JPH0425629B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention records a video signal and a PCM audio signal, for example, on one track formed on a magnetic tape, and a PCM audio signal section on the track. The present invention relates to a magnetic recording/reproducing device (hereinafter referred to as VTR) that performs after-recording of video signals, and particularly to a device that avoids crosstalk to a reproduced video signal during after-recording in the device.

[Prior art]

Figure 1 shows, for example, an extension of a video track.
Conventional methods that time-compress and record PCM audio signals
This is a schematic diagram showing the relationship between the head drum of a VTR, the magnetic tape wound around it, and the rotating head. In the figure, 1 is the head drum, 2 is the magnetic tape that runs diagonally around this drum, and It wraps around 1 at an angle of about 220°. 3a and 3b are rotary heads arranged with an angular spacing of 180°.

FIG. 2 shows the main parts of a transmission section for transmitting and receiving signals to and from the rotary heads 3a and 3b, in which 4 is a rotary transformer consisting of transformers 4a and 4b, and 5 is a recorder for recording on the rotary heads 3a and 3b. This is a changeover switch for introducing a signal or deriving a reproduced signal from the rotary heads 3a, 3b. 6,
10 is a recording amplifier, and 7 and 11 are input terminals to which a video signal V and a PCM audio signal P are applied in a time-division manner during recording. Reproduction amplifiers 8 and 12 amplify the reproduction signal from the rotary head derived via the changeover switch 5 during reproduction, and output the amplified signal to output terminals 9 and 13. 15,1
6 is the video signal V and PCM by the changeover switch 14.
This is an output terminal for a signal separated into audio signal P.

Next, the operation will be explained.

The magnetic tape 2 is wound diagonally around the head drum 1 and runs at a constant speed in the direction of arrow A in the figure. During recording, the rotary heads 3a and 3b rotate in the direction of arrow B in the figure in synchronization with a vertical synchronizing signal included in the video signal to be recorded. ) is controlled by During recording, the video signal is alternately applied to the rotary head 3a or 3b for each field, and the video signal is recorded on the magnetic tape 2 at an angle of 180 DEG as shown in FIG. Further, in the 40 DEG section shown in FIG. 1, the PCM audio signal to be recorded is alternately applied to the rotary head 3a or 3b. During this period, the rotary heads 3a and 3b are in contact with the magnetic tape 2 at the same time;
a and 3b are forming adjacent tracks. For example, when the rotary head 3a starts recording a PCM audio signal and is forming one track, the rotary head 3b is already forming the latter half of the previous track and is recording a video signal.

The video signal and PCM audio signal are applied to the rotary head 3a or 3b in a time-division manner. That is, during the period when the rotary head 3a is at the 40° angle in FIG. 1, a PCM audio signal is applied to the input terminal 7 shown in FIG. 2, and this PCM audio signal is amplified by the recording amplifier 6. The magnetic tape 2 is connected via one switch 5a in the changeover switch 5, one transformer 4a in the rotary transformer 4, and the rotary head 3a.
reach. Next, during the period when the rotary head 3a passes the 40° portion and is present at the 180° portion in FIG. 1, a video signal is applied to the input terminal 7, and this video signal follows the same path as described above. The magnetic tape 2 is reached through the magnetic tape 2.

On the other hand, the same can be said about the rotary head 3b, including the input terminal 11, switch 5b, and transformer 4.
b. PCM audio signals and video signals are delivered to the magnetic tape 2 in a time-division manner via the rotary head 3b.

An example of a pattern recorded on a magnetic tape in this manner is shown in FIG. In the figure, a and b are tracks recorded by the rotary heads 3a and 3b, respectively, P of which corresponds to the 40° portion shown in Fig. 1 in the recording area of the PCM audio signal, and V is the track recorded by the rotary heads 3a and 3b, respectively. The video signal recording area is shown in Figure 1.
Corresponds to the 180° part.

Next, during playback, the rotation of the head drum 1 is controlled by a servo circuit (not shown) so that it rotates at approximately the same speed as during recording, and the rotating head correctly scans the tracks on the running magnetic tape. The tape running is controlled by a tracking servo (not shown) so that signals are reproduced from tracks a and b by rotary heads 3a and 3b.

The signal thus reproduced from the track a by the rotary head 3a is transferred to the transformer 4 shown in FIG.
a, switch 5a, terminal 9 via playback amplifier 8
reach. Similarly, the signal reproduced from track b by rotary head 3b is transferred to transformer 4b and switch 5.
b. It reaches the terminal 13 via the reproduction amplifier 12.

The signal reproduced in this way is schematically shown in the fourth
Shown in Figures a and b. Both of these signals include video signals and
Since the PCM audio signal is included in time division,
These signals are applied to the changeover switch 14 shown in FIG. 2 to perform distribution. That is, as shown in FIG.
a and only the video signal V portion of the signals shown in FIG. 4 a and b is output to the output terminal 15.
lead to. As a result, a continuous video signal is obtained as shown in FIG. 4e. On the other hand, the switch 14b is controlled by a signal schematically represented as the PCM audio signal extraction timing as shown in FIG. Of the signals shown in
Only the portion of the PCM audio signal P is guided to the output terminal 16. As a result, only the PCM audio signal is extracted as shown in FIG. 4f. Note that both of the above two types of timing signals are configured to be generated in synchronization with the rotation of the head drum 1.

The video signal thus obtained and
The PCM audio signal is returned to its original signal by a video signal demodulation circuit and a PCM audio demodulation circuit, both not shown in FIG.

The above is a description of the normal recording and playback operations, and next, the after-recording (hereinafter referred to as post-recording) operation of audio signals will be explained.

Post-recording usually involves re-recording only the audio signal from a desired point while visually viewing the playback screen. To explain this using FIG. 4, in FIGS. 4a and 4b, the 180° portion is in the reproduction state, and the 40° portion is in the process of recording new audio. After-recording is performed by overwriting new audio on top of the original recording signal, thereby erasing the original signal and recording a new signal.

The operation during dubbing is exactly the same as the operation during playback described above regarding the video signal. on the other hand
PCM audio is recorded by the recording amplifier 6 or 1 while the rotary head 3a or 3b is at the 40° position in FIG.
Recording is performed by applying a PCM audio signal to 0.
For example, when the rotary head 3a reaches the 40° portion in FIG. 1, the timing signal shown in FIG.
Switch 5a shown in the figure switches to the recording side and PCM
An audio signal is applied to the rotary head 3a.

Here, when performing dubbing with the above VTR,
One head must play while the other head records at the same time. Therefore, during this time, it was necessary to avoid crosstalk from the recording system to the reproduction system, and in particular, the rotary transformer 4 required strict shielding. For example, the playback output of the head is several microvolts, while the voltage applied to the recording head is several hundred mV, so to prevent the post-recording signal from leaking into the playback video signal, the crosstalk must be kept below 80dB. There is a need to. Also, when crosstalk enters the playback video signal, beat disturbances occur, making the TV playback screen unsightly. Furthermore, if the crosstalk is large, the reproduction amplifier may become saturated in the portion corresponding to the above-mentioned 40°, and a reproduced image may not be obtained.

[Summary of the invention]

The present invention was made to eliminate the above-mentioned drawbacks of the conventional apparatus, and in addition to the above-mentioned rotary head, an auxiliary rotary head is newly provided for reproducing video signals at a timing different from that of the rotary head. The video signal reproduced by the auxiliary rotary head is stored in a memory device, and the reproduced signal from the normal reproduction rotary head that is interfered with by dubbing is replaced with the reproduced signal stored in the memory. It is an object of the present invention to provide a magnetic recording/reproducing device that can solve the above-mentioned crosstalk problem.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 5, 20a and 20b are the first
In addition to the conventional rotary head shown in the figure, this is a newly added auxiliary rotary head for signal reproduction, and these rotary heads 20a and 20b are arranged with an angular interval of 180 degrees. Further, the rotating head 20a is mounted at an angle θ (≧40°) with respect to the rotating head 3a. In addition, the rotating heads 20a, 2
0b is provided with an appropriate step relative to the rotating heads 3a and 3b, respectively, so that the rotating heads 3a and 3b can correctly scan the tracks scanned by the rotating heads 3a and 3b. For example, in the case of FIG. 5, if the widths of the heads are the same, then for the magnetic pattern shown in FIG.
It is sufficient to add a step above a and 3b by (θ°/180°)×(track pitch).

FIG. 6 is a block diagram of the main parts of this embodiment. In the figure, 20a and 20b are the first and second rotating heads 3.
The third and fourth rotary heads 4c and 4d which reproduce signals at different timings from a and 3b are transformers in the rotary transformer 4, 21 is a changeover switch,
22 is a reproduction amplifier that amplifies the reproduction signal, 23 is a video signal demodulation circuit, 24a and 24b are the third,
First and second memory circuits for storing video signals reproduced by the fourth rotary heads 20a and 20b; 25 is a video signal demodulation circuit; 28 is a video signal demodulation circuit for storing video signals reproduced by the fourth rotary heads 20a and 20b; This is a changeover switch for reading out signals in synchronization with the reproduced video signals of the first and second rotary heads 3a and 3b, and this changeover switch 28 is controlled by readout control means (not shown). 26
are the reproduced video signals from the first and second rotary heads 3a and 3b and the first and second memory circuits 24a and 24b.
This is a changeover switch (reproduction signal sending means) that switches between and sends out the signal read from 24b, and its switching timing is controlled by a control circuit (not shown). 27 is a video signal demodulation output terminal. Further, the other configurations are similar to those shown in FIG.

Next, the operation will be explained.

In FIG. 6, normal recording and reproducing operations are performed in the same manner as described in connection with FIG. 2, so the explanation thereof will be omitted, and the dubbing operation will be explained below.

In the playback state, when the rotation of the head drum 1 is controlled as described above and the tape running is controlled by the tracking servo, the terminal 15 is
and terminal 16 for the playback video signal and the playback
PCM audio signal is being output. The situation at this time is exactly the same as a to f in FIG. At this time, since the rotary heads 20a and 20b are arranged as described above, in this case, the rotary head 3
It is in a state where signals can be reproduced from the track before tracks a and 3b. Here, since the angle θ shown in FIG. 5 is set to be larger than 40°, when the rotary head 3b reaches the 40° portion in FIG. The scanning of the video signal area of track a (see FIG. 3) has already been completed. Similarly, rotating head 3
When a reaches the 40° portion in FIG. 5, the rotary head 20b has finished scanning track b. Rotating heads 3a, 3b with such a relationship
The relationship between the reproduction output of the rotary heads 20a and 20b is shown in FIGS. 7a, b, c, and d. FIGS. 7a and 7b are the same as those shown in FIGS. 4a and 4b. In the example shown in FIG. 5, the rotary head 20a,
20b scans the track in advance of the rotary heads 3a and 3b, so that signals are reproduced from the track at earlier timings as shown in FIGS. 7c and 7d.

The outputs of the rotary heads 20a, 20b thus obtained are guided to a changeover switch 21 via transformers 4c, 4d. This switch 21 is controlled by a timing signal schematically shown in FIG. . Note that the timing signal is configured to be generated in synchronization with the rotation of the head drum 1. and playback amplifier 2
The output of 2 is applied to the video signal demodulation circuit 23,
The original video signal is restored. This video signal is then applied to memory circuits 24a, 24b.
The memory circuit is composed of, for example, an A/D converter, a 1-field digital memory, and a D/A converter, and the output of the rotary head 20a is transferred to the memory circuit 24a by the timing signal shown in FIG. 7e.
while the output of rotary head 20b is written to memory circuit 24b. In this way, the playback signal is alternately transmitted to the memory circuit 24 for each field.
a and 24b.

By the way, if dubbing is currently being performed, a PCM audio signal is applied to terminal 7 or 11 in Figure 6, and as mentioned above, during the period shown in Figure 4d, the PCM audio signal is in the recording state. Therefore, the signal currently being reproduced is disturbed due to the crosstalk interference mentioned above. This situation is shown in Figure 7a,
Indicated by diagonal lines b, c, and d. For example, rotating head 3
Assuming that a is recording (dub-recording) a PCM audio signal on a magnetic tape during the period P in Fig. 7a, the output of the rotary head 3b and the output of the rotary head 20a currently performing playback are as shown in Fig. 7b. , c are disturbed during the period shown by the shaded area.

When writing to the memory circuits 24a and 24b, the entire reproduced signal that has been disturbed as described above may be written for one field, or only the disturbed portion may be written using the timing signal shown in FIG. 4d. It is also possible to stop the process and write only the normal reproduced signal part.

Next, the reproduced signal stored by such writing is read out from the memory circuits 24a and 24b in synchronization with the output of the rotary head corresponding to this reproduced signal. This can be done by using the timing signal shown in FIG. 4c and the synchronization signal of the video signal demodulated from the reproduction output of the rotary heads 3a, 3b. The memory circuit 24a thus read out,
The output of 24b is schematically shown in FIGS. 7f and 7g. That is, the readout output of the memory circuit 24a is synchronized in timing with the reproduction output of the rotary head 3a, and the readout output of the memory circuit 24b is synchronized in timing with the reproduction output of the rotary head 3b.

When the reading is completed, the memory circuit 24
a and 24b are cleared, and the next write is performed in the same manner as described above.

Memory circuits 24a, 2 obtained in this way
The readout output from 4b is alternately extracted by the changeover switch 28 and becomes a continuous signal. However, when writing to the memory is stopped by the above-described interference section, the signal is lost during the periods corresponding to the shaded areas in FIG. 7f and g. For controlling the changeover switch 28, for example, the timing signal shown in FIG. 4c can be used. The readout output derived by the changeover switch 28 is outputted to the output terminal 27 via the changeover switch 26. However, this output is
As shown in Figures f and g, there is interference in the shaded area, so only during this period is the
The changeover switch 26 is changed so that the playback output of b is replaced. As can be seen from FIGS. 7a and 7b, there is no disturbance in the outputs of the rotary heads 3a and 3b during this period. The changeover switch 26 is controlled by using, for example, the timing signal shown in FIG. 4d and delaying it to obtain a timing signal as shown in FIG. 7h.

In the manner described above, a reproduced video signal from which interference has been removed is obtained at the output terminal 27, and this situation is schematically shown in FIG. FIG. 8a shows the output of the video signal demodulation circuit 25, in which the shaded area in the figure is disturbed by the PCM audio recording signal, and the rest are normal signals. FIG. 8b shows the memory circuit 24.
a, 24b, and the changeover switch 28
The shaded area in the figure is the output derived through
Interfered with PCM audio recording signal, otherwise normal. Figure 8c shows changeover switch 2.
6, this signal is obtained by replacing only the disturbed portion of FIG. 8b with the signal of FIG. 8a.

In this embodiment, the signals reproduced by the third and fourth rotary heads 20a and 20b are stored in the memory 24.
a, 24b, and among the reproduced signals obtained by the first and second rotary heads 3a, 3b, the signals during the period of interference are replaced with the read signals from the memories 24a, 24b. , the video signal with interference removed is sent to terminal 2.
7, and if this signal is sent to a television during dubbing, an undisturbed playback screen can be obtained.

In the above embodiment, two rotating heads are added, but the number of rotating heads may be one. That is, in the case of television signals, since images are very similar between adjacent fields, there is no practical problem even if the video signals stored in the memory circuits 24a and 24b are used for two fields. In this case, the memory circuit 24
The first reproduction signal is stored in a, and read out twice over two fields, and during this time, the second reproduction signal is stored in the memory circuit 24b,
Next, this may be read out twice over two fields, and this may be repeated thereafter.

Further, the rotary head added in the above embodiment may be a head dedicated to special playback such as slow still, which has been commonly used in the past.

In addition, the rotating head added in the embodiment shown in FIG. You may also use a head.

In addition, in the embodiment shown in FIG. 6 above, when recording and reproducing an FM audio signal superimposed on a video signal, it is possible to obtain an uninterrupted audio signal by adding a memory circuit to the reproduced audio signal as well. Needless to say.

In the above embodiment, the front part of the truck is
Although a system in which a PCM audio signal is recorded followed by a video signal has been described, the present invention can be easily applied even if the relationship between these is reversed.
The same effects as in the above embodiment can be obtained.

Further, in the above embodiment, the rotating heads 20a, 20
Although the rotary heads 3a and 3b are arranged in front of each of the rotary heads 3a and 3b, they may be arranged in a manner that they follow the rotary heads 3a and 3b.
In this case, the read timing should be delayed by one field, or the rotary head should be
It is also possible to align the timing by inserting a memory circuit into the output paths of a and 3b.

〔Effect of the invention〕

As described above, according to the present invention, signals on a track are played back at different timings using a normal recording/playback head and another head, and after storing one playback signal in memory, it is combined with the other playback signal. The read signal is read out at the same timing, the read signal and the other reproduced signal are guided to a changeover switch, and the switch is switched so that the disturbed portion is replaced with a normal reproduced signal. Therefore, interference with the playback signal by the PCM audio signal to be dubbed can be avoided, and a clear playback screen without disturbance can be obtained even during the dubbing.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the head drum, rotary head, and magnetic tape of a conventional VTR that records and reproduces video signals and PCM audio signals in a time-division manner, and Figure 2 shows the main parts of the transmission system for recording and reproduction of the above device. A diagram showing
FIG. 3 is a recording pattern diagram of a magnetic tape recorded by the above device, FIG. 4 is a diagram for explaining the operation of the above device and an embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. FIG. 6 is a diagram showing the main parts of a VTR according to an embodiment of the present invention, and FIGS. 7 and 8 are diagrams showing the operation of an embodiment of the present invention. FIG. 2 is a waveform diagram for explaining. 2... Magnetic tape, 3a, 3b... First and second rotating heads, 20a, 20b... Third and fourth rotating heads, 24a, 24b... First and second memories, 2
6...Selector switch (playback signal sending means), 28...
Changeover switch. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1 A plurality of rotary heads attached to a head drum at predetermined angular intervals are successively brought into sliding contact with a magnetic tape to sequentially form parallel inclined tracks. The magnetic tape is wound over the above angular interval to form a track longer than the track length corresponding to the above predetermined angular interval, and when one rotating head comes into contact with the end of the track, the plurality of rotating heads At the same time, mutually opposite ends of adjacent tracks of the magnetic tape are brought into contact with each other, and a first information signal is applied to one end area of each track, and a first information signal is applied to the remaining part of each track. a magnetic recording and reproducing apparatus configured to record a second information signal, at least one auxiliary rotary head that reproduces the second information signal at a timing different from that of the plurality of rotary heads; a memory for storing at least a reproduced signal of the second information signal reproduced during a period other than the period in which after-recording of the first information signal is performed; readout control means for synchronizing and reading out corresponding portions of the second information signals reproduced by the plurality of rotary heads; and at least the after-recording of the second information signals reproduced by the plurality of rotary heads. 1. A magnetic recording and reproducing apparatus comprising: reproduction signal sending means for replacing the reproduction signal of the period with a second information signal read from the memory and transmitting the same. 2. The plurality of rotary heads includes first and second rotary heads, and the auxiliary rotary head has a track end portion on which the first information signal is recorded for the first and second rotary heads. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the magnetic recording and reproducing apparatus is arranged at a position separated by an angle equal to or more than the area. 3 The auxiliary rotary head is connected to the first and second rotary heads.
(θ°/180°) × (track pitch) for the rotating head of A magnetic recording and reproducing apparatus according to claim 2 characterized in that the magnetic recording and reproducing apparatus is characterized in that: 4. The invention according to claim 2 or 3, wherein the first and second rotary heads are normal recording/playback rotary heads, and the auxiliary rotary head is a special playback head. Magnetic recording and reproducing device. 5 The auxiliary rotary head has a second rotary head regenerated by the first rotary head and the second rotary head, respectively.
5. A magnetic recording and reproducing apparatus according to claim 2, comprising a third rotary head and a fourth rotary head, each of which reproduces an information signal of the magnetic head. 6. The magnetic tape runs at first and second tape speeds, the first and second rotary heads are dedicated rotary heads corresponding to the first or second tape speed, and the third and second rotary heads are dedicated rotary heads corresponding to the first or second tape speed. Claim 5, wherein the fourth rotary head is a dedicated rotary head for the second or first tape speed.
The magnetic recording and reproducing device described in 2.