JPS61251386A - Video tape recorder - Google Patents

Abstract

PURPOSE:To lower a noise at a time reproducing and recording a signal by disposing a noise lowering circuit connected selectively to a video recording circuit and a video reproducing circuit respectively on at the time recording and reproducing the signal. CONSTITUTION:A video tape recorder 21 has change over switches 23,24 at the front and rear sections of a noise reducing circuit 22. The switches 23 and 24 are respectively changed over to a luminance signal input terminal 2 and a buffer circuit 3 side on the recording, and respectively changed over to a deemphasis circuit 11 and the luminance signal output terminal 13 side on the reproducing. According, the circuit 22 used for improving the quality of a reproduced picture is interposed between the terminal and the circuit 3 when recording. Thereby, on dubbing from a magnetic tape having a deteriorated quality of the picture by the recording of a TV broadcasting picture having a bad SN ratio or the repetition of the dubbing, if the switches 23,24 are changed over to the recording side, the noise reduction is attained for the signal to be recorded.

Description

[Detailed description of the invention] [Industrial application field] This invention provides a noise reduction circuit for improving playback image quality.

This invention relates to a video tape recorder used for improving image quality during recording.

[Conventional technology]

Magnetic tapes that record audio or video signals have an increase in noise in the recorded signals each time they are dubbed, so this is to improve the playback quality of magnetic tapes that have been copied after multiple dubbings.

A video tape recorder with a built-in noise reduction circuit has been proposed.A conventional video tape recorder 1 of this type shown in FIG. The signal is supplied to the FM modulation circuit 5 via the emphasis circuit 4, and the FM-modulated luminance signal is supplied to the rotating magnetic head 8 via the recording amplifier circuit 6 and the cut-off switch 7. During playback, the selector switch 7 is switched to supply the signal read out by the one-rotation magnetic head 8 to the FM demodulation circuit 10 via the preamplifier circuit 9, thereby producing an FM demodulated luminance signal.

The signal is supplied to a noise reduction circuit 12 via a de-emphasis circuit 11.

The noise reduction circuit 12 reduces noise contained in the luminance signal sent from the de-emphasis circuit 11 and supplies it to the luminance signal output terminal 13 .

Note that the buffer amplifier circuit 3. brien 7 assist circuit 4
．． The FM modulation circuit 5, the recording amplifier circuit 6, etc. are included as part of the video recording circuit 14, and the preamplifier circuit 9. FM demodulation circuit 10. The de-emphasis circuit 11 and the like are included as part of the video reproduction circuit 15.

[Problem that the invention seeks to solve]

In the conventional video tape recorder 1 described above, the noise reduction circuit 12 is interposed only in the signal reproduction system, and no noise reduction processing is performed on the video signal to be recorded.
The noise contained in the video signal itself ends up being recorded on the magnetic tape. Therefore, when a magnetic tape recorded in this manner is played back by a video tape recorder, there are problems such as unavoidable deterioration of the playback image quality due to noise.

Furthermore, in order to reduce noise during signal recording, it is conceivable to insert a noise reduction circuit similar to the noise reduction circuit 12 in the preceding stage of the buffer amplifier circuit 3.

In that case, there were problems such as an unavoidable increase in manufacturing costs due to the noise reduction circuit provided in the new nine.

[Means for solving problems]

The present invention solves the above problems, and includes a video recording circuit that supplies a video signal to be recorded to a rotating magnetic head that rotates in contact with a magnetic tape during signal recording, and a video recording circuit that supplies a video signal to be recorded to a rotating magnetic head that rotates in contact with a magnetic tape during signal recording, and a A video playback circuit that plays back video signals read from the tape, and a common connection between the output side of this video playback circuit and the input side of the video recording circuit, and the video recording circuit and video playback circuit are connected to each other during signal recording and signal playback. The main feature is that the noise reduction circuit is selectively connected to the circuit.

[Effect]

In this invention, a noise reduction circuit commonly connected to the output side of the video playback circuit and the input side of the video recording circuit is selectively connected to the video recording circuit and the video playback circuit during signal recording and signal playback, respectively. A single noise reduction circuit is shared by the video playback circuit and the video recording circuit.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a circuit diagram of main parts showing an embodiment of the video tape recorder of the present invention;
FIG. 3 is a circuit configuration diagram showing each embodiment of the noise reduction circuit shown in FIG. 1, respectively.

In FIG. 1, the video tape recorder 21 is provided with changeover switches 23 and 24 before and after the noise reduction circuit 220, so that the brightness signal input terminal 2 and the de-emphasis circuit 11 are switched on the input side of the noise reduction circuit 220, and on the output side. This allows the brightness signal output terminal 13 and the buffer amplifier circuit 3 to be switched. That is, the changeover switch 23
and 24.

During recording, they are switched to the luminance signal input terminal 2 and buffer amplifier circuit 3111, respectively, and during reproduction, they are switched to the de-emphasis circuit 11 and the luminance signal output terminal 13, respectively.

Therefore, the noise reduction circuit 22 used for improving the reproduced image quality can be interposed between the luminance signal input terminal 2 and the buffer amplifier circuit 3 during recording. This is J
, for recording television broadcast images with poor signal-to-noise ratios, and for dubbing from magnetic tapes whose image quality has deteriorated due to repeated dubbing.

By leaving the changeover switches 23 and 24 on the record 4 side, it is possible to reduce noise in the signal to be recorded.

The noise reduction circuit 22 used in this embodiment includes a high-frequency door wave circuit 25 that separates the input signal into high-frequency components consisting of transverse sound components and edge components, and other low-frequency components, as shown in FIG. A low-frequency P-wave circuit 26 is provided in parallel, and a high-frequency F-wave circuit 2
The adder 28 adds the output of the slice circuit 27 and the output of the low-pass filter circuit 26, which output only signals having a certain level or higher among the outputs of the filter 5. The slice level in the slice circuit 27 is the same as that of the high-frequency p-wave circuit 2.
The noise components and edge components included in the output of 5.

Since the levels are set such that they can be separated based on the mutual level difference, only the edge components are supplied to the adder 2B. As a result, the output of adder 28 is:

The signal is a combination of the low frequency component from the low frequency F wave circuit 26 and the edge component from the slice circuit 27.

This results in a signal with reduced noise.

Also, a noise reduction circuit 32 shown in FIG.

The polarity of the noise component extracted using the high-frequency p-wave circuit 33 and the IJ mitter circuit 34 is inverted by the 1-inverting circuit 35.

A configuration in which the noise component is canceled by adding it to the original signal in the adder 36 is also possible.Of course, the limiter circuit 3
The amplitude limiting level in 4 is set at a level such that the noise component and edge component included in the output of the high-frequency door wave circuit 33 can be separated by the mutual level difference, so the output of the limiter circuit 34 is only a noise component. Become.

In this way, the video tape recorder 21.

The noise reduction circuit 22 or 33 commonly connected to the output side of the video playback circuit 15 and the input side of the video recording circuit 14 is connected to the tl!
! The video recording circuit 14 is used for signal recording and signal reproduction.
Since the noise reduction circuit 22 is configured to be selectively connected to the video playback circuit 15 and the video playback circuit 15, the single noise reduction circuit 22 can be shared by the video playback circuit 15 and the video recording circuit 14, and therefore only performs noise reduction during signal playback. In addition, it is possible to reduce the noise of the video signal in advance during signal recording, and this can slightly improve the noise reduction effect during signal playback. It is also possible to create video tapes that can be played back on.

〔Effect of the invention〕

As explained above, according to the present invention, the noise reduction circuit commonly connected to the output side of the video playback circuit and the input side of the video recording circuit is connected to the video recording circuit during signal recording and during signal playback, respectively. Since it is configured to be selectively connected to the video playback circuit, the noise reduction circuit of jtl- can be shared by the video playback circuit and the video recording circuit, so it not only reduces noise during signal playback but also performs signal recording. In some cases, the noise in the video signal can be reduced in advance, thereby further increasing the noise reduction effect during signal playback, and the videotape is designed for playback on other video tape recorders that do not have a noise reduction circuit. It has excellent effects, such as being able to create

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a main part of an embodiment of a video tape recorder according to the present invention, and FIGS. 2 and 3 are circuit diagrams. FIG. 1 is a circuit configuration diagram showing each embodiment of the noise reduction circuit shown in FIG. 1, and FIG. 4 is a circuit configuration diagram of main parts showing an example of a conventional video tape recorder. 8... Rotating magnetic head, ]4... Video recording circuit, 1
5... Video playback circuit, 21... Video tape recorder. 22.32... Noise reduction circuit, 23.24... Changeover switch.

Claims (1)

[Claims] A video recording circuit supplies a video signal to be recorded to a rotating magnetic head that rotates in contact with a magnetic tape during signal recording, and a video reproducing circuit that reproduces the video signal read from the magnetic tape by the rotating magnetic head during signal reproduction. , a noise reduction circuit commonly connected to the output side of the video playback circuit and the input side of the video recording circuit, and selectively connected to the video recording circuit and the video playback circuit during signal recording and signal playback, respectively. A video tape recorder.