JP2974364B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type magnetic recording / reproducing apparatus for recording / reproducing a video signal, and in particular, it can extend the recording time and shorten the reproducing time. And a magnetic recording / reproducing apparatus.

[Prior Art] In a conventional helical scan type magnetic recording / reproducing apparatus (hereinafter, referred to as VTR), the time length of a broadcast program to be recorded (hereinafter, referred to as a required recording time) depends on the remaining amount of a magnetic tape to be used. When the recordable time length (hereinafter referred to as tape recordable time) is short and the entire broadcast program cannot be recorded only in the SP (standard) mode, as disclosed in, for example, JP-A-63-94451. To SP
To record the entire broadcast program by extending the recordable time of the tape by combining the mode and the long-time mode (the mode in which the recording speed of the magnetic tape is made slower than the SP mode (hereinafter referred to as the tape speed)). There is a known technology that allows the user to do this.

For example, in the case of a VHS VTR based on the NTSC system, if the required recording time is 150 minutes for a magnetic tape capable of 120 minutes in the SP mode, the recording is performed in the SP mode for the first 105 minutes. Recording is performed in the EP mode as the long-time mode for the remaining 45 minutes (the tape speed is 1/3 times that in the SP mode, also referred to as the triple mode). In the case of the VHS system VTR based on the PAL system, the long-time mode has a tape speed 1/2 times that of the SP mode, and is called the LP mode (or double mode). Recording in SP mode is performed and the remaining 60 minutes
Recording is performed in the LP mode.

In addition, in the conventional VTR, as a reproduction mode, in addition to a normal reproduction mode in which a magnetic tape is run at the same speed at the time of recording for reproduction, a high-speed reproduction can be performed by running the magnetic tape at a higher speed than in the normal reproduction mode. Such a function is also provided, so that the reproduction time of a fixed length of the magnetic tape can be shortened, and the cueing and search for a desired recording portion can be performed quickly. I have.

[Problems to be Solved by the Invention] By the way, when recording in the EP mode or the LP mode, the S / N of the reproduced video signal is reduced due to a narrower width of the track on the magnetic tape than in the case of recording in the SP mode. And the image quality of the reproduced image is degraded. Therefore, as described above,
When recording is performed by combining the SP mode and the EP or LP mode, the tape recording time is extended, but on the other hand, the image quality of the reproduced image from the part recorded in the EP or LP mode is deteriorated. There was.

In addition, the high-speed playback mode in the conventional VTR is limited to a double speed playback mode in which the tape speed is twice that in the normal playback mode and a fast-forward search mode in which the tape speed is sufficiently higher than in the normal playback mode. In the high-speed reproduction mode, the quality of the reproduced image is significantly deteriorated as compared with the normal reproduction mode. In addition, the sound cannot be reproduced in the fast-forward search mode, and the sound is reproduced in the double speed reproduction mode, but the change is too fast, and the sound is increased, so that it is very difficult to grasp the contents. Will be.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording / reproducing apparatus which can solve the above-mentioned problem and extend the recordable time of a tape while ensuring the image quality of a reproduced image and the sound quality of a reproduced sound.

Another object of the present invention is to provide a magnetic recording / reproducing apparatus capable of reproducing a reproduced image at an arbitrary tape speed higher than that in a normal reproducing mode without significantly deteriorating the sound quality of reproduced sound. Is to provide.

Means for Solving the Problems To achieve the above object, the present invention firstly reduces the running speed of the magnetic tape by causing the magnetic tape to run at a low speed and the magnetic head to rotate at a low speed during recording. The video signal to be recorded is decimated at a ratio corresponding to the ratio of, and the time axis is extended by the decimated value, and the audio signal to be recorded is pitch-shifted at a ratio corresponding to the reduction ratio of the running speed of the magnetic tape.

Second, during reproduction, the recording tape is run at high speed and the magnetic head is rotated at high speed, and the video signal reproduced from the magnetic tape is reproduced at a rate corresponding to the rate of increase in the running speed of the magnetic tape. The audio signal reproduced from the magnetic tape is pitch-shifted at a rate corresponding to the rate of increase in the traveling speed of the magnetic tape, while the time axis is expanded and thinned out.

[Operation] The present invention is to reduce the running speed of the magnetic tape during recording by the conventional VT.
By making the recording time lower than when recording with R (normal recording), the recordable time of the tape is extended, but at the same time, the rotational speed of the magnetic head also decreases, and the width of the track formed on the magnetic tape is reduced. This is the same as when the track format such as pitch, inclination and the like does not lower the running speed of the magnetic tape. In addition, the video signal to be recorded is thinned out at a rate corresponding to the rate of decrease in the running speed of the magnetic tape, and the time axis is extended by the thinning out. Since the audio signal to be recorded is pitch-shifted at the same ratio, each track formed on the magnetic tape must record a video signal and an audio signal of the same time length as when the running speed of the magnetic tape is not reduced. become.

This allows the magnetic head to run at the same speed as when recording on a conventional VTR, rotate the magnetic head and perform playback, and the magnetic head correctly reproduces and scans each track on the magnetic tape to correct the time. The video signal of the axis is reproduced, and the reproduced image and reproduced sound with the video signal longer than the recordable time of the tape when the magnetic tape is run at the same speed as that of recording with the conventional VTR are stabilized. And it will be obtained with good quality.

In addition, the present invention reduces the reproduction time by increasing the running speed of the magnetic tape during reproduction from that in the normal reproduction mode. At this time, by simultaneously increasing the rotation speed of the magnetic head, The head reproduces and scans the tracks of the magnetic tape sequentially and correctly. The video signal reproduced by this method is compressed on the time axis because the relative speed between the magnetic tape and the magnetic head is higher than that at the time of normal reproduction. Since the video signal is thinned out at a suitable ratio and the time axis is extended by the thinning out, the video signal on the correct time axis is obtained, and the frequency of the reproduced audio signal is also increased. Since the pitch is shifted at a rate corresponding to the rate of increase of the sound signal, the sound signal is quick, but the listening is reduced.

Thereby, the reproduced image is stabilized and the image quality is high.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention, wherein 1-4 are input terminals and 5 is Y / C.
(Luminance / chroma) separation circuit, 6 and 7 are switches, 8 is an input terminal, 9 is a TBC (time axis correction circuit), 10 and 11 are synchronization separation circuits, 12 is a luminance signal processing circuit, and 13 is DC (direct current). Level shift circuit, 14 is a frequency modulation circuit (hereinafter referred to as FM modulation circuit), 15 is a demodulation circuit, 16 is TBC, 17 is a modulation circuit, and 18 and 19 are
OSC (oscillation circuit), 20 is an audio signal processing circuit, 21 is a pitch shift circuit, 22 is an FM modulation circuit, 23 is a mixing / amplifying circuit, 24
Is a servo / tape system, 25 is a magnetic tape, 26 and 27 are magnetic heads, 28 is a tack sensor, 29 is a cylinder motor, 30 is a capstan motor, 31 is a servo circuit, 32 is a frequency divider circuit, 33
Is an OSC, and 34 and 35 are input terminals.

In the recording mode, a recording instruction signal REC is input from an input terminal 34 in the servo / tape system 24 in the recording mode, and the servo circuit 31 starts operating. The OSC 33 generates a reference clock RCLK. This reference clock RCLK is supplied to a servo circuit 31 and is also divided by a frequency dividing circuit 32, so that the input terminal 1, 3 or the input terminal 2
A vertical synchronizing pulse _VDR synchronized with the vertical synchronizing signal of the color video signal input from is generated and supplied to the servo circuit 31.

The servo circuit 31 has a reference clock RCLK and a vertical synchronization pulse.
Referenced to the V _DR, generates a control signal CERR using signal CFG of frequency proportional to the rotational speed of the capstan motor 30, to which the running of the magnetic tape 25 by controlling the Yotsute capstan motor 30 While maintaining the speed constant, a control signal DERR is generated using a tack signal TP from the tack sensor 28 representing the rotation phase of the cylinder motor 29 and a signal DFG having a frequency proportional to the rotation speed of the cylinder motor 29. The magnetic heads 26 and 27 by controlling the cylinder motor 29.
Control the rotation phase and rotation speed of.

On the other hand, when the input color video signal is a component signal, the switches 6 and 7 are closed to the A contact side by the switching control signal from the input terminal 8, and the luminance signal Y is input from the input terminal 1 and the switch 6 The chroma signal C is input from the input terminal 3 and supplied to the A contact of the switch 7. When the input color video signal is a composite signal, the switch 6,
7 is closed to the B side, and this color video signal is inputted from the input terminal 2 and separated into a luminance signal Y and a chroma signal C by a Y / C separation circuit 5, and the luminance signal Y is connected to the B contact of the switch 6,
The chroma signal C is supplied to contacts B of the switch 7, respectively.
Therefore, in any case, the luminance signal Y is output from the switch 6 and the chroma signal C is output from the switch 7.

The luminance signal Y from the switch 6 is transmitted to the TBC 9 and the sync separation circuit 10.
The horizontal separation signal HS1 is separated by the synchronization separation circuit 10. In the TBC 9, the horizontal sync signal HS1 from the sync separation circuit 10 and the reference clock R generated by the servo / tape system 24 are used.
CLK, the vertical synchronizing pulse V _DR, thinning of the connexion luminance signal in a ratio corresponding to the ratio of the tape recordable time of the extension of the magnetic tape 25, the time base expansion processing is performed. When the tape recordable time is extended, the oscillation frequency of the OSC 33 is reduced in accordance with the instruction signal from the input terminal 35 by the proportion of the extension. Reduces the frequency of the reference clock RCLK and vertical sync pulses V _DR accordingly, the rotational speed of the running speed and the magnetic head 26, 27 of the magnetic tape 25 by reducing the rotational speed of the capstan motor 30 and the cylinder motor 29 But for example VHS
This is smaller than when recording is performed on the magnetic tape 25 with a track pattern defined by the standard (hereinafter, this recording is referred to as normal recording). The tape recording time is extended by reducing the tape speed.However, the rotational speed of the magnetic heads 26 and 27 is also reduced to the same extent as the tape running speed. When the recordable time is not extended (that is, during normal recording)
The same format track pattern is obtained.

In general, the rotation period of the magnetic heads 26 and 27 is set to one frame period length of the video signal,
One field is recorded in each track above. However, when the rotation speed of the magnetic heads 26, 27 is reduced as described above, the time required for each magnetic head 26, 27 to form one track increases by the rate of the expansion of the tape recordable time, and one time of the video signal. The length is longer than the field period length, the relative speed between the magnetic tape 25 and the magnetic heads 26 and 27 is also reduced, and the recordable band is narrowed.

TBC9 the reference was reduced frequency in proportion to the tape recordable time of the expansion clock RCLK, a vertical synchronizing pulse V _DR
Is used, the luminance signal Y is thinned out / expanded on the time axis at a rate corresponding to the rate of expansion of the tape recordable time, and the time required for the magnetic heads 26 and 27 to form one track on the magnetic tape 25 is reduced. One field period of the luminance signal to be recorded is made equal, one field is recorded in each track, and the frequency band of the luminance signal to be recorded (actually, FM modulated) is magnetic. It should be within the recordable band on the tape 25.

Here, the TBC 9 and its operation will be described with reference to FIG. 2 and FIG. However, FIG. 2 is a block diagram showing the configuration of TBC9, and 36 is A / D (analog / digital).
A conversion circuit, 37 is a memory, 38 is a D / A (digital / analog) conversion circuit, 39 is a PLL (phase locked loop) circuit, and 40 is a memory control circuit.

In the figure, a PLL circuit 39 includes a sync separation circuit 10 (first
2), a horizontal synchronizing signal HS1 is supplied, and a write clock WCLK synchronized with the horizontal synchronizing signal HS1 and a vertical synchronizing pulse _VDW synchronized with the vertical synchronizing signal of the luminance signal Y from the switch 6 (FIG. 1) are generated. I do. The memory control circuit 40 generates a write reset pulse W _Rst and a read reset pulse R _Rst from the write clock WCLK and the vertical synchronization pulse V _DW .

The luminance signal Y from the switch 6 is digitized by an A / D conversion circuit 36 using a write clock WCLK from a PLL circuit 39 as a sampling pulse, and is supplied to a memory 37. The memory 37 has a storage capacity of an integral multiple of the field (or frame), and the digital data from the A / D conversion circuit 36 is arranged in the order of addresses specified by the output of a write address counter (not shown) for counting the write clock WCLK. The converted luminance signal is stored. The write reset pulse W _Rst has a period of a field (or a frame) equal to the storage capacity of the memory 37, and resets the write address counter. Therefore, in the memory 37, when the digitized luminance signal corresponding to the storage capacity is written, the write address counter is reset by the write reset palace W _Rst and writing is performed again from the first address.

On the other hand, in the memory 37, the reference clock RCLK from OSC33 (FIG. 1) is supplied as a read clock, also dividing circuit 32 vertical sync from (FIG. 1) pulse V _DR is supplied. The read clock RCLK is counted by a read address counter (not shown), and a digital luminance signal written in the address order designated by the output is read from the memory 37. The vertical synchronization pulse _VDR is stored in memory 3.
7 for determining the timing of reading the vertical synchronization signal in the digitized luminance signal,
For example, every time this vertical synchronization pulse _VDR is supplied,
The read address counter is preset so as to designate the recording address of the vertical synchronizing signal in the memory 37. Thereby, the vertical synchronization signal of the digitized luminance signal output from the memory 37 is phase-synchronized with the vertical synchronization pulse _VDR .

The digitized luminance signal read from the memory 37 is D /
The signal is supplied to the A conversion circuit 38 and is converted into an analog signal using the reference clock RCLK. This analog luminance signal Y 'is supplied to the luminance signal processing circuit 12 shown in FIG.

Read reset pulse R _Rst output from the memory control circuit 40 is set the phase difference for the write reset pulse W _Rst the same period a and the write reset pulse W _Rst, to reset the read address counter of the. As a result, in the memory 37, reading is started from the first address with a delay of this phase from writing.

In the case of normal recording in which no instruction signal is input from the input terminal 35 of FIG. 1 and the tape recordable time is not extended, the cycle of the reference clock RCLK is equal to the cycle of the write clock WCLK, and the vertical synchronization pulse V _DR Is equal to the period of the vertical synchronization pulse V _DW . Therefore, in this case, all the digitized luminance signals written in the memory 37 are read out on the same time axis.

When performing the extended tape recordable time is the reference clock period of RCLK is longer than WCLK cycle of the write clock, vertical sync pulses V _DR period also the vertical synchronizing pulses V _DW
Longer than the cycle of For this reason, the digital luminance signal read from the memory 37 is extended on the time axis with respect to the digital luminance signal written to the memory 37, and accordingly, the luminance signal Y obtained from the D / A conversion circuit 38 is obtained. Is extended on the time axis with respect to the luminance signal Y supplied to the A / D conversion circuit 36. Moreover, the period of the read reset pulse R _Rst output from the memory control circuit 40 since it is equally constant to the period of the write reset pulse W _Rst, written from Yotsute memory 37 to the reference clock RCLK and vertical sync pulses V _DR Read reset pulse R _Rst before all digital luminance signals are read
Resets the read address counter, and the read returns to the first address. For this reason, in the memory 37, there is a portion which is not read out, whereby thinning is performed.

Therefore, it is assumed that the cycle of the write clock WCLK is t, the cycle of the reference clock RCLK is αt (where α> 1), and the data amount of the digital luminance signal written to the memory 37 in one cycle of the write reset pulse W _Rst is Q. Then, the data amount Q 'of the digital luminance signal read from the memory 37 in one cycle of the read reset pulse R _Rst is as follows: Q' = Q × t / αt = Q / α Is thinned out without being read.

Here, the thinned data amount ΔQ is an integral multiple of the data amount for one field (or one frame).

Next, the operation of the TBC 9 shown in FIG. 2 when the required recording time is 150 minutes for a magnetic tape having a tape recording available time of 120 minutes as described above will be described with reference to FIG. Incidentally, FIG. 3 (a) shows a sequential field (or frame) of the digital luminance signal to be written into the memory 37, T _F
Is the time length of the field (or frame). FIG. 3B shows a sequential field (or frame) of the digital luminance signal read from the memory 37, and T _F ′ is the time length of the field (or frame).

In this case, it is necessary to extend the tape recordable time by 150/120 = 5/4. Therefore, assuming that a digital luminance signal is written in the memory 37 for 10 fields (or 10 frames) in one cycle of the write reset pulse W _Rst , as shown in FIG.
An eight-field (or eight-frame) digitized luminance signal is read for each frame) with a ten-field (or ten-frame) period length of the digitized luminance signal to be written. In this way, the time length T _F of one field of the digital luminance signal read from the memory 37 (or one frame) 'is one field of the digital luminance signal to be written into the memory 37 of (or one frame) of the time length T _F It is stretched 5/4 times.

In FIG. 1, the luminance signal Y 'obtained by the processing in the TBC 9 as described above is supplied to the luminance signal processing circuit 12, the DC level is set to a predetermined level by the DC level shift circuit 13, and the FM level is set. The signal is FM-modulated by the modulation circuit 14 and supplied to the mixing / amplification circuit 23. The DC level shift circuit 13 includes a clamp circuit, but the clamp level is changed according to a command signal from the input terminal 35 (that is, according to the rate of extension of the tape recordable time). As a result, even if the relative speed between the magnetic tape 25 and the magnetic heads 26 and 27 is changed in order to extend the recordable time of the tape, the magnetic tape 2
The recording wavelength on the line 5 is not changed, and this point will be described with reference to FIG.

FIG. 4 is a diagram showing characteristics of the FM modulation circuit 14 in FIG.

In the figure, the solid line a indicates the modulation characteristic of the FM modulation circuit 14. Now, the amplitude of the input signal is 2V ₂ and the center level is V ₀
And the center level of the input signal in the output signal
It is assumed that the frequency with respect to V ₀ is f ₀ and the frequency shift is deV 1. Therefore, if the relative speed between the magnetic tape and the magnetic head is reduced in order to extend the tape recordable time, the wavelength of a signal recorded on the magnetic tape becomes longer than when the relative speed is not reduced.

By the way, as described above, the running speed of the magnetic tape 25 and the rotating speed of the rotary heads 26 and 27 are reduced because the track pattern formed on the magnetic tape 25 does not decrease when the track pattern does not decrease. This is in order to extend the recordable time of the tape so as to match the pattern, and when reproducing the magnetic tape 25, in the case of normal reproduction, the running speed of the magnetic tape 25 and the magnetic heads 26, 2
The rotation speed of 7 is set equal to that during normal recording, and therefore, the relative speed between the magnetic tape and the magnetic head is higher than during recording.

Therefore, in the case of normal reproduction of the magnetic tape 25 on which the tape recording time has been extended and recorded as described above,
As described above, when the relative speed between the magnetic tape and the magnetic head increases, the frequency of the reproduced signal increases. This is, in other words, equivalent to recording with the frequency of the recording signal increased, so that the modulation characteristic of the FM modulation circuit 14 is changed from the solid line a to the broken line b, and the output signal The frequencies for the center level V ₀ of the signal are f ₁ and f ₀
It is equivalent to being increased.

The DC level shift circuit 13 in FIG.
Even if the modulation characteristic of the FM modulating circuit 14 is changed equivalently, the frequency of the output signal relative to the center level V ₀ which the input signal does not change
f ₀ can be fixed. For this reason, in FIG. 4, when the modulation characteristic equivalently changes as shown by the broken line b, the center level of the input signal is reduced from V ₀ to V ₁ , and the output frequency with respect to this center level V ₁ is reduced. f ₀ .

As for the frequency shift, since the modulation characteristic is linear, it is not necessary to change the amplitude of the input signal.

 Next, processing of a chroma signal will be described.

The chroma signal C output from the switch 7 is supplied to the demodulation circuit 15
And demodulated by the OSC 18 into two baseband color difference signals RY and BY using the chrominance subcarrier. These color difference signals RY and BY are supplied to the TBC 16 and subjected to thinning / time-axis expansion processing similarly to the TBC 9. The two color difference signals RY and BY output from the TBC 16 are supplied to a modulation circuit 17, where quadrature two-phase balanced modulation is performed on the color subcarrier from the OSC 19.

Here, the luminance signal Y 'output from the TBC 9 is supplied to the synchronization separation circuit 11, where the horizontal synchronization signal HS2 is separated. For example, for an NTSC VHS VTR, OSC19
Its frequency f _H from the horizontal synchronizing signal HS2 'about 40 times (i.e., about 40f _H') for generating the color subcarrier frequency. Thereby, the modulation circuit 17 outputs an FM-modulated luminance signal (hereinafter referred to as FM) output from the luminance signal processing circuit 12.
Chroma signal (hereinafter referred to as low-frequency conversion chroma signal) C _{L in a} frequency band lower than the frequency band of Y _FM
Is obtained. The low-band converted chroma signal C _L is supplied to the mixing / recording circuit 23.

Although not shown, the OSC 18 is supplied with a color burst signal of the chroma signal C from the switch 7 and generates the above-mentioned color subcarrier synchronized with the color burst signal.

The audio signal A input from the input terminal 4 is supplied to the audio signal processing circuit 20. In the audio signal processing circuit 20, the audio signal A is pitch-shifted by the pitch shift circuit 21 in accordance with the extension ratio of the recordable time of the magnetic tape 25, and then FM-modulated by the FM modulation circuit 22. Pitch shift circuit
As described above, 21 is provided to alleviate the difficulty of listening to the reproduced sound due to the tape speed at the time of reproduction and the rotation speed of the magnetic heads 26 and 27 being set higher than at the time of recording, The frequency of the audio signal A is lowered by the pitch shift. This pitch shift is performed, for example, by thinning out the audio signal A at a cycle corresponding to the rate of expansion of the tape recordable time without changing on the time axis.

FM modulated audio signal output from the audio signal processing circuit 20 (hereinafter, FM referred audio signals) A _FM during the frequency band of the frequency band of the FM luminance signal Y _FM and the low frequency converted chrominance signal C _L is set to, after being amplified is mixed with a FM luminance signal Y _FM and downconverted chrominance signal C _L in a mixed / amplifier circuit 23, the magnetic tape 25 is supplied to the magnetic head 26, 27
Recorded above.

Here, as described above, if the tape recordable time of the magnetic tape 25 is 120 minutes and the required recording time is 150 minutes, the tape recordable time must be increased by 5/4 times,
The running speed of the magnetic tape 25 is reduced to 4/5 times the normal speed,
Accordingly, in order to form the same track pattern on the magnetic tape 25 as in normal recording, the magnetic head 25 is used.
26 and 27 reduce the time required to form one track on the magnetic tape 25 to 5/4 times that in normal recording. When extending the tape recordable time in this way, as described above, TBC9,16
Thus, one field period length of the FM luminance signal Y _FM and the low-frequency conversion chroma signal C _L is equal to one of the input luminance signal Y and the input chroma signal C.
It is 5/4 times the length of the field period.
Each track formed on the magnetic tape 25 on, so that the FM luminance signal Y _FM and low-band converted chroma signal C _L is recorded by one field.

Further, the track pattern on the magnetic tape 25 is the same as that at the time of normal recording, but the video signal of the broadcast program for 150 minutes is divided into 2 fields (or 2 frames) every 10 fields (or 10 frames) as described above. Therefore, the number of fields (or frames) of the video signal is equal to the number of fields (frames) of the video signal for 120 minutes. Will be recorded.

As described above, the tape recordable time can be extended, and the tape format is not impaired at this time, and the frequency of the video signal and audio signal is not affected by the recording speed. The quality of the reproduced image and the sound quality of the reproduced sound can be maintained satisfactorily.

FIG. 5 is a block diagram showing another embodiment of the magnetic recording / reproducing apparatus according to the present invention, wherein 41 is an ACC (automatic chroma control) circuit, 42 is a frequency conversion circuit, 43 is an LPF (low pass filter), and 44 is This is a TBC, and parts corresponding to those in FIG.

This embodiment differs from the embodiment shown in FIG. 1 only in the processing of the chroma signal.

In FIG. 5, a chroma signal C output from a switch 7 is supplied to a frequency conversion circuit 42 after being amplified by an ACC circuit 41 so that a color burst signal has a constant amplitude. In the frequency conversion circuit 42, the chroma signal C is frequency-converted to a lower frequency side, and for example, a VHS VTR according to the NTSC system.
In this case, a low-frequency conversion chroma signal whose color subcarrier frequency is about 40 times the horizontal synchronization frequency of the luminance signal Y output from the switch 6 is generated. This low-frequency conversion chroma signal is LPF4
After the unnecessary components are removed in step 3, it is supplied to TBC44.

TBC44 is a TBC9 as described in FIGS. 2 and 3.
The same operation as that described above is performed, the low-frequency conversion chroma signal supplied at the same ratio as that of TBC9 is thinned out, and the time axis is expanded, so that the horizontal synchronization frequency of the luminance signal Y 'output from TBC9 is about 40 times ( generating a low-frequency converted chroma signal C _L color sub-carrier frequency in the case of the VTR for the NTSC system by the VHS system). FM luminance signal in the low-band converted chroma signal C _L is mixed / amplifier circuit 23
The Y _FM and FM audio signals _AFM are mixed and amplified, supplied to the servo tape system 24, and recorded as in the embodiment shown in FIG.

As described above, in this embodiment, with regard to the processing of the chroma signal, it is only necessary to add the TBC to the chroma signal processing circuit of the conventional VTR, and the same effect as the embodiment shown in FIG. 1 can be obtained.

Although the TBC 9 is provided in the preceding stage of the luminance signal processing circuit 12 in the embodiment of FIGS. 1 and 5 described above, it may be provided in the subsequent stage. However, in this case, the FM modulation circuit
In FIG. 14, since the center level of the luminance signal Y is fixed to V ₀ in FIG. 4 similarly to the conventional VTR, the DC level shift circuit
13, the frequency of the FM luminance signal supplied from the FM modulation circuit 14 to the TBC 9 becomes higher than the frequency of the luminance signal Y. Therefore, in the TBC 9, the write clock WCLK and the read clock RCLK (FIG. 2) are used. ) Must be increased, and the memory 37 (FIG. 2) of the TBC 9 must have a large storage capacity.

In addition, these embodiments use a VHS VTR based on the NTSC system.
However, the present invention is not limited to this, and a VTR of another system or an 8 mm video may be used.

Further, an audio signal recorded by a fixed head in the longitudinal direction of the magnetic tape may be similarly recorded by pitch-shifting.

1 and 5, the FM luminance signal Y
_A signal indicating the thinned position may be added to the _FM .

FIG. 6 is a block diagram showing still another embodiment of the magnetic recording / reproducing apparatus according to the present invention.
46 is a Y / C separation circuit, 47 is a luminance signal processing circuit, 48 is a frequency demodulation circuit (hereinafter referred to as FM demodulation circuit), 49 is an attenuation circuit,
50 is a sync separation circuit, 51 is a TBC, 52 is a demodulation circuit, 53 is a TBC,
54 is a modulation circuit, 55 and 56 are OSC, 57 is a frequency divider circuit, 58 is a mixing circuit, 59 to 61 are output terminals, 62 is an audio signal processing circuit, 63 is FM
A demodulation circuit, 64 is a pitch shift circuit, and 65 is an output terminal, and portions corresponding to those in FIG.

In this embodiment, the magnetic tape is played at a higher traveling speed than in the normal playback mode, and the quality of the reproduced image and the sound quality of the reproduced sound can be prevented from deteriorating when the reproduction time is shortened. It is. The magnetic tape used here is the same as the magnetic tape used for the conventional VTR,
A mixed signal of the M luminance signal, the low-frequency conversion chroma signal, and the FM audio signal is recorded so as to be one field per track.

In FIG. 6, when a reproduction command signal is inputted from the input terminal 3, the servo tape system 24 starts a reproducing operation and starts reproducing the magnetic tape (not shown). When the instruction signal is not input from the input terminal 35, the running speed of the magnetic tape and the rotation speed of the magnetic head (not shown) are the same as those in the normal playback mode of the VHS VTR according to the NTSC system. Playback is performed. To shorten the playback time, an instruction signal indicating the rate of the reduction is input from the input terminal 35, and the running speed of the magnetic tape and the rotation speed of the magnetic head are increased at a rate corresponding to the rate. Therefore, the relative speed between the magnetic tape and the magnetic head is increased. Thus, the magnetic head sequentially reproduces and scans the tracks on the magnetic tape.

The reproduction signal obtained from the magnetic tape in this way is
After being amplified by the reproduction amplification circuit 45, the Y / C separation circuit 4
6 is supplied with FM luminance signal Y _FM and the low frequency converted chrominance signal C _L is separated into.

The FM luminance signal Y _FM is supplied to a luminance signal processing circuit 47. The luminance signal processing circuit 47, firstly, FM luminance signal Y _FM is F
The signal is demodulated by the M demodulation circuit 48 to become a baseband luminance signal, and then processed by the attenuation circuit 49.

 Here, the operation of the attenuation circuit 49 will be described.

In order to shorten the reproduction time, as described above, the running speed of the magnetic tape and the rotation speed of the magnetic head are (1 + α) times that in the normal reproduction mode (where α ≧ 0, but when the reproduction time is shortened, α > 0, α = 0 at the time of normal reproduction), the reproduction time at this time is reduced to 1 / (1 + α) times of the normal reproduction.

Incidentally, the demodulation characteristic of the FM demodulation circuit 48 is shown by a solid line a in FIG.
And the FM luminance signal Y in the normal reproduction mode (α = 0)
_{When FM} is demodulated, its center frequency f ₂ and frequency deviation de
Assuming that a luminance signal having a center level of V ₃ and an amplitude range of V ₄ is obtained with respect to V ₂ , if the reproduction time is reduced to 1 / (1 + α) times that in the normal reproduction mode as described above, magnetic When the relative speed between the tape and the magnetic head is
+ Alpha) from the fold, the central frequency of the FM luminance signal Y _FM is played (1 + α) f _2, the frequency shift becomes (1 + α) deV2. Therefore, the demodulated output of this FM luminance signal Y _FM is
As shown in FIG. 7, the center level is (1 + α) V ₃ and the amplitude range is (1 + α) V ₄ .

Since the fact that the center level of the demodulated luminance signal becomes (1 + α) times that in the normal reproduction mode merely means that the DC level has increased, the DC component is removed by using a coupling capacitor. Although not a particular problem, the amplitude range expanded by (1 + α) times must be corrected similarly. For this correction, an attenuation circuit 49 is used in the luminance signal processing circuit 47 of FIG. The amount of attenuation of the attenuation circuit 49 is changed at a rate corresponding to the rate of reduction of the playback time, and the playback time is 1 / (1) of the normal playback mode.
When the input luminance signal is reduced to (+ α) times, the attenuation circuit 49 attenuates the input luminance signal by 1 / (1 + α) times. Thus, the amplitude range of the output luminance signal Y 'of the luminance signal processing circuit 47 obtained from the attenuation circuit 49 becomes the same as in the normal reproduction mode.

This luminance signal Y 'is supplied to the synchronization separation circuit 50 to separate the horizontal synchronization signal HS3 and to the TBC 51. TBC51 is the same configuration as the TBC9 first diagram shown in FIG. 2, the vertical synchronizing pulses V _DR from the reference clock RCLK 'and divider circuit 57 from the horizontal synchronizing signal HS3, OSC56 from the sync separation circuit 50 By using this, the input luminance signal Y 'is thinned out at a rate corresponding to the rate of reduction of the reproduction time, and the time axis expansion processing is performed.

The TBC 51 will be described with reference to FIG. 2 (however, a hash mark is added to each signal in FIG. 2 to distinguish it from a signal at the time of recording).
39, write clock WCLK 'and vertical sync pulse
V _DW ′ are generated. The period of the vertical synchronization pulse V _DW 'is equal to the field period (or frame period) of the luminance signal Y' supplied to the TBC 51. Memory control circuit 40
Are the write reset pulse W _Rst ′ and the read reset pulse having a period that is an integral multiple of the period of the vertical synchronization pulse V _DW ′.
Generate R _Rst ′. Reference clock RCLK from OSC56 as write clock 'is a constant period, also, a vertical synchronizing pulse V _DR' by connexion reference clock RCL The frequency divider 57
It is obtained by dividing K 'and is equal to the field period (or frame period) of a standard video signal. In the case of normal reproduction, the write clock WCLK 'and the reference clock RCL
K ′ and the vertical synchronization pulses V _DW ′ and V _DR ′ have the same period. However, when the relative speed between the magnetic head and the magnetic tape is increased to shorten the reproduction time, the input degree signal Y supplied to the TBC 51 is increased. ′ Is compressed on the time axis, and its field cycle and horizontal synchronizing cycle are shorter than those in the normal reproduction mode at a rate corresponding to the shortening rate. However, write clock WC
Since the ratio between the period of LK 'and the period of the vertical synchronizing pulse V _DW ' and the write reset pulse W _Rst 'is always constant, the memory
The number of fields (or the number of frames) of the luminance signal Y 'written in 37 is also constant.

Therefore, in the normal reproduction, the part that requires time T
It shall be played back with the time axis shortened by 4/5 times (in this case,
If α is 1/4) and the storage capacity of the memory 37 is 10 fields, the field period T _F ″ of the input luminance signal Y ′ is
If the field period of a standard video signal is T _F , It is. Was but connexion, reference clock RCLK period of ', vertical synchronizing pulses V _DR' is 5/4 of the respective write clock WCLK ', vertical synchronizing pulses V _DW', as shown in FIG. 8, the reference clock RCLK ' With the vertical synchronizing pulse _VDR ', the luminance signal Y' is read out from the memory 37 by 8 fields every 10 fields, and each field is extended in time axis by 5/4 times. As a result, each field cycle of the luminance signal Y output from the TBC 51 is larger than that of the luminance signal Y '.
The time axis is expanded by a factor of 5/4 to form a _TF , which is a standard luminance signal.

The above is the processing of the luminance signal. Next, the processing of the chroma signal will be described.

Downconverted chrominance signal C _L obtained in the Y / C separation circuit 46 is supplied to the demodulation circuit 52, the color difference signal R-Y of two baseband using the color subcarrier from OSC55, demodulated B-Y Is done. OSC55, although not shown, a horizontally by a synchronizing signal HS3 the color burst signal separated from the low-band converted chroma signal C _L based on connexion control from the sync separation circuit 50, to the color burst signal frequency, phase Generate synchronized color subcarriers.

The two color difference signals obtained by the demodulation circuit 52 are decimated and time-base expanded in the TBC 53 in the same manner as in the TBC 51.
The modulator 54 performs quadrature two-phase balanced modulation of the chrominance subcarrier from the OSC 56 to obtain a standard chroma signal C.

The luminance signal Y output from the TBC 51 and the chroma signal C output from the modulation circuit 54 are output on the one hand from output terminals 59 and 61 as component signals, respectively, and on the other hand are mixed by a mixing circuit 58 and mixed to produce a composite signal. Is output from the output terminal 60.

The reproduction signal amplified by the reproduction amplification circuit 45 is also supplied to an audio signal processing circuit 62 where the FM audio signal is separated and
The signal is supplied to the demodulation circuit 63 and demodulated into a baseband audio signal. When the relative speed between the magnetic tape and the magnetic head is increased in shortening the reproduction time, the audio signal is also time-axis-compressed at a rate corresponding to the shortening rate (1 / (1 + α) times). . Then, the audio signal is supplied to the pitch shift circuit 64, and the audio signal is pitch-shifted at a rate corresponding to the rate of reduction of the reproduction time. The audio signal A thus processed is output from the output terminal 65.

As described above, in this embodiment, since the time required to reproduce one track is reduced to 1 / (1 + α) times that in the normal reproduction mode, the reproduction time can be reduced to 1 / (1 + α) times.
In addition, the running speed of the magnetic tape is increased and the rotating speed of the magnetic head is also increased so that the magnetic head scans the tracks on the magnetic tape correctly. Since the field (or frame) period is made to match that of the standard system, a reproduced image whose contents change faster than in the normal reproduction mode can be displayed stably and with high quality. In this case, assuming that the number of fields (or the number of frames) written to the TBC is N, the αN / (1 + α) field (or the frame) is thinned out every N fields (or N frames).
Since the content of the reproduced image changes at a high speed, the influence of this thinning is not so noticeable.

Also, the reproduced audio signal is compressed on the time axis by an increase in the relative speed between the magnetic tape and the magnetic head, and the frequency is also increased by this. Since the frequency is lowered without conversion such as decompression and compression, the difficulty in hearing can be reduced even if the voice is fast. Moreover, since there is no conversion of the audio signal on the time axis, there is no time lag between the reproduced image and the reproduced audio.

FIG. 9 is a block diagram showing still another embodiment of the magnetic recording / reproducing apparatus according to the present invention, wherein 66 is a TBC, 67 is a frequency conversion circuit, 68 is a VCO (voltage controlled oscillation circuit), and 69 is a frequency conversion circuit. , 70 denotes an OSC, 71 denotes a frequency dividing circuit, and 72 denotes a synchronization separating circuit. The parts corresponding to those in FIG.

This embodiment differs from the embodiment shown in FIG. 6 in the processing of the reproduced chroma signal.

In FIG. 9, the low-frequency conversion chroma signal C _L separated by the Y / C separation circuit 46 is supplied to the TBC 66, decimated at the same ratio as the TBC 51, and expanded on the time axis. The thinning out of the TBC 66 and the time base expansion processing are performed by the horizontal synchronization signal HS3 from the synchronization separation circuit 50, the reference clock RCLK from the OSC 70, and the vertical synchronization pulse V obtained by dividing the reference clock RCLK by the frequency divider 71. _Performed using _DR .

Downconverted chrominance signals outputted from the TBC66 is supplied to the frequency converting circuit 67, it is frequency-converted chroma signal C of the color sub-carrier frequency f _SC of the O connexion standard method to the output signal of the frequency conversion circuit 69. Here, VTR of VHS system by NTSC system
In the case of, the color subcarrier frequency f _L of the low-frequency conversion chroma signal output from the TBC 66 is about 40 times the horizontal synchronization frequency f _H of the luminance signal Y output from the TBC 51 (ie, about 40 f _H ).
The luminance signal Y is supplied to a synchronization separation circuit 72, where a horizontal synchronization signal HS4 is separated.
O68 generates a signal of a frequency of about 40f _H. Further, OSC70 the color subcarrier frequency f _SC are also generated, the signal of the color subcarrier output signal and is supplied to the frequency conversion circuit 69 frequency VCO68 about (f _SC + 40f _H) is generated You. This signal is supplied to the frequency conversion circuit 67, the low-band converting chrominance signal of the color sub-carrier frequency of about 40f _H is converted into a chroma signal C of the color sub-carrier frequency F _SC.

In this embodiment, it is only necessary to add TBC66 to a conventional color signal processing circuit as a color signal processing circuit.
The structure can be simplified as compared with the embodiment shown in the figure, and the same effect can be obtained. However, since the frequency of the low-frequency conversion chroma signal is higher than the frequency of the baseband color difference signal, the TBC66 uses a memory having a slightly larger storage capacity than the TBC53 in FIG.

By the way, in the embodiment described with reference to FIGS. 6 and 9, the thinning-out at the TBC when the reproduction time is shortened is performed for an arbitrary field (or frame) determined by the operation of the TBC irrespective of the motion of the image. Was. However, even if there is no motion in the image, if there is little motion, or if there is a lot of movement,
Although the effect of this thinning is not conspicuous on the playback screen, if the thinning is performed in a portion where the motion of the image is slow, the movement of the image becomes awkward for a moment in the portion where the thinning is performed on the playback screen.

FIG. 10 is a block diagram showing still another embodiment of a magnetic recording / reproducing apparatus according to the present invention which can prevent this. In FIG. 10, reference numeral 73 denotes a motion detecting circuit, and portions corresponding to FIG. Reference numerals are given and duplicate description is omitted.

In the figure, the baseband luminance signal output from the luminance signal processing circuit 47 is written to the memory of the TBC 57, and is also supplied to the motion detection circuit 73, and is decimated by the field (or frame) correlation of the luminance signal. An inconspicuous part of the screen is detected,
Control is performed so that the TBCs 51 and 53 perform thinning.

As the motion detection circuit 73, a conventionally known one can be used. The motion detection circuit 73 performs motion detection for a predetermined number of fields (or a predetermined number of frames) of the luminance signal, and determines a portion having the least effect even if thinning is performed based on the detection result. Do it. For this reason, in the TBCs 51 and 53, it is necessary to hold the luminance signal of the number of fields (or the number of frames) in the unit period in which the motion detection circuit 73 detects the motion during the period in which the motion detection circuit 73 detects the motion. For example, TBC51,
In the case of 53, the thinning is performed in units of fields. In order to reduce the reproduction time by 5%, one field must be thinned out every 20 fields.
73 performs motion detection every 20 fields, and the TBCs 51 and 53 need to have two memories with a storage capacity of at least 20 fields.

Of course, while sequentially detecting the field (or frame) correlation, the motion detection circuit 73 detects a portion where the effect hardly appears on the screen even if the thinning is performed, and causes the TBC 51, 53 to perform the thinning process on this portion. It may be.

As described above, in this embodiment, FIGS.
As compared with the embodiment shown in the figure, an effect is obtained that the influence of the thinning on the reproduced image can be further prevented.

In the embodiment shown in FIGS. 1, 5, 6, and 9, the thinning-out should be performed at a portion which does not affect the image as in the embodiment shown in FIG. Can be.

6, 9 and 10, the TBC51
May be provided before the luminance signal processing circuit 47. However, in this case, the attenuation circuit 49 becomes unnecessary,
Needless to say, the storage capacity of the memory in the TBC 51 must be larger than that of the TBC 51 provided after the luminance signal processing circuit 47.

Further, in FIGS. 6, 9 and 10, NT
It is needless to say that the present invention can be applied to a VTR other than the VHS system VCR based on the SC system and an 8 mm video.

In addition, the audio signal reproduced from the magnetic tape by the fixed head is similarly pitch-shifted, so that it is possible to reduce the difficulty in hearing the reproduced audio.

[Effects of the Invention] As described above, according to the present invention, it is possible to extend the recordable time on a magnetic tape while securing the stability and image quality of a reproduced image to about the conventional SP mode, Playback time can also be reduced.

In addition, when extending the recordable time or shortening the reproduction time, it is possible to reduce the difficulty of hearing the reproduced sound.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention, FIG. 2 is a block diagram showing a specific example of a time axis correction circuit in FIG. 1, and FIG. FIG. 4 is a view showing the characteristics of the frequency modulation circuit of the luminance signal processing circuit and the operation of the DC level shift circuit in FIG. 1, and FIGS. FIG. 7 is a block diagram showing an embodiment, FIG. 7 is a diagram for explaining the operation of the attenuation circuit in the luminance signal processing circuit in FIG. 6, FIG. 8 is an operation explanatory diagram of the time axis correction circuit in FIG. FIGS. 9 and 10 are block diagrams showing still another embodiment of the magnetic recording / reproducing apparatus according to the present invention. 9: time axis correction circuit, 12: luminance signal processing circuit, 13:
... DC level shift circuit, 14 ... Frequency modulation circuit, 15 ...
Demodulation circuit, 16: Time axis correction circuit, 17: Modulation circuit, 20
…… Audio signal processing circuit, 21… Pitch shift circuit, 22…
... frequency modulation circuit, 24 ... servo / tape system, 25 ... magnetic tape, 26, 27 ... magnetic head, 31 ... servo circuit, 3
2 frequency divider circuit 33 oscillator circuit 35 input signal input terminal 42 frequency conversion circuit 44 time axis correction circuit 46 Y / C separation circuit 47 luminance Signal processing circuit, 48
…… Frequency demodulation circuit, 49 …… Attenuation circuit, 51 …… Time axis correction circuit, 52 …… Demodulation circuit, 53 …… Time axis correction circuit, 54…
... Modulation circuit, 62 ... Audio signal processing circuit, 63 ... Frequency demodulation circuit, 64 ... Pitch shift circuit, 66 ... Time axis correction circuit, 67 ... Frequency conversion circuit, 73 ... Motion detection circuit.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideo Nishijima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (72) Inventor Koichi Ono 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock (56) References JP-A-62-186681 (JP, A) JP-A-2-206979 (JP, A) JP-A-63-224489 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) H04N 9/79-9/898 H04N 5/91-5/956

Claims (8)

(57) [Claims] A luminance signal is frequency-modulated, and a chroma signal is converted into a low-frequency conversion chroma signal in a frequency band lower than a frequency band of the frequency-modulated luminance signal. A magnetic recording / reproducing apparatus which mixes a low-frequency conversion chroma signal with a low-frequency converted chroma signal and records the magnetic tape on a magnetic tape by a rotary head, wherein a running speed of the magnetic tape is reduced, and a rotating speed of the rotary head is reduced. (1) the luminance signal obtained by frequency-modulating the luminance signal with respect to the luminance signal is decimated at a rate corresponding to a reduction rate of the running speed of the magnetic tape, and the decimated minute and time axis is extended. 2
And means for reducing the converted chroma signal with respect to the chroma signal at a rate corresponding to a reduction rate of the running speed of the magnetic tape, and extending the thinned minute and time axis. And fourth means for pitch-shifting the audio signal at a rate corresponding to the rate of reduction of the running speed of the magnetic tape; and fifth means for frequency-modulating the audio signal output from the fourth means. The frequency-modulated audio signal output from the fifth means is mixed with the frequency-modulated luminance signal and the reduced conversion chroma signal and recorded on the magnetic tape, without changing the tape format. A magnetic recording / reproducing apparatus characterized in that the recording time on the magnetic tape can be extended. 2. The apparatus according to claim 1, further comprising: a sixth means for lowering the DC level of the output luminance signal of the second means at a rate corresponding to a rate of reduction in the running speed of the magnetic tape. A magnetic recording / reproducing apparatus for frequency-modulating an output luminance signal of the means. 3. The apparatus according to claim 1, wherein said third means comprises: seventh means for demodulating said chroma signal into two color difference signals; and eighth means for thinning out each of said color difference signals to extend the time axis. And a ninth means for modulating two color difference signals output from the eighth means to form the reduced conversion chroma signal. 4. A magnetic recording / reproducing apparatus according to claim 1, wherein a signal indicating a thinning position is added to the luminance signal output from said second means. 5. The apparatus according to claim 1, further comprising: motion detecting means for detecting a degree of motion of an image from the luminance signal; A magnetic recording / reproducing apparatus, wherein the thinning timing is set. 6. A luminance signal processing means for reproducing a mixed signal from a magnetic tape on which a mixed signal of a luminance signal, a chroma signal and an audio signal is recorded by a rotary head, and processing the luminance signal of the mixed signal. And a chroma signal processing means for processing the chroma signal of the mixed signal, wherein the running speed of the magnetic tape is increased and the luminance signal of the reproduced mixed signal is First means for generating a luminance signal which is thinned out at a rate corresponding to the rate of increase of the running speed of the magnetic tape and which is expanded in time axis, and which runs the magnetic tape in response to the reproduced chroma signal of the mixed signal; Thinning out at a rate corresponding to the rate of increase in speed,
A second means for generating a chroma signal expanded on the time axis, and a third means for generating an audio signal pitch-shifted from the reproduced audio signal by a ratio corresponding to the rate of increase of the running speed of the magnetic tape. A magnetic recording / reproducing apparatus comprising: means for reproducing an image by shortening a reproducing time on the magnetic tape. 7. The chroma signal processing means according to claim 6, wherein said chroma signal processing means demodulates said chroma signal of said reproduced mixed signal into two color difference signals, and said mixed signal reproduced said two color difference signals. Modulation means for modulating the chroma signal of the signal with a color subcarrier frequency to generate the high-frequency chroma signal, wherein the second means thins out the two color difference signals from the demodulation means, A magnetic recording / reproducing apparatus characterized in that a time axis expansion process is performed and supplied to the modulation means. 8. The apparatus according to claim 6, further comprising: motion detecting means for detecting a degree of motion of an image from the luminance signal of the reproduced mixed signal, wherein the first signal is detected in accordance with a detection result of the motion detecting means. A magnetic recording / reproducing apparatus, wherein a thinning timing is set by a second means.