JPS63226190A - Video tape recorder - Google Patents

Abstract

PURPOSE:To improve the quality of a dubbing picture by providing an editing switch, and controlling the attenuation quantity of a burst signal. CONSTITUTION:In case of dubbing, an editing switch 12 is turned off, and a High level is inputted through R8 from a power source 30 to an AND gate 31. Also, a burst gate pulse is inputted to the other input terminal of the AND gate 31, therefore, a signal of High is outputted to an output of the AND gate 31, in a burst period, and TR2 is turned on. Accordingly, at the time of dubbing, the burst signal is attenuated by parallel resistances of R1, and R2, R3. In such a way, even if dubbing is repeated, such a problem point as a color signal becomes faint can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 21.-7 The present invention relates to a video tape recorder (hereinafter referred to as VTR) which is useful for improving the quality of dubbing images.

Conventional technology In recent years, VTR technology has progressed in the direction of higher image quality.
At the same time, the improvement in dubbing image quality is also promising.

Hereinafter, an example of a conventional video signal processing circuit will be explained using FIGS. 2 and 3 with reference to the drawings. Second
The figure is a block diagram showing video signal processing during recording, and FIG. 3 is a block diagram showing video signal processing during playback.

In FIG. 2, reference numeral 13 denotes a video signal input terminal, into which a composite video signal consisting of a luminance signal and a carrier color signal is input. The input composite video signal is processed by the LPF 14 to remove color signals, and by the recording luminance signal processing circuit 16 to process video emphasis, white clip, dark clip, etc.
The M modulator 16 performs FM modulation. On the other hand, only the color signal is extracted with BPF (band pass filter) 17, and ACC3
Page 7 (Automatic, chroma level control) 18 sets the color signal to a constant level, and the burst level amplification circuit 19 amplifies it only during the burst period. The burst level amplification circuit 19 receives a burst gate pulse generated from a horizontal synchronization signal separated from the horizontal synchronization signal by the recording luminance signal processing circuit. The low frequency converter 20 converts the color signal to a low frequency (for example, 629 KHz in the VH3 system).
), the adder 21 adds the FM-modulated luminance signal and the low-frequency-converted chrominance signal, the recording amplifier 22 amplifies the signal, and the magnetic head 1 records the signal on a magnetic tape (not shown).

Next, signal processing during reproduction will be explained using FIG. 3.

In FIG. 3, a video signal recorded on a magnetic tape by a magnetic head 1 is reproduced and amplified by a reproduction amplifier 2.

The signal amplified by the regenerative amplifier 2 passes through the HPF 3
The M demodulator 4 demodulates the signal into a video signal, and the reproduced luminance signal processing circuit 5 performs processing such as video de-emphasis and noise cancellation. On the other hand, the color signal extracted by the LPF 6 is converted to the original carrier color signal frequency by the frequency converter 8 after reproduction level fluctuations are removed by the ACC 7. At this time, the time axis fluctuation component is also removed by a well-known APC circuit. The color signal returned to the original carrier color signal is passed through the burst level attenuation circuit 9. The burst level attenuation circuit 9 also includes the reproduction brightness signal processing circuit 5.
A burst gate pulse is input.

The output of the reproduced luminance signal processing circuit 5 and the output of the burst level attenuation circuit 9 are added by an adder 10 and outputted from an output terminal 11 as a reproduced composite video signal.

As mentioned above, during recording, the S/N in the recording and playback process is
In order to improve the color quality, the burst signal in the color signal is amplified and recorded, and then restored to its original state during playback.

The amplification of the burst signal is approximately 6 dl), and the attenuation during reproduction is not 6 db but 4 to sdb in order to improve the S/N of the burst signal as much as possible.

5 Page 7 Problems to be Solved by the Invention However, with the above configuration, there is no problem in normal self-recording and playback, but when dubbing is repeated, for example, amplification of burst signals during recording may occur. If the level is 6 db and the attenuation level of the burst signal during playback is 5 db, the level of the color signal will be attenuated by 3 db after dubbing 3 times and 5 (lb) when dubbing 5 times. The problem was that the color became pale.

The present invention has been made in view of the above problems and provides a video tape recorder in which the color signal does not become weaker even when dubbing is repeated.

Means for Solving the Problems In order to solve the above problems, the video tape recorder of the present invention, when recording a composite video signal consisting of a luminance signal and a carrier color signal, frequency modulates the luminance signal and modulates the carrier color signal. A video terrorism 1\-hoop recorder configured to convert the carrier color signal to a low frequency signal, amplify and record a burst signal of the carrier color signal, and attenuate the burst signal during playback, the amount of attenuation of the burst signal being and an edit switch means, and the edit switch means controls the attenuation switching means for the burst signal during editing.

According to the above-described structure, the present invention is configured so that the amount of attenuation of the burst signal during dubbing is attenuated by the same amount as the amount of amplification of the burst signal during recording by the signal of the edit switch. This eliminates the problem that the color signal becomes weak even when the color signal is used.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a video signal reproducing circuit in an embodiment of the present invention. In FIG. 1, a magnetic head 1 reproduces a video signal recorded on a magnetic tape and amplifies it with a reproduction amplifier 2. The amplified signal is passed through the HPF
3, the low frequency converted color signal is removed, and an FM demodulator 4 demodulates the video signal into a 7ba/2 signal, and a reproduced luminance signal processing circuit 5 undergoes processing such as video de-emphasis and noise cancellation. On the other hand, the color signal extracted by the LPF 6 is converted into the original carrier color signal frequency by the frequency converter 8 after the reproduction level fluctuation is removed by the AC07. At this time, the well-known AP
The time axis fluctuation component is removed by the C circuit. The color signal returned to the original carrier color signal is sent to the burst level attenuation circuit 9.
to attenuate the burst level. The burst gate pulse is inputted to the burst level attenuation circuit 9 from the reproduced luminance signal processing circuit 5, and the burst signal is attenuated by the burst signal period. The output of the reproduced luminance signal processing circuit 5 and the output of the burst level attenuation circuit 9 are added by an adder 1o and outputted from an output terminal 11 as a reproduced composite video signal.

Reference numeral 12 denotes an edit switch, which is normally on and turned off when in the edit mode. The burst level attenuation circuit is composed of R1, R2, R3, R4, R5, R6, R7, TR1, TR2, and an AND gate 31. During normal playback, edit switch 12/i is turned on. The input of the pAND gate 31 is at LOW level, and TR2 is cut on. On the other hand, TR1 has R4
burst period Hi by the burst gate pulse via
The signal gh is input, and TR1 is turned on only during the burst period. Therefore, during the burst period, the burst signal is R1
and R2, and the burst level is attenuated. At this time, the ratio of the resistance values of R1 and R2 is set to a value that attenuates the burst level by 4 to 5 dB.

When dubbing is to be performed next, the edit switch is turned off, a high level is input to the AND gate 31 via Rs from the power supply 30, and a burst gate pulse is input to the other input terminal of the AND gate 31. Therefore, a high signal is outputted from the AND gate 3.1 during the burst period, and TR2 is turned on. Therefore, when dubbing, if the parallel resistors R1, R2, and Rs are used as a bar, the burst signal will be attenuated by 6 (iB).

9 Vane As explained above, in this embodiment, during normal playback, the attenuation amount of the burst signal is set to 4 to 5 dB, and the burst signal S
/N carefully, and when dubbing, use the edit switch to configure the amount of attenuation of the burst signal to be the same as the amount of amplification of the burst signal during recording. This eliminates the problem of weak signals.

Effects of the Invention As described above, the present invention provides an edit switch,
By controlling the amount of attenuation of the burst signal, it is possible to significantly improve the dubbing image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram for reproducing a video signal in an embodiment of the present invention, FIG. 2 is a block diagram for recording a video signal in a conventional example, and FIG. 3 is a block diagram for reproducing a video signal in a conventional example. 1... Magnetic head, 2... Regenerative amplifier, 7... AOC18... Frequency converter, 9... Burst ray 10 l.- 7 Bell attenuation circuit, 12...Edit switch.

Claims (2)

[Claims] (1) When recording a composite video signal consisting of a luminance signal and a carrier color signal, the luminance signal is frequency modulated, the carrier color signal is converted to a low frequency signal, and the burst signal of the carrier color signal is amplified and recorded; The burst signal is configured to attenuate the burst signal during playback, and includes a burst signal attenuation amount switching means and an edit switch means, and the burst signal attenuation amount switching means is controlled by the edit switch means during editing. A videotape recorder with special features. (2) The video tape recorder according to claim 1, wherein the amount of attenuation of the burst signal by the attenuation amount switching means during editing is attenuated by the same amount as the amount of amplification of the burst signal during recording.