Method and apparatus for dubbing a recording tape loaded with information

Each of slave recorders includes a rotary drum, heads mounted on the rotary drum at positions spaced from a phase reference position on the rotary drum by different angular intervals respectively, and an arrangement for selecting at least one from the heads as an active head in accordance with a designated recording mode. Non-delayed stream data are delayed by a delay time interval to form delayed stream data. A distributor operates for distributing the delayed stream data to the slave recorders. Each of the slave recorders records the delayed stream data on a slave recording medium by the active head. The delay time interval corresponds to the angular interval between the phase reference position and the position of the active head.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of dubbing information from a recording tape onto other recording tapes. This invention also relates to an apparatus for dubbing information from a recording tape onto other recording tapes.

2. Description of the Related Art

A conventional simple dubbing system reproduces analog information from a recording tape, and records the reproduced analog information on another recording tape. A prior-art multiple dubbing system reproduces analog information from a recording tape, and records the reproduced analog information on a plurality of recording tapes at the same time. The prior-art multiple dubbing system is incapable of handling digital information.

SUMMARY OF THE INVENTION

It is a first object of this invention to provide an improved method of dubbing information from a recording tape onto other recording tapes.

It is a second object of this invention to provide an improved apparatus for dubbing information from a recording tape onto other recording tapes.

A first aspect of this invention provides an apparatus for dubbing information onto a plurality of slave recording mediums. The apparatus comprises a plurality of slave recorders each including a rotary drum, heads mounted on the rotary drum at positions spaced from a phase reference position on the rotary drum by different angular intervals respectively, and means for selecting at least one from the heads as an active head in accordance with a designated recording mode; means for delaying non-delayed stream data by a delay time interval to form delayed stream data; and a distributor for distributing the delayed stream data to the slave recorders, wherein each of the slave recorders records the delayed stream data on a slave recording medium by the active head; wherein the delay time interval corresponds to the angular interval between the phase reference position and the position of the active head.

A second aspect of this invention provides a method of dubbing information onto a plurality of slave recording mediums. The method comprises the steps of delaying non-delayed digital data by a delay time interval to form delayed digital data; distributing the delayed digital data to slave recorders each including a rotary drum, and at least one head mounted on the rotary drum; and recording the delayed digital data on a plurality of slave recording mediums by the slave recorders; wherein the delay time interval corresponds to a phase of a position of the head relative to a phase reference on the rotary drum.

A third aspect of this invention is based on the second aspect thereof, and provides a method further comprising the step of generating parity data in response to the delayed digital data.

A fourth aspect of this invention is based on the second aspect thereof, and provides a method further comprising the steps of generating parity data in response to the non-delayed digital data, checking the non-delayed digital data in response to the parity data, and indicating a result of said checking.

A fifth aspect of this invention is based on the second aspect thereof, and provides a method further comprising the steps of storing original digital data into a recording disk, and reading out the original digital data from the recording disk as the non-delayed digital data.

A sixth aspect of this invention is based on the second aspect thereof, and provides a method further comprising the step of descrambling scrambled digital data into the non-delayed digital data.

DETAILED DESCRIPTION OF THE INVENTION

A prior-art dubbing system will be explained below for a better understanding of this invention.

In the prior-art dubbing system of FIG. 1 , the master VTR 1 reproduces an analog video signal and an analog audio signal from a master magnetic tape. The master VTR 1 feeds the reproduced analog video signal to the video distributor 2 . The master VTR 1 feeds the reproduced analog audio signal to the audio distributor 3 .

The video distributor 2 and the audio distributor 3 compose a first stage while the video distributor 4 and the audio distributor 5 form a second stage following the first stage. The device 2 distributes the analog video signal to video lines, one of which leads to the video distributor 4 . Thus, the video distributor 4 receives the analog video signal. The device 3 distributes the analog audio signal to audio lines, one of which leads to the audio distributor 5 . Thus, the audio distributor 5 receives the analog audio signal. The device 4 distributes the analog video signal to the slave recorders 61 , . . . , and 6 n . The device 5 distributes the analog audio signal to the slave recorders 61 , . . . , and 6 n.

The slave recorders 61 , . . . , and 6 n dub the analog video signal and the analog audio signal onto slave magnetic tapes. Accordingly, the analog video signal and the analog audio signal are dubbed from the master magnetic tape onto the slave magnetic tapes.

During operation of the prior-art dubbing system in FIG. 1 , the master VTR 1 is controlled by the system controller 10 while the slave recorders 61 , . . . , and 6 n are controlled by the slave controller 8 . The card reader 11 and the system controller 10 can communicate with each other. The line controller 9 and the slave controller 8 can communicate with each other. Furthermore, the line controller 9 and the system controller 10 can communicate with each other.

Each of the slave recorders 61 , . . . , and 6 n has a rotary drum d . As shown in FIG. 2 , four heads h 1 , h 2 , h 3 , and h 4 are mounted on the rotary drum d . The heads h 1 and h 2 are diametrically opposed to each other. Similarly, the heads h 3 and h 4 are diametrically opposed to each other. A suitable device (not shown) generates detection pulses which depend on the rotational speed of the rotary drum d . Another suitable device (not shown) generates a D-FF signal in response to the detection pulses. The heads h 1 , h 2 , h 3 , and h 4 record the analog video signal and the analog audio signal on the slave magnetic tape on a frame-by-frame basis responsive to the D-FF signal. Specifically, the heads h 1 and h 2 are used for the analog video signal while the heads h 3 and h 4 are used for the analog audio signal. The heads h 1 and h 3 are assigned to a first channel 1 ch . The heads h 2 and h 4 are assigned to a second channel 2 ch . As shown in FIG. 3 , the analog video signal (data) is alternately fed to the heads h 1 and h 2 (the first and second channels 1 ch and 2 ch respectively) at a period equal to half the period of the D-FF signal. The analog audio signal (data) is alternately fed to the heads h 3 and h 4 (the first and second channels 1 ch and 2 ch respectively) at a period equal to half the period of the D-FF signal.

In the prior-art dubbing system of FIG. 1 , the signal checker 71 monitors signals at the output sides of the master VTR 1 , that is, at the input sides of the video distributor 2 and the audio distributor 3 . The signal checker 72 monitors signals at the output sides of the video distributor 2 and the audio distributor 3 , that is, at the input sides of the video distributor 4 and the audio distributor 5 . The signal checkers 73 and 74 monitor signals at the output sides of the video distributor 4 and the audio distributor 5 , that is, at the input sides of the slave recorders 61 , . . . , and 6 n . Each of the video distributors 2 and 4 and the audio distributors 3 and 5 has a gain adjustment function. The prior-art dubbing system of FIG. 1 is incapable of handling a digital video signal and a digital audio signal.

Embodiment

FIG. 4 shows a D-VHS digital dubbing system according to an embodiment of this invention. The digital dubbing system of FIG. 4 includes a DLT (digital linear technology) device 20 , a master server 21 , a host personal computer (PC) 22 , a slave controller 23 , lines 24 and 31 , slave recorders 2501 , 2502 , 2503 , . . . , and 2517 , a distribution amplifier 26 , a monitor decoder 27 , an MPEG decoder 28 , and a monitor 29 . The DLT device 20 includes a tape drive developed by Digital Equipment Corporation. A DLT tape (a master magnetic tape) 30 can be placed in and driven by the DLT device 20 . The host personal computer 22 includes a selector and a start button. It should be noted that the total number of the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 may differ from 17 .

The DLT device 20 is connected with the master server 21 via a SCSI. The master server 21 and the host personal computer 22 are connected with each other via an Ethernet. The master server 21 is connected with the distribution amplifier 26 . The slave controller 23 is connected with the host personal computer 22 via an RS-232C interface. The slave controller 23 is connected with the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 31 . The distribution amplifier 26 is connected with the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 24 . The monitor decoder 27 is connected with the distribution amplifier 26 . The MPEG decoder 28 is connected with the monitor decoder 27 . The monitor 29 is connected with the MPEG decoder 28 .

As shown in FIG. 5 , the master server 21 includes a personal computer (PC) 21 a , a hard disk drive (HDD) 21 b , and an interface (I/F) board 21 c . The personal computer 21 a is connected with the DLT device 20 . In addition, the personal computer 21 a is connected with the hard disk drive 21 b and the interface board 21 c . The interface board 21 c is connected with the distribution amplifier 26 .

As shown in FIG. 5 , the distribution amplifier 26 includes a first distributor 26 a , a second distributor 26 b , and a standard signal generator (SSG) 26 c . The first distributor 26 a is connected with the interface board 21 c in the master server 21 . In addition, the first distributor 26 a is connected with the monitor decoder 27 .

Furthermore, the first distributor 26 a is connected with the second distributor 26 b and the standard signal generator 26 c . The second distributor 26 b is connected with the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 24 .

Operation of the digital dubbing system of FIG. 4 can be changed among different modes including a preliminary mode and a digital dubbing mode. The preliminary mode of operation precedes the digital dubbing mode of operation.

During the preliminary mode of operation, the DLT device 20 reproduces digital stream data from a DLT tape 30 . The DLT device 20 feeds the reproduced stream data to the master server 21 . The personal computer 21 a in the master server 21 receives the reproduced stream data. The personal computer 21 a outputs the stream data to the hard disk drive 21 b and controls the hard disk drive 21 b , thereby storing the stream data into a recording medium (a hard disk) within the hard disk drive 21 b as a file having a name.

In some cases, digital stream data of interest are recorded on only one DLT tape 30 . In these cases, the DLT device 20 reproduces digital stream data from only one DLT tape 30 . In other cases, digital stream data of interest are divided into successive portions recorded on a plurality of DLT tapes 30 respectively. In these cases, the DLT device 20 sequentially reproduces digital stream data from a plurality of DLT tapes 30 .

The preliminary mode of operation will be explained below in more detail. During the preliminary mode of operation, when a first DLT tape 30 is set in the DLT device 20 , the DLT device 20 outputs a corresponding tape set signal to the personal computer 21 a in the master server 21 . The personal computer 21 a makes an information file and a stream data accommodation file in the recording medium within the hard disk drive 21 b in response to the tape set signal. Subsequently, the personal computer 21 a controls the DLT device 20 to read out information data from the first DLT tape 30 . The information data indicate the total size or the total track size of related digital stream data (digital stream data to be dubbed). The information data also indicate a title number and a title name concerning the stream data. The personal computer 21 a receives the information data from the DLT device 20 . The personal computer 21 a controls the hard disk drive 21 b , thereby storing the information data into the information file (in the recording medium within the hard disk drive 21 b ). Then, the personal computer 21 a outputs a signal to the DLT device 20 which orders the reproduction of a first unit segment of digital stream data from the first DLT tape 30 . As a result, the DLT device 20 reproduces the first unit segment of the stream data from the first DLT tape 30 . The personal computer 21 a receives the first unit segment of the stream data from the DLT device 20 . The personal computer 21 a controls the hard disk drive 21 b , thereby storing the first unit segment of the stream data into the stream data accommodation file (in the recording medium within the hard disk drive 21 b ). The personal computer 21 a calculates the size (the amount) of digital stream data currently placed in the stream data accommodation file. Thereafter, the personal computer 21 a outputs a signal to the DLT device 20 which orders the reproduction of a second unit segment of the stream data from the first DLT tape 30 . As a result, the DLT device 20 reproduces the second unit segment of the stream data from the first DLT tape 30 . The personal computer 21 a receives the second unit segment of the stream data from the DLT device 20 . The personal computer 21 a controls the hard disk drive 21 b , thereby storing the second unit segment of the stream data into the stream data accommodation file. The personal computer 21 a calculates the size (the amount) of digital stream data currently placed in the stream data accommodation file. The sequence of the unit-segment receiving step, the unit-segment storing step, the size calculating step is repetitively executed.

During the preliminary mode of operation, the DLT device 20 outputs an EOT (end of tape) signal to the master device 21 when the currently accessed point on the first DLT tape 30 reaches the tape end position. The personal computer 21 a within the master device 21 receives the EOT signal. The personal computer 21 a derives the total size of the stream data of interest (the stream data to be dubbed) from the information data in the information file. The personal computer 21 a repetitively compares the calculated size of the stream data in the stream data accommodation file with the total size. The personal computer 21 a repetitively decides whether or not the EOT signal is received before the calculated size of the stream data in the stream data accommodation file reaches the total size. In the case where the EOT signal is received before the calculated size of the stream data in the stream data accommodation file reaches the total size, the personal computer 21 a judges a next DLT tape (a second DLT tape) 30 to be present. In this case, the personal computer 21 a displays a command to replace the first DLT tape 30 in the DLT device 20 with a next one (a second DLT tape 30 ). Therefore, the first DLT tape 30 is removed from the DLT device 20 , and a second DLT tape 30 is set therein. According to steps similar to the previously-mentioned steps about the first DLT tape 30 , digital stream data are reproduced from the second DLT tape 30 by the DLT device 20 before being stored into the stream data accommodation file by the personal computer 21 a . Digital stream data on third and later DLT tapes 30 are similarly handled as long as the calculated size of the stream data in the stream data accommodation file does not reach the total size.

During the preliminary mode of operation, the personal computer 21 a repetitively compares the calculated size of the stream data in the stream data accommodation file with the total size as previously mentioned. When the calculated size of the stream data in the stream data accommodation file reaches the total size, the personal computer 21 a decides that all the stream data of interest have been reproduced and been stored into the stream data accommodation file. In this case, the personal computer 21 a controls the DLT device 20 to halt the reproduction of digital stream data from the current DLT tape 30 . Thus, the personal computer 21 a stops the reception of digital stream data from the DLT device 20 . As a result of the preliminary mode of operation, all the stream data to be dubbed are stored in the stream data accommodation file in the hard disc drive 21 b within the master server 21 .

A DLT tape 30 is formed with an array of slant recording tracks along which a signal containing digital stream data is recorded. In general, the stream data are of a scrambled version for copy protection. Each recording track on the DLT tape 30 is composed of equal-size data blocks sequentially arranged in the direction of the scanning by a head. The data blocks are also referred to as the sync blocks. As shown in FIG. 6 , one recording track has a sequence of a front margin area 91 of 2 sync blocks, a preamble area 92 of 3 sync blocks, a sub code area 93 of 4 sync blocks, a post-amble area 94 of 3 sync blocks, an IBG area 95 of 3 sync blocks, a preamble area 96 of 1 sync block, a main code area (data area) 97 of 336 sync blocks, and a post-amble area 98 of 2 sync blocks. Preferably, the post-amble area 98 is followed by a rear margin area. The main code area 97 and the sub code area 93 can be used for storing digital stream data.

During the preliminary mode of operation, the personal computer 21 a descrambles every unit segment of the reproduced stream data into a unit segment of the stream data of a non-scrambled version. Immediately thereafter, the personal computer 21 a controls the hard disk drive 21 b , thereby storing the unit segment of the non-scrambled version into the stream data accommodation file (in the recording medium within the hard disk drive 21 b ). Specifically, the personal computer 21 a generates key data in response to identification data peculiar to and owned by the master server 21 . The personal computer 21 a subjects the key data to a prescribed calculation procedure (a prescribed operation procedure), thereby generating an initial value for descrambling. The personal computer 21 a descrambles every unit segment of the reproduced stream data into a unit segment of the stream data of a non-scrambled version in response to the initial value for descrambling.

The personal computer 21 a operates in accordance with a control program stored in its internal memory or recording medium. FIG. 7 is a flowchart of a portion of the control program which relates to the preliminary mode of operation. The program portion in FIG. 7 is started in response to a tape set signal outputted from the DLT device 20 .

As shown in FIG. 7 , a first step S 1 of the program portion makes an information file in the hard disk drive 21 b . A step S 2 following the step S 1 makes a stream data accommodation file in the hard disk drive 21 b . After the step S 2 , the program advances to a step S 3 .

The step S 3 controls the DLT device 20 to read out information data from a current DLT tape 30 . The information data indicate the total size of related digital stream data (digital stream data to be dubbed). The step S 3 receives the information data from the DLT device 20 .

A step S 4 following the step S 3 controls the hard disk drive 21 b , and thereby stores the information data into the information file. After the step S 4 , the program advances to a step S 5 .

The step S 5 controls the DLT device 20 to reproduce a current unit segment of digital stream data from the DLT tape 30 . The step S 5 receives the current unit segment of the stream data from the DLT device 20 .

A step S 6 subsequent to the step S 5 controls the hard disk drive 21 b , and thereby stores the current unit segment of the stream data into the stream data accommodation file.

A step S 7 following the step S 6 decides whether or not an EOT signal is received from the DLT device 20 . When an EOT signal is received, the program returns from the step S 7 to the step S 3 .

Accordingly, in this case, the step S 3 and the later steps are executed for a next DLT tape 30 . On the other hand, when an EOT signal is not received, the program advances from the step S 7 to a step S 8 .

The step S 8 calculates the size (the amount) of digital stream data currently placed in the stream data accommodation file. The step S 8 derives the total size of the stream data of interest (the stream data to be dubbed) from the information data in the information file. The step S 8 compares the calculated size of the stream data in the stream data accommodation file with the total size to decide whether or not all the stream data of interest (the stream data to be dubbed) have been reproduced and been stored into the stream data accommodation file. When the calculated size is smaller than the total size, that is, when all the stream data of interest have not been reproduced and not been stored yet, the program returns from the step S 8 to the step S 5 . On the other hand, when the calculated size is equal to the total size, that is, when all the stream data of interest have been reproduced and been stored, the program exits from the step S 8 and then the current execution cycle of the program portion ends.

The step S 6 in FIG. 7 implements descrambling. Specifically, the step S 6 descrambles the current unit segment of the stream data into a unit segment of the stream data of a non-scrambled version. The step S 6 controls the hard disk drive 21 b , and thereby stores the unit segment of the non-scrambled version into the stream data accommodation file. In more detail, as shown in FIG. 8 , the step S 6 includes sub-steps S 11 , S 12 , and S 13 . The sub-step S 11 generates key data in response to identification data peculiar to and owned by the master server 21 . The sub-step S 12 which follows the sub-step S 11 subjects the key data to a prescribed calculation procedure (a prescribed operation procedure), thereby generating an initial value for descrambling. The sub-step S 13 which follows the sub-step S 12 descrambles the current unit segment of the stream data into a unit segment of the stream data of a non-scrambled version in response to the initial value for descrambling.

As previously mentioned, the preliminary mode of operation is followed by the digital dubbing mode of operation. Digital stream data are selected among digital stream data in the steam data accommodation file as designated digital stream data by operating the selector in the host personal computer 22 . In addition, the master server 21 and the line 24 are selected. Subsequently, the start button in the host personal computer 22 is depressed. When the start button is depressed, the host personal computer 22 transmits a start confirmation command to the master server 21 . The digital dubbing mode of operation is commenced in response to the start confirmation command.

The master server 21 receives the start confirmation command. The master server 21 reads out the information data from the information file in response to the reception of the start confirmation command. The information data indicate the total size or the total track size of related digital stream data (digital stream data to be dubbed), and also a title number and a title name concerning the stream data. The master server 21 returns the read-out information data to the host personal computer 22 as a response to the start conformation command. The master server 21 displays the read-out information data on its monitor screen. Also, the host personal computer 22 displays the information data on its monitor screen. Thereafter, the host personal computer 22 transmits a dubbing start command to the slave controller 23 . In the case where the slave controller 23 successfully receives the dubbing start command, the slave controller 23 returns a signal of command reception confirmation to the host personal computer 22 which represents the successful reception of the dubbing start command.

The host personal computer 22 receives the command reception confirmation signal. The host personal computer 22 transmits a stream data output command to the master server 21 in response to the reception of the command reception confirmation signal. The stream data output command contains an identification signal corresponding to the designated stream data. The master server 21 receives the stream data output command. The master server 21 extracts the identification signal from the stream data output command. The master server 21 selects the designated stream data among the stream data in the stream data accommodation file in response to the identification signal. The master server 21 transfers the designated stream data from the stream data accommodation file toward the distribution amplifier 26 . The distribution amplifier 26 receives the designated stream data. The distribution amplifier 26 delays the received stream data by a time interval depending on a recording mode, and distributes the delayed stream data to the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 24 . The slave recorders 2501 , 2502 , 2503 , . . . , and 2517 dub the stream data on slave magnetic tapes, respectively, by digital recording. In this way, the digital dubbing mode of operation is implemented. The distribution amplifier 26 passes the received stream data to the monitor decoder 27 . The contents of the stream data are transmitted from the monitor decoder 27 to the monitor 29 via the MPEG decoder 28 , being displayed on the monitor 29 . Thus, the contents of the stream data which are being dubbed are displayed on the monitor 29 .

During the digital dubbing mode of operation, the master server 21 generates information related to conditions of the progress of the dubbing. In addition, the master server 21 generates information related to alarm when a given warning state occurs. The master server 21 continuously or intermittently transmits the dubbing-progress-related information and the alarm-related information to the host personal computer 22 . The host personal computer 22 receives the dubbing-progress-related information and the alarm-related information. The host personal computer 22 displays the conditions of the progress of the dubbing on its monitor screen which correspond to the dubbing-progress-related information. The host personal computer 22 displays alarm occurrence time in response to the reception of the alarm-related information.

During the digital dubbing mode of operation, the host personal computer 22 continues to transmit a status request command to the slave controller 23 . The slave controller 23 receives the status request command. The slave controller 23 gets status information from each of the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 31 . The slave controller 23 returns the status information to the host personal computer 22 as a response to the status request command. The host personal computer 22 receives the status information. The host personal computer 22 successively displays the status information on its display screen.

When the transfer of the designated stream data to the distribution amplifier 26 from the master server 21 terminates, the master server 21 transmits an end command to the host personal computer 22 . The host personal computer 22 receives the end command. The host personal computer 22 transmits a stop command to the slave controller 23 in response to the reception of the end command. The slave controller 23 receives the stop command. In response to the reception of the stop command, the slave controller 23 transmits a recording stop command and a tape-cassette ejection command to each of the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 31 . The slave recorders 2501 , 2502 , 2503 , . . . , and 2517 receive the recording stop command and the tape-cassette ejection command. Each of the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 moves out of a recording operation state in response to the received recording stop command. Each of the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 ejects the cassette of the slave magnetic tape in response to the received tape-cassette ejection command. As a result, the digital dubbing mode of operation ends.

A specified file is provided in the host personal computer 22 . When the digital dubbing mode of operation ends, the host personal computer 22 loads the specified file with pieces of information which represent various dubbing-related parameters such as dubbing start time and dubbing end time. At a later stage, the contents of the dubbing can be known by referring to the information pieces in the specified file.

With reference to FIG. 5 , the DLT device 20 reproduces the stream data from the DLT tape 30 set therein. The master server 21 receives the reproduced stream data from the DLT device 20 . The master server 21 stores the received stream data into the stream data accommodation file in the hard disk drive 21 b via the personal computer 21 a.

The master server 21 reads out the stream data from the stream data accommodation file via the personal computer 21 a at a suitable timing such that the read-out stream data will fit the recording timings of digital dubbing by the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 and will conform to the D-VHS format. In general, the read-out stream data divide into first stream data DATA 1 and second stream data DATA 2 . In other words, the read-out stream data are composed of first stream data DATA 1 and second stream data DATA 2 . The master server 21 feeds the read-out stream data to the interface board 21 c from the personal computer 21 a . The stream data are outputted from the interface board 21 c of the master server 21 toward the distribution amplifier 26 as digital data Sig. A .

Specifically, the stream data are outputted from the interface board 21 c in synchronism with a clock signal (a bit clock signal) generated in the digital dubbing system. The clock signal is outputted from the interface board 21 c together with the stream data. The interface board 21 c generates parity data for checking conditions of the transmission of the stream data. The parity data are outputted from the interface board 21 c in synchronism with the clock signal. The interface board 21 c groups or combines the stream data, the parity data, and the clock signal into the digital data Sig. A . The interface board 21 c outputs the digital data Sig. A to the distribution amplifier 26 .

FIG. 9 shows a cable of the connection between the interface board 21 c and the distribution amplifier 26 . The connection cable has signal lines including ones as follows:

(1) a positive clock signal line CLK( ) and a negative clock signal line CLK( ) for the transmission of the clock signal;

(2) first and second ground lines SIGNAL GND;

(3) a first positive dubbing data signal line DATA 1 ( ), a first negative dubbing data signal line DATA 1 ( ), a second positive dubbing data signal line DATA 2 ( ), and a second negative dubbing data signal line DATA 2 ( ) for the transmission of the stream data;

(4) a positive parity data signal line PARITY( ) and a negative parity data signal line PARITY( ) for the transmission of the parity data;

(5) a positive sync signal line SYNC( ) and a negative sync signal line SYNC( ) for the transmission of a sync signal (a field sync signal or a frame sync signal);

(6) a positive frame discrimination data signal line SFG( ) and a negative frame discrimination data signal line SFG( ) for the transmission of picture-frame-frequency discrimination data indicating whether the frame frequency of a picture represented by the stream data is equal to 30 Hz or 29.97 Hz;

(7) a positive recording mode discrimination data signal line HS( ) and a negative recording mode discrimination data signal line HS( ) for the transmission of dubbing-recording-mode discrimination data indicating whether the dubbing recording mode is equal to a standard recording mode or a high-picture-quality recording mode (a standard-speed recording mode or a high-speed recording mode); and

(8) a first positive external data signal line EXT 1 ( ), a first negative external data signal line EXT 1 ( ), a second positive external data signal line EXT 2 ( ), and a second negative external data signal line EXT 2 ( ) for the transmission of external data.

Generally, the sync signal transmitted along the positive and negative sync signal lines SYNC( ) and SYNC( ) is generated by a suitable device in the digital dubbing system. For example, the sync signal may be produced on the basis of the output signal from the standard signal generator 26 c (see FIG. 5 ). Alternatively, the sync signal may be fed from an external with respect to the digital dubbing system. The digital dubbing system implements internal synchronization or external synchronization in response to such a sync signal. The stream data and the sync signal compose main data included in the digital data Sig. A .

With reference back to FIG. 5 , the digital data Sig. A from the master server 21 are fed to the first distributor 26 a in the distribution amplifier 26 . The first distributor 26 a branches the digital data Sig. A into first data and second data which are a first output signal and a second output signal respectively. The first data (the first output signal) are directed toward the monitor decoder 27 . The second data (the second output signal) are directed toward the second distributor 26 b . Specifically, the first distributor 26 a includes a through transmission line. The digital data Sig. A are propagated through the first distributor 26 a along the through transmission line before being outputted as the first data (the first output signal) toward the monitor decoder 27 . Accordingly, the digital data Sig. A are transmitted through the first distributor 26 a before reaching the monitor decoder 27 . The contents of the digital data Sig. A are transmitted from the monitor decoder 27 to the monitor 29 via the MPEG decoder 28 , being displayed on the monitor 29 . The first distributor 26 a generates the second data (the second output signal) from the digital data Sig. A . The second data (the second output signal) are outputted from the first distributor 26 a toward the second distributor 26 b as digital data Sig. B . The digital data Sig. B contain digital stream data which result from delaying the stream data in the digital data Sig. A by a time interval depending on the current recording mode. The digital data Sig. B contain parity data which are generated in response to the delayed stream data, and which replace the parity data in the digital data Sig. A .

The standard signal generator 26 c produces a reference signal (a standard signal). The standard signal generator 26 c feeds the reference signal to the first distributor 26 a . The first distributor 26 a generates and outputs the sync signal in response to the reference signal. In addition, the first distributor 26 a feeds the sync signal to the maser server 21 . The standard signal generator 26 c is capable of producing a new clock signal (a new bit clock signal) and a new sync signal.

The second distributor 26 b receives the digital data Sig. B from the first distributor 26 a , and distributes the digital data Sig. B to the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 24 . The second distributor 26 b implements parity check responsive to the parity data in the digital data Sig. B fed from the first distributor 26 a . Then, the second distributor 26 b outputs the digital data Sig. B toward the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 via the line 24 . The line 24 is formed by a cable similar in structure to the cable in FIG. 9 . Preferably, the second distributor 26 b informs the monitor 29 of the parity check results. In this case, the monitor 29 displays the parity check results.

The slave recorders 2501 , 2502 , 2503 , . . . , and 2517 are of the same structure. Therefore, only the slave recorder 2501 will be explained below in more detail.

As shown in FIG. 10 , the slave recorder 2501 includes a main section 25 a . The slave recorder 2501 includes three units (a unit 1 , a unit 2 , and a unit 3 ) similar to each other and following the main section 25 a . Each of the three units has an intermediate section 25 b , a recording section 25 c , a servo section 25 d , rotary heads 25 e and 25 f , and a control head 25 g . The main section 25 a is connected with the distribution amplifier 26 via the line 24 . The main section 25 a is connected with the slave controller 23 via the line 31 . The main section 25 a is connected with the intermediate section 25 b in each of the three units. The intermediate section 25 b is connected with the recording section 25 c and the servo section 25 d . The recording section 25 c is connected with the servo section 25 d and the rotary heads 25 e and 25 f . The servo section 25 d is connected with the control head 25 g.

The main section 25 a contains distributors 25 a 1 and 25 a 2 . The distributors 25 a 1 and 25 a 2 are connected between the distribution amplifier 26 and the intermediate section 25 b in each of the three units.

The main section 25 a receives a serial control signal CTL from the slave controller 23 via the line 31 . The main section 25 a can generate warning signals AA , B , and C related to the three units respectively. The main section 25 a transmits the warning signals A , B , and C to the slave controller 23 via the line 31 . The main section 25 a receives first stream data DATA 1 , second stream data DATA 2 , dubbing-recording-mode discrimination data HS/STD, picture-frame-frequency discrimination data SFG, and a sync signal from the distribution amplifier 26 via the line 24 .

The rotary heads 25 e and 25 f are mounted on a rotary drum. A slave magnetic tape is wound on the rotary drum. The rotary heads 25 e and 25 f rotate together with the rotary drum. The speed of rotation of the rotary heads 25 e and 25 f corresponds to either 60 Hz or 59.94 Hz (PAL or NTSC) in both the standard recording mode and the high-picture-quality recording mode (the high-speed recording mode).

The slave recorder 2501 has a self diagnosis function such as a parity check function. The slave recorder 2501 can output three warning signals (the warning signals A , B , and C ) regarding the three units therein respectively. The warning signals are transmitted to the slave controller 23 . By referring to the warning signals, the slave controller 23 can grasp the operating conditions of each of the three units in the slave recorder 2501 . The slave recorder 2501 distributes the first stream data DATA 1 and the second stream data DATA 2 among information streams. The slave recorder 2501 writes the information streams on slave magnetic tapes via the three units therein. Specifically, the first stream data DATA 1 and the second stream data DATA 2 are transmitted from the main section 25 a to the recording section 25 c in each of the three units via the intermediate section 25 b therein. The recording section 25 c in each of the three units records the first stream data DATA 1 and the second stream data DATA 2 on a slave magnetic tape via the rotary heads 25 e and 25 f . The recording section 25 c controls the recording of the first stream data DATA 1 and the second stream data DATA 2 in response to control information fed from the servo section 25 d . The dubbing-recording-mode discrimination data HS/STD and the sync signal are transmitted from the main section 25 a to the servo section 25 d in each of the three units via the intermediate section 25 b therein. The picture-frame-frequency discrimination data SFG are transmitted from the main section 25 a to the servo section 25 d in each of the three units via the intermediate section 25 b therein as a 29.97/30-Hz signal. The servo section 25 d in each of the three units generates a control signal on the basis of the dubbing-recording-mode discrimination data HS/STD, the sync signal, and the 29.97/30-Hz signal. The servo section 25 d records the control signal on the slave magnetic tape via the control head 25 g . In addition, the servo section 25 d generates control information on the basis of the dubbing-recording-mode discrimination data HS/STD, the sync signal, and the 29.97/30-Hz signal. The servo section 25 d feeds the control information to the recording section 25 c.

As shown in FIG. 11 , the first distributor 26 a in the distribution amplifier 26 includes an interface receiver 26 a 1 , an interface driver 26 a 2 , a selector circuit 26 a 3 , a parity check circuit 26 a 4 , a memory 26 a 5 , a memory control circuit 26 a 6 , a parity circuit 26 a 7 , an output circuit or an interface driver 26 a 8 , a sync separation circuit 26 a 9 , a PLL block 26 a 10 , a clock/sync generation circuit 26 a 11 , and an output circuit or an interface driver 26 a 12 .

The interface receiver 26 a 1 is connected with the interface board 21 c in the master server 21 . The interface receiver 26 a 1 is followed by the interface driver 26 a 2 , the selector circuit 26 a 3 , and the parity check circuit 26 a 4 . The interface driver 26 a 2 is connected with the monitor decoder 27 . The selector circuit 26 a 3 is connected with the memory 26 a 5 , the memory control circuit 26 a 6 , and the clock/sync generation circuit 26 a 11 . The memory 26 a 5 is connected with the memory control circuit 26 a 2 and the parity circuit 26 a 7 . The parity circuit 26 a 7 is connected with the interface driver 26 a 8 . The interface driver 26 a 8 is connected with the second distributor 26 b . The sync separation circuit 26 a 9 is connected with the standard signal generator 26 c . The sync separation circuit 26 a 9 is followed by the PLL block 26 a 10 and the clock/sync generation circuit 26 a 11 . The PLL block 26 a 10 is connected with the clock/sync generation circuit 26 a 11 . The clock/sync generation circuit 26 a 11 is followed by the interface driver 26 a 12 . The interface driver 26 a 12 is connected with the interface board 21 c in the master server 21 .

The PLL block 26 a 10 includes a phase error detection circuit 26 a 10 a , a low pass filter 26 a 10 b , a VCO (voltage controlled oscillator) 26 a 10 c , and a counter 26 a 10 d . The counter 26 a 10 d acts as a frequency divider. The phase error detection circuit 26 a 10 a is connected with the sync separation circuit 26 a 9 . The phase error detection circuit 26 a 10 a is also connected with the low pass filter 26 a 10 b and the counter 26 a 10 d . The low pass filter 26 a 10 b is connected with the VCO 26 a 10 c . The VCO 26 a 10 c is connected with the counter 26 a 10 d . The VCO 26 a 10 c is also connected with the clock/sync generation circuit 26 a 11 . The phase error detection circuit 26 a 10 a , the low pass filter 26 a 10 b , the VCO 26 a 10 c , and the counter 26 a 10 d compose a phase lock loop operating as a frequency multiplier.

The digital data Sig. A from the master server 21 are received by the interface receiver 26 a 1 . The received digital data Sig. A are fed from the interface receiver 26 a 1 to the interface driver 26 a 2 , the selector circuit 26 a 3 , and the parity check circuit 26 a 4 . The interface driver 26 a 2 outputs the digital data Sig. A to the monitor decoder 27 . Thus, the digital data Sig. A are propagated through the interface receiver 26 a 1 and the interface driver 26 a 2 before being transmitted to the monitor decoder 27 .

As shown in FIG. 12 , in the high-picture-quality recording mode (the high-speed recording mode), the fields represented by the first stream data DATA 1 and the second stream data DATA 2 in the digital data Sig. A have a prescribed phase relation with the sync signal. As shown in FIG. 13 , in the standard recording mode, the fields represented by the first stream data DATA 1 in the digital data Sig. A have a prescribed phase relation with the sync signal. The sync signal has a frequency of either 30 Hz or 29.97 Hz in both the high-picture-quality recording mode and the standard recording mode. The sync signal has a duty ratio of 1:1. The sync signal is the same as a switching pulse signal for providing alternate change between two heads in a pair (or each pair) on the rotary drum.

The standard recording mode uses only the first stream data DATA 1 . The high-picture-quality recording mode (the high-speed recording mode) uses both the first stream data DATA 1 and the second stream data DATA 2 . As shown in FIGS. 12 and 13 , in the standard recording mode or the high-picture-quality recording mode, a field 1 represented by the first stream data DATA 1 and the second stream data DATA 2 in the digital data Sig. A occurs during a time interval t 1 for which the sync signal is in its high-level state. In addition, a next field 2 represented by the first stream data DATA 1 and the second stream data DATA 2 in the digital data Sig. A occurs during a next time interval t 2 for which the sync signal is in its low-level state. These conditions are iterated. The time interval t 1 starts at the moment of the occurrence of a rising edge in the sync signal, and ends at the moment of the occurrence of a falling edge therein. The time interval t 2 starts at the moment of the occurrence of a falling edge in the sync signal, and ends at the moment of the occurrence of a rising edge therein.

With reference back to FIG. 11 , the parity check circuit 26 a 4 detects stream-data errors in response to the parity data in the digital data Sig. A . The parity check circuit 26 a 4 checks a related transmission system on the basis of the detected stream-data errors. Preferably, the parity check circuit 26 a 4 informs the monitor 29 of the error check results. In this case, the monitor 29 displays the error check results. The selector circuit 26 a 3 receives a set of a clock signal (a bit clock signal) and a sync signal from the clock/sync generation circuit 26 a 11 . The selector circuit 26 a 3 selects one among a set of the clock signal and the sync signal in the digital data Sig. A and a set of the clock signal and the sync signal fed from the clock/sync generation circuit 26 a 11 . When the selector circuit 26 a 3 selects a set of the clock signal and the sync signal in the digital data Sig. A , the digital data Sig. A are passed to the memory 26 a 5 and the memory control circuit 26 a 6 through the selector circuit 26 a 3 without being processed thereby. When the selector circuit 26 a 3 selects a set of the clock signal and the sync signal fed from the clock/sync generation circuit 26 a 11 , a set of the clock signal and the sync signal in the digital data Sig. A are replaced by a set of the clock signal and the sync signal fed from the clock/sync generation circuit 26 a 11 . In this case, the resultant digital data Sig. A are outputted from the selector circuit 26 a 3 to the memory 26 a 5 and the memory control circuit 26 a 6 . In the event that the master server 21 fails, the selector circuit 26 a 3 selects a set of the clock signal and the sync signal fed from the clock/sync generation circuit 26 a 11 and outputs them to the later stage. The selection of a set of the clock signal and the sync signal fed from the clock/sync generation circuit 26 a 11 enables the operation of the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 to be checked.

The memory control circuit 26 a 6 generates a delay control signal in response to the dubbing-recording-mode discrimination data HS/STD in the digital data Sig. A . The delay control signal provides delay conditions for delaying the first stream data DATA 1 and the second stream data DATA 2 in the digital data Sig. A by a time interval from the moment of the occurrence of a rising edge of the sync signal in the digital data Sig. A . The memory control circuit 26 a 6 outputs the delay control signal to the memory 26 a 5 . The digital data Sig. A are written into and read out from the memory 26 a 5 before being fed to the parity circuit 26 a 7 . Preferably, only the first stream data DATA 1 and the second stream data DATA 2 in the digital data Sig. A are written into and read out from the memory 26 a : 5 . In this case, the digital data Sig. A except the first stream data DATA 1 and the second stream data DATA 2 bypass the memory 26 a 5 . The timing of writing the first stream data DATA 1 and the second stream data DATA 2 into the memory 26 a 5 or the timing of reading out the first stream data DATA 1 and the second stream data DATA 2 therefrom is controlled in response to the delay control signal. This timing control is designed so that the first stream data DATA 1 and the second stream data DATA 2 outputted from the memory 26 a 5 will have a phase retardation (a phase delay) relative to the moment of the occurrence of every rising edge in the sync signal. The moment of the occurrence of every rising edge in the sync signal is defined as a phase reference. The timing control uses the bit clock signal so that a unit change in the timing corresponds to a 1-bit period. The phase retardation (the phase delay) provided by the memory 26 a 5 is chosen in accordance with angular positions of used heads (active heads) on each rotary drum in the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 .

The above-indicated delay conditions are as follows. There are heads on each rotary drum. One or more are selected from the heads on the rotary drum as active heads in accordance with the standard recording mode or the high-picture-quality recording mode. The active heads correspond to the heads 25 e and 25 f in FIG. 10. A phase reference position corresponding to the previously-indicated phase reference is defined on the rotary drum. The stream data assigned to the selected heads (the active heads) are delayed by time intervals corresponding to the angular positions of the heads relative to the phase reference position, that is, corresponding to the angular intervals from the phase reference position to the heads.

As shown in FIG. 14 , a rotary drum RD is provided with a pair of diametrically-opposed heads EP 2 /SP 1 and EP 1 /SP 2 , a pair of diametrically-opposed heads HS 1 - 1 and HS 1 - 2 , a pair of diametrically-opposed heads HS 2 - 1 and HS 2 - 2 , and a pair of diametrically-opposed heads SD 1 and SD 2 . The position of the head EP 2 /SP 1 is defined as the phase reference position. The head EP 1 /SP 2 is spaced from the head EP 2 /SP 1 by an angular interval of (180 ). The head SD 1 is spaced from the phase reference position by a prescribed angular interval 1 in the clockwise direction. The head SD 2 is spaced from the head SD 1 by an angular interval of (180 ). The head HS 1 - 1 is spaced from the phase reference position by a prescribed angular interval 2 in the clockwise direction. The head HS 1 - 2 is spaced from the head HS 1 - 1 by an angular interval of (180 ). The head HS 2 - 1 is spaced from the phase reference position by a prescribed angular interval 3 in the clockwise direction. The head HS 2 - 2 is spaced from the head HS 2 - 1 by an angular interval of (180 ). The recording section 25 c includes an arrangement for selecting ones from the head pairs in response to the dubbing-recording-mode discrimination data HS/STD. The pair of the heads SD 1 and SD 2 are assigned to the standard recording mode. The pair of the heads HS 1 - 1 and HS 1 - 2 , and the pair of the heads HS 2 - 1 and HS 2 - 2 are assigned to the high-picture-quality recording mode. Specifically, in the standard recording mode, the stream data DATA 1 are recorded on a related slave magnetic tape by the pair of the heads SD 1 and SD 2 while a head switching arrangement in the recording section 25 c periodically implements change between the heads SD 1 and SD 2 in response to the switching pulse signal (the sync signal). In this case, the stream data DATA 1 are delayed by a time interval corresponding to the prescribed angular interval 1. In the high-picture-quality recording mode, the first stream data DATA 1 are recorded on a related slave magnetic tape by the pair of the heads HS 1 - 1 and HS 1 - 2 while the second stream data DATA 2 are recorded thereon by the pair of the heads HS 2 - 1 and HS 2 - 2 . In the high-picture-quality recording mode, the head switching arrangement periodically implements change between the heads HS 1 - 1 and HS 1 - 2 and change between the heads HS 2 - 1 and HS 2 - 2 in response to the switching pulse signal (the sync signal). In this case, the first stream data DATA 1 are delayed by a time interval corresponding to the prescribed angular interval 2, and the second stream data DATA 2 are delayed by a time interval corresponding to the prescribed angular interval 3.

As shown in FIGS. 15 and 16 , every rising edge in the sync signal provides the phase reference. As shown in FIG. 15 , in the standard recording mode, the starting point of every field 1 represented by the stream data DATA 1 outputted from the memory 26 a 5 delays from the phase reference by a time interval DLY 1 corresponding to the prescribed angular interval 1. The delay of the stream data DATA 1 causes an agreement between the starting point of every field 1 or 2 represented by the stream data DATA 1 and the timing of the change between the heads SD 1 and SD 2 . As shown in FIG. 16 , in the high-picture-quality recording mode, the starting point of every field 1 represented by the first stream data DATA 1 outputted from the memory 26 a 5 delays from the phase reference by a time interval DLY 2 corresponding to the prescribed angular interval 2 while the starting point of every field 1 represented by the second stream data DATA 2 outputted from the memory 26 a 5 delays from the phase reference by a time interval DLY 3 corresponding to the prescribed angular interval 3. The delay of the first stream data DATA 1 causes an agreement between the starting point of every field 1 or 2 represented by the first stream data DATA 1 and the timing of the change between the heads HS 1 - 1 and HS 1 - 2 . The delay of the second stream data DATA 2 causes an agreement between the starting point of every field 1 or 2 represented by the second stream data DATA 2 and the timing of the change between the heads HS 2 - 1 and HS 2 - 2 .

In the case where the frame frequency related to the first stream data DATA 1 and the second stream data DATA 2 is equal to 30 Hz, the delay DLYn of the stream data assigned to the heads spaced from the phase reference position by n and n is given as follows.

where DLYn means DLY 1 , DLY 2 , or DLY 3 , and n means 1, 2, or 3. The stream-data delays or the stream-data delay time intervals DLY 1 , DLY 2 , and DLY 3 are provided by the memory 26 a 5 . The determination of the delay timings by the memory 26 a 5 is responsive to the bit clock signal so that a unit change in the delay timings corresponds to a 1-bit period. Accordingly, the stream-data delays (the stream-data delay time intervals) DLY 1 , DLY 2 , and DLY 3 can be accurately and finely set. Furthermore, the stream-data delays DLY 1 , DLY 2 , and DLY 3 can be managed by a single place, that is, the combination of the memory 26 a 5 and the memory control circuit 26 a 6 . In the case where the frame frequency related to the first stream data DATA 1 and the second stream data DATA 2 is equal to 29.97 Hz, the delay DLYn of the stream data assigned to the heads spaced from the phase reference position by n and n is given similarly. Specifically, desired stream-data delays (the stream-data delay time intervals) DLY 1 , DLY 2 , and DLY 3 are predetermined for a frame frequency of 30 Hz, and also desired stream-data delays (the stream-data delay time intervals) DLY 1 , DLY 2 , and DLY 3 are predetermined for a frame frequency of 29.97 Hz. Corresponding ones of the desired stream-data delays DLY 1 , DLY 2 , and DLY 3 are selected in response to the frame discrimination data signal which indicates whether the frame frequency is equal to 30 Hz or 29.97 Hz. The memory control circuit 26 a 6 controls the memory 26 a 5 to provide the selected stream-data delays DLY 1 , DLY 2 , and DLY 3 .

As shown in FIG. 17 , the parity circuit 26 a 7 includes an operation circuit 26 a 71 , a latch or a counter 26 a 72 , and a NOT circuit 26 a 73 . The operation circuit 26 a 71 receives the first stream data DATA 1 and the second stream data DATA 2 from the memory 26 a 5 . The operation circuit 26 a 71 executes given operation (for example, Exclusive-OR operation) between the first stream data DATA 1 and the second stream data DATA 2 , thereby generating new parity data for checking conditions of the transmission of the stream data DATA 1 and DATA 2 . The operation circuit 26 a 71 outputs the parity data to the latch 26 a 72 . The clock signal generated in the digital dubbing system is applied to the latch 26 a 72 and the NOT circuit 26 a 73 . The device 26 a 72 latches the first stream data DATA 1 , the second stream data DATA 2 , and the parity data, and outputs the latched data to the interface driver 26 a 8 in response to the clock signal. Thus, the first stream data DATA 1 , the second stream data DATA 2 , and the parity data are outputted from the latch 26 a 72 to the interface driver 26 a 8 in synchronism with the clock signal. The NOT circuit 26 a 73 inverts the clock signal. The NOT circuit 26 a 73 outputs the inversion-resultant clock signal to the interface driver 26 a 8 . As shown in FIG. 18 , the timing of every change of the first stream data DATA 1 , the timing of every change of the second stream data DATA 2 , and the timing of every change of the parity data are provided by a falling edge in the clock signal.

The first stream data DATA 1 , the second stream data DATA 2 , the parity data, and the clock signal propagate through the interface driver 26 a 8 before being outputted from the first distributor 26 a to the second distributor 26 b as the digital data Sig. B (see FIGS. 5 , 11 , and 17 ). The sync separation circuit 26 a 9 in the first distributor 26 a of FIG. 11 receives the output signal of the standard signal generator 26 c (see FIG. 5 ). The sync separation circuit 26 a 9 extracts a timing signal (a sync signal) from the output signal of the standard signal generator 26 c by a sync separation procedure. The sync separation circuit 26 a 9 outputs the timing signal (the sync signal) to the PLL block 26 a 10 and the clock/sync generation circuit 26 a 11 . The PLL block 26 a 10 generates a clock signal (a bit clock signal) in response to the timing signal. The PLL block 26 a 10 outputs the clock signal to the clock/sync generation circuit 26 a 11 .

The clock/sync generation circuit 26 a 11 produces a desired sync signal and a desired clock signal (a desired bit clock signal) from the output signals of the sync separation circuit 26 a 9 and the PLL block 26 a 10 . The clock/sync generation circuit 26 a 11 feeds the sync signal and the clock signal to the selector circuit 26 a 3 and the interface driver 26 a 12 . The interface driver 26 a 12 outputs the sync signal and the clock signal to the interface board 21 c in the master server 21 .

As previously mentioned, the first stream data DATA 1 and the second stream data DATA 2 are delayed from the reference timing by the time intervals corresponding to the angular intervals between the used heads and the phase reference position. The delays of the first stream data DATA 1 and the second stream data DATA 2 compensate for phase errors which would be caused by the structure and arrangement of the heads. As a result of the delays, the first stream data DATA 1 and the second stream data DATA 2 are normally recorded on a slave magnetic tape by the heads in pairs which are changed in response to the reference timing signal (the sync signal).

As previously mentioned, the parity circuit 26 a 7 (the operation circuit 26 a 71 ) in the first distributor 26 a generates the parity data on the basis of the delayed first stream data DATA 1 and the delayed second stream data DATA 2 . During the transmission of the delayed first stream data DATA 1 and the delayed second stream data DATA 2 , errors caused therein are checked by referring to the parity data. Preferably, the error check arrangement is provided in the second distributor 26 b or the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 . The error check arrangement is simple in structure, and is highly efficient in error detection.

As previously mentioned, the interface board 21 c in the master server 21 generates the parity data on the basis of the stream data. The parity check circuit 26 a 4 in the first distributor 26 a detects stream-data errors in response to the parity data. The parity check circuit 26 a 4 informs the monitor 29 of the error check results. The monitor 29 displays the error check results. The error check arrangement is simple in structure, and is highly efficient in error detection.

As previously mentioned, the stream data to be dubbed are reproduced from a DLT tape 30 while the DLT tape 30 is driven by the DLT device 20 . The reproduced stream data are stored into the hard disk drive 21 b . Each time dubbing is required, the stream data are transferred from the hard disk drive 21 b to the slave recorders 2501 , 2502 , 2503 , . . . , and 2517 . In this case, it is unnecessary to access the DLT tape 30 . Thus, it is possible to prevent the occurrence of a damage to the DLT tape 30 which might be caused by frequent accesses thereto.

As previously mentioned, stream data recorded on a DLT tape 30 are scrambled, and the personal computer 21 a in the master server 21 descrambles the stream data reproduced from the DLT tape 30 . The scrambled stream data are effective to copy protection.