal. The output of frequency 
demodulator 35 is coupled through de-emphasis circuit 36 to a combining 
circuit 37. De-emphasis circuit 36 is the complement of pre-emphasis 
circuit 18 and functions in conventional manner. Thus, combining circuit 
37, which may comprise a summing circuit, is provided with a substantially 
original version of the luminance component. 
The chrominance channel is comprised of a low pass filter 33, an ACC 
circuit 38, a frequency re-converter 39, a selective delay circuit formed 
of a delay circuit 40 and a switching circuit 41, and a bell filter 43. 
Low pass filter 33 is connected to heads 12a and 12b via the playback 
contact P of change-over switch SW.sub.1 and playback amplifier 31. The 
low pass filter is adapted to pass the relatively lower frequency band 
containing the frequency-converted chrominance component and the inserted 
discriminating signal, while attenuating the higher frequency band of the 
FM luminance component. The output of low pass filter 33 is coupled to ACC 
circuit 38 which is similar to ACC circuit 25 and serves to eliminate 
undesired amplitude fluctuations in the reproduced frequency-converted 
chrominance component. The output of ACC circuit 38 is connected to 
frequency re-converter 39 which is adapted to re-convert the chrominance 
component substantially back to its original frequency band. Hence, 
frequency re-converter 39 may include a modulating or heterodyning circuit 
which is supplied with a re-converting signal for heterodyning both the 
reproduced frequency-converted chrominance component and the re-converting 
signal. The lower side band of the heterodyned signals is selected, this 
lower side band constituting the frequency re-converted chrominance 
component. As is recognized, frequency re-converter 39 should be 
compatible with frequency converter 28. One type of frequency re-converter 
may be as described in copending application Ser. No. 960,839. 
The output of frequency re-converter 39 is coupled to the selective delay 
circuit. More specifically, the selective delay circuit includes a 1H 
delay circuit 40 which is adapted to impart a time delay equal to one 
horizontal line interval to the frequency re-converted chrominance 
component supplied thereto. The selective delay circuit also includes 
switching circuit 41 which is provided with a fixed input contact a 
connected directly to the output of frequency re-converter 39 and a fixed 
input contact b which is connected to the output of 1H delay circuit 40. 
Switching circuit 41 is schematically illustrated as including a movable 
output contact c which is selectively engageable with input contacts a and 
b, depending upon the state of a switch control signal supplied to a 
control input thereof. The output of switching circuit 41, that is, the 
output derived at output contact c, is connected to bell filter 43 which 
is provided with a frequency characteristic that is complementary to the 
frequency characteristic of reverse bell filter 24. Thus, bell filter 43 
is adapted to restore the frequency re-converted chrominance component 
back to its original frequency characteristic. 
The switch control signal which is supplied to switching circuit 41 is the 
phase-inverted version of the switch control signal P.sub.f, described 
above, and used to control switching circuit 27 in the recording section. 
Accordingly, switch control signal P.sub.f, produced by frequency divider 
48, is supplied to the control input of switching circuit 41 via an 
inverter 42. It is appreciated that, for the proper operation of the 
reproducing section, the switch control signal which is produced during 
the reproducing operation must be synchronized with the switch control 
signal which is produced during the recording operation. This is provided 
by making sure that the output of frequency divider 48 is at its proper 
level at the time that the discriminating signal S.sub.f is reproduced. 
The circuit for controlling frequency divider 48 accordingly is comprised 
of gating circuit 52, a tuned amplifier 53, a detector 54 and a wave 
shaper 55. Gating circuit 52 has been described hereinabove with respect 
to the recording section of the illustrated apparatus. During the 
reproducing operation, the input of this gating circuit is connected to 
low pass filter 33 via the playback contact P of change-over switch 
SW.sub. 3, and the output of this gating circuit is connected to tuned 
amplifier 53 via the playback contact P of change-over switch SW.sub.4. 
Tuned amplifier 53 is adapted to amplify a signal having a frequency equal 
to the frequency to which the amplifier is tuned. In the illustrated 
apparatus, tuned amplifier 53 is adapted to amplify the discriminating 
signal S.sub.f whose frequency corresponds to the tuned frequency of the 
tuned amplifier. The output of tuned amplifier 53 is coupled to detector 
54 which, in turn, is coupled to wave shaper 55. The detector serves to 
detect the amplified discriminating signal S.sub.f supplied thereto by 
tuned amplifier 53 and to produce an output pulse when this discriminating 
signal is so detected. Wave shaper 55 is adapted to shape the output pulse 
produced by detector 54 to a desired pulse waveform. The output of wave 
shaper 55 is coupled to frequency divider 48. If the frequency divider is 
a triggerable flip-flop circuit, as suggested above, then the shaped pulse 
provided by wave shaper 55 is adapted to set the triggerable flip-flop 
circuit to a predetermined state, such as to "force-set" the flip-flop 
circuit. Hence, if the output P.sub.f of frequency divider 48 is a binary 
"0" at the time that the reproduced discriminating signal S.sub.f is 
detected, frequency divider 48 will be "forced-set" so as to change the 
state of the output P.sub.f to a binary "1". Conversely, if the output 
P.sub.f is a binary "1" when the reproduced discriminating signal is 
detected, the shaped pulse produced by wave shaper 55 will not affect this 
output. 
Gating circuit 52 is supplied with the gate pulse P.sub.g produced by 
monostable multivibrator 50, described above. However, during the 
reproducing operation, change-over switch SW.sub.2 does not coupled the 
output of frequency divider 48 to monostable multivibrator 49. Rather, the 
playback contact P of this change-over switch couples the rectangular 
pulse signal output P.sub.25 of flip-flop circuit 47 to monostable 
multivibrator 49. 
In describing the operation of the reproducing section of the illustrated 
apparatus, it is assumed that heads 12a and 12b which were used to record 
the video signals in successive tracks, as shown in FIG. 2, also are used 
to reproduce those recorded signals. It is further assumed that motor 13, 
magnetic detectors 45a and 45b and flip-flop circuit 47 are used both 
during the recording operation and during the reproducing operation. Of 
course, if separate VTR's are used for recording and reproduction, then 
separate heads will be used for these purposes. Nevertheless, the 
operation of motor 13, magnetic detectors 45a and 45b and flip-flop 
circuit 47 in the reproducing VTR will be the same as in the recording 
VTR, and as described hereinabove with respect to the recording section. 
It is also recognized that if separate recording and reproducing VTR's are 
employed, the azimuth angles of the air gaps in heads 12a and 12b for 
reproduction will be the same as the azimuth angles which are used for 
recording. 
In a reproducing operation, all of change-over switches SW.sub.1 -SW.sub.4 
are changed over to their playback P contacts. As motor 13 rotatably 
drives heads 12a and 12b, the recorded video signals in tracks T.sub.a and 
T.sub.b, as shown in FIG. 2, are reproduced and supplied via the playback 
contact P of change-over switch SW.sub.1 to playback amplifier 31. High 
pass filter 32 separates the FM luminance component from the reproduced 
video signals, and the luminance channel functions in a manner known to 
those of ordinary skill in the art to reproduce the original luminance 
component. This luminance component is supplied to combining circuit 37. 
Low pass filter 33, included in the chrominance channel, separates the 
chrominance component and inserted discriminating signal to supply these 
combined signals (S.sub.s +S.sub.f) through ACC circuit 38 to frequency 
re-converter 39. ACC circuit 38 removes undesired amplitude fluctuations 
from the reproduced chrominance component S.sub.s ; and frequency 
re-converter 39 operates to re-convert the reproduced chrominance 
component substantially back to its original frequency band. The 
re-converted chrominance component includes alternating delayed and 
undelayed frames, the delayed frame exhibiting a 1H delay with respect to 
the undelayed frame. These alternating frames are supplied directly to 
input contact a of switching circuit 41, and through 1H delay circuit 40 
to input contact b of the switching circuit. 
The manner in which switching circuit 41 is controlled now will be 
described with reference to FIG. 6. The operation of flip-flop circuit 47 
in producing rectangular pulse signal P.sub.25 has been described 
previously with respect to FIG. 4A. This rectangular pulse signal is shown 
again in FIG. 6A. The frequency of this rectangular pulse signal is 
divided in frequency divider 48 to produce output P.sub.f, this output 
being used as the switch control signal for controlling the operation of 
switching circuit 27 in the recording section. FIG. 4B shows this output, 
shown again in FIG. 6B, and FIG. 6C shows the phase-inverted version 
P.sub.f of this output. It is appreciated that the phase-inverted version 
P.sub.f is used as the switch control signal for switching circuit 41 in 
the reproducing section. It is assumed that switching circuit 41 is 
substantially similar to switching circuit 27 and operates in an analogous 
manner. Hence, when switch control signal P.sub.f is at its binary "1" 
level, switching circuit 41 operates to couple input contact a to output 
contact c. Conversely, when switch control pulse P.sub.f is at its binary 
"0" level, the switching circuit operates to couple input contact b to 
output contact c. As will be described, during reproduction, output 
P.sub.f is identical to output P.sub.f during recording. That is, output 
P.sub.f is a binary "1" at each odd frame and is a binary "0" at each even 
frame. It is recalled that the even frames are subjected to a 1H delay. 
Since switching circuit 41 is controlled by the phase-inverted switch 
control pulse P.sub.f, the phase-inverted switch control pulse is a binary 
"0" when each odd-numbered frame is reproduced and is a binary "0" when 
each even-numbered frame is reproduced. This, of course, is the opposite 
of the state of the switch control pulse P.sub.f during the recording 
operation. As a consequence thereof, when inverted switch control pulse 
P.sub.f is a binary "0", the odd-numbered undelayed frame is being 
reproduced. Switching circuit 41 is controlled by this inverted switch 
control pulse P.sub.f to couple the output of 1H delay circuit 40 to bell 
filter 43. This means that the reproduced undelayed frame is frequency 
re-converted and then subjected to a delay equal to one horizontal line 
interval, that is, equal to the delay imparted to the even-numbered frames 
during recording, and switching circuit 41 supplies the 1H delayed output 
of frequency re-converter 39 to bell filter 43. When the even-numbered 
frames are reproduced from tape 10, inverted switch control pulse P.sub.f 
is a binary "1" to operate switching circuit 41 whereby input contact a is 
connected to output contact c. Thus, when the even-numbered frames are 
reproduced, the output of frequency re-converter 39 is connected directly 
to bell filter 43 without passing through any delay circuit. Since the 
even-numbered frames had been delayed by one horizontal line interval 
during the recording operation, these delayed frames are not further 
delayed during the reproducing operation. 
Thus, it is seen that since those reproduced frames which had not been 
delayed during the recording operation are delayed by one horizontal line 
interval, while those reproduced frames which had been delayed during the 
recording operation are not delayed during the reproducing operation, the 
relative delay between odd-numbered and even-numbered frames which had 
been imparted during recording is compensated, or eliminated, during 
reproduction. That is, whereas the even-numbered frames had been delayed 
during recording, it is the odd-numbered frames (i.e., the originally 
undelayed frames) that are delayed during reproduction. 
The reproduced frequency-converted chrominance component and inserted 
discriminating signal (S.sub.s +S.sub.f), shown in FIG. 5E, are supplied 
through low pass filter 33 and the playback contact P of change-over 
switch SW.sub.3 to gating circuit 52. The purpose of this gating circuit 
during the reproducing operation is to search for the inserted 
discriminating signal S.sub.f. In this regard, the rectangular pulse 
signal P.sub.25 (FIG. 6A) produced by flip-flop circuit 47 and 
representing the particular track which is reproduced by heads 12a and 12b 
is supplied through the playback contact P of change-over switch SW.sub.2 
to monostable multivibrator 49. As in the recording operation, monostable 
multivibrators 49 and 50 respond to the positive transition in each pulse 
signal supplied thereto to produce the gating pulse P.sub.g (FIG. 6D) at 
the output of monostable multivibrator 50. This gating pulse, having the 
duration .tau..sub.2, is supplied to gating circuit 52 to operate (i.e., 
open) the gating circuit during the selected time intervals established by 
the gating pulse. During the reproducing operation, it is seen that this 
gating pulse is produced during the vertical blanking interval VBLK in 
each frame. This differs from the generation of the gating pulse P.sub.g 
during the recording operation, wherein the gating pulse is produced 
during the vertical blanking interval during alternate frames (e.g. the 
odd-numbered frames) only, as shown in FIG. 4C. Thus, during the 
reproducing operation, gating circuit 52 is opened during the vertical 
blanking interval in the first field in each frame. 
When the discriminating signal S.sub.f is supplied to gating circuit 52, 
the coincidence of the gating pulse P.sub.g and the discriminating signal 
results in passing the reproduced discriminating signal from the gating 
circuit to tuned amplifier 53. The tuned amplifier amplifies this 
discriminating signal, and the amplified discriminating signal is detected 
by detector 54. Wave shaper 55 shapes the pulse produced by the detector 
to supply a correction pulse P.sub.c to frequency divider 48, as shown in 
FIG. 6F. From a comparison of FIGS. 6B and 6F, it is seen that the 
correction pulse P.sub.c is produced when output P.sub.f from frequency 
divider 48 is a binary "1". This corresponds to the gating of the 
discriminating signal S.sub.f when switch control pulse P.sub.f is a 
binary "1", as shown in FIGS. 4B and 4D, during the recording operation. 
In the event that the output P.sub.f of frequency divider 48 during the 
reproducing operation is a binary "0" at the time that the discriminating 
signal S.sub.f is reproduced, correction pulse P.sub.c changes the state 
of output P.sub.f, as shown in FIG. 6G. That is, correction pulse P.sub.c 
is used to "force-set" the triggerable flip-flop circuit which may be 
provided as frequency divider 48 in the event that this triggerable 
flip-flop circuit is in its reset state at the time that the 
discriminating signal S.sub.f is reproduced. Consequently, the output 
P.sub.f of frequency divider 48 is synchronized during the reproducing 
operation so as to be identical to the state thereof during the recording 
operation. 
When the output P.sub.f from frequency divider 48 during the reproducing 
operation is identical to the output P.sub.f during the recording 
operation, switching circuit 41 is controlled so as to pass the 
even-numbered frames of the frequency re-converted chrominance component 
directly to bell filter 43, and to pass the odd-numbered frames of the 
frequency re-converted chrominance component through 1 H delay circuit 40 
to the bell filter. Thus, during the reproducing operation, only those 
frames which had not been delayed during the recording operation are 
subjected to a 1H delay. Hence, at the output of bell filter 43, the 
successive frames are provided in an equalized time relationship with 
respect to each other. 
It is appreciate that if those frames of the chrominance component which 
had been delayed during the recording operation also are delayed during 
the reproducing operation, then such frames, at the output of bell filter 
43, will exhibit a time delay of two horizontal line intervals relative to 
the remaining frames. It is for this reason that, in the reproducing 
operation, the previously delayed frames are not further delayed, while 
the previously undelayed frames are subjected to a delay which is equal to 
the delay imparted in the recording section. Thus, and as one example 
thereof, during the recording operation, the odd-numbered frames of the 
chrominance component are not delayed, whereas the even-numbered frames of 
the chrominance component are delayed. In the reproducing operation, the 
odd-numbered frames of the chrominance component (which had not been 
delayed) are delayed, while the even-numbered frames of the chrominance 
component (which had been delayed) are not delayed. 
In the foregoing discussion, the discriminating signal S.sub.f is inserted 
into the first field of the odd-numbered, undelayed frames of the 
chrominance component during the recording operation. As an alternative 
thereof, the discriminating signal may be inserted into the first field of 
the even-numbered, delayed frames. In either embodiment, the 
discriminating signal serves to represent which frames have been delayed 
and which frames have not been delayed. Furthermore, although it has been 
assumed that, during the recording operation, the even-numbered frames had 
been delayed, it is recognized that, if desired, the odd-numbered frames 
can be delayed while the even-numbered frames will not be delayed. In the 
present invention, alternate frame intervals of the chrominance component 
are delayed. 
Referring to FIGS. 7A-7E, timing diagrams are illustrated therein which 
represent the manner in which the present invention operates. FIG. 7A 
represents the chrominance component S.sub.c1 produced at the output of 
ACC circuit 25 in the recording section and supplied directly to input 
contact a of switching circuit 27. FIG. 7B represents the delayed version 
S.sub.c2 of this chrominance component. It is seen that the delayed 
chrominance component is delayed by one horizontal line interval. In these 
figures, the cross-hatched areas represent those line intervals in which 
the R-Y red color difference signals are present, and the unhatched areas 
represent those line intervals in which the B-Y blue color difference 
signals are present. Switching circuit 27 is operated such that undelayed 
chrominance component S.sub.c1 is supplied to frequency converter 28 
during odd-numbered frames, and the delayed chrominance component S.sub.c2 
is supplied to the frequency converter during the even-numbered frames. 
FIG. 7C represents the alternating delayed and undelayed frames of the 
chrominance component S.sub.c3 supplied to the frequency converter. These 
frames are frequency-converted and recorded in successive parallel tracks. 
It is seen that the first and last line intervals in each recorded frame 
contain color information signals relating to the same color, e.g., the 
blue color difference signals. From FIG. 2, it is recognized that this 
results in color-alignment of the record tracks. 
During reproduction, the alternating delayed and undelayed frames, shown in 
FIG. 7C, are reproduced. These frames of the frequency-converted 
chrominance component are re-converted by frequency re-converter 39, whose 
output is shown in FIG. 7C as the chrominance component S.sub.c3. This 
reproduced chrominance component S.sub.c3 is delayed by 1H delay circuit 
40 and supplied as the delayed chrominance component S.sub.c4 to input 
contact b of switching circuit 41. The undelayed version S.sub.c3 of this 
reproduced chrominance component is supplied directly to input contact a 
of the switching circuit. As discussed above, this switching circuit 
operates so as to supply the output of 1H delay circuit 40 to bell filter 
43, that is, delayed circuit S.sub.c4, for those frames which had not been 
delayed during recording. In the illustrated example, this means that the 
odd-numbered frames, which had not been delayed during the recording 
operation, are delayed during reproduction and supplied to bell filter 43. 
The chrominance component S.sub.c3, which contains delayed even-numbered 
frames, is supplied by switching circuit 41 to bell filter 43 without 
further delay. FIG. 7E represents the chrominance component S.sub.c5 
supplied to the bell filter by switching circuit 41. It is recognized 
that, in the reproducing operation, by delaying the previously undelayed 
frames of chrominance component and by not delaying the previously delayed 
frames, successive line intervals from one frame to the next will be 
substantially in the proper line sequential arrangement. Only the first 
line interval in each odd-numbered frame, which is equal to delayed line 
interval 624 of the previous frame, may contain an improper color signal. 
That is, only this first line interval may appear out of proper color 
sequence during a normal reproducing operation; however, the remaining 
line intervals in the odd frames are, of course, in proper color sequence. 
Hence, this has only negligible effect upon the switching circuits 
included in the conventional SECAM television receiver. 
While the present invention has been particularly shown and described with 
reference to a preferred embodiment thereof, it should be readily apparent 
to those of ordinary skill in the art that various changes and 
modifications in form and details may be made without departing from the 
spirit and scope of the invention. Some of these changes and modifications 
have been discussed and suggested above. In addition to these, it is 
appreciated that, in the recording section, the selective delay circuit 
comprised of 1H delay circuit 26 and switching circuit 27 may be connected 
to the output of frequency converter 28. Similarly, in the reproducing 
section, the selective delay circuit comprised of 1H delay circuit 40 and 
switching circuit 41 may be connected to the input of frequency 
re-converter 39. Also, although the delay imparted to the alternate frames 
by delay circuits 26 and 40 is equal to one horizontal line interval, it 
is seen from FIG. 2 that color-alignment will be attained during recording 
if a delay equal to an odd multiple (2n-1) of horizontal line intervals is 
imparted by these delay circuits. Furthermore, although the embodiment 
shown in FIG. 3 is operative to delay the frames of the chrominance 
component, the incoming SECAM video signal may, alternatively, be delayed. 
It is intended that the appended claims be interpreted as including all of 
the foregoing changes, as well as equivalents thereof.