GB2254182A

GB2254182A - High speed dubbing system

Info

Publication number: GB2254182A
Application number: GB9205803A
Authority: GB
Inventors: Shinji Takemoto; Kunio Suesada
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1991-03-28
Filing date: 1992-03-17
Publication date: 1992-09-30
Also published as: FR2680035A1; JPH04301283A; GB9205803D0

Abstract

One of N master tapes having the same information recorded thereon is mounted on each of N (N is a positive integer) master VTRs 1, 2, and the N master VTRs are operated to reproduce the recorded information out of phase with one another. N video or sound reproduced signals are input into the rate converter 4 through cable 3, and converted into a single continuous video or sound signal in compliance with the order in which the signal was recorded on the master tape by compressing the time base of the information to 1/N times than that at the time of recording. Thus, the signal of the same form as the signal produced on track can be obtained, and the signal is recorded by a plurality of slave VTRs 8 in which the numbers of revolutions of the cylinder and the capstan are increased to N times higher than normal speed. <IMAGE>

Description

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a transfer rate converter for dubbing a large amount of video tape at high speed by using as a master VTR a VTR set having a cylinder which rotates at a speed of 90 Hz or higher, and a dubbing method therefor.

Description of the Related Art A prior-art high speed dubbing system comprises a master VTR having a master tape mounted thereon, slave VTRs of the same number as a plurality of slave tapes mounted thereon, and a distributor connecting a reproduced signal output terminal of the master VTR with input terminals of said plurality of slave VTRs, in which dubbing system, to do dubbing of the video signal or sound signal at high speed, the numbers of revolutions of the cylinder and the capstan of the master VTR are increased M times (M is a positive integer) greater than those used in recording, the master tape is played in on-track reproduction, the reproduced signal is sent through the distributor and the cables to the plurality of slave VTRs, in which the numbers of revolutions of the cylinder and the capstan have been increased to M times, and recorded, so that the information is dubbed at M times normal speed, namely, in 1/M of the recording time of the master tape. (JP-A-61-246925).

However, with the prior-art arrangement and method mentioned above, if, for example, a digital VTR having high picture quality and high sound quality is used as the master VTR, since the number of revolutions of the cylinder is 90 Hz under NTSC system or 150 Hz under PAL system even in normal-speed playback, for on-track reproduction at two times normal speed, the cylinder speed must be increased to 180 Hz or 300 Hz.

If the master tape is played under this condition, the vibration or durability of the cylinder or the tape head contact or the frequency characteristics of the head will deteriorate. If those problems are addressed by increasing the cylinder rotating speed, for example, huge development expenses will incur. Therefore, so long as the prior-art method is kept, the above attempt to use the digital VTR is difficult, so that the advantages of the digital VTR, such as the superb picture and sound quality, cannot be exhibited to the full, which has been a problem.

SUMMARY OF THE INVENTION This invention has been made to solve those problems, and has as its object to provide a high speed dubbing system using as the master VTR a VTR having a high cylinder speed in normal-speed playback, such as a digital VTR.

To achieve the above object, in place of the master VTR of a conventional high speed dubbing system, the high speed dubbing system according to the present invention comprises N master tapes (N is a positive integer) each having the same information recorded thereon, N master VTRs, having one each of said master tapes mounted thereon, for playing back the tape at a tape speed N times the recording speed of the tape but out of phase with one another, and a rate converter for receiving N discontinuous video or sound reproduced signals from said N master VTRs and outputting a continuous video or sound signal made by time-base compression of the N signals to 1/N of the time base at the time of recording.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of the general construction of the high speed dubbing system according to an embodiment of the present invention: Fig. 2 is a tape pattern diagram for explaining the regenerative tracks of master VTRs in this embodiment; Fig. 3 is a time chart for explaining the operation of the high speed dubbing device in this embodiment; Fig. 4 is a block diagram showing the internal construction of the rate converter for video signal in this embodiment; and Fig. 5 is a block diagram showing the internal construction of the rate converter for sound signal in this embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. 1, reference numerals 1 and 2 denote master VTRs for sampling an 8-bit-quantified digital NTSC video signal at a frequency (4 fsc) four times greater than that of the color subcarrier, and recording and reproducing the video signal in digital form on three tracks for one field, 3 denotes a digital cable, 4 denotes a rate converter for joining reproduced data from the two master VTRs 1 and 2 into one data, 5 and 7 denote coaxial cables, 6 denotes a distributor, and 8 denotes slave VTRs.

Description will now be made of the operation of the high speed dubbing system according to this embodiment, which is structure as described above.

One master tape having the same information recorded thereon is loaded on both master VTRs 1 and 2, and the VTRs 1 and 2 simultaneously reproduce the information out of phase with one another, for example, reproduce different fields at two times normal speed in the variable mode (the mode in which reproduction can be performed at different speeds by the reproduction head which is mounted on a piezoelectric element to control the head so that it follows the recorded tracks). In this embodiment, the master VTR 1 is assigned the operation of reproducing odd-number fields, while the master VTR 2 is assigned the operation of reproducing even-number fields.

Fig. 2 shows how the regenerative tracks are handled in the above-mentioned operation. The upper one is the regenerative track of the master VTR 1 and the lower one is the regenerative track of the master VTR 2. In the master VTRs used in this embodiment, three tracks are used to record one field, so that reproduction is done in units of three continuous tracks.

Therefore, in reproduction at two times normal speed in the variable mode, groups of three continuous tracks indicated by the solid lines in Fig. 2 are the regenerative tracks on which the signals are reproduced. Those tracks indicated by the broken lines located between the solid lines are the non-regenerative tracks not used for reproduction. To be more specific, the master VTR 1 reproduces fields 1, 3 and 5, while the master VTR 2 reproduces fields 2, 4 and 6.

The fields reproduced by the above-described method by the master VTRs 1 and 2 are output at timings shown by the upper and middle thick lines in Fig. 3.

The axis of abscissa in Fig. 3 represents time (in seconds). T denotes a period of a field which occurs in cycles, and is 1/59.94 sec. in NTSC system and 1/50 sec.

in PAL system. In Fig. 3, the upper thick line represents reproduced data by the master VTR 1 with field numbers, and the middle thick line represents reproduced data by the master VTR 2 with field numbers. To take a period from 0 sec. to T sec. for example, the master VTR 2 reproduces the field 2 at the timing of the master VTR 1 reproducing the field 1.

Data output from the master VTRs 1 and 2 is sent to the rate converter 4 through the digital cable 3.

The operation of the rate converter 4 will be described with reference to block diagrams in Figs. 4 and 5. Fig. 4 is a block diagram showing the internal construction of a video signal processing unit of the rate converter 4. Fig. 5 is a block diagram showing the internal construction of a sound signal processing unit.

In Fig. 4, reference numeral 9 and 10 denote video data input terminals for inputting digital video data; 11 and 12 denote field memories for storing video data supplied from the video data input terminal 9; 13 and 14 denote field memories for storing video data supplied from the video data input terminal 10; 15 denotes writing means for controlling write addresses of the field memories 11 and 12; 16 denotes writing means for controlling write addresses of the field memories 13 and 14; 17 denotes reading means for controlling read addresses of the field memories 11, 12, 13 and 14; 18 denotes a process circuit for adding synchronizing signals and a color burst signal; 19 denotes a D-A converter, and 20 denotes a video signal output terminal to the slave VTRs.

In Fig. 5, reference numerals 21 and 22 denote sound data input terminals for inputting digital sound data; 23 and 24 denote field memories for storing data input from the sound data input terminal 21; 25 and 26 denote field memories for storing data input from the sound data input terminal 22; 27 denotes writing means for controlling write addresses of the field memories 23 and 24; 28 denotes writing means for controlling write addresses of the field memories 25 and 26; 29 denotes reading means for controlling read addresses of the field memories 23, 24, 25 and 26; 30 denotes a D-A converter; and 31 denotes a sound signal output terminal. The thick lines in Figs. 4 and 5 indicate the flow of the video data (signal) or the sound data (signal), the broken lines indicate clock signals, and the two-dot chain lines indicate the specification of addresses.

The thus constructed rate converters according to this embodiment use the same processing method for video data and sound data. Description will be made of the operation of those rate converters using video data as an example.

Parallel video data reproduced by the master VTRs 1 and 2 and having a word length of eight bits and a transfer rate of 4 fsc is input from the video data input terminals 9 and 10. The data input from the video data input terminal 9 is sent to the field memories 11 and 12, and to the writing means 15, while the data input from the video data input terminal 10 is sent to the field memories 13 and 14, and to the writing means 16. The writing means 15 and 16 detect the sampling clock signal (4 fsc) and the horizontal and vertical synchronizing signals, and calculate write addresses of the video data. The writing means 15 specifies the write address to the field memory 11 or 12, while the writing means 15 specifies the write address to the field memory 13 or 14.The field memories, for which the write addresses were specified, store the video data at the specified addresses at the rate of 4 fsc.

On receiving the sampling clock signal and the write addresses, the reading means 17 generates read addresses, and sequentially specifies the read addresses to the two field memories, which are not doing write operations, by using read clock pulses (8 fsc) two times greater than the frequency of the sampling clock signal. More specifically, the reading means first gives a read address to the field memory 11 or 12 and reads data, and then gives the same read address to the field memory 13 or 14 and reads data for two fields sequentially at the rate of 8 fsc and at a T-sec. period for each field, by which digital video data two times the amount of data obtainable at a normal vertical scanning speed is obtained.

If reading and writing are performed at the timing mentioned above, output of the rate converter of Fig. 1 is as shown at the lower thick line in Fig. 3, that is to say, the signal output from the rate converter 4 is the signal formed by joining the outputs of the two master VTRs, compressed to a half in terms of time base by time-base compression. For example, the reproduced signal of the field 1 from the master VTR 1 and the reproduced signal of the field 2 from the master VTR 2 are joined to form one continuous video signal compressed to a half in terms of time base by time-base compression, and output during a time period from T sec.

to 2T sec. in which fields 3 and 4 are input. The above-mentioned relation between input and output is the same with the subsequent fields.

Finally, the video data read from the field memories 11, 12, 13 and 14 in Fig. 4 is added with synchronizing signals and a color burst signal in the process circuit 18, the digital video signal is converted by the D-A converter 19 into an analog video signal in step with the clock pulses generated by the reading means 17, and output from the video signal output terminal 20.

The video signal output from the video signal output terminal 20 has the same form as a reproduced signal of an analog type master VTR, in which the numbers of revolutions of the cylinder and the capstan are increased two times higher than normal speed, in a prior-art high speed dubbing system. Consequently, for the coaxial cables 5 and 7, the distributor 6, and the slave VTRs 8 in Fig. 1, the technologies heretofore used can be used. In addition, dubbing can be done in a time half as long as the recording time of the master tape without increasing the cylinder speed of the master VTR.

In Fig. 5, the sound data input through the sound data input terminals 21 and 22 is serial data, one word of which comprises 64 bits obtained from the two channels, and which has been formed by sampling at a sampling frequency fs of 48 kHz, and has a transfer rate of 64 fs. The processing of the sound data is basically the same as the processing of the video signal, only differences being that the process circuit is not used and that the read clock pulses are synchronized in phase with the read clock pulses for the video data. Therefore, only the block diagram is shown in Fig. 5, and description of sound data processing is omitted.

In this embodiment, description has been made of a case in which two master VTRs are operated in field units in the variable mode, but as applications of this embodiment, if master VTRs are increased to three units, dubbing can be done at three times normal speed by playback at three times normal speed in variable mode, and high speed dubbing using the variable mode in frame units is also possible. If N units of analog VTRs are used which are high in cylinder speed such as high vision VTRs, by providing an A-D converter between their output stages and the rate converter 4 in Fig. 1, dubbing can be done at N times normal speed, so that the picture quality of the dubbed tape can be improved.

Constructed as described, the high speed dubbing system according to the present invention can reproduce N master tapes, which have the same information recorded thereon, by N master VTRs out of phase with one another, compresses the reproduced signals to 1/N in terms of time base in the rate converter, and joins the N discontinuous reproduced signals into one continuous signal in the order in which the information was recorded on the master tape. Thus, a signal continuous reproduced signal can be obtained which has the same form as the one obtained by on-track reproduction performed at N times normal speed by a master VTR in a prior-art high speed dubbing system. Therefore, it is not necessary to increase the number of revolutions of the cylinder of the master VTR. In addition, this invention makes it possible to preclude the technical problems of the cylinder durability, the contact between tape and head, and the deterioration of the head's frequency characteristics. And, huge amounts of development investment for solving those problems can be avoided. Furthermore, this invention enables easy dubbing at N times higher than the ordinary reproducing speed with the conventional component units still used for the master VTRs.

Claims

WHAT IS CLAIMED IS:

1. A high speed dubbing system comprising: a rate converter including N (N is a positive integer) input connectors; N memory means for having written therein and read therefrom data input from said N input connectors; writing means for controlling write addresses and write timing of said N memory means; reading means for determining read addresses and read timing of said N memory means; and read timing of said N memory means; an output connector for outputting data read from said N memory means; N master VTRs for having mounted thereon one of N master tapes having the same information recorded thereon and sending a video or sound signal to said rate converter; and at least one slave VTR in which the number of revolutions of the cylinder is increased two times normal speed for recording an output signal from said rate converter, wherein dubbing is done in a time 1/N times the recording -time of the master tape by converting N discontinuous video or sound reproduced signals, obtained by playing back said master VTRs out of phase with one another at a tape speed N times higher than a tape speed used in recording, into a continuous video or sound signal compressed in time to 1/N times the recording time of the master tape.

2. A high speed dubbing system according to claim 1, wherein VTRs having the cylinder speed of 90 Hz or more are used as said master VTRs.

3. A high speed dubbing system according to claim 1, wherein said N master VTRs are operated to reproduce the video or sound signal in frame units out of phase with one another, and wherein said rate converter comprises memory means with a capacity for storing at least one frame of the video or sound signal.

4. A high speed dubbing system according to claim 1, wherein said N master VTRs are operated to reproduce the video or sound signal in field units out of phase with one another, and wherein said rate converter comprises memory means with a capacity for storing at least one field of the video or sound signal.