JPS5870406A - Device for correcting jitter of rotary head type magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate a noise due to jitter, by frequency-modulating a sound signal, also recording a jitter correcting signal simultaneously, and subtracting a demodulating output of the jitter correcting signal from a demodulating sound signal, when reproducing. CONSTITUTION:When recording, a luminance signal is FM-modulated by a recording side video signal processing circuit 3, and a chrominance signal is converted to a low band. A sound signal is FM-modulated by an FM modulating circuit 4, a jitter correcting signal is also inputted to a mixing circuit 6 by a jitter correcting oscillator 5, and is supplied to the recording and reproducing head. When reproducing, the luminance signal and the chrominance signal are processed by a reproducing picture processing circuit 7. The sound signal is selected by a BPF1, and is supplied to a demodulating circuit 8. The jitter correcting signal is selected by a BPF2, is supplied to an FM demodulating circuit 9, and only a level variation part caused by jitter is fetched. This level variation portion is added to the demodulating circuit 8 by an adder 11, and the jitter component is offset completely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a jitter correction device for a rotary head type magnetic recording/reproducing apparatus which performs FM modulation on an audio signal so as to be superimposed on a video signal and can be recorded on a magnetic tape.

In general, as a method of superimposing and recording an audio signal and a video signal, the spectrum of the low-frequency converted color signal C and the F
A method in which an audio signal is FM-modulated in the gap that exists between the spectrum of the M-modulated luminance signal Y (Figure 1 shows the case of 2 channels, and the frequency is shown as f+12). is used. In devices that use a rotating magnetic head, recording and playback are performed while the magnetic tape is wrapped around the outer circumference of the rotating head (approximately 180 degrees), so the relative speed of the rotating head and magnetic tape is Due to the non-uniformity, jitter occurs in the signal due to fluctuations in the time axis, and this fluctuation in the time axis results in fluctuations in frequency, but fluctuations in frequency become fluctuations in amplitude after FM post-adjustment. That is, after demodulating an FM-modulated audio signal by 1.1x, if there is jitter, level fluctuations based on it are heard as noise, which gives an unpleasant feeling both in terms of sound quality and hearing.

The present invention was developed in order to eliminate the above-mentioned problems, and is applicable to a rotary head type magnetic recording/reproducing device which is capable of recording an audio signal on a magnetic tape by subjecting it to FM modulation and superimposing it on a video signal. A jitter correction apparatus is provided below. An embodiment of the jitter correction apparatus for a rotary magnetic recording/reproducing apparatus of the present invention shown in FIG. 2 will be described in detail below.

FIG. 2 is a block diagram showing one embodiment of the present invention, in which 1 indicates a recording side circuit and 2 indicates a reproduction side circuit. The recording side circuit 1 inputs a video output signal from a video camera, tuner, etc. (not shown), and performs FM modulation on the luminance signal Y (
The recording side video processing circuit 3 converts the color signal C into a low frequency band (color low frequency conversion signal) together with the YFM signal and supplies it to the recording/reproducing heads RPI and RP2, and the audio output signal (color low frequency conversion signal) from a video camera, tuner, etc. (not shown). In Figure 1, the frequency is f, 72
) is input and performs FM modulation so that it can be superimposed and recorded with the luminance signal Y11 signal C, and a jitter correction oscillator that oscillates a jitter correction frequency f to correct jitter as described later. 5. A mixing circuit 6 which mixes the outputs of the recording side video processing circuit 3, the FM modulation circuit 4, and the jitter correction oscillator 5 and supplies the mixture to the recording/reproducing heads RPI and RP2. Note that the jitter correction oscillator 5 must have a stable oscillation frequency, and is preferably a crystal controlled oscillator or the like. The reproducing side circuit 2 is a recording/reproducing head RPI.

A composite signal of the YFM signal obtained from RP2, the color low frequency conversion signal, the frequency f for jitter correction, and the audio FM signal is input, and the YFM signal and the color low frequency conversion signal are converted into a luminance signal Y and a color signal C. A playback side video processing circuit 7 outputs a video signal to be supplied to a television receiver (not shown) or the like to a video output terminal V, a bandpass filter BPF1. Bandpass filter BPF'1) A demodulation circuit 8 that demodulates the obtained audio FM signal and converts it into an audio signal, and bandpass filters BPF2 and BPF2 that select and pass only the jitter correction frequency 1 from the composite signal. FM demodulation circuit 9 and F'M demodulation circuit 8 that demodulate the jitter correction frequency f obtained from
A level adjuster IO1 is installed at the output of the demodulation circuit 8 to adjust the level of the output.
The adder 11 adds the inverted signal of the output of the demodulation circuit 9 obtained through the adder 11 and outputs the resultant signal to the audio output terminal A-\. Note that an audio FM signal and a jitter correction frequency f are also input to the reproduced video processing circuit 7, but these frequencies are the luminance signal Y.

Since it is cut when color No. 48 C etc. are separated and converted, no problem occurs at all. S is the record/playback switch,
It is composed of interlocking switches S□ and s2, and when the respective movable contacts X and X2 are switched to R, R2, the recording state is entered and the recording side circuit 1 switches the recording head RPI.
, RP2, and the movable contact pieces X, , X2 are connected to P
When it is switched to P2, it is in a playback state and the playback side circuit 2 is connected to the recording/reproducing heads RPI and RP2.

The jitter correction device for a rotary head type magnetic recording/reproducing device according to the present invention has the above-mentioned configuration, and its operation will be described in further detail.

During recording, as described above, the recording-side video signal processing circuit 3 performs FM modulation on the luminance signal Y, and the color signal C undergoes low frequency conversion 4, and the FM modulation circuit 4 performs FM modulation on the audio signal, which are then sent to the mixing circuit 6. is input. At the same time, the frequency f for jitter correction is also input to the mixing circuit 6 by the jitter correction oscillator 5, so that the recording/reproducing head RPI.

These combined signals will be supplied to RP2.

At this time, if jitter occurs between the recording/reproducing heads RPI, RP2 and a magnetic tape (not shown), the frequency of each signal will fluctuate, and each signal will be modulated by the jitter and recorded on the magnetic tape (not shown). It will be recorded.

Next, when this magnetic tape is reproduced, the video signal is again converted into a luminance signal Y and a color signal C by the reproduced video processing circuit 7 and supplied to a television receiver (not shown), etc., and an FM-modulated audio signal Huband bus filter BPF'l
It is further demodulated by the demodulation circuit 8 and supplied to the adder 11. Therefore, if jitter correction is not performed, the amount of frequency fluctuation due to jitter during recording will be F
These become noise because they appear as level fluctuations (amplitude fluctuations) due to M demodulation.

In the present invention, the jitter correction frequency f is extracted by the BPF'2 and supplied to the FM demodulation circuit 9, but since this frequency f is also subject to frequency fluctuations due to jitter during recording, the kneading is performed by the FM demodulation. By doing so, it is possible to obtain an output corresponding to only the level fluctuation due to jitter, and this output has the same waveform as the noise due to jitter contained in the writing signal outputted from the lyrics writing circuit 8. Therefore, the addition 1γ
The output of the demodulating circuit 9 is inverted to the demodulating circuit 8 by the converter 11.
By adding the ξ-fold signal, noise (level fluctuation) due to jitter can be completely canceled out. Note that the level adjuster 10 is for adjusting the level of the jitter correction output obtained from the demodulation circuit 9 to be the same level as the noise included in the output of the demodulation circuit 8.

In addition, although this embodiment takes as an example the case where an audio signal is FM modulated and superimposed on a video signal, the same structure can be used when only an audio signal is FM modulated and recorded on a magnetic tape. effect can be obtained.

Although the number of channels of the audio signal is 2 channels (frequency/'x, , /;) in the embodiment, it is not limited to this, and the number of channels can be increased or decreased as necessary. It goes without saying that there is.

As described above, according to the rotary head type magnetic recording/reproducing apparatus of the present invention, especially when using a method in which an audio signal is FM modulated and recorded by superimposing it on a video signal, the jitter correction frequency is adjusted during recording. When both are recorded and played back, the jitter correction frequency is demodulated to detect only the noise due to jitter (level fluctuations) and cancel it out with the noise due to jitter included in the audio signal. It is possible to almost completely cancel the noise caused by
An extremely good reproduced signal can be obtained. Furthermore, the configuration is simple and the practical benefits are significant.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing frequency spectra of luminance signals, chrominance signals, etc., and FIG. 2 is a block diagram of essential parts of a rotary head type magnetic recording/reproducing apparatus showing an embodiment of the present invention. Explanation of symbols

Claims (1)

[Claims] In a rotary head type magnetic recording and reproducing apparatus which is configured to perform F''M modulation of an audio signal and record it on a magnetic tape, and to demodulate and reproduce the FM modulated audio signal recorded on the magnetic tape, means for mixing and recording a frequency signal for time jitter correction with the FM modulated audio signal;
means for demodulating the jitter correction frequency signal during reproduction to output a jitter correction signal; and adding the signal obtained by the means to the demodulated audio signal in reverse phase to compensate for jitter contained in the audio signal. A jitter correction device for a rotary head type magnetic recording/reproducing device, comprising means for canceling noise.