Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
This invention relates to appiaratus for generatillg coded
characters and, more particularly, to such apparatus wherein a
bi-phase coded character is generated ha~ing a constant relation
between the phases at the beginning and end of each coded chiaracter
regardless of the number o~ "1 " s and "0" s included in that character.
In accordance witn a specific aspect of this invention, an SMPTE time
code character is generated having ~ level transition at the start thereof
which is of the sanrle phase, or polarity, as the leveI transition at the
end thereot.
With the advent of lrideo recording alld playback devices9 such
as the ~ideo tape recorder (VTR~9 ~arious situations may arise wh~rein
a recorded medium, such as recorded video tape, should be edited such
that a certain iniormation thereon is replac0d by other, desired infor-
~ ~ mation, or that a certialn additional information is recorded immediately
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following a previously recorded segment. The former editing ope-
ration is known as an insert edit whereinJ for example, one or more frames
of video signals which are recorded on one video tape are replaced by an
equal number of l~rames of video signals which has been recorded on another
video tape. The latter edit operation is known as an assemble edit where-
in one of more frames of video signals which had been recorded on another
video tape are transferred, or re~recorded, onto the main video tapeJ
whereby an entire program may be "assembled".
As may be appreciated, in order to carry out an insert edit or
an assemble edit operationJ that is, an operation wherein video signals which
had been recorded on a secondary tape are transferredJ or re-recorded,
onto a primary tape J two separate VrrR ' s are needed for controlling the
respective playback and recording operations of the seconclary and primary
tapes. The secondary VTR must be operated to ascertain those frames
containing the video information which must be transferred to the primary
tape and the primary VTR must be controlled so as to ascertain the precise
location on the primary tape at which the secondary information is to be
recorded. FurthermoreJ both VTR ' s must be operated in synchronism
with each other.
In order to facilitate such editing operationsJ and particularly,
to identify the specific frames of video signals which are to be edited, a
standardi~ed code has been de~eloped, known as the SMPTE time code~
This SMPTE time code is a serial code formed of a predetermined number
of binary bits which are recorded as phase-modulated, or bi-phase signals.
In accordance with the present standardJ the SMPTE time code cvntains
eighty bi-phase bits which representJ in BCD format~ an inclication of
the time at which each frame of ~ideo signals is recorded, a frame count
and optional binary word information. This time code also includes a
sixteen bit synchroni~ing word and a number of so called binary groups
which may be used either for future information or as the user of the video
, . .~. . . . . :
tape so desires. A more complete description of this ~MPTE
time code is described in "Standardization for Time and ~ontrol
Code for Video Tape and Audio Recorders" by E~ K. Dahlin, I)ecember
1970, Journal of the S~IPTE, Volurnne 79~ page 1086. Another
proposal for a standardized time code for viàeo recording is the EBU time
code .
In the bi-phase representation of binary bits, the beginning
of each bit period is marked by a level transition, either a positive
transition ïrom a lower to a higher level or a negative transitionO
A binary "1 " is represented by yet another level transition during the
bit period, while a binary "0" is represented by the absence of any
additional bit transitions throughout the bit period. In recording
the SMPTE time code on a video tape~ the bi-phase signals are record-
ed in seriatum along a longitudinal edge of the tape such that the begin-
ning of an SMPTE character starts at the beginning of the frame of
video signals and ends at the end of that frame of signals. Thus,
the end of one SMPTE character is coincident with the beginning of the
next following SMPTE character,. Accordingly, it is important that
the phase of the beginning of an SMPTE character, that is, the direction
of the level transition at the start of the SMPTE character, be con-
sistent, or compatible, with the phase at the end of the preceding SMPTE
character. This means that if the preceding SMPIE character ends
with a negative-going transition, the next following SMPTE character
should start with a negative-going transition.
In the insert edit operation wherein video signals which
had been recorded on the primary tape are replaced by ~ideo si~nals
which are played back from the secondary tape, that is, the secondary
video signals are "insertec~" between two existing segments on the
primary tape, the SMPTE time code characters which had been recorded
for the particular segment on the primary tape which is being replaced
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n~rmally remain on the primary tape. Thus, in the insert edit opera
tion, there is no change in the recorded SMPTE characters and, there-
fore, there is no problem in making sure that the phase at the end of
a preceding SMPTE character is compatible with the phase at the begin-
ning of the next following SMPTE character. However, in the
assemble edit operation, a new SMPTE time code is recorded together
with the new video signals which are recorded from the secondary video
tape~ Since the new SMPTE time code characters are not recorded
during the same operation that the preceding SMPTE time code charac-
ters were recorded! it is possible `that tlle phase at the beginning oî
a new character may not be compatible with the phase at the end of the
preceding, previously recorded character. It has been thought that
this problem can be solved by, for examplel reading the next-to last
SMPTE time code character which is recorded on the primary tape just
prior to the assemble edit location thereon and then interpolate the
information represented by the read character such that the content of ;-
the last character can be ascertained, and thus the phase at the end of
that last character will be known. Once this phase is known, the
new SMPTE time code characters can be generated so as to be compatible
therewith. However, this assumes that the last few frames of the
previously recorded video signals on the primary tape has been recorded
in successionO Thus, the frame count contained in the last character
will be one greater than the frame count included in the preceding charac-
ter, and so on. This technique is not successful if successive frames
of video signals are assembled on a frame-by-frame basis, such as for
assembling an animat0d video picture. In that event, the content of
the last-recorded SMPTE time code character will not merely be one
frame greater than the SMPTE time code character which precedes it.
The U. S . Patent No . 4 ,189, 756 pro~oses
~he apparatus which will sol~e the above defectsO In this apparatus,
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since the number of ~'0"s irl the time code of one word is selected as an
even number, the continuation of time codes is good under an~ conditions.
~owever, since the number is necessary to be an even number, there
occurs such a defect that its circuit construction becomes complicated.
OBJECTS OF THE INVENTION
_
Therefore, it is an object of the present invention to record
SMPTE time codes in a manner which overcomes the aforenoted problems
heretofore present in the prior art.
Another object of this invention is to provide improved SMPTE
time code generating apparatus wherein the phase at the beginning of
an SMPTE time code character always is compatible with the phase at
the end of a preceding SMPTE time code character, even if these two
characters are not generated in succession.
~ further object of this invention is to provide an improved
SMPTE time code generator in which the phase relation at the beginning
and end of each character remains constant regardless of the contents
of that character.
In a broader aspect thereof, it is an aclditional object of this
invention to provide apparatus for generating bi-phase coded characters
- 20 having a constant phase relation, such as the same phase relation, at the
beginning and end of each coded character regardless of the number of
bi -phas e " 1 " s and " 0 " s incl uded therein .
Yet ano-ther object of this invention is to provide improved
SMPTE time code generating apparatus which generates SMPTE time code
characters which are particularly useful in assemble edit operations of
a video tape.
Various other objects, advantages and features of the present
invention will become readily apparent from the ensuing detailed description,
and the novel features will be particularly pointed out in the appended
claims. -
In accorc1ance with this in~ention, there is provided a
recording time cocle signal generating apparatus having a time code data
signal generating circuit and a time code signal forming circuit which is
supplied with the time code data signal from the time code data signal gene-
rating circuit and produces a recording time code signal including bi~phase
code signals, in which the recording time code signal is corresponded
to an information signal and recorded continuously on a recording medium
per word unit. In this case, it is soformed that even if the recording
time code signal of word unit which consists of bi phase code signals is
connected in a desired number and then recorded on the recording medium,
there is produced no discontinuity at the connection point of the time code
signals .
BRIEF DESCRIPTION OF THE DRAWINGS
The following description, given by way of example, will best
be understood in conjunction with the accompanying drawings in which;
Fig. 1 is a block diagram of editing apparatus according to
this invention which can be used in, for example, an assemble edit operation;
Fig. 2 is a partial block, partial logic diagram showing a
practical example of a part Or Fig. 1; and
Figs. 3A to 3F are waveform diagrams which are useful in
understanding the operation of the example shown in Fig. 2.
DESCRIPTION F THE PREFERRED EMBODIMENT
An electronic edition apparatus in which the present invention
is incorporated will be firstly described with re-ierence to Fig. 1. In
the figure, pro~ided is an electronic editing VTR 5 which has provided
with, for example, a pair of recording and reproducing rotary magnetic
heads and a pair of rotary erasing magnetic heads on a tape guide drum
(not shown), and also provided is a VTR ~ which serves to reproduce a
video signal as an information signal from a magnetic tape which is not
edited. In the VTR ~, the video signal reproduced from the magnetic
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tape is selected and then fed to the VTR 5 which then records the applied
video signal on a new magnetic tape ;n an edited state. In this case,
separate time code signals (such as the above SMPTE time code signals)
are recorded on the respective magnetic tapes in V t`Rs ~ and 5.
One dot chain line block 6 in Fig. 1 designates an electronic
editing apparatus which includes a recording time code signal generating
apparatus 3. This time code signal generating apparatus 3 produces
a time code signal to be recorded on the magnetic tape in the electronic
editing VTR 5 and hence is formed of a time code data signal generator
12 and a time code signal forming circuit 11 which is supplied with a time
code data signal from the time code data signal generator 12 and produces
a recording time coc3e signal consisting of bi-phase coded s;gnals.
The recording time code signal from the tirne cocle signal forming circuit
11 is fed through an output terminal 1~ to the VTR 5 and recorded therein
on a cue track or audio track of a magnetic tape as a recording medium
per word unit in correspondence with the respective frames of a video
signal as an information signal.
The electronic editing apparatus 6 further including VTR
control circuits 7 and 8 corresponding to the VTR ' s ~ and 5, which are
connected to VTR ' s 4 and 5 through control huses, respectively, and
time code reading-out circuits 9 and 10, which read out the time codes
contained in the time code signals reproduced from VTR ' s ~ and 5 and
which control circuits 9 and 10 are connected through data buses to a
system control circuit 13, respectively. The time code data signal
generator 12 is also connected to the system control circuit 13 through
- a control bus.
The recording time code signal generating apparatus 3
will be described with reference to Fig. 2. As described above, this
recording time code signal generating apparatus 3 is formed of the
time code data signal generator 12 and the time code signal forming
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circuit 11. Especially, in the time code signal forming circuit 11,
provided is means 15 which detects the polarity of a specific bit signal
of a fixed binary Yalue or bit in the recording time code signal of word
unit ( bi-phase code signals) and change the fixed binary bit in accordance
with the detected po]arity.
The time code data signal generator 12 produces at its one
output term;nal 12a time code data signal T~ of a binary code correspond-
ing to the above ~MYTE time code, as shown in Fig. 3D, and at its other
output terminals 12d and 12c first and second clock signals CL1 and
CL2 as shown in Figs. 3A and 3B, respectively. The clock signals
CL1 and CL2 are such clock signals which serve to provide a time code
signal TC consisting of bi~phase code signals as shown in Fig. 3E.
The clock signal CL1 is so selected that its frequency is twice as that
of the clock signal CL2 and the falling-down of, clock signal CL2 is in
synchronism with the falling-down of clock signal CL1, and the time code
data signal TD shown in Fig. 3D is so formed that its bit signal is syn-
chronized with one period of clock signal CL2. Each period of clock
signal CL2 i.e. each bit of time code data signal TD is marked with numbers
of Tn-3, Tn-2, ---- Tn+~ as shown in Fig. 3.
Although the changing means 15 is formed of AND-circuits
19, 20 and an invertsr 18 in the example of Fig. 2, at first, this means
15 is not considered in the following description. The time code data
signal TD and çlock signal CL2 are fed to an OR~circuit 16, and the
output therefrom is fed commonly to J-and K-input terminals of a JK~flip~
-flop circuit 17 which is also supplied at its CK (clock)-input terminal
with clock signal CL1 after being phase-inverted. Thus, the flip~flop
circuit 17 produces at its Q-output terminal i.e. output terminal 1~ a
time code signal TC consisting of bi~phase code signals as shown in
Fig. 3E. This time code signal TC is provided by making the time code
data signal TD as a bi-phase coded signal . In the case where the abo~e
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changing means 15 is not provided, when the time code data signals
TD shown in F;gs. 3D and 3D' are bi-phase-coded, there will occur
such a case that a time code signal TC ' is produced as shown ;n Fig. 3F
which is inversed itl polarity as compar0d with the time code signal TC
shown in Fig. 3E~ (in the figure only bits of Tn_3 to Tn_1 are shown)~
To avoid this clefect, the above changing means 15 is provided to change
the phase of time code signal TC ' to be in phase with the time code signal
TC of word unit at its specific bit signals or respective bit signals
after the bit signals of the Tn bit sigrnal in this example. To this end,
a strobe signal ST (refer to Fig. 3C), which has a time width correspond-
ing to the period of the specific bit signal whose binary bit is fixed to,
for example, "0" such as an empty bit of the SMPTE time cocle signal
for a user, is derived fi~om an output terminal 12b of time code data
signal generator 12 once per the time code signal of one word. Thls
strobe signal ST is fed after being inversed in phase by inverter 18 to the
AND-circuit 19 and fed, as ;t is, to the other AND-circuit 20. The
output from AND-circuit 19J which is supplied with the time code data
signal TD as set forth above, is fed to OR-circuit 160 The AND-circuit
20 is also supplied with the output at the Q-output terminal of the JK-flip-
-flop circuit 17, and the output from the AND-circuit 20 is fed to OR-circuit
16 .
If the above strobe signal ST is produced at, for example, the
Tn bit in the empty bits Tn_1 to Tn+2 for the user wherein the binary
bits are "0", when the output in the former half period in the Tn bit of
JK-flip-flop circuit 17 is in low level as shown in Fig. 3E, the output
in -the ]atter half period is made in the same low level, while when the
level in the former half period is high as shown in Fig. 3F~ the level
in the latter half period is changed into the low level. Thus, in Fig.
3F the binary bit "0" is changed into "1 " in the Tn bit~ Accordingly,
as shown in Figs~ 3E and 3F, after arrows indicating the boundary
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between the Tn and Tn-~1 bits, the time code signals TC and TC' become
same in polarity and hence the respective bit signals of the time code
signals TC and TC ' after the Tn ~1 bit become same in polarity.
As a result, since the polarity of the bit signal of the t;me
code signal of one word at its end is fixed, the continuous time code
signals of one word are recorded on the magnetic tape with a continuous
recording pat-tern.
Next, the manner to carry out the electronic editing operation
will be described. A video signal which is not edited is recorded on
the magnetic tape of VTl~ 4 together with aninherent time code signal.
The editing VTR 5 selects the reproduced video signal from VTR 4 and
records the same on the magnetic tape together with a ne~,v time code
signal. In the case that the video signal of N frames reproduced from
the magnetic tape of VTR ~ at a certain portion is recordecl on the mag-
netic tape of VTR 5 as one cut, the video signals having frames more
than N frames by several frames (several m sec. to several 10 m sec)
are recorded together with an inherent time code signal and the video
signals of M frames of another one cut from the VTR 4 are recorded in
superimposed on the excessive portion of the former one cut video signals
i~e. erasing the excessive portion together with inherent time code signal
so as to make the junction between the video signal and time code signal
smooth .
Meanwhile, in the recording time code signal geneIating
apparatus 3, the time code signal is automatically delivered to the output
~5 terminal l4 in accordance with the constant travelling speed of the magnetic
tape in the VTR 5, but the time code data signal generator 12 can be preset
by the time code data signal ïrom the time code reading out circuit 10.
~ccordingly9 the recorcding of the video signal at the second cut in VTR
5 is carried out in the following manner. That is, the VTR 5 is rewound
to reproduce the video signal of the first one cut and the recording of the
S~
video signal of the second one cut from VTR ~ is initiated at the time
when the video signal Or N frames is reproduced completely. In this
case, the video signals more than M frames by several frames are also
recorded. Meanwhile, during time period in which the video signal Or
one cut is reproduced, the time code signal, which is recorded in corres-
pondence with the video signal of one cut, is reproduced and then read
out by the time code reading out circuit 10, and the termination oî the video
signal of N frames is detected by the read-out time code signal. Then,
the time code data signal from the time code reading out circuit 10 at that
time is fed to the time code data signal generator 12 to preset the same,
and ~hereafter the time code signal corresponding to the video signal at-
the second cut is recorded continuously on the magnetic tape~
~s the above information signal, an audio signal of PCM and
so on could be used in addition to the video signal of a television signal,
and as the recording medium, a magnetic medium such as a magnetic disc,
magnetic drum or the like and a recording medium of an optical system,
pressure sensitive system and so on can be used in addition to the mag-
netic tape.
Further, it is of no need that the change of the binary bit
of the specific bit signal in the time code signal consisting Or bi-phase
coded signals is limited from "0" to "1 " but the change could be carried
out from "1 " to "0".
According to the present invention described as above, a
signal generating apparatus is provided by which even if the time code
signal of word unit consisting of bi phase coded signals is recorded
on the recording medium continuously in a desired number, the recording
time coded signal of word unit consisting of the bi-phase coded signals
with no discontinuity at the junction point between adjacent time coded
signa]s can be produced. ~ccordingly, if such time coded signal is
recorded on the recording medium per word unit in correspondence
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with the track unit, f;eld unit or frame unit of the information signal,
the assemble edition of the info:rma-tion signal at the track unit9 field unit
or ïrame unit thereof can be easily carried out.
It will be apparent that many modirications and variations
could be effected by one skilled in the art without departing ïrom the
spirits or scope of the novel concepts oï tlle present invention.
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