JPS594280A - Magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To avoid the effect of wow and flutter and jitter, by frequency-discriminating a horizontal synchronizing signal of a reproduced video signal for detecting the jitter generated at the recording and reproduction, and eliminating the jitter included in the reproduced audio signal. CONSTITUTION:A monostable multivibrator 35 generates a pulse having a pulse width less than one horizontal scanning period and a 1/2 horizontal scanning period or over while being triggered with the horizontal synchronizing signal. This pulse is applied to a frequency discriminator 36, the fluctuation in the frequency, i.e., the jitter produced at the recording and reproduction is detected as an output level fluctuation, the jitter detecting signal is adjusted into a suitable level with a variable resistor 37 and applied to an inverting input of a subtractor 27. A reproduced audio signal from an FM demodulator 26 is subtracted with the jitter detecting signal at the subtractor 27 and the jitter is eliminated, restored into the audio signal form before the high frequency component is emphasized at a de-emphasis circuit 38 having the inverse characteristic as a pre-emphasis circuit 15 and outputted from an output terminal 39.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus, and includes detecting jitter by frequency-discriminating a horizontal synchronizing signal of a reproduced video signal and removing the jitter from a reproduced audio signal.

It is an object of the present invention to provide a magnetic recording and reproducing device that can obtain reproduced audio signals that are not affected by wow and flutter and jitter.

In magnetic recording and reproducing devices such as general video tape recorders, video signals are recorded by a rotating head on tracks that are inclined in the longitudinal direction of the magnetic tape, and audio signals are recorded by a fixed head on tracks that are inclined in the longitudinal direction of the magnetic tape. recorded on the track. in this case.

The relative speed between the fixed head and the magnetic tape is slow, and the reproduced audio signal suffers from wow and flutter due to fluctuations in the running speed of the magnetic tape. There is something to record on the track. This conventional magnetic recording and reproducing apparatus uses, for example, a low-converted carrier color signal of a color subcarrier frequency path 630 KH2 and an FM carrier frequency side shift of 3.5M.
In order to avoid the influence of the side bands of the carrier color signal and FM luminance signal, an FM-modulated audio signal is added to the video signal consisting of the II'M luminance signal of H2 to 4.5 MHz, with the carrier frequency path selected to be 1 MHz. This multiplexed signal is recorded on a track inclined in the longitudinal direction of the magnetic tape by a rotating head. Here, the relative speed between the rotating head and the magnetic tape is more than 100 times the running speed of the magnetic tape, and the ratio of the running speed of the magnetic tape to the relative speed of the rotating head and the magnetic tape is less than 1%, so the reproduced signal Although the effects of wow and flutter mentioned above can be ignored, jitter occurs in the playback signal due to uneven rotation of the magnetic tape's 9-turn head, expansion and contraction of the magnetic tape, etc., and is included in the FM audio signal in the playback signal. There is a drawback that the jitter component is output as noise when the FM audio signal is demodulated.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to the drawings.

The figure shows a block system diagram of an embodiment of a magnetic recording/reproducing apparatus according to the present invention. In the figure, reference numeral 1 denotes an input terminal into which, for example, an NTSO color video signal is input, and this color video signal is supplied to a bandpass filter 2 and a low-pass filter 3. Band fill 2 is approximately 3.5aM from the color video signal
Take out the carrier color signal of Hg±500 KH2. This carrier color signal is converted to a low frequency of, for example, a color subcarrier frequency of about 63 DKHz in a low-pass conversion processing circuit 4, and then a low-pass filter 3 removes components with a frequency of about 1M or higher, for example, and the signal is sent to a mixer 6. Supplied. It's a trench.
The low-pass filter 3 is approximately 3M from the supplied color Kaitai signal.
Extract the luminance signal below H2. This brightness signal is AGO
After the level on the circuit has been stabilized, the clamp circuit 8
The sync tip level is accurately clamped so that it does not change, and then the high frequency component is amplified in the pre-emphasis circuit, and the overshoot in the white direction is white-clipped in the clamp circuit IO, and the undershoot in the black direction is suppressed in the clamp circuit IO. FM modulator 11 after dark clipping
supplied to For example, the FM modulator +1 modulates the sync tip level of the ri luminance signal to 3.4 MHz and the sync tip level of the white signal to 4.4 MHz. Sidebands below approximately 1.55 MHz are removed and the signal is supplied to the mixer 6. Along with this, an audio signal 1dAGo circuit f'4ic is provided to the input terminal +3.
After the level is stabilized, the high-frequency components are amplified by the pre-emphasis circuit 15 and supplied to the FM modulator 6. The FM modulator 16 converts a carrier wave with a frequency of approximately 1.4 MHz into an audio signal from the pre-emphasis circuit 15, for example.
M modulates. The resulting FM audio signal is filtered by a bandpass filter 11 to a frequency of approximately j, 4MHz±100K.
The H2 component is taken out and supplied to the mixer 6. The mixer 6 receives low-pass converted carrier color signals of different frequency bands,
The FM luminance signal and FM audio signal are mixed and multiplexed. This multiplexed signal is amplified by the recording amplifier 1B, and then the head 1 rotates once.
9, the information is recorded on tracks inclined in the longitudinal direction of the magnetic tape 20.

Next, during reproduction, the reproduction signal reproduced by the rotary head 19 from the track of the magnetic tape 2o is passed through the bandpass filter 21. High-pass filter 22. It is supplied to each of the low-pass filters 23. The bandpass filter 21 has a frequency of approximately 1 from the reproduced signal.
．． The reproduced FM audio signal of 4MH2±100KIIz is extracted. This reproduced audio FM signal is sent to the amplifier 24.
After being amplified by the limiter 25, amplitude fluctuations are removed and the signal is supplied to the 7M demodulator 26. The 7M demodulator 26 FM demodulates the reproduced audio FM signal and supplies it as a reproduced audio signal to the positive input terminal of the subtracter 2T. The high-pass filter 22 also filters the reproduced signal at a frequency of approximately 1. The reproduced FM luminance signal of li5MH2 or higher is extracted. The reproduced FM brightness 1 signal is subjected to amplitude fluctuations removed by a limiter 28, then FM demodulated by an FM demodulator 2g to become a reproduced brightness signal, and is then processed by a de-emphasis circuit 30 having characteristics opposite to those of the pre-emphasis circuit 9. After being returned to the luminance signal form before high frequency component enhancement, it is supplied to the mixer 31 and the horizontal synchronizing signal separation circuit 32. Further, the low-pass filters 2 and 3 extract a reproduced low-pass-converted carrier color signal having a frequency of approximately 1M or less from the reproduced signal. This reproduced carrier color signal after low frequency conversion is processed in the reproduction processing circuit 33 at a color subcarrier frequency of approximately 3.58.
The signal is returned to the MH reproduced carrier color signal and supplied to the mixer 31. The mixer 31 mixes the reproduced carrier color signal and the reproduced luminance signal to form a reproduced video signal, which is outputted via the output terminal 34.

Next, the horizontal synchronization signal separation circuit 32 separates the reproduced luminance signal and the horizontal synchronization signal and supplies them to a monostable multivibrator C (hereinafter referred to as "mono multi") 35. mono multi 3
5 generates a pulse having a pulse width less than one horizontal scanning IM period and greater than or equal to 1/2 horizontal scanning IJd period in response to a horizontal synchronizing signal. This eliminates the effects of the equivalent pulse and the vertical synchronization pulse within the vertical blanking period. This pulse is supplied to the frequency discriminator 36, and the fluctuation in the repetition frequency of this pulse and the jitter that occurs during recording and reproduction are detected as fluctuations in the output level, and this jitter detection signal is adjusted to an appropriate level by the volume 3γ. and is supplied to the negative input terminal of the subtracter 27. The reproduced audio signal from the 7M demodulator 26 is subtracted by the jitter detection signal in the subtracter 2T to remove jitter, and then the high-frequency component is enhanced by the de-emphasis circuit 38, which has the opposite characteristics to the pre-emphasis circuit 15. The audio signal is returned to its previous form and output from the output terminal 39.

In this way, it is possible to extract a reproduced audio signal that is not affected by wow, flutter and jitter that occur during recording and reproduction.

Note that color video signals are not limited to the NTSO format.

The PAL or SEOAM system may be used, and the low frequency conversion frequency of the carrier color signal, the carrier wave frequency of the FM luminance signal, and the carrier wave frequency of the FM audio signal are not limited to the above embodiments.

In the above embodiment, the video signal and the audio signal are frequency-division multiplexed and recorded and reproduced using a single rotating head. Even if a video signal head and an audio signal head are installed adjacent to each other and video and audio signals are recorded and played back using the respective heads, the jitter included in the playback video signal and playback audio signal is approximately Therefore, the jitter of the reproduced audio signal can be corrected in the same manner as in the above embodiment.

It is not limited to the above embodiments.

As described above, the magnetic recording and reproducing apparatus according to the present invention is as follows.

The horizontal synchronization signal of the reproduced video signal is frequency-discriminated to detect the jitter that occurs during recording and reproduction, and the jitter contained in the reproduced audio signal is removed. It has features such as being able to extract high-quality reproduced audio signals that are not affected by any effects.

[Brief explanation of the drawing]

The figure is a block system diagram of an embodiment of a magnetic recording/reproducing apparatus according to the present invention. , 4... Low-frequency conversion processing circuit, 6.31... Mixer,
11.18... IFM modulator, 19... Rotating head. 20...Magnetic tape, 26.29...FM post-tuner,
2T... Subtractor, 32... Horizontal synchronizing signal separation circuit, 33... Reproduction processing circuit, 35... Monostable multivibrator (mono multi), 3B... Frequency discriminator, 37... volume.

Claims (1)

[Claims] The video signal and the audio signal can be recorded and played back by respective heads mounted adjacent to a common support, or the video signal and the audio signal can be frequency-division multiplexed and recorded by a single head. In a video signal recording and reproducing device for reproducing, the horizontal synchronizing signal of the reproduced video signal is frequency-discriminated to detect jitter that occurs during recording and reproducing, and the jitter contained in the reproduced audio signal is removed. A magnetic recording and reproducing device.