JPS6021402B2 - video to video dubbing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal dubbing system, and more particularly to an apparatus for preventing flicker in a reproduced picture that can be used during high-speed video-to-video dubbing.

Both master and slave video tape recorders (VTRs)
) is used to transmit the playback signal from the master side to the slave side VT.
When dubbing on R, the master and slave side N
The number of rotating video heads of the TR is m times (for example, 4 times) that of a normal VTR, the rotation speed is n times (for example, 5 times), and the tape feeding speed of the capstan is (m x n).
By making the dubbing speed twice the normal speed (mxn
) A high-speed dubbing method has been proposed that enables the recording to be doubled, for example, by 2 times.

In this case, when dubbing is performed video-to-video, a plurality of demodulators and modulators are required, and if the carrier levels of the modulators are not accurately matched, flickering will occur in the reproduced picture. An object of the present invention is to accurately and stably match the carrier levels of a plurality of modulators.

The figure is a circuit diagram of one embodiment of the present invention that achieves this purpose,
Heads 1 and 2 of the master VTR are connected to terminals 10 and 12.
Video signals 1 and 2 reproduced from are provided.

These are intensifiers 14, 16 and module 18, respectively.
and 20 to terminals 22 and 24 which are connected to recording intensifiers for each head of the slave VTR.
If video-to-video dubbing is performed in this manner, flickering will occur in the reproduced image of the dubbed video unless the carrier levels of the modulators 18 and 20 are accurately matched as described above. Therefore, according to the present invention, the DC level of at least one of the intensifiers 14 and 16 is controlled, and the carrier levels of the modulators 18 and 20 are adjusted accurately and stably. The outputs of modulators 18 and 20 are provided to first and second gates 26 and 28, respectively.

The gate control signals controlling the respective gates 26, 28 are provided by constant level reference signals, such as blanking or bedside pulses, of the first and second video signals applied to terminals 30, 32. The signals from the gates 26 and 28 are applied to a demodulator (which may be an LPF, an envelope detector, etc.) 36 via a summing point 34 to be demodulated, and then to a third gate 3
8, applied to the fourth gate 40. These gates 38
, 40 also receive signals from the above-mentioned terminals 30, 32, respectively, and then the signals from the gates 38, 40 are held in hold circuits 42, 44, and then given to the differential sardine intensifier 46 to increase the voltage of the sardines. taken out. This error voltage is applied to one of the intensifiers 16, for example, and is used to control its DC level. With this configuration, differences in the carriers of multiple modulators are detected, the obtained error signal is fed back to the modulator, and the carriers of the modulators are automatically and stably adjusted.

[Brief explanation of drawings]

The figure is a circuit diagram of an embodiment of the present invention, in which 14 and 16 are multipliers, 18 and 20 are modulators, and 26, 28, 38, 4
0 is a gate, 36 is a demodulator, 42 and 44 are hold circuits, and 46 is a multiplier.

Claims (1)

[Claims] 1. In a device for matching the carrier levels of modulators of each playback video head of an apparatus for video-to-video dubbing, means for gating the output of each of the modulators at a fixed level position of the associated input video signal; means for level detecting the gate output;
A dubbing device comprising means for comparing the outputs at each of the above-mentioned level positions, and means for feeding back an error signal from this to each of the above-mentioned modulators.