Speed controlling circuit of dubbing recorder and dubbing equipm

Details Speed controlling circuit of dubbing recorder and dubbing equipm Speed controlling circuit of dubbing recorder and dubbing equipm

1998-08-10

2000-12-26

Nguyen, Huy

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

386 66, H04N 576, H04N 5783

Patent

active

061671878

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a dubbing apparatus to duplicate video tapes on which video programs have been recorded, and in particular to a circuit to automatically switch dubbing speed of a dubbing recorder by detecting the frequency of a particular portion of the frequency modulated video signal to be used as the input for dubbing.


BACKGROUND OF THE INVENTION

Conventional video tape dubbing apparatus consists of a master VTR (Video Tape Recorder) to send out video signal for dubbing, a distributor to distribute the sent out video signal, and a number of dubbing recorders arranged in parallel to record the distributed video signal. The master VTR sends out video signal of either standard speed, i.e., same-speed, or double-speed signal, and a number of dubbing recorders corresponding to each speed perform dubbing.
Referring now to FIG. 4, the construction of a speed control circuit of a conventional dubbing recorder will be described in the following. In this figure, a frequency modulated video signal, namely, RF signal 1, which is distributed by a master VTR is modulated by a demodulation circuit 4, the output of which is then inputted to a sync separation circuit 5. The control of the recording speed is performed by inputting into a servo circuit 6 the output signal from the sync separation circuit 5 and the output signal from a system control circuit 3, thereby allowing recording of duplicated tapes at the same speed or the double speed. The dubbing apparatus in this arrangement is a dedicated apparatus for each respective speed and is not designed to record by switching a single apparatus between the same speed and double speed.
As an example of a dubbing apparatus, Japanese Laid-open Patent No. Hei 5191,774 discloses a high-speed dubbing apparatus. As this apparatus is a dedicated apparatus for a double speed, there has been a demand from users of the apparatus to allow them to duplicate at the standard speed by switching this same apparatus. When making a double-speed dubbing using the apparatus of this application, it is necessary to prepare 2 identical rolls of master tape. In the case of duplicating tapes in a small lot such as 100 to 5,000 rolls, dubbing at the standard speed will be acceptable, making it unnecessary to adopt double speed and to take the trouble of preparing 2 rolls of master tape. However, when using this apparatus, it is necessary to change dubbing recorder from a double-speed recorder to a same-speed dubbing recorder thereby presenting a cumbersome handling of dubbing recorders. Consequently, with this conventional example, too, there has been a demand for making it possible to switch between double-speed dubbing and same-speed dubbing using a same dubbing recorder and also for making handling of the apparatus easier.


SUMMARY OF THE INVENTION

To address the above described demand, the present invention intends to provide an apparatus by using a dubbing recorder in which the recording speed is detected from the frequency of a particular portion of the input signal for dubbing and in which the recording speed can be switched between the same speed and double speed or faster speed, based on the output of the detection circuit thereof the recording speed of the dubbing recorder is automatically switched to assure dubbing at a proper speed. The speed control circuit for a dubbing recorder in accordance with the present invention comprises a demodulation circuit to which video signal for dubbing is inputted from a master VTR, a sync separation circuit to separate sync signal from the output signal of the demodulation circuit, a detection circuit to detect the frequency of a particular portion of the video signal using the above sync signal, and a system control circuit to determine mode of speed of the master VTR based on the output signal of the detection circuit.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing construction of the speed control circuit of a dubbing recorder in an exemplary embodiment of the present invention

REFERENCES:
patent: 4772966 (1988-09-01), Sharples et al.
patent: 5040081 (1991-08-01), McCutchen
patent: 5392164 (1995-02-01), Takahashi

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