Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ACKGROIJND OF THE INVENTION
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Field of the Invention
This invention relates generally to recording
apparatus and, more particularly, to a recording apparatus
having a digital signal input for recording such input
digital signal on a record medium.
Descri tion of the Background
P _ _
Digital tape recoraers that use a rotary head to
record an audio signal in the form of pulse code modulation
~PCM~ digital data on a magnetic tape are known. This kind
of digital tape recorder is frequently called a rotary
head-type digital audio tape recorder ~R-DAT). In such
R-DAT apparatus, a magnetic tape is obliquely wrapped around
a small rotary drum of about 30 mm in diameter over an
angular extent of 90, for example. Two rotary heads having
different azimuth angles are mounted on the ro~ary drum with
an angular separation of about 180 between them. These two
rotar~ heads are rotated at a rate of 2000 r.p.m., for
example, and the two rotary heads alternately scan the width
of the magnetic tape by an amount corresponding to the tape
wrappina angle of 90. Typically, the audio signal i5
sampled at a sampling fre~uency of 48 kHz and each sampled
value is processed in the so-called 16-bit linear
quantization manner, thereby producing the PCM data. The
PCM data is time-compressed by a time-compressing ratio
based upon the tape wrap angle of 90 at every 1/2 rotation
period of the rotary head and is subse~uently recorded on
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the magnetic tape by the rotary heads as a series of
adjacent slanted tracks.
Upon playback, the PCM data is reproduced from the
magnetic tape by the two rotary heads and is decoded,
time-expanded, and then reconverted into an analog audio
signal. In this kind of digital recorder, in addition to
the PCM data, sub-codes such as a time coae, a program
number, a start identifying signal or the like are also
recorded on each track in specified regions different than
those where the PCM data is recorded. Generally, a switch
is provided that permits the user to switch input sources,
for example, between an analo~ audio signal and a digital
signal, such as from a broadcast satellite or the like. llhe
selected input signal is then apportioned between the two
rotating heads and recorded in slant tracks on the tape.
Upon playback, the signals reproduced by the rotary heads
are amplified and passed through a switching circuit before
being fed through an error correction circuit to a
digital-to-analog convertor. The output from the error
correction circuit is typically employed to detect the
sub-code information, which is used to control a
micro-computer included in the recording apparatus. In such
digital recorders, if the digital audio signal at the input
changes either by being interrupted or by having an altered
sampling rate, the recorder continues in the recording mode
and results in an unstable signal being recorded on the
magnetic medium. Such unstable signal is undesirable and
produces annoying clicks and the like during playback.
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OBJECTS AMD SUMMARY OF THE INVENTION
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Accordingly, it is an object of the present
invention to provide a method and apparatus for recording a
signal that can eliminate the above-noted defects inherent
in the prior art.
Another object of this invention is to provide a
recording apparatus that can produce excellent recordings
even when the condition of the digital signals supplied to
the input terminal changes.
A further object of this invention is to provide a
recording apparatus that can avoid an undesired, unstable
signal from being recorded on the recording medium.
A still further object of this invention is to
provide a recording apparatus that can indicate to the user
that the recording apparatus has been automatically set into
a recording pause mode.
Still another object of the invention is to
provide a recording apparatus that can prevent the user from
being ill at ease and overl~ concerned when a recording
pause mode continues for what may seem to be a long period
of time.
~ n accordance with one a~spect of the present
invention, there is provided a recording apparatus that has
an input kerminal for receiving a digital signal, a
recording mechanism for recording the digital input signal
onto a record medium and which includes a detector that
detects whether the condition of the digital input signal
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has changed, and a mode setting system for setting the
apparatus into various operating modes including the
recording mode, a pause mode, and a recording stop mode. A
system is provided for operating a recording mode setting
mechanism so that the recording apparatus is set in the
recording mode and for operating a pause mode setting
mechanism to set the recording apparatus into the pause mode
when the detecting means detects that the condition o the
input digital signal has changed while the recording
apparatus has been in the recording mode. A system is
provided to release the pause mode setting mechanism when
the detecting means detects that the input condition of the
digital input has remained steady for a predetermined period
of time while the apparatus is in the pause mode and thereby
operates the recording mode setting mechanism to set the
recording mode back into a recording mode. The invention
then provides a means for releasing the pause mode setting
mechanism when the detector detects that the input condition
has changed within a predetermined time while in the pause
mode and setting the recording apparatus into the stop mode.
The above and other ob~ects~ features and
advantages of the present invention will become apparent
from the followinq detailed description of illustrative
embodiments thereof to be read in conjunction with the
accompanying drawings, in which like reference numerals
identify the same or similar elements.
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BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a schematic in block diagram form o-f an
R-~AT recording apparatus embodying the present invention;
Fig. ~ is a flow chart useful in explaining the
operation of the pr~sent invention; and
Figs~ 3A and 3B are pictorial representations of
respective modes of operational indicators of the R-DAT
recording apparatus.
DETAILED DESCRIPTION OF PREFERRED E~IBODIMENTS
The embodiment of the present invention described
herein-below is applied to a R-DAT recording apparatus as
shown for example in Fig. 1. This R-DAT recording apparatus
is operated in accordance with the flow chart of Fig. 2. In
Fig. 1, an analog audio signal fed to input terminal 1 lS
supplied through a low pass filter 2 and through an
analog-to~digital convertox 3 (A/D), where it is converted
into a digital audio signal using a sampling frequency of
48kEIz and the so-called 16-bit linear quantization method.
The output of the A/D convertor 3 is fed to a fixed terminal
4a of switch 4, whose output in turn is fed to an input of a
recording signal generating circuit 5. In the event that an
original digital signal is available for recording, such
digital signal is fed in at input terminal 6 to a digital
I/O circuit 41 and as an output therefrom to another fixed
terminal 4b of switch 4. Accordingly, upon operation of
switch 4, either the digitally converted analo~ audio signal
fed in at terminal 1 or the original digital signal, which
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might be provided from a tuner for satellite broadcasts or
from another R-DAT recording apparatus, fed in ak terminal 6
is connected to recording signal generating circuit 5.
The timing of recording signal generating circuit
5 is controlled by a signal from a timing generator 7 so
that the recording signal generating circuit 5 can perform
the necessary signal processing operations such as -~he
addition of an error correcting code, data interleaving,
modulation, and the like. Accordingly, the output of
recording signal generating circuit 5 is a serial recording
data signal corresponding to one track and is fed to an
input terminal of switching circuit 8. Switching circuit 8
is adapted in the well-known fashion to switch the input
signal between rotary heads llA and llB so that the switch 8
is alternately changed in position during each respective
1/2 rotation period that corresponds to the tape contact
period of rotary head llA and of rotary head llB, in
response to a switching signal from timing ~enerating
circuit 7. This switching signal from timing generator 7 is
preferably produced in response to pulses indicating the
rotary phase of rotary heads 11A and llB from a pulse
generator, not shown.
The digital recording data from switching circuit
8 is fed through recording amplifiers 9A and 9B and then
supplied through fixed contents R of switching circuits lOA
and lOB to rotary heads llA and llBr respectively, which
record the data on a magnetic tape as slanted tracks. The
magnetic tape 14 is shown in Fig. 1 as being wound between
take-up and supply reels 12 and 13, respectively~
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Upon playback, signals reproduced from magnetictape 14 by rotary heads llA and llB are fed through fixed
contacts P of switches lOA and lOB, respectively, to
playback amplifiers 15A and 15B. The outputs of playback
amplifiers 15A and 15B are fed to the fi~ed contacts of a
switch 16, which is under control of switching signals from
the timing generator circuit 7 to alternately change the
switch connection during each 1/2 rotation period that
includes the tape contacts periods of rotary heads llA and
llB.
The output of switching circuit 16 is fed through
an equalizer circuit 17, a comparator circuit 18, and a
phase~locked loop circuit (PLL) 19 to an error correcting
circuit 20. In the error correcting circuit 20 any errors
that may be present and that can be corrected by the earlier
provided error correction codes and parity symbols are
corrected. The equalizer 17, comparator 18, and PLL circuit
19 comprise the so-^called electro-magnetic transducing
system, as known heretofore~ The output of error correction
circuit 20 is fed to a digital~to-analog convertor ~D/A) 21
and converted into an analog signal that is then passed
through a low-pass filter (LPF) 22 and made available at an
output terminal 23. This signal at terminal 23 then in the
appropriate circumstances is the original analog audio
signal that can be fed to a suitable playback transducer of
the audio system.
The output signal from error correcting circuit 20
is also fed into the digital I/O circuit 41 and also made
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a~ailable as a digital output at digital output terminal 24.
In addition, $he digital output from error correcting
circuit 20 is also fed to a sub-code microcomputer 25 that
operates as an interface to extract the sub-cQde signal that
typically includes the timing code, the program number, the
start ID signal and the like.
rThe operation of the entire recording apparatus
may be controlled by a system conkroller 26 that would
include a number of operational control buttons or switches,
such as the play control, the stop button~ and the like that
although not shown are necessary for operation of the
recording apparatus. Accordingly, the system controller 26
is seen to provide suitable control signals to digital I/O
circuit 41 and error correcting circuit 20, for example.
During recording, digital data at the sampling frequency is
fed through digital I/O circuit 41 that operates to detect
any change in sampling frequency Fs that might occur in the
incoming digital audio signal fed into input terminal 6.
The result of this detection of any change in the sampling
frequency Fs is fed to system controller 26. In the event
that a change in the sampling frequency Fs of the incoming
digi~al audio signal is detected by digital I/O circuit 41,
data of various sampling frequencies are sequentiall~,J
supplied from the system controller 26 to the digital I/O
circuit 41, which detects the sampling frequency Fs of the
incoming digital audio signal, thereby changing a circuit
constant or the like to accommodate for this change in
sampling frequency. For e~ample, the sampling frequency of
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the incoming digital audio signal from a broadcast satellite
tuner may have a samplinq frequency of 32kHz, 44kHz, or
48kHz and it i5 data concerning these different requencies
that i9 provided to I/O circuit 41 by system controller 26.
System controller 26 also provides an input signal
to a drum servo circuit 30 that contrc,ls a drum motor 31
; that rotates the rotary drum (not shown) on which rotar~
heads llA and llR are mounted. Svstem controller 26 also
provides a control signal to a reel drive circuit 32 that
provides drive signals to the reel drive motors 33 and 34
that operate take-up and supply reels 12 and 13,
respectively.. System controller 26 provides a mode (pla~,
fast forward, reverse) switching signal to reel drive
circuit 32, so that the level of the drive signals supplied
to reel motors 33 and 34 can be changed accordingly.
Similarly, system controller 26 provides a control signal to
a capstan servo circuit 35 *hat operates to control a
capstan motor 37 that rotates a tape drive capstan, shown
schematically at 36. Of course, also provided but not shown
are a pinch roller for capstan 36, and a plunger circuit for
controlling the operation of the pinch roller against
capstan 36. System controller 26 receives as an input
signal, in additional to the information from the di~ital
I/O circuit 41, a signal from an RF envelope detecting
circuit 38 that has as an input the reproduced digital
signal from switching circuit 16.
As pointed out hereinabove, one problem present in
the R-DAT recording apparatus is that durin~ the recording
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operation if the aigital signal being fed in at digital
input terminal 6 changes, either the sampling frequency Fs
changes or the digital signal is interrupted, the recording
operation continuous regardless. It is this situation that
produces the undesired signals, such as clicks or pops and
the like, that are recorded on maqnetic tape 14.
Upon operating the apparatus of Fig. 1 in
correspondence with the procedure shown in Fig. 2, this
undesirable recording situation can be alleviated. Turning
then to the flow chart of Fig. 2, following the Start of the
operation, it is initially determined at decisional step ST1
whether the digital audio signal fed in at input terminal 6
is being recorded. If such digital input signal at terminal
6 is not being recorded then the routine simply exits to a
Return to the main program command located at the end of
this sub-routine.
On the other hand, if it is determined at step ST1
that the digital input signal at terminal 6 is being
recorded, then the program proceeds to the next decisional
step ST2 where it is determined whether the supply of the
digital audio signal at digital input terminal 6 is being
interrupted or not. In this operation, the digital I/O
circuit 41 detects the presence or absence of the input
audio signal and the results of that detection are supplied
to the system controller 26 that carries out the above
decision~ For example, it is determined that the supply of
digital audio signal at input terminal 6 is continuous and
not interrupt d, as represented by a NO in decisional step
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ST2, the sub-routine goes to the next decisional step ST3.
At step ST3 determination is made whether the sampling
frequency Fs of the digital audio input signal fed at input
terminal 6 is undergoing change. As noted hereinabove, in
the embodiment of Fig. 1 data representing the current
sampling frequency is supplied from system controller 26 to
digital I/O circuit 41 where it is compared with the
sampling frequency Fs. Thus, any change of sampling
frequenc~ Fs is detected at digital I/O circuit 41 and the
results thereof are fed to and judged by system controller
26. On the other hand, if it is determined that sampling
frequency Fs of the digital audio signal is not changed, a
NO is output at step ST3 and the sub-routine returns to the
main operating program.
If it is determined that the sampling frequency
has changed then the sub-routine moves to step ST4 where the
R~DAT recording apparatus is set into the pause mode,
represented as REC pause. This pause mode is also selected
i it is determined in step ST~ that the input signal is
interrupted, so that either a sampling frequency change or
signal interruption results in the setting of the R-DAT into
the recording pause mode at step ST4.
While the recording apparatus is set into the
pause mode in step ST4, the next decision is made at step
ST5 as to whether the digital audio signal is being supplied
to input terminal 6. If so, the sub-routine moves to
decisional step ST6 where it is determined whether the
sampling ~requenc~ of the digital audio signal has
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stabilized. Of course, such stabili~ation can be easily
determined by simply detecting the sampling fre~uency Fs.
As pointed out above, in this case, data representing the
various sampling frequencv values can be sequentially fed
from system controller 26 to digital I/O circuit A1, wherein
such data can be compared to the actual sampling fre~uency
Fs of the signal being received at input terminal 6.
Sampling frequency Fs is then detected by digital I/O
circuit 41 and the detection results fed to and judged by
system controller 26. If it is determined that sampling
frequency Fs has not stabilized a NO is output from step ST6
and fed to the next decision ST7 where it is determined
whether a predetermined period of time, for example, one
minute, has passed after the initial R-DAT setting into the
pause mode as that occurred in step ST4. If at step ST7 it
is determined that a minute has elapsed from the time that
the R-DAT apparatus is set into the pause mode, then a YES
is produced at step ST7 and the sub-routine moves to ST8
where the R-DAT apparatus is set into the stop pause mode.
:In the stop pause mode, rotation of the rotary
drum on which heads llA and llB are mounted and rotation of
the capstan 36 are stopped and the mechanical elements of
the R-DAT recording apparatus are released from the pause
mode and set into the stop mode. Upon having set the
mechanism into the stop pause mode, the sub-routine moves to
;step ST9 that serves to command the light emitting diode
that serves as the recording indicator to flash and then the
sub-routi.ne returns to the step ST5.
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On the other hand, if in step ST7 it is determined
that the time limit has not elapsed, as represented by a NO,
the program then moves back to step ST5 after passing
through the step ST9 whereat the recorcling indicator is
caused to flash. Accordingly, it is seen that when the
digital audio signal is not supplied at: input terminal 6 or
when the sampling frequency is not stable even though the
audlo signal is being supplied, the recording indicator is
caused to flash at step ST9, thereby indicating that the
R-DAT recording apparatus is set into the recording pause
mode.
Such recording pause mode is pictorially
represented in Fig. 3B r which represents a first light
emitting diode 51 that indicates the forward running mode, a
second light emitting diode 52 that indicates the recording
mode, and a third light emitting diode 53 that indicates the
pause mode of the R-DAT.~ Fiq. 3B is intended to represent
that light emitt1ng diodes 51 and 53 are energized or
illuminated, while light emitting diode 52 is caused to
flash. On the other hand, Fig. 3A illustrates that the
R-DAT is set into the recording mode in which light emitting
diodes 51 and 52 are turned on, while light emitting diode
53 representing pause is turned off.
If it is determined in step ST6 that sampling
frequency Fs is stable then the next decisional step ST10 is
performed whereat it is determined whether one second has
passed since the time the sampling frequenoy was stabilized.
If it is determined in step ST10 that the sampling frequenc~
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is not stable for a period of one second, then this step is
repeated continuously. It is noted that when the sampling
frequency Fs of the digital audio signal fed in at input
terminal 6 is being chan~ed, the necessary switching of the
circuit constant and the like will be carried out within a
time period of one second.
On the other hand, if it is determined in step
ST10 that the sampling frequency Fs is stabilized, the
sub-routine moves to step ST11 at which the R-DAT recording
apparatus is set into the reverse or rewind mode. Upon
setting the R-DAT recording apparatus into the rewind mode,
it is then determined in step ST12 whether one second has
elapsed. If not, this time check is executed continuousl~.
The provision of setting the R-DAT apparatus into
the rewind mode at step ST11 is p~rformed to erase by an
overwriting operation an undesired or unstable signal that
was recorded on magnetic tape 14 while the R-DAT apparatus
was set in the pause mode when the supplying of the digital
audio signal at input terminal 6 was interrupted or when the
sampling frequency Fs was changed. The duration of the time
period in step ST12 is not limited to one second but ma~ be
longer than the time in which the undesired or unstable
signal was recorded. If if it determined that one second
has passed after the R-DAT recording apparatus was set into
the rewind mode, as represented by a YES at step ST12, the
sub-routine procedes to step ST13 where the R~DAT is set
into the recording mode and the sub-rou~ine returns to the
main program.
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According to this embodiment OL the present
invention, if any change in the digital input signal at
input terminal 6 takes place, either b~ the supply of the
signal ~eing interrupted or by the sampling frequency Fs
being changed, the R DAT recording apparatus is quickly set
into the pause mode. If the supply of the digital audio
signal to input terminal 6 has not stabilized within one
minute after the setting into this pause mode, the recording
apparatus is set into the stop pause mode. In the pause
mode, as well as in the stop pause mode, a light emitting
diode 52 is caused to flash indicating that the recording
apparatus remains set in the recording pause mode. While in
the recording pause mode when the digital input signal at
terminal 6 becomes stabilized the recording apparatus is set
in the rewind mode for one second and after one second has
passed the recording apparatus is then returned to the
recording mode.
Thus, as seen from the above, when the condition
of the audio signal being supplied at input terminal 6
changes the recording apparatus is placed into a pause mode
ana then into a stop pause mode so that after the input
digital signal becomes stabilized, magnetic tape 14 is then
rewound by a tape length corresponding to the duration of
time during which the undesired or unstable signal was
recorded and then recording is commenced again. Therefore~
even when the supply of the digital input signal changes any
undesirable or unstable signal is prevented from being
recorded and an excellent recording is produced.
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OE course, as seen in the above, when the supply
of the digital audio signal to input terminal 6 does not
stabili~e within one minute after the recording apparatus
has been set into the pause mode, then the apparatus is set
into the stop pause mode thereby preventing the magnetic
tape from being damaged. Further, because light emitting
diode 52 flashes to indicate that the apparatus is set into
the recording pause mode, such as the pause mode or the stop
pause mode, there is a positive indication to the user that
there should be no concern about the existence of a long
recording pause mode.
In the system of Fig. 2, steps ST7 and ST8 are
provided in order to protect magnetic tape 14 from being
damaged and, thus, are not always required. In addition,
the time limit of one minute in ST7 may be selected based
upon individual system requirements.
Furthermore, although light emitting diode 52 is
adapted to flash to indicate that the recording apparatus
has been set in the recording pause mode, all of the light
emitting diodes 51, 52, and 53, could be made to flash. In
addition, an individual indicating element could also be
provided.
While the above embodiment is directed to a R-DAT
recording apparatus using a tape, the present invention
could be similarly applied to any recording apparatus
employing a disc, semiconductor memory, or the like as the
recording medium
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It should be understood that the above is
presented by way of example only and many modifications and
variations could be effected by one skilled in the art
without departing form the spirit or scope of the novel
concepts of the invention, which should be determined by the
appended claims.
