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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an information signal recording apparatus and,
more particularly, to an apparatus for recording main information signals
in tracks formed on a recording medium. Still more particularly, it
relates to an apparatus for recording not only main information signals,
but also additional information signals.
2. Description of the Related Art
The following in this written specification is described by taking an
example of a helical scan type video tape recorder (VTR) as the apparatus
of this kind.
The helical scan type VTR has been known to provide a model in which a
magnetic tape is wound around a cylinder in an angular coverage of
221.degree., the cylinder having a pair of recording or reproducing rotary
magnetic heads located in spaced relation by an angular difference of
180.degree.. Of the coverage, a region of 180.degree. is assigned to
recording of video signals, and another region of 36.degree. to recording
of sound signals compressed in the time axis.
FIG. 1 shows an example of the record format of such a model of VTR. The
rotary magnetic head starts to contact the tape from the left side and
forms a helical track. Within this helical track, there is provided an
inrush portion 6 of 5.degree. in rotation angle, of which the latter part
of 2.06.degree. forms a clock run-in portion 7 to make synchronize it with
PCM data. This clock run-in portion 7 is followed by a
time-axis-compressed PCM audio data portion 8 of 26.32.degree.. Successive
to this PCM audio data portion 8 there is provided a back margin portion 9
of 2.06.degree. to cope with the recording position gap produced when
after-recording by the difference between apparatus. Between the PCM audio
data portion 8 and the next video signal portion 11 there is further a
guard band portion 10. The next 180.degree. part contains a video signal
portion 11 and a separation portion 12 of 5.degree..
According to such a record format, the video signals for every one field
are recorded in, or reproduced from, the video signal portion 11 of every
one track, while the PCM audio data obtained by compressing the audio
signal for 1/60 sec. in the time axis is recorded in, or reproduced from,
the PCM data portion 8.
Meanwhile, the video signal portion 11 in the record format described above
is divided into five parts, so that, as they are equalized to each other,
each subtends 36.degree., thus totaling six segments in constituting the
PCM audio portion. Such a record format, too, has been proposed. FIG. 2
shows this record format adapted solely to be used for PCM audio data.
First of all, each track has six segments 5, 13, 14, 15, 16 and 17, of
which the first segment 5 comprises the aforesaid inrush portion 6 of the
rotary head through the guard band portion 10, the next or second segment
13 is constructed in the same form, comprising an inrush portion 19, a
clock run-in portion 20, a PCM data portion 21, a back margin portion 22
and a guard band portion 23, and the third to the sixth segments 14, 15,
16 and 17 are formed likewise.
The use of such a record format provides a possibility of recording or
reproducing PCM audio data independent of each other in the respective
segments. Also, by using the flying erase head, it is also possible to
erase the PCM audio signal of the desired segment and then rewrite in this
segment.
With the conventional VTR model having the fixed head, heading signal time
code, date and other items of additional information, are generally
recorded by that fixed head in the track assigned to the control (CTL)
signal for tracking along with the CTL signal.
Without using the fixed head, the aforesaid additional information may be
recorded only by the rotary head. In a known method, besides the area
assigned to record the main information signals, such as video signals and
audio signals, there is provided a recording area for the additional
information, and the items of additional information to be recorded in
this new area are broadened.
Also, as to the recording signal form of this additional information,
either digital signals or analog signals has been proposed.
Meanwhile, in recent years, use of a new type of VTR with a video camera in
unified form, or a so-called camera-unified type VTR, is spreading.
FIG. 3 shows an example of the construction of the conventional
camera-unified type VTR. A time information recording and reproduction
device in the camera-unified type VTR comprises, as shown in FIG. 3, a
time code generator 36 and a character generator 35 responsive to the time
code for producing an output signal which is then multiplexed by an adder
34 on the video signal produced from the known circuit comprising an image
sensor 32 with an optical system 31, a camera signal processing circuit 33
and others. In short, it has been the common practice that the time code
is recorded as the character information in the form of a video signal.
This character information-multiplexed video signal, along with four pilot
signals (4f) to be used in the 4-frequency type tracking control of audio
signals, is converted to a recording signal of the form suited to be
recorded by a recorder signal processing circuit 37. This recording signal
passes through an amplifier 38 and a head switch 41 to the rotary heads
39-a and 39-b by which it is recorded on a tape-shaped recording medium or
magnetic tape 40.
When the aforesaid signal is reproduced, the recorded information of the
time code generator 36 appears in a portion of the picture taken by the
optical system 31.
Another method of recording the time code is by using the longitudinal
track formed in the vicinity of the tape. Yet another method is to create
a sub-code recording area in each track as separated from the recording
area for the main information so that the time code is recorded as a
sub-code in this sub-code recording area.
By the way, in a case where the time code is recorded as the character
information in the form of a video signal, because it is multiplexed on
the video signal, it always is displaced in superimposed relation on the
picture when reproduced. Therefore, when reproducing, the date letters and
the picture cannot be separated from each other. Also, in recording
foreseeing whether the date will be necessary or unnecessary when
reproducing, the photographer must determine in advance which position the
selector switch should be set in. Further, this leads to the impossibility
of knowing the time information of those picture frames which lack the
character information representing the time code imposed thereon.
Also, in a case where the time code is recorded in the longitudinal track,
because the relative speed of the tape and the fixed head is low, a lot of
information cannot be expected to record. Therefore, it is difficult to
record those fractions of the time code which are in shorter time units,
and a wide variety of items of additional information. Further, because
the necessity of providing the fixed head arises, it is unfavorable since
the tape will wear out fast and an increase of the complexity of the
mechanisms is called for.
Further, in a case where the time code is recorded as a sub-code in the
sub-code recording area provided in each track, this sub-code information
is difficult to read when in reproduction with the tape running at a high
speed, for example, for forward or backward searching of the VTR. This
tendency is more prominent particularly when the so-called azimuth
recording is effected.
In more detail, generally when the additional information is recorded as
the digital signal, the additional information is hardly extracted at the
time of the fast running of the tape. This arises because the clock
synchronism is broken due to the change of the relative speed of the head
and the tape from when usually recorded. Also, when the so-called azimuth
recorded tape is reproduced, the rotary heads are caused to move across
some tracks. Therefore, the difficulty of extracting the additional
information is increased.
Meanwhile, in a case where the additional information is recorded as the
analog signal, regardless of the speed of transportation of the tape, the
additional information can be extracted relatively easily. However,
generally the track cannot afford so much large recording area as the
additional information recording area. In accompaniment with this, the
quantity of additional information available to record in the form of
analog signals is caused to be very little.
SUMMARY OF THE INVENTION
An object of the present invention is to solve all the above-described
problems.
Another object of the invention is to provide an information signal
recording apparatus in which taking a larger recording area for additional
information, a lot of information as the information quantity of the
additional information can be recorded without taking a larger recording
area for additional information, and in which the necessary additional
information can be extracted even when the recording medium is transported
at the high speed.
Under such an object, according to the invention, in one embodiment
thereof, an information signal recording apparatus is proposed, comprising
head means for recording a signal on a recording medium, main generating
means for producing a first recording signal concerning a main information
signal, first forming means for producing a digital additional information
signal, second forming means for producing an analog additional
information signal, mixing means for mixing the digital additional
information signal and the analog additional information signal to produce
a second recording signal, and time-division multiplex means for supplying
the first recording signal and the second recording signal in
time-divisionally multiplex to the head means.
Still another object of the invention is to provide a video signal
recording apparatus which enables additional information to be recorded in
such a way that even when the recording medium is transported at the high
speed, it can be extracted, and in which a lot of additional information
codes can be recorded while allowing the density of recorded information
to.
Under such an object, according to the invention, in one embodiment
thereof, a video signal recording apparatus is proposed, comprising means
for producing a video signal, means for producing a pilot signal for
tracking control, means for digital additional information comprising at
least two bits, modulating means for modulating the digital additional
information by an analog carrier wave signal to produce an analog
additional information signal, the analog carrier wave signal having a
frequency in between the frequency band of the video signal and the
frequency of the pilot signal, mixing means for frequency-multiplexing the
video signal, the pilot signal and the analog additional information
signal to produce a recording signal, and recording means for recording
the recording signal obtained by the mixing means on a recording medium.
Other than those described above, objects of the invention and its features
will become apparent from the following detailed description with
reference to the drawings:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating the record the conventional VTR.
FIG. 2 is a diagram illustrating another record format of the conventional
VTR.
FIG. 3 is a diagram illustrating an example of the construction of the
recording system of the conventional camera-unified type VTR.
FIG. 4 is a diagram roughly illustrating the construction of an embodiment
of a VTR according to the invention.
FIGS. 5(a) to 5(d) are timing charts illustrating the timing in which the
VTR of FIG. 4
FIGS. 6(a) and 6(b) are diagrams illustrating the frequency allocation of
the recording signals by the VTR of FIG. 4.
FIG. 7 is a diagram illustrating another example of the record format by
the VTR of FIG. 4.
FIG. 8 is a diagram roughly illustrating the construction of another
embodiment of a camera-unified type VTR according to the invention.
FIG. 9 is a diagram to explain the recording signal by the VTR of FIG. 8.
FIG. 10 is a diagram illustrating the record format on the tape by the VTR
of FIG. 8.
FIG. 11 is a diagram illustrating the record format of additional
information data by the VTR of FIG. 8.
FIG. 12 is a diagram roughly illustrating the construction of the
reproducing system of the VTR of FIG. 8.
FIG. 13 is a flowchart to explain the operation of the system control
microcomputer when searching by the arrangement of FIG. 12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is next described in connection with embodiments
thereof applied to the VTR by reference to the drawings.
FIG. 4 schematically shows the construction of a VTR in one embodiment of
the invention. The video signal enters into and exits from a video signal
processing circuit 101 through an input terminal 124 and an output
terminal 125 respectively. The output of this video signal processing
circuit 101, at which the video signals to be recorded are produced, is
connected to the X terminals of selection switches 103a and 103b. Also, an
input terminal 126 and an output terminal 127 of the PCM audio signal are
connected to a PCM audio signal processing circuit 102. The output of this
PCM signal processing circuit 102, at which the audio signals to be
recorded are produced, is connected to the Y terminals of the selection
switches 103a and 103b. Meanwhile, a system control circuit 119 reads the
state of an operation switch 118 to control the whole VTR, and supplies
the required data to a code signal generating circuit 120. This circuit
120 produces additional information such as music number, index and time
code as the additional information to be converted to digital data. The
system control circuit 119 sends the aforesaid additional information to
an f.sub.6 generating circuit 121 and a digital data generating circuit
122.
The f.sub.6 generating circuit 121 produces an analog pilot signal of
predetermined frequency (hereinafter abbreviated to the "f.sub.6 " signal)
in response to those data in the aforesaid additional information, such as
index information for heading whose necessity to read is high when the
tape runs at the high speed. On the other hand, the digital data
generating circuit 122 produces an output including all items of
additional information, including the index information for heading, music
number and time code described above.
This f.sub.6 signal and the digital data signal are frequency-multiplexed
by an adding circuit 123, of which the output is applied to the Z
terminals of the selection switches 103a and 103b. Here, the timing in
which the selection switches 103a and 103b operate is explained by using
the timing chart of FIGS. 5(a) to 5(d). FIG. 5(a) shows the timing in
which the video signal is recorded. When the signal shown in FIG. 5(a) is
at high level, a rotary head 111, or when at low level, another rotary
head 112, is selected to record the video signal That is, the switch 103a
is connected to the X terminal for a period shown by "a" in the FIG. 5(a),
and the switch 103b is connected to the X terminal for a period shown by
"b". Also, FIG. 5(b) shows the timing in which the PCM audio signal is
recorded. During a period when the signal shown in FIG. 5(b) is at high
level, the PCM audio signal is recorded by the rotary head 111 or 112. For
the period labeled "a" in FIG. 5(b), the switch 103a is connected to the Y
terminal, and for the period labeled "b", the switch 103b is connected to
the Y terminal. Further, during the periods in which the signal shown in
FIG. 5(c) is at a high level, for the one labeled "a" the switch 103a is
connected to the Z terminal, while for the other labeled "b", the switch
103b is connected to the Z terminal. Incidentally, in the switches 103a
and 103b, for the periods other than the recording periods of each signal
shown in FIGS. 5(a), 5(b) and 5(c), the movable pole of each switch may be
arranged either to connect to an arbitrary throw, or to be grounded. It is
to be noted that the control of these switches 103a and 103b is made
according to the timing control signals "a" and "b" from a timing
generating circuit 117.
The output signals from the selection switches 103a and 103b are supplied
to adding circuits 132a and 132b, where pilot signals f.sub.1, f.sub.2,
f.sub.3 and f.sub.4 for tracking control according to the known
4-frequency scheme from a pilot signal generating circuit 131 are
selectively added. Their outputs are then supplied to the rotary magnetic
heads 111 and 112 located by a phase difference of 180.degree. from each
other. FIG. 5(d) shows the signals the head 11 records.
When reproducing a selection switch 110 is moved to its P side in response
to an output of a system control circuit 119. The reproduced signals from
the heads 111 and 112 are applied through reproducing amplifiers 108 and
109 to selection switches 105a, 105b, 105c, 105d and 105e. By a switching
pulse "c" from a timing generating circuit 117, the selection switch 105a
selectively puts the outputs of the reproducing amplifiers 108 and 109
onto its output. This switch 105a supplies the reproduced video signal to
the video signal processing circuit 101 according to the timing of FIG.
5(a). In accompaniment with this, the reproduced video signal of the
original signal form is obtained from the output terminal 125. Also, the
switches 105b and 105c are turned on according to switching pulses "d" and
"e" from the timing generating circuit 117 respectively in the timing
according to FIG. 5(b). For the periods they are on, the PCM audio signal
reproduced from each head 111 or 112 is supplied to the PCM signal
processing circuit 102. In accompaniment with this, the original analog
audio signal is produced from the output terminal 127. Also, the switches
105d and 105e are likewise turned on according to switching pulses "f"
and "g", from the timing generating circuit 117, and supply the frequency
multiplexed additional information signal according to FIG. 5(c) to an
f.sub.6 separation circuit 124 and a digital data processing circuit 125.
The additional information signals from the f.sub.6 separation circuit 124
and the digital data processing circuit 125 each are applied to the system
control circuit 119 where they are processed as the music number, index,
time code and heading information. That is, according to each of the
aforesaid items of additional information data, the system control circuit
119 controls the operation of a capstan control circuit 133 and others to
realize the publicly known index scan reproduction, heading and other
functions.
The capstan control circuit 133 performs the tracking control according to
the known 4-frequency scheme by using the pilot signals f.sub.1, f.sub.2,
f.sub.3 and f.sub.4 in the output signals of the reproducing amplifiers
108 and 109. Also, the timing generating circuit 117 produces a signal for
erasing at an E terminal thereof. This signal for erasing is supplied
through an erasing amplifier 115 to a rotary erasing head 113 when the
signal on the tape is erased. Also, a rotation phase detecting head 114
detects the phase of rotation of the rotary cylinder having the heads 111
and 112 mounted thereon and produces pulses (shown in FIG. 5(a))
synchronized with the changeover timing for the video signal of the
recording or reproducing heads. This pulse is supplied through the
amplifier 116 to the timing generating circuit 117, becoming the reference
phase for all the timing pulses.
FIGS. 6(a) and 6(b) are diagrams illustrating the frequency allocation of
the recording signals in the VTR of the above-described embodiment. FIG.
6(a) concerns the recording signal in a video signal recording part 11,
and FIG. 6(b) concerns the recording signal in the guard band portion 10
constituting an additional information signal recording part. On FIG.
6(a), it is known. So its explanation is omitted. As shown in FIG. 6(b),
the frequency f.sub.6 of the f.sub.6 signal is set lower than that of the
low-band converted chrominance signal, but higher than those of the pilot
signals according to the 4-frequency scheme. This enables the f.sub.6
signal to be reproduced irrespective of the difference of the azimuth
angle so that even when the tape is transported at a very high speed, it
can sufficiently be detected. Also, the frequency spectrum of the signal
the digital data generating circuit 122 produces is predetermined to fall
in a range of higher frequencies than the frequency of the f.sub.6 signal.
The VTR of the above-described embodiment has a function of performing
recording according to the format for recording the PCM audio signals of 6
channels as shown in FIG. 2. Selection of this 6-channel PCM audio record
mode and the ordinary mode is realized by controlling the system control
circuit 119 by actuating an operation switch 118. That is, the system
control circuit 119 controls the switches 105a, 105b, 105c, 105d and 105e
so as to perform recording according to the record patterns as shown in
FIG. 7. In the format of FIG. 7, the guard band portion 10 in the format
of FIG. 2 is divided into a clock run-in portion 134 and a data portion
135, wherein the aforesaid digital additional data are recorded in the
data portion 135, while the f.sub.6 signal is multiplexed in both of the
clock run-in portion 134 and the data portion 135. , Also, these are
performed in every segment. This results in the recording of additional
information about each of the channels of PCM audio signals.
In such a VTR of the embodiment described above, even when the tape is
transported at a very high speed, it is possible to read the additional
information by the f.sub.6 signal. Thus, the functions such as heading and
index scanning can be realized. Also, in a case where it is also desired
to record the time code, music number and others the recording can be done
by the digital additional information data.
As has been described above, according to the information signal recording
apparatus of the above-described embodiment, without taking a large
recording area for the additional information, an additional amount of
information can be recorded. Moreover, even at the time of high speed
transportation of the recording medium, it is made possible to extract the
necessary additional information.
FIG. 8 is a diagram roughly illustrating the construction of a
camera-unified type VTR as another embodiment of the invention. Light rays
coming from an object (not shown) to be photographed and entering through
an optical system 201 form an image on an image sensor 202. The output of
the image sensor 202 is converted to the form of television signals by a
known camera signal processing circuit 203.
A time code generator 204 in a similar form to the conventional example of
the circuit using the so-called digital clock produces time codes (year,
month, day, hour, minute and second) in the form of digital signals. This
data is the time code concerning the date and time of shooting or the time
counter from the head of the tape in use.
The aforesaid time code is converted likewise as in the conventional
example by the character generator 205, if necessary, to the television
signal form and is multiplexed on the picked-up television signal. This
picked-up television signal produced from the camera signal processing
circuit 203 and the character signal concerning the time code produced
from the character generator 205 are image-combined by an adder 206.
The combined television signal by the adder 206 is converted to a known
recording signal according to the prescribed record format of the VTR.
That is, a sound-collected audio signal by a microphone 216 is
FM-modulated by an audio processing circuit 215. This FM-modulated signal,
along with the pilot signals for tracking of the 4-frequency scheme a
4-frequency generator 213 produces is combined with the video signal
produced from the recorder signal processing circuit 207 by an adder 214.
The output of the aforesaid time code generator 204, along with the code
output from an ID signal generator 209 for discriminating various modes
according to the actuation of the operation switch 226, is supplied to a
data encoder 208. By using the output of the data encoder 208, the signal
of frequency f.sub.6 (hereinafter referred to as the "f.sub.6 " signal
produced by) the f.sub.6 generating circuit 211 is subjected to switching
(amplitude modulation) by a gate circuit 212. The output of this gate
circuit 212 is superimposed by an adder 218 on what is obtained by
trapping the f.sub.6 component of the signal according to the
predetermined record format described before by a trapping circuit 217.
The frequencies of the pilot signals are chosen so that their interference
with each of the signals which have conventionally been utilized in the
VTR becomes as small as possible. As these frequencies are being
conventionally used, there are the four pilot signals (100K-200K) for
tracking according to the 4-frequency scheme, the pilot signal (200K-300K)
of frequency f.sub.5 for use in the DTF control or in multichannel record
discrimination of the PCM audio and the low-band converted chrominance
signals (743K.+-.350 K). The time code in the VTR of the present
embodiment, if in support of the SEMPTE time code, can be recorded when
there is a band of about 10 KHz. So, a frequency in between the upper
limit (about 300 K) of the f.sub.5 signal and the lower limit (about 400
K) of the low-band converted chrominance signal minus a margin of more
than 10K is taken f.sub.6 and made to be a modulation carrier.
It is to be noted that the aforesaid trapping circuit 217 is provided for
removing the corresponding frequency component to the f.sub.6 from the
intrinsic recording signal to prevent a faulty operation from occurring.
The arrangement diagram of the aforesaid frequency spectrum after the
superimposition of the f.sub.6 signal is shown in the upper half of FIG.
9, and the frequency characteristic curve of the trapping circuit 217 is
shown in the lower half of FIG. 9.
The thus-obtained recording signal is amplified by a recording amplifier
219 and applied through a switch 224 which is operated by 30 PG pulses of
the frame period to be described later to two rotary heads 220-a and 220-b
of different azimuth angle, by which it is recorded on the tape while
forming tracks.
The rotation of the rotary drum carrying the rotary heads 220-a and 220-b
is detected by a rotation phase detecting head 222 and an amplifier 223 to
perform delay processing or the like so that the timing circuit 225
produces the aforesaid 30 PG pulses in the predetermined timing. This 30
PG pulse, as the reference timing of sync. data generation of time
information array from track to track, is utilized in the data encoder
circuit 208.
The recorded track pattern of the VTR of the present embodiment is shown in
FIG. 10. The recording signals including the video signals, FM-modulated
audio signals and the modulated signals of the f.sub.6 signals, are
recorded in the video signal recording area with the plus azimuth;- and
the minus azimuth alternating each other. In the aforesaid modulated
signal of the f.sub.6 signal, the information representing the shooting
date and time is recorded in the plus azimuth track, while the information
representing the counted time from the end of the tape in use is recorded
in the minus azimuth track. Those parts in the figure which are labeled ID
are the mode data representing the content of the time code of each track.
"01" and "10" of this ID correspond respectively to the two items of time
information, or the shooting date and time, and the time from the tape
end. This ID word is positioned in the central portion of each track so as
to be convenient when the search mode to be described later is operated.
When the tape runs at the high speed, the reproduction envelope is not
obtained over the entire length of the track. As a result, the mode
information is located near to affecting information to the actual
searching. Thus, the probability of reproducing and detecting them at the
same time is increased.
Also, as the check bits for preventing the faulty operation from occurring
when the tape which was recorded by the apparatus not employing this
system is reproduced, that ID word can be used. For this purpose, the bits
are allocated by averting "11" and "00".
For example, the information representing the shooting date and time, the
year, month and day of the shooting date, the mode information and the
hour, minute and second of the shooting time are recorded in this order
from the lower side of the tape. The digital recording, in actual
practice, besides the aforesaid contents, as shown in FIG. 11, is headed
with the information of the clock run-in (32 bit) and the sync. data (16
bit) and, behind the information, is provided with a CRC (8 bit) for error
correction. It is to be noted that the code representing the month, day,
hour, minute, second, frame and ID has 7 bits at maximum and is provided
with 1 bit as the parity check bit, thus being treated as 8 bits in total.
That is, when searching, the error detection is carried out only by the
aforesaid parity of 1 bit, while when in the ordinary reproduction, the
error correction can be carried out by track unit.
For reference, an example of mode settings by utilizing 2 bits of the ID
data 7 bits is shown in Table 1 below.
______________________________________
Mode Content
______________________________________
00 No use (spare)
01 Dating Information
10 Counter Information
11 Heading Signal
______________________________________
Next, the data detecting and searching operations when in reproduction are
described.
An example of the construction of the corresponding reproduction system to
the camcorder of FIG. 8 is shown in FIG. 12. The signals detected from the
tape 221 by the rotary heads 220-a and 220-b are selected one at a time by
a switch 260 in response to 30 PG by each 180.degree. rotation of the head
drum, amplified by a head amplifier 261 and supplied to various filters.
The drum rotation phase signal detected by the drum rotation detecting
head 222 is amplified by an amplifier 223 and applied to a timing circuit
251, which then produces 30 PG pulses of predetermined timing. The PG
pulses are supplied to the switch 260 and a data decoder 275. The data
decoder 275 discriminates .+-. of the azimuth angle by the 30 PG pulses.
BPF 266 designates a band pass filter for audio signal extraction, BPF 267
designates a band pass filter for chrominance signal extraction, and HPF
268 designates a high pass filter for luminance signal extraction. The
signal extracted by these filters is subjected to the reverse processing
to that when recording by a recorder reproduced signal processing circuit
270.
BPF 269 designates a band pass filter for f.sub.6 signal extraction whose
central frequency and band are made to match the frequency and side-band
of the f.sub.6 signal carrier. The output of this BPF 269 is converted to
a digital signal by a detector circuit 271 and a wave form shaping circuit
272. Further, this digital signal is demodulated to the time code by a
data decoder 275. When modulating, the aforesaid 30 PG pulse is used as
the auxiliary information to discriminate the azimuth angles for
determining the mode when detection of the start point of the clock run-in
or detection of the ID data cannot be carried out.
The thus-demodulated time code is supplied to a character generator 276 to
obtain the character information. This character information, after having
been superimposed on the luminance signal in an adder 277, is supplied to
an NTSC encoder 278 where a composite video signal is made up from it.
This signal is outputted together with the demodulated audio signal.
A major difference of the apparatus of the present embodiment from the
conventional apparatus is that the signal from the operating switch 279 is
supplied to the character generator 276 via the system control
microcomputer (hereinafter referred to as "syscon") 274. By this, it is
made possible to switch on or off superimposition of the time code on the
picture information at any desired time by manipulating the operating
switch 279. Means may be so constructed and so arranged that for example,
when the superimposition is cut off, the output data of the data decoder
275 are all replaced by the corresponding data to blank in the character
generator 276 in response to indication from the syscon 274.
The time code demodulated in such a way, besides its use in the
above-described display, can be utilized in searching. That is, since the
demodulated data obtained by the data decoder 275 is always supplied to
the syscon 274, it can be compared with the target value the operation
switch 279 has indicated when searching to derive the difference value
between these two time values. By this difference value, the tape
transportation is controlled. Thus, it is made possible to search the
desired tape position.
The normal tape transportation is controlled by a capstan servo. The
reproduced signal from the amplifier 261 is supplied to an LPF 262. By
this LPF 262, only the pilot signals that follow the 4-frequency rule are
extracted. They are then processed by a capstan servo circuit 263
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