JPH0459831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video and audio signal reproducing device for reproducing signals from a recording tape on which video and audio signals constituting a television signal are recorded.
In particular, the audio signal is considered to be a frequency modulated signal,
When a video signal and a frequency-modulated audio signal are mixed with a video signal and recorded on a recording tape with a tilted recording track, a common playback head is used to reproduce the video signal and the frequency-modulated audio signal. It is an object of the present invention to provide a video and audio signal reproducing device that can obtain signals.

When a color television signal is recorded on a magnetic tape, the carrier chrominance signal and luminance signal that form the color video signal are separated, the carrier chrominance signal is frequency-converted to the lower frequency band, and the luminance signal is frequency-converted to the higher frequency band. After frequency modulation (hereinafter referred to as FM modulation) on the band side, both are mixed and recorded on recording tracks arranged at an angle with respect to the running direction of the magnetic tape (hereinafter referred to as tilted tracks).
Furthermore, the mainstream format is one in which the audio signal is recorded with a recording track (hereinafter referred to as audio track) extending in the direction along the running direction of the magnetic tape.

In such a recording format, the gradient track on which the color video signal, that is, the carrier color signal converted to the low frequency range and the luminance signal modulated by FM on the high frequency side, is recorded as follows.
Two rotating magnetic heads to which both of these signals are supplied alternately scan the magnetic tape at an angle with respect to its traveling direction, thereby increasing the recording density. In order to enable long-term recording, it has been proposed to leave no gaps, or so-called guard bands, between adjacent inclined tracks, but to allow the inclined tracks to be adjacent to each other. In this case, crosstalk between adjacent tilted tracks becomes a problem during playback, but by making the azimuth angles of the two rotating magnetic heads different from each other, the brightness signal that is FM modulated on the high frequency side during playback can be For example, for a low-pass converted carrier color signal where the azimuth loss effect is small, the phase is changed by increasing the azimuth loss with respect to the crosstalk components from adjacent tracks. The tracks are made continuous, and the remaining tilted tracks are recorded in reverse every horizontal period, and a predetermined phase restoration is performed on the reproduced conveyed color signal to obtain a comb-shaped characteristic. By passing the signal through a filter, crosstalk components from adjacent tracks can be removed, thereby solving the problem of crosstalk. Further, the audio track is continuously formed, for example, at the upper end of the magnetic tape by constantly contacting the running magnetic tape with a fixed head that receives audio signals. At this time, if there are two types of audio signals, such as a stereo left signal and a right signal, the left and right signals are supplied to separate fixed heads, and these two fixed heads are used to output signals in parallel. Two audio tracks are formed.

By the way, when high-density recording of color video signals as described above is attempted, the running speed of the magnetic tape increases while the relative speed between the magnetic tape and the rotating magnetic head is maintained at a predetermined level. extremely slow,
For example, it can be set to about 1.33cm/sec. For this reason,
This has the disadvantage that the relative speed between the fixed head forming the audio track and the magnetic tape becomes extremely low, resulting in a reduction in the quality of the recorded audio signal.

Therefore, the audio signal is mixed with the color video signal as an FM modulated signal, supplied to the rotating magnetic head, and is recorded together with the color video signal on the inclined track where the color video signal is originally recorded. Systems have been proposed that attempt to prevent the quality of recorded audio signals from deteriorating due to the low relative speed between the recording head and the magnetic tape.

Based on this method of preventing the quality of recorded audio signals from deteriorating, a color video signal is recorded from a magnetic tape on which a color video signal and an FM-modulated audio signal are recorded with a common slope track. And when the audio signal is reproduced, a mixed signal of the recorded color video signal and the FM modulated audio signal is produced by two reproducing rotating magnetic heads that alternately scan every other inclined track formed in the array. ,
The FM modulated audio signal is reproduced for each tilt track with an overlap period, and the FM modulated audio signal being reproduced from each reproducing rotating magnetic head is demodulated to obtain a reproduced audio signal. However, in this case,
obtained alternately from two reproducing rotating magnetic heads.
Since the playback output of the FM modulated audio signal is divided for each slope track,
Finally, a synthesis process is required in which the reproduced audio signals based on the FM modulated audio signals from each reproduction rotating magnetic head are joined together to form a continuous reproduced audio signal. hand,
Pulse noise may be generated at the joint, which may cause quality deterioration such as loss of fidelity of the reproduced audio signal.

The present invention provides first and second signals obtained by frequency modulating an FM-modulated luminance signal, a carrier color signal frequency-converted to a lower frequency band side, and a pair of carrier waves having different frequencies using a first audio signal. FM-modulated audio signal, and third and fourth FM-modulated signals obtained by FM-modulating another pair of carrier waves having different frequencies with the second audio signal are FM-modulated. A luminance signal, a carrier color signal frequency-converted to the low frequency band side, and first and third
A mixture of FM modulated audio signals, an FM modulated luminance signal, a carrier color signal frequency-converted to the low frequency band side, and second and fourth
Two playback heads are used to reproduce video and audio signals from a recording tape in which FM-modulated audio signals are mixed and recorded on two adjacent inclined tracks. At the time of reproduction, a synthesis process is performed in which the reproduced audio signals based on the first to fourth FM modulated audio signals output from the two reproduction rotary heads are joined to form a continuous reproduced audio signal.
An object of the present invention is to provide a video and audio signal reproducing device which can perform reproducing audio signals without generating pulse noise or the like at the joints of the reproduced audio signals. Examples of the present invention will be described below.

First, prior to describing the embodiments of the present invention, a video and audio signal recording system for a recording tape that is reproduced by the video and audio signal reproducing apparatus according to the present invention will be described.

FIG. 1 shows the main parts of an example of such a video and audio signal recording system. In this example, two channels of stereo left and right signals are supplied as audio signals to be recorded, and these two channels of audio signals are converted into four FM modulated audio signals, first to fourth. , which is recorded together with a color video signal. In this example, left signal SL and right signal SR of stereo audio signals are supplied to audio input terminals 1 and 2, respectively. This left signal SL sequentially passes through an automatic gain control amplifier circuit 3, a noise reduction circuit 4, and a pre-emphasis circuit 5, and is supplied to first and second FM modulators 6 and 7, respectively. Similarly, the right signal SR passes through the automatic gain control amplifier circuit 8, the noise reduction circuit 9, and the pre-emphasis circuit 10 in order, and then passes through the third and fourth
The signal is supplied to each of FM modulators 11 and 12. The first and second FM modulators 6 and 7 have a frequency f ₁ and a frequency f ₂ higher than f ₁ , for example f ₁ =1.325MHz.
The carrier waves of f ₂ = 1.475 MHz are FM modulated with the same frequency shift width, for example, about 100 to 150 kHz, using the left signal SL, and FM signals with different frequency shift bands are sent to each output end. Modulated left signals (hereinafter referred to as left FM signals) LF ₁ and LF ₂ are obtained.
Also, the third and fourth FM modulators 11 and 12
is a frequency f ₃ higher than f ₂ and a frequency f ₄ even higher than f ₃ , for example, f ₃ = 1.625 MHz and f ₄ = 1.775 MHz,
The carrier waves of the respective carriers are FM modulated with the right signal SR with the same frequency shift width as mentioned above, and the FM modulated right signals with different frequency shift bands are sent to each output end (hereinafter referred to as right FM signal). RF ₃ and RF ₄ are obtained.
Here, the frequencies f ₁ , f ₂ , f ₃ and f ₄ are
The interval is selected such that the beat noise component between the left FM signal and the right FM signal after demodulation is outside the reproduced audio signal band, and in the above example, this interval is 150 kHz. The two left FM signals LF ₁ and LF ₂ and the two right FM signals RF ₃ and RF ₄ thus obtained pass through corresponding bandpass filters 13, 14, 15 and 16, respectively. These left FM signals LF ₁ and LF ₂ and the right
FM signals RF ₃ and RF ₄ have their level LF ₁
<LF ₂ <RF ₃ <RF ₄ , and the frequency spectrum is as shown in FIG. 2 (the axis is frequency/f).

The left FM signal LF ₁ from the bandpass filter 13 and the right FM signal RF ₃ from the bandpass filter 15 are supplied to a common mixing amplifier circuit 17, and the left FM signal LF 2 from the bandpass filter 14 and the right FM signal RF ₃ from the bandpass filter 15 are supplied to a common mixing amplifier circuit 17. The right FM signal RF ₄ from 16 is supplied to a common mixing amplifier circuit 18 . Further, a mixed output of the left FM signal LF ₁ and the right FM signal RF ₃ from the mixing amplifier circuit 17 and the left FM signal from the mixing amplifier circuit 18
In mixing circuits 19 and 20, the mixed output of LF ₂ and the right FM signal RF ₄ is outputted from the carrier color signal C from terminal 21, which is a video signal, and the carrier color signal C from terminal 22, which is a video signal.
The FM modulated luminance signal L _n is mixed.

Here, the carrier color signal C is a carrier color signal separated from a color video signal whose color subcarrier has a frequency f _c lower than the above-mentioned frequency f ₁ , for example,
f _c = 688kHz, and the FM-modulated luminance signal L _n is such that the leading edge of the synchronization signal of the luminance signal separated from the color video signal is lower than the frequency f ₄ mentioned above. The frequency f _s is sufficiently high, for example, f _s = 4MHz, and the white peak (maximum amplitude part) is higher than f _s at a predetermined frequency, for example,
1.2MHz, higher frequency f _p , e.g. f _p =5.2M
Hz, was obtained by performing FM modulation. Note that the level of the carrier color signal C is the left FM
The level of the FM-modulated luminance signal L _n is higher than any of the signals LF ₁ and LF ₂ and the right FM signals RF ₃ and RF ₄ , and the level of the FM-modulated luminance signal L n is even higher than the level of the carrier color signal C. These low-pass converted carrier color signal C and FM modulated luminance signal L _n and left
FM signals LF ₁ and LF ₂ , and right FM signals RF ₃ and
An example of the relationship between the frequency spectrum and each level with RF ₄ is as shown in FIG. 3 (the horizontal axis is the frequency f and the vertical axis is the level l). In addition, l _n
indicates a luminance signal separated from a color video signal.

Then, the carrier color signal C from the mixing circuit 19,
A first mixed output M ₁ in which the FM modulated luminance signal L _n , the left FM signal LF ₁ and the right FM signal RF ₃ are mixed is supplied to the rotating magnetic head 24 via the recording amplifier circuit 23 , and Carrier chrominance signal C, FM modulated luminance signal L _n , left FM signal from circuit 20
A second mixed output M ₂ in which LF ₂ and the right FM signal RF ₄ are mixed is supplied to the rotating magnetic head 26 via the recording amplifier circuit 25 . These magnetic heads 24 and 26 have azimuth angles different from each other, and alternately form oblique tracks without guard bands on the magnetic tape, and produce a first mixed output _M1.
and the second mixed output M ₂ are recorded alternately. That is,
The magnetic heads 24 and 26 form two adjacent inclined tracks on which the first and second mixed outputs M ₁ and M ₂ are azimuthally recorded. Here, the first mixed output _M1 has a frequency spectrum as shown in FIG. 4, and the second mixed output _M2 has a frequency spectrum as shown in FIG. As shown in Figure 6, these are as follows.
Magnetic heads 24 with different azimuth angles
and 26, the information is recorded on mutually adjacent inclined tracks _t1 and _t2 formed on the magnetic tape T, respectively. Incidentally, the inclined tracks t ₁ and t ₂
are set so that a temporal overlap occurs at their ends.

In FIG. 6, arrow a and arrow b are respectively
Running direction of magnetic tape and magnetic heads 24 and 2
6 indicates the scanning direction, and CTL indicates the control signal track. Further, it is assumed that the carrier color signal C and the FM-modulated luminance signal L _n recorded individually on the inclined tracks t ₁ and t ₂ correspond to one vertical period, that is, one field.

Furthermore, in this example, audio signal recording systems 27 and 28 with fixed heads for the left signal SL and right signal SR are also provided, and the audio input terminal 1
The left signal SL and right signal SR from 2 and 2 are respectively,
The signals are supplied to audio signal recording systems 27 and 28 using fixed heads, and are recorded on two audio tracks _tL ' and _tR ' formed at the upper end of the magnetic tape T in FIG.

As described above, the carrier color signal C which is a video signal, the FM modulated luminance signal _Ln , and the FM modulated audio signal are recorded with a tilt track formed by a common rotating magnetic head. Although a magnetic tape is obtained, the relative speed between the recording rotating magnetic head and the magnetic tape is said to be high enough to record video signals, resulting in a decrease in the quality of the recorded audio signal. There is no, and also,
In the case of the above-mentioned recording system, when reproducing a recorded magnetic tape, it is possible to obtain a reproduced audio signal in which the audio signals of multiple channels are sufficiently separated from each other and adjacent track crosstalk interference is extremely reduced. Records have been made so that this can be done. Then, such magnetic tape is reproduced by the video and audio signal reproducing apparatus according to the present invention. Next, embodiments of the present invention will be described.

FIG. 7 shows an example of a video and audio signal reproducing device according to the present invention. In this example, 31 and 32
is a reproducing rotating magnetic head, and these reproducing rotating magnetic heads 31 and 32, as shown in FIG. 6, are adjacent to each other, formed on a magnetic tape T recorded by the recording system shown in FIG. The magnetic head 31 reproduces the signal recorded on the slope track _t1 during one field period, and reproduces the signal recorded on _the slope track _t1 during the next field period. Magnetic head 32 is controlled to reproduce the signal recorded on slope track _t2 . Here, the magnetic head 31
has an azimuth angle that corresponds to the azimuth angle of the magnetic head 24 that formed the inclined track t ₁ , and the magnetic head 32 has an azimuth angle that corresponds to the azimuth angle of the magnetic head 26 that formed the inclined track t ₂ . This is what I did. Therefore, the magnetic head 31
A reproduced output of the first mixed output M1 having a frequency spectrum as shown in FIG. 4 is obtained from the magnetic head ₃₂ , and a reproduced output of the second mixed output M2 is obtained from the magnetic head ₃₂ . It will be done. The outputs from these magnetic heads 31 and 32 are supplied to a video signal processing unit 35 via head amplifier circuits 33 and 34, respectively, and are processed by the video signal processing unit 35 for normal carrier color signal C and FM modulated. Demodulation of the luminance signal L _n is performed.

Further, a band pass filter 3 is provided for allowing the output from the magnetic head 31 to pass the left FM signal _LF1 .
6 and a bandpass filter 38 for passing the right FM signal _RF3 . Since these left FM signal LF ₁ and right FM signal RF ₃ do not have adjacent frequency shift bands, they are sufficiently separated by the band pass filters 36 and 38, respectively, and the outputs of the charged pass filters 36 and 38 are The left FM signal LF ₁ and the right FM side have no crosstalk components with each other.
A signal RF ₃ is obtained respectively. In addition, the magnetic head 32
The output from the filter is supplied to a bandpass filter 37 for passing the left FM signal LF ₂ and a bandpass filter 39 for passing the right FM signal RF ₄ . Since these left FM signal LF ₂ and right FM signal RF ₄ also have nonadjacent frequency shift bands, they are sufficiently separated by the band pass filters 37 and 39, respectively, and the outputs of the band pass filters 37 and 39 are On the left side, there is no crosstalk component between each other.
An FM signal LF ₁ and a right FM signal RF ₃ are obtained, respectively.
The left FM signals LF ₁ and LF ₂ and the right FM signals RF ₃ and RF ₄ from the band pass filters 36 to 39, respectively, are transmitted to the amplitude limiting circuits 40, 41, 42 and 4.
3 and the corresponding FM demodulators 44, 45, 46
and 47 for demodulation, and reproduced left signals SL are obtained at the output sides of the FM demodulators 44 and 45 alternately for each field period with an overlap period at the end. 4
At the output of 7, the reproduced right signal SR is obtained alternately for each field period with an overlap period at the end. And each of these FM demodulators 44 to 4
The outputs of 7 are passed through low-pass filters 48, 49, 50 and 51 in the audio signal band, respectively.

Now, focusing on the reproduction left signal, it is obtained alternately from the reproduction outputs of the magnetic heads 31 and 32.
Left FM supplied to FM demodulators 44 and 45, respectively
The signals LF ₁ and LF ₂ are, as shown in FIGS. 8A and 8B, alternating and intermittent signal sections with an overlap period l _p between the respective leading and trailing ends. Each signal section corresponds, of course, to one inclined track t ₁ or t ₂ on the magnetic tape T. And these left FM signals LF ₁ and
LF ₂ is demodulated by FM demodulators 44 and 45, respectively,
The reproduced left signals SL obtained at the output terminals of the FM demodulators 44 and ₄₅ are, as shown in FIG. These pass through low-pass filters 48 and 49.

The same applies to the reproduction right signal, in which such signal divisions are formed at various locations.

In this way, the results from the low-pass filters 48 and 49, as shown in FIGS. 8C and 8D, are obtained.
The intermittent reproduction left signal SL is supplied to one and the other of the two selection input terminals of the switching circuit 53, respectively. The switching circuit 53 has a terminal 5
2, _{as shown} in FIG. high level q ₁
A control signal Q is supplied which takes a low level q ₂ in every other field period.

When the level of the control signal Q is high level _q1 , this switching circuit 53 takes out the reproduced left signal SL from the low-pass filter 48 as shown in FIG. Signal Q
When the level of _q2 is low, the reproduced left signal SL from the low-pass filter 49 as shown in FIG. 8D is taken out to the output terminal. As a result, at the output end of the switching circuit 53, the signal sections of _the reproduced left signals SL as shown in FIG. A continuous reproduced left signal as shown is obtained. The reproduced left signal SL as shown in FIG.
and a low frequency output signal after demodulation by 45,
In addition, since they are connected within the overlap period, the magnetic heads 31 and 3, which are the sources of their generation,
As long as the waveforms 2 and 2 are placed at appropriate positions on the rotation locus, there will be no difference in phase between the two at the joint j, and a smooth connection with continuous waveforms will be achieved. Therefore, a continuous reproduced left signal as shown in FIG. 8F is formed without generating pulse noise at the joint j.

Incidentally, the left FM signals LF ₁ and LF ₂ , which are high frequency signals before demodulation and are obtained alternately from the reproduction outputs of the magnetic heads 31 and 32, are sent to the FM demodulators 44 and 4.
5, even if the signals are connected within the overlap period _lp , the phases of the two signals at the joint do not match, and waveform continuity cannot be obtained. become. When the left FM signal having such a discontinuous portion is demodulated, pulse noise occurs in the discontinuous portion, and the reproduced left signal after demodulation contains pulse noise and has degraded quality. It becomes a thing.

In the above-described splicing of the reproduced audio signals after demodulation, the same is true for the reproduced right signal, and the reproduced right signal is obtained alternately and intermittently from the low-pass filters 50 and 51 with an overlap period. SR is supplied to one and the other of two selection input terminals of the switching circuit 54, respectively. The switching circuit 54 is supplied with a control signal Q as shown in _FIG .
SR is taken out, and when the level of the control signal Q is low level _q2 , the reproduced right signal SR from the low-pass filter 51 is taken out. As a result, the output terminal of the switching circuit 54 has a low-pass filter 50.
The signal division of the reproduced right signal SR from the low-pass filter 51 and the signal division of the reproduced right signal SR from the low-pass filter 51 are
A continuous reproduced right signal is obtained which is stitched together within the overlap period. In this case as well, the successive reproduced right signals are free from pulse noise being mixed in at the joints.

And these continuous reproduction left signal and right signal
SL and SR are the reinforcement circuit 55, respectively.
and 56, low-pass filters 57 and 58, and, if necessary, an audio reproduction system 59 with a fixed head.
The signals are outputted to audio output terminals 63 and 64 through switching circuits 61 and 62 for switching between the reproduction left signal and the reproduction right signal from 60 and 60.

In this way, the outputs of the switching circuits 53 and 54 are sent to the reinforcement circuits 55 and 5, respectively.
6 and low-pass filters 57 and 58, it is possible to repair waveform deterioration of the continuous reproduction left signal and reproduction right signal caused by positional deviation of the magnetic heads 31 and 32, etc. That is, if the relative positions of the magnetic heads 31 and 32 on the rotation locus are not appropriate, a shift occurs in the phase relationship of their reproduced outputs, and the switching circuit 5
The playback left signal or playback right signal supplied to each of the two selection output terminals 3 or 54 is the 9th
As shown in Figures A and B, there is a phase shift θ. Therefore, the continuous reproduced left signal or reproduced left signal from the switching circuit 53 or 54, in which these signals are connected, has a waveform discontinuity at the joint, as shown in FIG. 9C. However, when the continuous reproduced left signal or reproduced right signal with such waveform deterioration passes through the enhancement circuit 55 or 56 and the low-pass filter 57 or 58, the waveform is distorted as shown in FIG. 9D. Changes in the continuous portion are softened, and waveform deterioration is reduced.

As explained above, according to the video and audio signal reproducing device according to the present invention, the reproduction outputs obtained from the two reproduction circuit magnetic heads in the form of alternately FM-modulated audio signals are demodulated and converted into reproduced audio signals. After that, they are joined within the overlap period, so it is possible to obtain a continuous reproduced audio signal without pulse noise mixed in at the joint, and it is possible to reproduce a bulk quality audio signal with good fidelity. .

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing essential parts of an example of a video and audio signal recording system for a recording tape that is reproduced by the video and audio signal reproducing apparatus according to the present invention, and FIGS. 2, 3, and 4. 5 is a frequency spectrum diagram used to explain the operation of the example shown in FIG. 1, and FIG. 6 is a diagram of a recording pattern on a magnetic tape that is reproduced by the video and audio signal reproducing apparatus according to the present invention. A conceptual diagram showing an example; FIG. 7 is a block connection diagram showing essential parts of an example of the video and audio signal reproducing device according to the present invention; FIGS. 8 and 9 are explanations of the operation of the example shown in FIG. 7. FIG. In the figure, 31 and 32 are reproducing rotating magnetic heads;
6, 37, 38 and 39 are band pass filters, 40, 41, 42 and 43 are amplitude limiting circuits,
44, 45, 46 and 47 are FM demodulators, respectively;
8, 49, 50, 51, 57 and 58 low pass filters, 53 and 54 switching circuits, 55
and 56 are reinforcement circuits, 63 and 64
is the audio output terminal.

Claims (1)

[Claims] 1. A first signal obtained by frequency-modulating a frequency-modulated luminance signal, a carrier color signal whose frequency is converted to a lower frequency band side, and a pair of carrier waves having different frequencies, which are frequency-modulated by a first audio signal. and a second frequency modulated signal, and third and fourth frequency modulated signals obtained by frequency modulating another pair of carrier waves having different frequencies with the second audio signal, recording of signals, a mixture of a carrier chrominance signal and first and third frequency modulated signals, and a mixture of said luminance signal, a carrier chrominance signal and second and fourth frequency modulated signals; From a magnetic tape recorded in such a manner that the recording is performed on two mutually adjacent inclined recording tracks,
first and second reproducing rotary heads that sequentially and alternately reproduce the signals recorded on each of the tilted recording tracks with an overlap period; and respective outputs of the first and second reproducing rotary heads. four filter sections that separate the first, second, third and fourth frequency modulated signals, respectively; and the first, second, third and fourth frequency modulated signals separated by the four filter sections. four demodulators that respectively demodulate the four frequency modulated signals to obtain first, second, third and fourth reproduced audio signals; a first switching unit that obtains first continuous reproduced audio by switching and alternately extracting each of the first reproduced audio signal and the second reproduced audio signal within the overlap period; The third reproduction audio signal and the fourth reproduction audio signal obtained from the other two demodulators are switched and taken out alternately within the overlap period, thereby producing a second continuous reproduction. a second switching unit that obtains audio;
A video and audio signal reproducing device comprising: