JPS6117205A - Reproducing device of video signal and sound signal - Google Patents

Abstract

PURPOSE:To prevent a reproducing image from being disturbed by a component of an FM-modulated sound signal, by eliminating the component of the FM- modulated sound signal from a signal supplied to a video signal reproducing processing circuit. CONSTITUTION:By level adjusting circuits 71, 73, sound signals LFA, RFA whose output has been FM-modulated are adjusted so that they become a level equal to that of FM-modulated sound signals LFA, RFA in a synthesizing signal HA supplied to a subtracting circuit 85 through a phase equalizing circuit 81. In the subtracting circuit 85, the FM-modulated sound signal LFA and RFA are eliminated from the synthesizing signal HA. In this way, a video signal VA consisting of a chrominance signal which does not contain the FM-modulated sound signal and has been brought to a low band conversion, and an FM-modulated luminance signal YF is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for converting a carrier color signal that has been converted into a low band, a luminance signal that has been modulated by FM, and a color signal that has been subjected to FM modulation from a high band portion of the carrier color signal that has been converted to a low band. The present invention relates to a video signal and audio signal reproducing device for reproducing video and audio signals from a magnetic recording medium on which a composite signal of an audio signal that has been FM modulated in the low frequency band of a luminance signal is recorded.

BACKGROUND TECHNOLOGY AND PROBLEMS A helical scan type video tape recorder is one in which the audio signal is FM-modulated, frequency-multiplexed with the video signal, and recorded on a track tilted with respect to the running direction of the tape using a rotating head. According to this, it is possible to improve the quality of the audio signal. In particular, when recording video signals at high density so that adjacent tracks are adjacent to each other by slowing down the tape running speed for long-term recording, audio signals are transferred to one side of the tape using a fixed head. When recording on a track that extends in the running direction of the tape,
Since the relative speed between the fixed head and the tape becomes slow, the quality of the recorded audio signal deteriorates, so it is desirable to record the audio signal together with the video signal using the rotating head.

Specifically, the audio signal is frequency-multiplexed in the band from the high-frequency part of the carrier color signal that has been converted to a low frequency range to the low-frequency part of the FM-modulated luminance signal, but during playback, crosstalk components from adjacent tracks are FM-modulated first and second audio signals with different first and second center frequencies are obtained for the same channel audio signal so that the first and second audio signals of the same channel can be removed. A second audio signal is recorded on every other trunk, and a second audio signal is recorded on every other trunk.

Figure 2 shows the mode of frequency multiplexing when recording two channel audio signals, and for the audio signal of one channel, FM modulated audio signals LFA and LFB with center frequencies of f and f2 are obtained. At the same time, FM-modulated audio signals RFA and RF'B with center frequencies of f3 and f4 are obtained for the audio signal of the other channel, and in every other track, as shown in the top row of FIG. A low-pass converted carrier color signal CL, an FM-modulated luminance signal YF, and an FM-modulated audio signal LFA and R.
The frequency multiplexed signal of the FA is recorded, and every other trunk has a low frequency converted carrier color signal C (not shown).
A frequency multiplexed signal of L, an FM-modulated luminance signal YF, and FM-modulated audio signals LFB and RFB is recorded. - as an example, f r =1.325 MHz,
f z =1.475 MHz.

f s =1.625 MHz, f 4 =1.
775 MHz and FM modulated audio signal LFA
, LFB, RFA.

The maximum frequency deviation of R'F B is ±50kHz or ±7
The frequency is set to 5kHz.

In this way, the FM modulated carrier color signal, the FM-modulated luminance signal, and the FM in the band from the high-frequency range of the low-frequency-converted carrier color signal to the low-frequency range of the jMM-modulated luminance signal are used. To reproduce a video signal and an audio signal from a magnetic recording medium on which a composite signal of a modulated audio signal is recorded, the composite signal is reproduced from this magnetic recording medium by a magnetic head, and the reproduced composite signal is The signal is supplied to a video signal reproduction processing circuit and an audio signal reproduction processing circuit, and in the video signal reproduction processing circuit, the FM-modulated luminance signal is extracted and demodulated by the bypass filter, and the carrier signal is low-frequency-converted by the low-pass filter. The color signal is extracted and converted to the original frequency, and the audio signal reproduction processing circuit extracts and demodulates the audio signal that has been FM modulated by the bandpass filter. In the manner described above, the center frequencies are f+, fz, f3 . When the four FM modulated audio signals LFA, LFB, RFA, and RFB of fn are recorded, the audio signal reproduction processing circuit performs the following:
An audio signal LFA that is FM modulated by four bandpass filters whose center frequencies are f, , f, , f, and f4, respectively.
Take out LFB−, RFA, and RFB separately, for example,
Each demodulated audio signal is separately demodulated, and then the two demodulated audio signals of the same channel are alternately switched and extracted using a switch to obtain a reproduced audio signal.

By the way, if the signal supplied to the video signal reproduction processing circuit of the reproduction device contains an FM-modulated audio signal component, the FM-modulated audio signal component may cause beat disturbance and excessive noise in the reproduced image. This causes disturbance of the modulation phenomenon and deteriorates the quality of the reproduced image.

However, as mentioned above, the video signal reproduction processing circuit
A bypass filter and a low-pass filter are provided to separate and extract the M-modulated video signal and the low-pass converted carrier color signal, but depending on these filters, the F
It is not possible to suppress the M-modulated audio signal component.

Therefore, by inserting a band suppression filter before the video signal reproduction processing circuit and suppressing the FM modulated audio signal component in the signal supplied to the video signal reproduction processing circuit, or by suppressing the FM modulated audio signal component, It has been considered to prevent the above-mentioned interference from occurring by limiting the band of the luminance signal demodulated in the reproduction processing circuit. However, the band of the composite signal reproduced by the magnetic head is suppressed. When the video signal is supplied to the video signal reproduction processing circuit through the filter, a difference in delay time is created between the FM-modulated luminance signal and the low-frequency converted carrier color signal due to the phase characteristics of the band suppression filter, resulting in a color difference in the reproduced image. smearing occurs, making the reproduced image unsightly. Furthermore, when the band of the demodulated luminance signal is limited, the resolution of the reproduced image is reduced.

Purpose of the Invention In view of the above, the present invention has been made to provide the following advantages: from the signal supplied to the video signal reproduction processing circuit without affecting the video signal;
By removing the FM modulated audio signal component, the reproduced image is prevented from being interfered with by the FM modulated audio signal component without causing color blurring or resolution degradation of the reproduced image. This is what I did.

Summary of the Invention In the present invention, first, an audio signal reproduction processing circuit is configured.
A phase locked loop (PLL) with a voltage controlled oscillator (VCO) is used as an FM demodulation circuit for demodulating audio signals.
) is used. That is, a signal mainly consisting of the desired FM modulated audio signal output from the bandpass filter is supplied to a phase comparator circuit, the phase is compared with the signal output from the voltage controlled oscillation circuit, and the comparison error output is looped. By supplying the signal through the filter to the voltage controlled oscillation circuit and controlling its oscillation frequency, the desired demodulated audio signal is obtained as the output of the loop filter and therefore the input of the voltage controlled oscillation circuit. In this way, when the phase-locked loop constituting the FM demodulation circuit is locked, the output signal of the voltage-controlled oscillation circuit of the phase-locked loop is transferred from the bandpass filter to the phase comparison circuit as the input of the phase-locked loop. The frequency will be the same as the desired FM modulated audio signal in the supplied signal, and depending on the configuration of the phase comparator circuit, the phase will also be the same. However, the signal supplied from the bandpass filter to the phase comparator circuit is
The components include an FM-modulated luminance signal component, a low-frequency-converted carrier color signal component, and an FM-modulated audio signal component other than the desired FM-modulated audio signal, but in the phase-locked loop, Since the high frequency components of the output of the phase comparison circuit are removed by the loop filter and not supplied to the voltage controlled oscillation circuit, these unnecessary signal components do not appear in the output of the voltage controlled oscillation circuit.

In the present invention, paying attention to this point, the FM modulated audio signal obtained at the output of the voltage controlled oscillation circuit of the phase-locked loop constituting the FM demodulation circuit is synthesized by regenerating the output of the magnetic head. By adjusting the level to be equal to the FM modulated audio signal included in the signal and subtracting it from the reproduced composite signal of the output of the magnetic head, a low level signal that does not include the FM modulated audio signal is A video signal consisting of a range-converted carrier color signal and an FM-modulated luminance signal is obtained and is supplied to a video signal reproduction processing circuit.

Therefore, according to the present invention, the reproduced image is not interfered with by the components of the FM-modulated audio signal. Moreover, since the calculation method is used to remove the FM-modulated audio signal component from the signal supplied to the video signal reproduction processing circuit, it does not affect the video signal and does not cause color blurring in the reproduced image. It never occurs. Furthermore, since there is no need to limit the band of the demodulated luminance signal, the resolution of the reproduced image does not deteriorate.

Embodiment FIG. 1 shows an example of a video signal and audio signal reproducing apparatus of the present invention, in which a video signal and two channels of audio signals are recorded on a magnetic tape in the manner explained in FIG. This is the case when an audio signal is reproduced.

As shown in the top row of FIG. 3, the rotary magnetic head 11 outputs the low frequency converted carrier color signal CL and the FM signal from every other track in every other field period.
Modulated luminance signal YF and FM modulated audio signal L
The composite signal HA of FA and RFA is reproduced, and the rotary magnetic head 12 reproduces a low frequency converted carrier color signal CL from every other track in every other field period (not shown). and FM modulated luminance signal YF
A composite signal HB of the FM-modulated audio signals LFB and RFB is reproduced, and the composite signal HA is transmitted to the reproduction amplifier circuit 21.
The synthesized signal HB is taken out through the regenerative amplifier circuit 22.
taken out through.

The regenerative amplifier circuits 21 and 22 are equipped with an automatic gain control (AGC) function, and are configured to obtain the output composite signals HA and HB at a constant level.

The composite signal HA output from the regenerative amplifier circuit 21 is FM
The synthesized signal HB output from the regenerative amplifier circuit 22 is supplied to bandpass filters 31 and 33 with center frequencies f, , f3 for separating and extracting the modulated audio signals LFA and RFA, respectively. The audio signal LFB,R
To separate and extract the FB, the center frequency is f,,f
, are supplied to bandpass filters 32, 34 of . However, due to the characteristics of the bandpass filters 31 to 34, the signal LFAv obtained at the output of the bandpass filter 31 is
As shown in the second row of the figure, in addition to the desired FM-modulated audio signal LFA, there is also a low-band-converted carrier color signal CL, an FM-modulated luminance signal YF, and an FM-modulated audio signal RFA. Similarly, the signal LFBv obtained at the output of the bandpass filter 32, 33, 34
.

Although not shown, RFAv and RFBv are desired FM-modulated audio signals LFB and RFA, respectively.

In addition to RFB, a carrier color signal C'L that has been converted to a low frequency band,
It includes an FM-modulated luminance signal YF and FM-modulated audio signals RFB, LFA, and LFB.

The output signals LFAv, RFAv, RFBv of the bandpass filters 31, 32, 33.34 are transmitted to FM demodulation circuits 41, 42, 43. 44 and the FM modulated audio signals LFA, LFB, R
FA and RFB are demodulated. That is, the signals LFAv, LF
Bv, RFAv, and RFBv are supplied to the phase comparator circuit 46 of the FM demodulation circuits 41, 42, 43, and 44 configured by phase-locked loops, respectively, and the voltage-controlled oscillation circuit 45
The comparison error output is supplied to the voltage controlled oscillation circuit 45 through the loop filter 47, and its oscillation frequency is controlled. As the output of the filter 47 and therefore the input of the voltage controlled oscillator circuit 45, the FM modulated audio signals LFA, LFB, RFA, R are provided, respectively.
Demodulated audio signals LA, LB, RA, and RB of FB are obtained.

The demodulated audio signals LA and LB output from the FM demodulation circuits 41 and 42 are supplied to terminals A and B of the switch 51, and the demodulated audio signals RA' and RB output from the FM demodulation circuits 43 and 44 are supplied to terminals A and B of the switch 51, respectively. The switches 51 and 52 are supplied to the terminals A and B of the switch 52, and the switches 51 and 52 respectively switch the rotating magnetic head 11 from every other trunk by the switching signal SW which is inverted every one field period given from the terminal 60. During the field period when the signal is reproduced, on the terminal A side,
During the field period when signals are reproduced from every other trunk by the rotating magnetic head 12, the signal is switched to the terminal B side, and the reproduced audio signal of one channel is sent to the output of the switch 51, and the reproduced audio signal of one channel is sent to the output of the switch 52. Reproduction audio signals R of the other channel are obtained, respectively, and the reproduction audio signals R and R are respectively led out to audio signal output terminals 55.56 through de-emphasis circuits 53.54.

FM demodulation circuit 41.4 configured with a phase-locked loop
The outputs of the voltage controlled oscillation circuits 45 of 2, 43 and 44 are connected to band pass filters 31, 32, 33 and 34 respectively.
Phase comparison circuit 46 of M demodulation circuits 41, 42, 43, 44
The signals LFAv,' LFBv, RFAv,
desired FM modulated audio signal LFA in RFBv,
LFB, RFA, signal with the same frequency as RFB, i.e. FM
The modulated audio signals LFA, LFB, RFA, and RFB themselves are obtained.

FM-modulated audio signals LFA, LFB, and RFA are obtained from the output of the voltage-controlled oscillation circuit 45 of the FM demodulation circuits 41, 42, 43, and 44.

RFB are level adjustment circuits 71, 72, 73.7, respectively.
4, the level is adjusted, and the level adjustment circuit 71.4 is supplied to the level adjustment circuit 71.
．． The FM-modulated audio signals LFA, RFA, whose levels have been adjusted by the level adjustment circuits 72 and 73, are supplied to the adder circuit 75 and added thereto, and the FM-modulated audio signals LFB, whose levels have been adjusted by the level adjustment circuits 72 and 74. RFB is supplied to the adder circuit 76 and added thereto, and the addition signal FA, which is the output of the adder circuit 75, is supplied to the subtractor circuit 85 and added to the adder circuit 76.
An output addition signal FB is supplied to a subtraction circuit 86.

On the other hand, the composite signal HA, which is the output of the regenerative amplifier circuit 21 set to a constant level, is supplied to the subtraction circuit 85 through the phase equalization circuit 81, and the composite signal HB, which is the output of the regenerative amplifier circuit 22 which is set to a constant level, is supplied to the subtraction circuit 85 through the phase equalization circuit 81. , is supplied to a subtraction circuit 86 through a phase equalization circuit 82, and in the subtraction circuit 85, the addition signal FA output from the addition circuit 75 is subtracted from the composite signal HA passed through the phase equalization circuit 81. The output of the adder circuit 76 is obtained from the composite signal HB passed through the converter circuit 82. The sum signal FB of is subtracted. ,here,
The level adjustment circuits 71 and 73 adjust the FM of the composite signal HA in which the output FM-modulated audio signals LFA and RFA are supplied to the subtraction circuit 85 through the phase equalization circuit 81.
The level adjustment circuits 72 and 74 adjust the level of the modulated audio signals LFA and RFA to be equal to that of the modulated audio signals LFA and RFA. FM modulated audio signal LFB, R in the composite signal HB supplied to
Adjusted to a level equal to 2FB. Also,
The phase equalization circuit 81 converts the FM in the output composite signal HA.
Modulated audio signal LFA.

The phase equalization circuit 82 delays the composite signal HA so that RFA has the same phase as the FM-modulated audio signals LGA and RFA in the addition signal FA output from the addition circuit 75, respectively. The FM-modulated audio signals LFB and RFB in the output composite signal HB are added to the adder circuit 7, respectively.
FM modulated audio signal L in the summed signal FB of the output of 6
The composite signal HB is delayed so that it has the same phase as FB and RFB.

Therefore, in the subtraction circuit 85, FM
The modulated audio signals LFA and RFA are removed, and the FM-modulated audio signals LFB and vRFB are removed from the composite signal HB in the subtraction circuit 86, and the output of the subtraction circuit 85 is as shown in FIG. As shown in the bottom row, a video signal VA consisting of a low frequency-converted carrier color signal CL and an FM-modulated luminance signal YF, which does not contain the FM-modulated praise signal component, is obtained. Although not shown in the drawings, similarly, a video signal VB is obtained which is composed of a low-frequency-converted carrier color signal CL and an FM-modulated luminance signal YF, which does not include the FM-modulated audio signal component.

The video signal VA of the output of the subtraction circuits 85 and 86.

VB is supplied to the terminals A and B of the switch 87, and the switch 87 causes the rotating magnetic head 11 to output signals from every other trunk by the switching signal SW which is inverted every one field period given from the terminal 60. During the field period during which the signals are reproduced, the signal is switched to the terminal A side, and during the field period when the rotating magnetic head 12 reproduces the signal from every other track, the signal is switched to the terminal B side, and the signal is continuously output to the output of the switch 87. A video signal V can be obtained. The video signal (2) output from this switch 87 is then supplied to the video signal reproduction processing circuit 90.
, the FM-modulated luminance signal YF is taken out by the bypass filter and demodulated, and the carrier color signal CL, which has been low-pass converted by the low-pass filter, is taken out and converted to the original frequency, and is sent to the brightness signal output terminal 91. The demodulated luminance signal Y is derived, and at the same time, the carrier color signal C at the original frequency is derived to the carrier color signal output terminal 92.

Effects of the Invention According to the present invention, a phase locked loop (P'LL) having a voltage controlled oscillator (VCO) is used as an FM demodulation circuit for demodulating an audio signal, which constitutes an audio signal reproduction processing circuit.
), the FM obtained at the output of the voltage controlled oscillator circuit is
The level of the modulated audio signal is adjusted to be equal to the FM modulated audio signal contained in the reproduced composite signal of the output of the magnetic head, and the reproduced composite signal of the output of the magnetic head is generated. By subtracting from FM
By obtaining a video signal that does not include a modulated audio signal and consisting of a low-frequency-converted carrier color signal and an FM-modulated luminance signal, and supplying this to the video signal reproduction processing circuit, the reproduced image is There is no interference from the components of the FM modulated audio signal, and no color blurring or resolution degradation of the reproduced image occurs.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of an example of the video signal and audio signal reproducing device of the present invention, and Fig. 2 is a frequency multiplexed signal when an audio signal is FM modulated and frequency multiplexed with a video signal and recorded on a magnetic recording medium. A frequency spectrum diagram showing an example of
FIG. 2 is a frequency spectrum diagram showing the mode of signals obtained in each part of the example of the video signal and audio signal reproducing device of the present invention shown in the figure. In the figure, 11 and 12 are rotating magnetic heads, 21 and 22 are regenerative amplifier circuits equipped with an automatic gain control (AGC) function, and 3
1 to 34 are band pass filters, 41 to 44 are FM demodulation circuits constituted by phase-locked loops (PLL),
45 is a voltage controlled oscillation circuit, 71 to 74 are level adjustment circuits, 75 and 76 are addition circuits, 81 and 82 are phase equalization circuits, 85 and 86 are subtraction circuits, and 90 is a video signal reproduction processing circuit.

Claims (1)

[Claims] The carrier color signal subjected to low frequency conversion, the luminance signal subjected to FM modulation, and the high frequency portion of the carrier color signal subjected to low frequency conversion to the above F
a magnetic head for reproducing a composite signal of an FM-modulated audio signal in a low frequency band of an M-modulated luminance signal from a magnetic recording medium on which the composite signal is recorded;
A band-pass filter for separating and extracting the FM-modulated audio signal from the reproduced composite signal of the output of the magnetic head, and demodulating the FM-modulated audio signal obtained at the output of the band-pass filter. in order to,
An FM demodulation circuit constituted by a phase locked loop having a voltage controlled oscillation circuit, and an FM modulated audio signal obtained at the output of the voltage controlled oscillation circuit of this FM demodulation circuit,
The level is adjusted to be equal to the FM modulated audio signal included in the reproduced composite signal output from the magnetic head, and the FM modulated audio signal is subtracted from the reproduced composite signal output from the magnetic head. An audio signal removal circuit that obtains a video signal consisting of a low frequency-converted carrier color signal and an FM-modulated luminance signal that does not include a modulated audio signal, and the above-mentioned signal obtained at the output of the audio signal removal circuit. The video signal is supplied to the video signal reproduction processing circuit, and its F
A reproducing device for video signals and audio signals, in which an M-modulated luminance signal is demodulated, and a low frequency-converted carrier color signal is frequency-converted.