JPH0212774Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a video and audio signal recording and reproducing device, and more specifically, the present invention relates to a video and audio signal recording and reproducing device that records and reproduces a video signal and a signal modulated by an audio signal on a magnetic tape. Regarding a playback device.

In a conventional video and audio signal recording and reproducing device (hereinafter, the video and audio signal recording and reproducing device will be referred to as a VTR in this specification), the audio signal is magnetically transmitted along the running direction of the magnetic tape as shown in FIG. It was recorded on one end of the tape. In FIG. 1, 1 indicates a magnetic tape, 2 indicates an audio signal track, and 3 and 4 indicate a video track for the first field and a video track for the second field.

However, in conventional VTRs, the running speed of the magnetic tape is not exactly constant, resulting in many wows and flutters, and the narrow audio track width and slow running speed of the magnetic tape result in poor S/N. For this reason, there was a drawback that the quality of the reproduced audio was very poor.

The present invention has been made in view of the above, and it is an object of the present invention to provide a video and audio signal recording and reproducing apparatus that can eliminate the above-mentioned drawbacks and obtain reproduced sound of good quality.

According to the invention, this purpose is achieved by using a rotary head type
In a VTR, in addition to rotary heads for video signals provided at positions facing each other (hereinafter, the rotary heads for video signals are referred to as video signal heads), An audio signal rotary head (hereinafter, the audio signal rotary head is referred to as an audio signal head) is provided at approximately the middle position, and the signal modulated by the audio signal is not synchronized with the vertical synchronization signal in the video signal. The audio signals are recorded on a magnetic tape by the audio signal heads, and the reproduction of the signals recorded by the audio signal heads is based on the vertical synchronization signal in the video signal. This is achieved by reproducing the audio signal by switching the output signal from the audio signal head so that there is a difference of at least three horizontal synchronizing signal periods between the output period of the audio signal head and the output period of the other audio signal head. .

The present invention will be explained below with reference to examples.

FIG. 2 is a plan view showing a main part of an embodiment of the present invention, and is an example in which an audio signal is pulse code modulated and recorded.

In FIG. 2, reference numeral 1 denotes a magnetic tape, and the magnetic tape 1 is fed in the direction of arrow A along a tape guide 5 and a head cylinder 6 that is rotationally driven in the direction of arrow B. In FIG. Head cylinder 6
Inside the head cylinder 6, video signal heads 7 and 8 are provided at positions directly opposite to the center of the head cylinder 6, and are approximately separated from the video signal heads 7 and 8.
Audio signal heads 10 and 11 are provided at positions separated by an angle of 90 degrees. Head 7, 8,
10 and 11 are rotationally driven together with the head cylinder 6 in the direction of arrow B. Further, the heightwise positions of the video signal heads 7 and 8 on the head drum and the heightwise positions of the audio signal heads 10 and 11 on the head drum are set at the same height.

Further, the recording track width on the magnetic tape 1 by the audio signal heads 10 and 11 is set to be the same or narrower than the recording track width on the magnetic tape 1 by the video signal heads 7 and 8.

This configuration is similar to the head configuration of a VTR configured for long-term recording.

The video signal heads 7 and 8 receive the video signal,
A pulse code modulated audio signal is applied to the audio signal heads 10 and 11, respectively, and a video signal and a pulse code modulated audio signal are respectively recorded on the magnetic tape 1. In this case, the running speed of the magnetic tape 1 is set so that the recording track of the video signal and the recording track of the pulse code modulated audio signal do not overlap, for example, when the VTR has only the video signal heads 7 and 8. Approximately 2 times the running speed of magnetic tape 1
It is set to double.

On the other hand, the video signal heads 7 and 8 are connected to a detection amplification switching circuit 9 to switch and output their outputs. As shown in FIG. 3a, the detection amplification switching circuit 9 includes coupling transformers _T1 and _T2 connected to the video signal heads 7 and 8, respectively, and transistors _Q1 to _Q4 , similar to a conventional VTR. A recording/playback switching circuit consisting of a coupling transformer _T1 and
Preamplifier that amplifies the video signal detected by T ₂
Consisting of A ₁ and A ₂ , and transistors Q ₅ and Q ₆ which are alternately switched by the output signal of a pulse generator attached to the rotating head shaft and ground the outputs of preamplifiers A ₁ and A _2. For video signals. It consists of a switching circuit that switches the outputs of heads 7 and 8. R ₁ is a resistance for synthesis.

On the other hand, the audio signal heads 10 and 11 are connected to a detection amplification switching circuit 12 to switch their outputs. The detection amplification switching circuit 12 includes, for example, coupling transformers connected to the audio signal heads 10 and 11, respectively, as shown in FIG. 3b.
T ₃ and T ₄ , a recording/playback switching circuit consisting of transistors Q ₇ to Q ₁₀ , and a coupling transformer T ₃ and
Preamplifiers A ₃ and A ₄ detect and amplify the pulse code modulated audio signal at T ₄ and the voltage applied to the bases of transistors Q ₅ and Q ₆ with a phase difference of approximately 90°. A voltage is applied, and a monostable multivibrator MM ₁ delays the rise of the applied voltage by 1.5H (H is the horizontal synchronization signal period), and Fi− is triggered by the rise of the output of the monostable multivibrator MM ₁ . The monostable multivibrator MM ₂ outputs a pulse with a width of 1.5H (Fi is 1 field period), and the preamplifier is switched alternately with the output of the monostable multivibrator MM ₂ .
Transistor _Q11 to ground the outputs of _A3 and _A4
and _Q12 , and a switching circuit for switching the output of the audio signal head. R ₂ is a resistance for synthesis.

Figure 4 shows a known method for pulse code modulating an audio signal and decoding the pulse code modulated audio signal.
A block diagram of a PCM adapter is shown, with error detection and error correction circuitry omitted for simplicity.

In FIG. 4, A and B respectively indicate the audio signal PCM encoding circuit portion and the decoding circuit portion of the PCM adapter, and C has audio signal heads 10 and 11 and detection amplification switching circuits 9 and 12. Shows a VTR.

The video signal input V _1N is input to VTR, C,
Magnetic tape 1 is connected to video signal heads 7 and 8.
record it.

On the other hand, the encoding circuit portion A of the PCM adapter includes amplifiers 14 and 15 that input and amplify the audio signals of the left and right channels, sample and hold circuits 16 and 17, a multiplexer 18, an analog-to-digital converter 19, a storage device 20, It comprises a recording synchronization signal oscillator 21 and an amplifier 22,
The left channel audio signal is sampled and held, the right channel audio signal is sampled and held, multiplexed, pulse code modulated, and the vertical synchronization signal of the standard television signal,
In addition to horizontal synchronizing signals and equalization pulses, for example, home VTRs specified by the Electronic Machinery Industries Association
Outputs a pulse code modulated audio signal that complies with the standards for PCM audio adapters that use . This output is applied to the VTR, C, and recorded on the magnetic tape 1 by audio signal heads 10 and 11.

The track pattern on the magnetic tape 1 of the video signal recorded by the video signal heads 7 and 8, and the track pattern on the magnetic tape 1 of the audio signal recorded by the audio signal heads 10 and 11 are shown in FIG. For example, the video signal of the first field is sent to the track E by the video signal head 7, the pulse code modulated audio signal is sent to the track F by the audio signal head 10, and the video signal of the second field is sent to the track E. The signal head 8 sequentially records the pulse code modulated audio signal on the track G, and the audio signal head 11 sequentially records the pulse code modulated audio signal on the track H.

Therefore, when the video signal and the pulse code modulated audio signal are reproduced, the video signal heads 7 and 8 reproduce the video signal from the recorded contents of tracks E and G, and the audio signal heads 10 and 11 reproduce the video signal from the recorded contents of tracks E and G. A pulse code modulated audio signal is reproduced from the recorded contents of tracks F and H. The reproduced pulse code modulated audio signal is sent to an amplifier 24, a synchronous separation circuit 25, a storage device 26, a digital-to-analog converter 27, and a demultiplexer 2.
8. Known device equipped with low-pass filters 29 and 30
It is decoded into an audio signal by the decoding circuit section B of the PCM adapter. 31 is a reproduction synchronization signal oscillator. Therefore, the audio signal output from the decoding circuit section B does not include the wow, flutter, jitter, etc. of the VTR.

Furthermore, as mentioned above, since the track width of the audio signal heads 10 and 11 is set to be the same or narrower than the track width of the video signal heads 7 and 8, when both track widths are equal, the magnetic tape 1 cannot be fed. Although it is necessary to double the speed of the conventional one, the audio signal heads 10 and 1
When the recording track width of the magnetic tape 1 is narrowed, there is no need to double the feeding speed of the magnetic tape 1 compared to the conventional one. Suppose, for example, that a video signal and a pulse code modulated audio signal are recorded using a conventional VTR that has separate heads for 2-hour recording and 6-hour recording. For example, the former is used as video signal heads 7 and 8, and the latter is used as audio signal head 10.
and 11, in which case the magnetic tape 1
Change the feeding speed to standard speed (for example, VHS type
By doubling the VTR standard (3.335 cm/sec), a sufficient guard band can be provided for the former track width of 58 μm and the latter track width of 19 μm. In this case, since the track width by the audio signal head is narrow, there is no need to increase the feeding speed of the magnetic tape 1 to twice the standard speed, and the recording track of the video signal and the pulse code modulated audio It is only necessary to speed up the signal to a speed that does not overlap with the recording track of the signal.

Next, switching of the reproduction signal from the video signal heads 7 and 8 and switching of the reproduction signal from the audio heads 10 and 11 will be explained.

Switching of the reproduction signals from the video signal heads 7 and 8 is the same as in the conventional case. During the recording state, positive voltage is applied to the bases of _the transistors Q ₃ , Q ₄ , _{Q 9 and Q 10 ,} and _the transistor Q ₃ , Q ₄ , Q ₉ and Q ₁₀ are in the on state, transistors Q ₁ , Q ₂ , Q ₇ and Q ₈ are in the off state, and the video signal is transmitted through the transformers T ₁ and T _2. The output signal of the amplifier 22, that is, the pulse code modulated audio signal, is applied to the audio signal heads 10 and 11 via transformers T ₃ and T ₄ as shown in FIG. recorded as such. On the other hand, during the regeneration state, transistors Q ₁ , Q ₂ ,
A positive voltage is applied to the bases of Q ₇ and Q ₈ , transistors Q ₁ , Q ₂ , Q ₇ and Q ₈ are in the on state, and transistors Q ₃ , Q ₄ , Q ₉ and Q ₁₀ are in the off state. The reproduced signals from the video signal heads 7 and 8 are amplified by amplifiers A ₁ and A ₂ , and the reproduced signals from audio signal heads 10 and 11 are amplified by amplifiers A ₃ and A ₄ . Ru. on the other hand,
The output signal of the pulse generator attached to the rotary head shaft, that is, the pulse wave shown in FIG. _6a , is applied to the transistors Q ₅ and Q 6, and the transistors Q 5 _and Q ₆ receive the pulse wave shown in FIG. It alternately turns on and off in sync with the waves. In addition, when the transistors Q ₅ and Q ₆ are switched, they are positioned outside the video screen. On the other hand, the monostable multivibrator MM ₁ has a 60° phase lag than that shown in Fig. 6a.
The pulse wave shown in Figure b is applied and triggered at its rising edge, the output of monostable multivibrator MM ₁ becomes the pulse waveform shown in Figure 6 c, and the output of monostable multivibrator MM ₂ is the output of monostable multivibrator MM ₁ . Triggered by the rising edge of the pulse,
The output pulses of the monostable multivibrator _MM2 are as shown in FIG. 6d. The output pulse shown in FIG. 6 d is applied to the bases of transistors Q ₁₁ and Q ₁₂ , and transistors Q ₁₁ and Q ₁₂ alternately turn on and off in synchronization with the pulse wave shown in FIG. 6 d. The on period of ₁₁ was delayed by 1.5H from the rise of the pulse waveform in Figure 6b (Fi-1.5H)
The transistor _Q12 remains on for a period of (Fi+1.5H). Therefore, the output signals of the audio signal heads 10 and 11 are alternately switched at intervals of (Fi - 1.5H) and (Fi + 1.5H), and the output signals of the audio signal heads 10 and 11 are changed. There is a difference of 3 hours in the period.

Next, the reason why the reproduction signal output periods from the audio signal heads 10 and 11 are set to have a difference of 3H will be explained. When reproducing an audio signal, the distinction between the first and second fields is detected from the vertical synchronizing signal of the first field and the vertical synchronizing signal of the second field in the reproduced signals from the audio signal heads 10 and 11, and the vertical synchronizing signal is detected. The data is stored in the storage device 26 at a certain timing, and is subjected to correction of time axis fluctuations due to jitter, error correction, deinterleaving, etc., and then converted into an analog signal and output. On the other hand, when recording video signals and audio signals using a rotating head as in one embodiment of the present invention,
As is clear from FIG. 4, the recording synchronization signal oscillator 21 is provided independently in the audio signal PCM encoding circuit section A, and the vertical synchronization signal generated from this output is completely synchronized with the synchronization signal in the composite video signal. The relative position of the vertical synchronization signal of the video signal recorded on the magnetic tape and the vertical synchronization signal of the pulse code modulated audio signal recorded on the adjacent track changes over time. A shift occurs gradually.

This is because if the recording synchronization signal oscillator 21 is, for example, a crystal oscillator, the vertical synchronization signal period itself is determined by the precision of the crystal oscillator and hardly changes. but,
The vertical synchronization signal period of the composite video signal and the vertical synchronization signal period of the pulse code modulated audio signal generated from the oscillation output of the recording synchronization signal oscillator 21 are set to be the same as possible, but there is an extremely small difference between the two. This is because the difference exists and the rotational drive of the cylinder head 6 is synchronized with the vertical synchronization signal of the composite video signal. Therefore, based on the vertical synchronization signal in the composite video signal, the playback signals from the video signal heads 7 and 8 and the audio signal head 1 are output.
When the reproduction signals from the video signal heads 7 and 11 are switched, the timing of switching the reproduction signals from the video signal heads 7 and 8 is the same as that of a conventional VTR, so there is no problem. That is, the noise that occurs at the time of switching occurs outside the image screen, and the screen is not disturbed by the noise.
However, although the frequency of the synchronization signal in the pulse code modulated audio signal applied to the audio signal heads 10 and 11 is very close to the frequency of the synchronization signal in the video composite signal, there is a slight difference. Therefore, as mentioned above, we will proceed little by little. For this purpose, audio signal heads 10 and 1
1, the recording position of the vertical synchronizing signal in the audio signal recorded on the magnetic tape 1 is not constant relative to the recording position of the vertical synchronizing signal recorded on the adjacent composite video signal recording track. , the recording tracks F and H in FIG. 5 will have different positions. Therefore, if the playback signals from the audio signal heads 10 and 11 are switched in synchronization with the vertical synchronization signal in the composite video signal, the timing of this switching will be within the vertical synchronization signal in the audio signals from the audio signal heads 10 and 11. There may be cases where it is switched. In this case, the noise caused by switching taints the vertical synchronization signal in the audio signal, resulting in erroneous detection. Therefore, it becomes impossible to determine the first field or the second field. The audio signal contains 3 words of left and right channel information (total 6 words) within 1H.
Two words are arranged for error correction and one word for error detection, and simple delay interleaving is performed with an interleaving delay amount of 16H. Therefore, deinterleaving is performed by counting the number of horizontal synchronizing signals based on the vertical synchronizing signal. However, if the vertical synchronization signal is incorrectly detected, it may cause trouble in deinterleaving the pulse code modulated audio signal.

Therefore, as an embodiment of the present invention, monostable multivibrators MM ₁ and MM ₂ as shown in FIG.
As shown in FIG. 6d, transistor _Q11 is turned on for a period of (Fi - 1.5H), transistor _Q12 is turned on for a period of (Fi + 1.5H), and the audio signal head is turned on. The audio signals from 10 and 11 are switched. Therefore, a period difference of 3H is created between the output period from the audio signal head 10 and the output period from the audio signal head 11. The reason why the period difference is 3H here is because the width of the vertical synchronization signal is 3H. If there is no difference in the period of 3H, audio signal heads 10 and 11
The output from the transistor switches the video signal heads 7 and 8.The pulse wave shown in FIG.
It is applied to the bases of Q ₁ ¹ and Q ₁₂ to switch the outputs from audio signal heads 10 and 11. However, even when the vertical synchronization signal position in the composite video signal and the vertical synchronization signal position in the audio signal shift little by little, the audio signal head 10
The switching of the outputs from the video signal heads 7 and 11 is delayed by 90 degrees from the switching of the outputs from the video signal heads 7 and 8. Therefore, the switching position between the output signal from the audio signal head 10 and the output signal from the audio signal head 11 and the switching position between the output signal from the audio signal head 11 and the output signal from the audio signal head 10 are different. The vertical synchronization signal in the audio signal may be confused. However, as in one embodiment of the present invention, since a period difference of 3H is provided, even if the switching position between the output signal from the audio signal head 10 and the output signal from the audio signal head 11 is different from that in the audio signal. Even if it is a vertical synchronization signal, the output signal from the audio signal head 11 and the audio signal head 1
The switching position from 0 to the output signal does not affect the vertical synchronization signal in the audio signal. There is also the opposite case, in which even if switching occurs during the vertical synchronization signal of one field and that vertical synchronization signal is contaminated by noise, the switching timing will occur during the vertical synchronization signal of the other field. Since the vertical synchronizing signal of the other field is not contaminated, at least the vertical synchronizing signal of the other field can be detected without error, and disturbances in the reproduced audio signal can be minimized.

Note that in the above case, it is not possible to distinguish between the odd and even numbers of one field and the other field using only the vertical synchronization signal of the other field, but if a field type discrimination circuit is used, it becomes possible to easily distinguish between odd and even numbers of the fields. There will be no hindrance.

FIG. 7 is a block diagram showing an example of a field type discrimination circuit.

This field type discrimination circuit consists of a sync signal separation circuit 35, a vertical sync signal separation circuit 36, monostable multivibrators 37 and 38, an inverter 39, NAND gates 40 and 41, and a flip-flop 4.
It consists of 2.

When a composite video signal is applied to the synchronization signal separation circuit 35, the output of the synchronization signal separation circuit 35 has a pulse waveform shown in FIG. 8a, and the monostable multivibrator 3
8 has a pulse waveform as shown in FIG. 8b, the output of the vertical synchronizing signal separation circuit 36 has a waveform as shown in FIG. 8c, and the output of the monostable multivibrator 37 has a pulse waveform as shown in FIG. 8d. , the outputs of the NAND gate circuits 40 and 41 are as shown in FIG. 8e and f. Therefore, the output of flip-flop 42 is the eighth
The output waveform is shown in FIG. g, and the first field and the second field can be distinguished by the output of the flip-flop 42.

As explained above, according to the present invention, since a signal modulated by an audio signal is recorded with a rotating head,
The reproduced audio frequency characteristics can be suppressed to within ±1 dB in the range of 20 to 20 kHz, wow and flutter can be improved to below the measurement limit, and S/N can be achieved with a dynamic range of 85 dB.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing recording tracks on a magnetic tape in the case of a conventional VTR. Figures 2a and 2b are a perspective view and a plan view showing essential parts of an embodiment of the present invention. FIG. 3 is a block diagram showing an example of a detection amplification switching circuit for a reproduced signal from a video and audio signal head used in an embodiment of the present invention. Figure 4 is
Block diagram of PCM adapter. FIG. 5 is a diagram showing recording tracks on a magnetic tape in one embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the operation of the detection amplification switching circuit of FIG. 3. FIG. 7 is a block diagram showing an example of a field type discrimination circuit in an embodiment of the present invention. FIG. 8 is a waveform diagram for explaining the operation of the field type discrimination circuit of FIG. 7. 1...Magnetic tape, 6...Head cylinder, 7
and 8...video signal head, 10 and 11
... Audio signal head, 9 and 12 ... Detection amplification switching circuit, MM ₁ , MM ₂ , 37 and 38 ...
Monostable multivibrator, 35... synchronous signal separation circuit, 36... vertical synchronous signal separation circuit, 42...
…flipflop.

Claims (1)

[Claims for Utility Model Registration] A rotary head type video and audio signal recording and reproducing device, comprising: a rotary head for video signals provided at 180 degree intervals on the head cylinder; A pulse code modulated audio signal that is provided approximately midway between the signal rotating heads, is supplied with a vertical synchronization signal, and is supplied in a state where the vertical synchronization signal is not synchronized with the vertical synchronization signal in the video signal. Based on output signals from a rotary head for audio signals recorded on a magnetic tape and reproduced from the magnetic tape, and a pulse generator for detecting the rotational phase of the head cylinder, the output signal has the same period as the output signal period from the pulse generator. ,
and generating a rotary head switching signal for an audio signal having a difference of at least three horizontal synchronization signal periods between one half-cycle period and the other half-cycle period;
1. A video and audio signal recording and reproducing apparatus comprising an audio signal rotary head switching circuit that switches the reproduction output from the audio signal rotary head using an audio signal rotary head switching signal.