JPH0142550B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an audio signal recording and reproducing method, which is used in a one-head helical scan type magnetic recording and reproducing apparatus to time-compress an audio signal and frequency-divide and superimpose the audio signal on a modulated video signal for multiplex recording. An object of the present invention is to provide an audio signal recording and reproducing method that allows audio signals to be continuously recorded even if there is a period in which a recording/reproducing signal is absent from a video head. In general, a one-head helical scanning type magnetic recording/reproducing apparatus winds a magnetic tape 1 around a head drum 2 at 360 degrees, as shown in FIG. 1, and performs recording and reproduction using one video head. In the magnetic tape 1 shown in FIG. 2, video signals are recorded on tracks 2a and 2b inclined with respect to the longitudinal direction of the tape by a rotating video head (not shown), and audio signals are recorded by a fixed head 4. A video signal is recorded on an audio track 3 extending in the longitudinal direction of the tape, and a similar rotary head 2 reproduces a video signal from this recording tape, and a fixed head 4 reproduces an audio signal. For example, when recording an NTSC color video signal with the frequency spectrum shown in FIG.
As shown in the figure, the luminance signal is subjected to low carrier frequency modulation, the carrier color signal is frequency converted to a low frequency converted carrier color signal, and these two signals are frequency multiplexed and divided into magnetic signals as shown in Figure 2. On a tape 1, one inclined video track 2a, 2b, . . . is formed for each field. On the other hand, the audio signal passes through an audio signal processing circuit that is separate from the video signal, enters the input terminal 6, passes through the high frequency bias circuit 5, and is sent to the upper edge of the magnetic tape 1 by the fixed audio head 4 as an audio track. 3 is formed and recorded. At the same time, a control pulse synchronized with the vertical synchronization signal of the color video signal to be recorded is recorded by forming a control track 7 on the lower edge of the magnetic tape 1. Also, during playback, from tracks 2a, 2b,...
They are sequentially reproduced, and the frequency spectrum of the reproduced signal is as shown in FIG. After being returned, both signals are multiplexed into a reproduced color video signal. However, in the above-mentioned well-known video signal and audio signal recording and reproducing methods, in order to further improve the utilization efficiency of the magnetic tape and lengthen the recording and reproducing time, it is necessary to reduce the running speed of the magnetic tape. , in Figure 2, a rotating video head (not shown)
than the decrease in relative speed between and the magnetic tape 1,
Since the audio head 4 is fixed, the relative speed decrease between the audio head 4 and the magnetic tape 1 is even greater, and recording and reproducing audio signals is more difficult than recording and reproducing video signals. Greater negative effects (deterioration of frequency characteristics and S/N ratio, etc.)
You will receive the following. Therefore, in order to solve these problems, the audio signal is frequency-modulated or amplitude-modulated, mixed and multiplexed into the upper and lower bands of the frequency-modulated video signal as shown in FIG. It is conceivable to record on a track without an audio track as shown in FIG. However, in the one-head helical scanning magnetic recording and reproducing method, the video head moves from track 2a to track 2b as shown in FIG.
When switching to , you will not be able to obtain a playback signal. In the case of a video signal, if the rotation of the drum of the video head is controlled by the control tracks 7a and 7b so that the missing portion of the reproduced signal falls within the vertical blanking period of the video signal, it will not appear on the television screen. do not have. However, in the case of an audio signal, if there is an absent period in the video playback signal, an absent period also occurs in the audio signal, and noise is introduced into the absent period. The present invention eliminates the above drawbacks,
An embodiment thereof will be described with reference to FIG. 7 and the following figures. FIG. 7 is a block diagram of an embodiment of the audio signal recording and reproducing method of the present invention, FIG. 8 is a time chart of the main part during recording, and FIG. 10 is a time chart of the main part during playback. First, the operation during recording will be explained. In FIG. 7, the color video signal input to the input terminal 8 passes through the video signal processing circuit 10 of the above-described recording method, and is scanned by the rotating video head 11 to form one video track for each field, and is then transferred to the magnetic tape. recorded on 12. However, in this embodiment, as shown in FIG. 5, the signal recorded on the rotating video head 11 is a frequency-division multiplexed signal of a low-pass conversion carrier chrominance signal and a frequency-modulated luminance signal, and a frequency-modulated compressed signal. The audio signal is frequency division multiplexed. On the other hand, the audio signal is supplied from the input terminal 9 to the low-pass filter 19, and frequency components having a cutoff frequency of approximately 10 kHz or higher are removed. This will be explained later in the bucket.
Bridate Device (hereinafter referred to as “BBD”)
This is to remove signal components outside the operating bands of 20 and 21. By the way, the recording/reproducing switches 18, 13, 27, and 28, which are switched in conjunction with each other during recording, are the seventh
As shown in the figure, the output audio signal of the low-pass filter 19 passes through the changeover switch 18 and is simultaneously supplied to each of the BBD 20 and BBD 21. This BBD20 and BBD21
are controlled so that read and write operations are repeated alternately by clock pulses generated based on drum pulses, and when one is in read operation, the other is in write operation. This control is carried out by switching the changeover switch 22 in accordance with the timing of the pulse shown in FIG. 8, which will be described later. These BBD20,21
The time-compressed audio signal output, which will be described later, is processed by a low-pass filter 23 to remove unnecessary frequencies, and then sent to a recording audio signal processing circuit 24, which includes an amplifier, a pre-emphasis circuit, a limiter, etc.
The signal is supplied to the modulation circuit 25 via. Modulation circuit 25
consists of a frequency modulator, low-pass filter, etc., and frequency-modulates the time-compressed audio signal.
After removing unnecessary frequency components, the signal is supplied to the rotating video head 11 via the contact a of the changeover switch 13. Here, as described above, the audio signal is frequency-division multiplexed onto a frequency-division multiplexed signal of a frequency-modulated luminance signal and a carrier chrominance signal that has been low-frequency converted, and is supplied to the rotating video head 11, where it is sent to the magnetic tape. 12 are multiplex recorded. Here, the operation timing of the BBD 20 and BBD 21 during audio recording will be explained with reference to the time chart of FIG. 8. The purpose of the operation timing of the BBD 20 and BBD 21 in this audio recording is to record the time-compressed audio signal within the period a of T ₁ and T ₂ while avoiding the absent period b of the drum pulse A shown in FIG. 8A. , and a
For period c within the period, BBD20, BBD2
1. Both are to read the same audio signal in an overlapping manner. First, a drum pulse A synchronized with a vertical synchronizing signal is input to the terminal 39 and connected to the phase comparator 33.
The phase comparator 33 compares the phases of the signal from the 1/N frequency divider 37 and the drum pulse A, and applies an error voltage according to their phase difference to the voltage controlled oscillator (hereinafter referred to as "VCO") 34. to control its oscillation frequency. The phase comparator 33, VCO 34, 1/2 frequency dividers 35, 36, and frequency divider 37 constitute a phase locked loop (hereinafter referred to as "PLL"). The signal input from the frequency divider 37 to the phase comparator 33 is as shown in FIG. 8B, and the signal B
The PLL is locked so that the signal A rises (or falls) approximately at the center of the high level of A. When A rises (or falls), head 11 is on tape 1.
2 and starts outputting a valid playback signal. When PLL is locked
If the dormitory frequency from the VCO 34 is 4, the output frequency of the 1/2 frequency divider 35 is 2, and the output frequency of the 1/2 frequency divider 36 is . The frequency is set to correspond to the clock frequency at which the BBDs 20 and 21 satisfy all the information necessary for the time T ₁ ', which will be described later. Output signals C, D, and E from the frequency divider 37 shown in FIG. 8C, D, and E are signals at each previous stage within the frequency divider 37. Signal B and these signals C, D, and E are input to the control circuit 38 and converted into signals F, G, H, and I shown in FIG. , H are outputted to control the switching of the rotary switches 29 and 31 through the output terminal, and the signal I is outputted to control the switching of the changeover switch 22 through the output terminal. Input signals B, C, to the control circuit 38
D and E pass through blocks as shown in FIG. 9 in the circuit to generate signals F, G, H, and I. That is,
Signal F is generated by C...E in AND circuit 41, signal G is generated by latching signal B in flip-flop 42 using signal F, and signal H is generated by latching signal B in flip-flop 42 using signal F.
is generated by inputting the signal G to the T flip-flop 43, and the signal I is generated by latching the signal H at the flip-flop 44 using the signal F. The signal I generated in this way causes the BBD20,
21 are alternately switched by a changeover switch 22. That is, during the period T ₁ ' in which T ₁ of the drum pulse A is delayed by T ₄ , the switch 22 is connected to b, and the BBD 20 reads the audio signal and starts the next one.
During the period T ₂ ', switch 22 is connected to a.
The audio signal from the BBD 20 is passed through the low-pass filter 23,
Output to 26. The reading and output of BBD21 is the reverse of this. Further, as mentioned above, the signals G and H are control signals for switching the rotary switches 29 and 31, and the details thereof are as follows. That is, the signals from each frequency divider are input to contacts A, B, C, and D of the rotary switch 29 in the order of f, f, 2f, and 4f, respectively, and the contacts A, B, and D of the rotary switch 31 are inputted in the order of f, f, 2f, and 4f, respectively.
C and D are input in the order of 2f, 4f, f, and f. The switching of the rotary switches 29 and 31 is as follows.
Control is based on a combination of signals G and H based on the table below.

[Table] 1: High level 0: Low level With such a control signal, first the switch 29
is connected to contact A, the BBD 20 reads the audio signal for a period T ₁ ' at a clock frequency of , as shown at J in FIG. next
The period switch 29 of _T5 is connected to A.
At the same time, the audio signal of the T ₁ ' portion read in at the clock frequency of 2 is compressed to 1/2 of the time and output. Further, during the period _T6 , the switch 29 is connected to D, and the audio signal of the _T5 portion read at the clock frequency 2 is compressed to 1/2 the time at the clock frequency 4 and output. In this way, BBD
20 compresses the audio signal in the period T ₁ ' and T ₅ into the period T ₅ and T ₆ and outputs it. Similarly, BBD2
1, like K in FIG. 8, compresses the audio signal in the period T ₂ ' and T ₇ into the period T ₇ and T ₈ and outputs it. These two audio signal outputs are switched by the changeover switch 22 under the control of the BBD changeover signal I.
The signal is input to the low-pass filter 23. In this way, audio signals are recorded in the above-mentioned bands of FIG. 5 at timings such as Ja, Jb, Ka, and Kb of FIG. 8. Next, reproduction of the audio signal will be explained. 7th
In the block system diagram shown in the figure, during reproduction, the recording and reproducing switches 18, 13, 27, and 28 are switched to b, and only the frequency modulated audio signal is frequency-selected and extracted by the bandpass filter 14, and then the preamplifier The signal is supplied to a demodulation circuit 15 comprising a frequency demodulator and the like, where it is demodulated to become a time-compressed audio signal. This time-compressed audio signal is subjected to predetermined signal processing in a reproduction audio processing circuit 16 consisting of a de-emphasis circuit, an amplifier, etc., and then is simultaneously supplied to the BBDs 20 and 21 via a low-pass filter 17 and a recording/reproduction switch 18. The audio is then time-stretched and restored to its original audio pitch. The low-pass filter 26 removes unnecessary bands from this signal to obtain a reproduced audio signal. Here, the operation timing of the BBD 20 and BBD 21 during audio reproduction will be explained with reference to the time chart shown in FIG. When playing this audio
The purpose of the operation timing of BBD20 and BBD21 is to return the time-compressed audio signal to the original frequency pitch, and to return the time-compressed audio signal to the original frequency pitch, and to
20, to generate a control signal 1' for switching the BBD 21. As in the case of audio recording, the input signals B, C, D, and E from the frequency divider 37 pass through the blocks shown in FIG.
Generate signals G', H', I', F' such as E, F, G. That is, the signal F' is sent to the AND circuit 45...
signal G' is generated by latching signal B in flip-flop 46 with signal F';
Signal H' is generated by inputting signal G' into T flip-flop 47, and signal I' is generated by latching signal H' in flip-flop 48 using signal F. With the signal I' generated in this way, T ₁₁ and BBD in A of FIG. 10 showing the output timing of BBD20 are
BBD20 and BBD21 are alternately switched at the center of the period with _T13 in FIG. Furthermore, the signals G' and H' are output as control signals for switching the rotary switches 30 and 32 through the output terminal I of the control circuit 38, but the input frequency and
2, 4, and the signal G′ that controls the rotary switch.
The relationship of H′ is as follows.

[Table] 1: High level 0: Low level With such a control signal, first the switch 30
is connected to contact A for a period of T ₉ of A, BBD
20 reads the audio signal at 4 clock cycles.
Next, the T ₁₀ period switch 30 is connected to B, and the BBD 20 reads the audio signal at 2 clock cycles, and at the same time doubles the T ₉ audio signal read at 4 clock cycles. Output in hours. The T ₁₁ period switch 30 is connected to C and D to output the T ₁₀ partial audio signal read in two clock cycles in twice the time. In this way, the BBD 20 time-expands the time-compressed audio signal in the period _T9 and _T10 into the period _T10 and _T11 , and outputs it as an audio signal at the original frequency pitch. Similarly, BBD21 has T ₁₂ and T ₁₃ as shown in B in Figure 10.
The time-compressed audio signal is time-expanded into the periods _T13 and _T14 and output as an audio signal at the original frequency pitch. These two audio signal outputs are the BBD switching signal
The low-pass filter 2 is switched alternately under the control of I'.
6. In this way, a reproduced audio signal is obtained. Here, the switching of the BBDs 20 and 21 is carried out during the period in which the audio signals overlap, _T11 and _T13 , so that the audio signals can be output continuously without generating noise due to lack of audio at the switching part. be able to. As described above, the audio signal recording and reproducing method of the present invention frequency-divides and multiplexes a time-compressed audio signal onto a video signal recorded on a video signal recording track formed on a recording medium, and in this case, There is no time overlap in the recorded portion of the carrier wave, and the time-compressed audio signal, which is played intermittently during playback, is time expanded and restored to the original audio pitch, and then played back as a continuous audio signal. This makes it possible to eliminate the deterioration of the frequency characteristics of the audio signal that occurs as a negative effect of slowing down the running speed of the recording medium when performing long-term recording and playback. The audio signal can be recorded and played back with high precision without making any changes to the video signal recording and playback method, and a portion of the audio signal can be recorded independently at two temporally different locations on the magnetic tape. Because there are
It is only necessary to set the start point of expansion within that part, and there is no need for much accuracy in determining the start point of expansion, and there is no need to worry about finding noise due to a shift in the start point of expansion, and time compression of the audio signal is achieved. , the time extension is BBD
Since this is done using a charge transfer element such as
Furthermore, since the rear part of the time-compressed audio signal of one track is recorded and reproduced overlappingly with the front part of the audio signal of the next track, the audio signal is continuously transmitted without noise caused by missing audio at the switching part. It has features such as being able to output .

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a rotating head in a one-head helical scan system, Figure 2 is a block system diagram of an example of a tape pattern on a conventional magnetic tape and an audio recording system, and Figure 3 is a frequency spectrum of an NTSC video signal. FIG. 4 is a diagram showing an example of the frequency spectrum of the reproduced signal from the video track of FIG. 2, and FIG. FIG. 6 shows a tape pattern on a magnetic tape according to an embodiment of the method of the present invention, FIG.
The figure is a block system diagram of one embodiment of the method of the present invention, Figures 8 A to K are time charts during audio recording in Figure 7, and Figure 9 explains the operation of the control circuit in Figure 7 during recording. 10A to 10G are time charts during reproduction of the audio of FIG. 7, and FIG. 11 is a circuit diagram illustrating the operation of the control circuit of FIG. 7 during reproduction. 1...Magnetic tape, 2...Head drum, 2
a, 2b...Video track, 3...Audio track, 4...Audio head, 5...High frequency bias circuit, 7, 7a, 7b...Control track, 10...Video signal processing circuit, 11...
... Rotating video head, 12 ... Magnetic tape, 13
...Selector switch, 14...Band filter, 15
... Demodulation circuit, 16 ... Playback audio signal processing circuit,
17...Low-pass filter, 18...Selector switch,
19...Low frequency filter, 20...BBD, 21...
... BBD, 22 ... Selector switch, 23 ... Low-pass filter, 24 ... Recording audio signal processing circuit, 25
... Modulation circuit, 26 ... Low-pass filter, 27 ...
Changeover switch, 28... Changeover switch, 29,3
0, 31, 32... rotary switch, 33...
Phase comparator, 34...VCO, 35, 36...1/2
Frequency divider, 37... Frequency divider, 38... Control circuit.

Claims (1)

[Claims] 1. In a method of recording and reproducing video signals on a recording medium with a diagonal track using a single rotating head, an audio signal that enters the first drum pulse period (T ₁ ') during recording. is written to the first charge transfer element with clock f, and in the first half period (T ₅ ) of the next second drum pulse period, the written audio signal is time-compressed and read out with double clock 2f, and the The incoming audio signal in the first half period (T ₅ ) is clocked twice as high as 2f.
The audio signal written in the first charge transfer element in the second half period (T ₆ ) of the second drum pulse period in the first half period (T ₅ ) is time-compressed and read out using a four-time clock 4f. , the operation of frequency division multiplexing recording of the read audio signal with the video signal on the first track, and the operation of performing a second charge transfer of the audio signal that comes in at the second drum pulse period (T ₂ ') using the clock f. The written audio signal is written to the element, and the written audio signal is time-compressed with the clock 2f twice and read out during the first half period (T ₇ ) of the next third drum pulse period, and the signal is input into the first half period (T ₇ ). The audio signal to be output is clocked twice as high as 2f.
The audio signal written in the second charge transfer element in the second half period (T ₈ ) of the third drum pulse period in the first half period (T ₇ ) is time-compressed with a four-times clock 4f and read out. , the operation of frequency division multiplexing recording the read audio signal and the video signal on the second track is repeated, and in this case, by avoiding the period (b) where the drum pulse is absent, there is no temporal overlap in the recorded portion. , the information at the rear of the audio signal of one track is also present and recorded in the audio signal of the next track, and when played back, the audio signal played from the first track is recorded in the first half of the first drum pulse period. ( _T9 )
The written audio signal is written to the first charge transfer element at 4 times the clock 4f, and the written audio signal is written at the 2 times clock 2f in the second half period ( _T10 ) of the first drum pulse period
The second half period (T ₁₀ ) is read out by extending the time with
The incoming audio signal is written to the first charge transfer element with the double clock 2f, and the written audio signal of the second half period (T ₁₀ ) is written into the next second drum pulse period (T ₁₁ ). is read out after time expansion using clock f, and the audio signal reproduced from the second track is transferred to a second charge using four times the clock 4f during the first half period (T ₁₂ ) of the second drum pulse cycle. The written audio signal is written to the element, and the written audio signal is clocked twice as clock 2f in the second half period (T ₁₃ ) of the second drum pulse period.
The second half period (T ₁₃ ) is read out by extending the time with
The incoming audio signal is written to the second charge transfer element at the twice the clock 2f, and the audio signal written in the second half period (T ₁₃ ) is written in the next third drum pulse period (T ₁₄ ). An audio signal recording and reproducing method characterized in that an operation of time-expanding and reading out with a clock f is repeated, and an intermittently reproduced audio signal is reproduced as the original continuous audio signal.