JPS6355702A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the quality of a monitor picture by after-recording a PCM sound signal that is hourly compressed to 1/2 only on the shallow layer part of a recorded track in an SP mode. CONSTITUTION:When the PCM sound signal obtained by compressing a reproduction signal to 1/2 in terms of time base is handled, a switch 11 comes to a side (a). Only a reproduction signal from a head 2 is inputted to a time base compression/expansion circuit 13. After it is expanded in terms of time base, it is inputted to a PCM signal processing circuit 16 through a switch 15, and a demodulated sound signal is outputted to a terminal 17. The signal is supplied to the sound head 2 through a switch 10, a recording amplifier 6, and a switch 4, and recorded on the shallow layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a home video tape recorder (hereinafter referred to as VTR).
(abbreviated as ), and particularly relates to a device suitable for recording audio signals.

[Conventional technology]

For example, a magnetic tape is wrapped around a rotating cylinder by more than 180 degrees (e.g. about 220 degrees), such as an 8 mm Pidao.
In a head helical scan type VTR, a so-called overlap period occurs in which the magnetic tape and two rotary heads are in simultaneous contact with each other. A method of recording, for example, a PCM audio signal (hereinafter abbreviated as PCM audio signal) during this overlap period is called an overlap recording method.

"'" in VTRs using this overlap recording method.
A method for after-recording CM sound P signals (hereinafter referred to as PCM post-recording) is disclosed, for example, in Japanese Patent Application Laid-Open No. 57-19047.
Publication No. 6: That is, when one of the two rotating magnetic heads is located at the extension of the recording track, that is, at the overlap area, it is possible to erase and record signals without affecting the already recorded video and audio signals. It is.

Therefore, while reproducing the video signal recorded on one side of the two rotating magnetic heads, the other side is used to record the recorded video signal in the overlap area.
After-recording of CM audio signals is possible.

When performing PCM dubbing as described above, during the overlap period when the recording current flows, the crosstalk component of the recording current is at the reproduction signal level (0.1 to G -2 mV).
(p-p), which deteriorates the reproduced image quality. In other words, the part of the image on the monitor corresponding to the overlap period becomes noise due to crosstalk, but it is possible to obtain the reproduced image in other parts, and it is possible to perform after-recording of the audio while viewing the reproduced image. . The technique disclosed in Japanese Unexamined Patent Publication No. 57-190476 describes a means for realizing PCM dubbing in a VTR that employs an overlap recording method and a means for solving crosstalk interference on a playback monitor. ] The above conventional technology is a VTR that uses an overlap recording method.
This is a normal 180 degree wrapped VTR (
For example, the PCM dubbing stage for 71B and β standard VTRs was not mentioned.

An object of the present invention is to provide a four-head VTR in which double azimuth heads with different azimuth angles are mounted close to each other on a rotating cylinder at intervals of 180 degrees, and on the same rotating cylinder for recording FM audio signals in the deep layer of a magnetic tape. In a device equipped with a dedicated audio head installed in Moreover, the object is to obtain a good monitor image even during audio dubbing.

[Means for solving problems]

In order to achieve the above object, the present invention compresses the time only in the shallow part of the track recorded with a wide video head with a playback margin of 8/N in the %SP mode.
Make the audio signal sound like dubbing.

C action] That is, by dubbing the PCM audio signal in the shallow layer,
Part of the wide track is erased by the audio head, making it possible to perform dubbing operations. As a result, the output of the video head after dubbing will decrease slightly, but it will approach the playback level of the narrow head, and therefore not only will it be possible to minimize the S/N deterioration of the playback image, but also due to the playback level difference between fields. Flicker can also be minimized. Further, since dubbing is performed for each field, during a period when the video signal is subject to crosstalk interference from the audio signal, a high-quality monitor image can be obtained by replacing the video signal with the previous one field without crosstalk interference.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a recording and reproducing circuit, in which 1 is a magnetic tape, 2 and 3 are audio heads, 4 and 5 are recording and reproduction changeover switches, and 6 and 8
is a recording amplifier, 7 and 9 are playback head preamplifiers, 1
0, 11, 14, and 15 are switch circuits, 12 is a channel switch, 13 is a time axis compression/expansion circuit, 16 is a PCM signal processing circuit, and 19 is a ? M audio signal processing circuit, 1
8.20 is the audio input terminal, 17'.

21 is an audio output terminal, 22 to 25 are video heads, 2
Reference numerals 6 to 29 are recording/reproduction changeover switches, 50 and 34 are recording amplifiers, and 51, 32, 35, and 56 are reproduction head preamplifiers.

55 and 57 are channel switches, 38 and 50 are side selector switches, 39 is a video signal processing circuit, and 40
is a video input terminal, 41 is a video output terminal, 42 to 44
゛ is a control signal input terminal. FIG. 2 is a head configuration diagram in this embodiment, where 2 and 3 are audio heads, 22
, 2!1 is a head dedicated to standard recording mode (hereinafter referred to as SP mode), and 24.25 is a head dedicated to the standard recording mode (hereinafter referred to as SP mode), and 24.25 is a head dedicated to the standard recording mode (hereinafter referred to as SP mode).
50 indicates a rotating cylinder. The head pairs 22, 25 and 25, 24 have different azimuth angles and a gap distance of 15 to several H (
It has a double azimuth head with 1 horizontal scanning period). For example, if we take a VH8 standard VTR as an example, the track pitches in sp mode and BP mode are 58 μm and 19 μm, respectively.
5 μm, so for example, the track @ of each head is the third
The settings are as shown in the figure. That is, the SP heads 22, 23 (D
) Rack width is 40JJfn, 60Am, MP
Track l1liFi30μm of head 24.25, 3
It is set to 0 μm. The reason why the track width of each head is set in this manner is the result of consideration of head selection during special playback as shown in Table 1.

Table 1 To explain briefly, recording and normal playback are BP.

BP Both types use dedicated heads, and still playback in sp mode uses field still and wide 0sp-
Head and 1! Using the IP-head, field steal is performed in the same way for still playback in EP mode, and the narrow day P+
Search playback in SP mode uses all four heads and selects the head output with the highest level to achieve noiseless performance.

Next, the audio heads 2 and 5 will be briefly explained. As is well known l), in a VH8 standard VTR, as shown in FIG.
2MI! ! Two audio signal channels (Rch and L
ch) is recorded on the deep layer of the magnetic tape, and then video signals are recorded on the surface layer of the magnetic tape using a video head.

FIG. 3 shows the relative height relationship of the video heads 22, 23, 24, 25 and the audio heads 2, 3. Further, FIG. 4 shows a method of recording video signals and audio signals on a magnetic tape, taking the 61F mode as an example. In the same figure, +aI is narrow head 22 (+azimuth)
and track pattern y with audio head 3 (-azimuth)
, (i) is the track pattern by the wide head 2.3 (-azimuth) and the audio head 2 (+azimuth). According to the standard, in the 8P mode, the audio track and the video track overlap in reverse azimuth, and the azimuth angle is set to ±6 degrees for the video track and ±3Q degrees for the audio track. At this time, the y and n shown in the figure must be set to 10 μm or more in consideration of compatibility. Also, in zp mode, the audio track and video track overlap with the same azimuth, and the overlapping part It is defined as 16 μm or more.From the above, as shown in Figure 3,
The height difference ΔH between audio heads 2 and 3 with respect to the video head is 5.
It can be seen that if it is set to 5 μm1j5FK, the standard is satisfied. If ΔH=55μm and the track width of audio radars 2 and 5 is 26tsm, then z == 1 = 16μ
m. Fig. 4(c)t(cQ is a schematic diagram of the cross section of the magnetic tape, and (st(s+Itc) is in convection. 75 and 78 are IPM audio signals 74 in the deep layer.
, 76 indicate the video signal of the surface layer. In this embodiment, the deep part 75, 78K Fh'-audio signal or P
A CM audio signal is recorded, and the PCM audio signal, which is time-axis compressed upward on the wide track side indicated by fjl, is dubbed onto the shallow layer 71/2 of the magnetic Qi-Goo using an audio head. By doing this, when playing back after dubbing, (on the track shown in αJ, 40 Am worth of video fN is played back, 13)
In the track shown in , I', -T In addition, since the signal recorded in the shallow layer 71/2 has an azimuth in the opposite direction to the video head, crosstalk interference from the post-recorded PCM audio signal is a problem. It is not.

In EP mode, as mentioned earlier, the audio track and video track overlap by more than 16J1m out of a track pitch of 19°3μm, so if PCM dubbing is performed, it is almost difficult to reproduce the video signal from the track on which dubbing was performed. . Therefore, in this embodiment, PCM post-recording is limited to the BP mode only.

Next, the spectrum of the PCM audio signal will be explained using FIG. For example, the PCM audio signal that is normally recorded is
Frequency frequency is 48Kliz, carrier frequency is approximately 2MTjz with QPSK modulation signal with 16-bit quantization.
be selected. This fcPcM audio is recorded in the deep layer of the magnetic tape, and during post-recording, the time axis is compressed to one level, and a 4 MHz PCM signal with twice the carrier frequency is recorded in the shallow layer of the magnetic tape.

Figure 7 shows the tape pattern on the magnetic tape.
, 83 is an audio signal written in the deep layer ('JPN audio signal or PCM audio signal), and 8tl, 81 is a video signal written in the surface layer. (The track 84 indicated by diagonal lines is a compressed PCM audio signal written in a shallow layer on a tape that has been PCM dubbed in SP mode, and is formed every other field.) (The tape pattern in IHP mode is As shown in 85.86, the audio signal in the deep layer and the video signal in the surface layer almost overlap.

As mentioned earlier, in II' mode, no post-recording of PCM signals is performed.

Returning to FIG. 1, the operation of the circuit configuration for realizing the above-mentioned post-recording will be explained. In this embodiment, rotary transformers (not shown) for transmitting and receiving signals between the magnetic head and the recording/reproducing circuit are provided independently for the audio head and the video head, or the TRP head and the video head are provided independently. This assumes that the channels are sufficiently magnetically isolated and that mutual interference between the audio system and the video system can be ignored. Switches 4, 5, 26, 27, 28° 29 are connected to the ↓ side during recording and to the b side during playback.

First, the time of recording will be explained. Regarding the video system, the video input signal from the terminal 40 is sent to the video signal processing circuit 59.
is FM modulated by
, 54, and then transmitted to the heads 22-25. The switch 50 is an SP/HP selection switch and is controlled by a control signal (D) from the terminal 44 so that it is connected to one side in SP mode and to the b side in IP mode. Regarding the audio system, the 4-way switch 10 for recording FM voice words is on the 6 side, and when recording PCM audio signals, the switch 14 is on the 1 side and the switch 10 is on the b side, and a recording amplifier of 6.8 is sufficient for each. After being amplified, the signal is supplied to the heads 2, 3 via the switch 4.5.

Next, the time of reproduction will be explained. The audio signal reproduced by the head 22.3 is input to the reproduction head preamplifier 7.9 via switches 4 and 5. When the reproduced signal is 7M audio, the switch 11 is set to one side, and the grid amplifier 7.9
The 0 output signal is made into a continuous signal by the channel switch 12, demodulated into the original audio signal by the FM audio signal processing circuit 19, and outputted to the terminal 21. When the playback signal is PCM audio, the switch 11 is connected to one side via the channel switch 12, and the switch 15 is connected to the other side via the PCM signal processing circuit 16.
The signal is demodulated into the original audio signal and output to terminal 11/2. In addition, when the playback signal is 20M audio (signal recorded by AFRAYS) compressed on the time axis, the switch 11 is set to the 4 side, and only one reproduced word from the head 2 is input to the time axis compression/expansion circuit 13. Switch 15 after the time axis has been extended
The audio signal inputted to the PCM signal processing circuit 16 via the PCM signal processing circuit 16 and decoded is outputted to the terminal 11/2.

Regarding the video system, the head is 22°25 in BP mode.
, E p mode, the signals from the heads 24 and 25 are amplified by the playback head preamplifiers 51, 32, 55.56, and input to the video signal processing circuit via the switches 33, 37. Output to.

The switches 35 and 57 are controlled by the head switching pulse (C), and the switch 58 is controlled by the SP/EP discrimination signal (D
) is controlled by

Next, the dubbing operation will be explained. As mentioned above, since there is no mutual interference between the audio system and the video system, the video signal is reproduced in the same manner as during reproduction and output to the terminal 41 to obtain a monitor image. Regarding the audio system, the switch 14 is connected to the a side, and after the time axis is compressed to 1 in the 1 time axis compression/expansion circuit 13, the signal is supplied to the audio head 2 via the switch 10, the recording amplifier 6, and the switch 4. Layer recording is performed.

Next, a second embodiment of the present invention will be described using FIG.

FIG. 8 shows a recording/reproducing circuit, where 45 is an A/D converter, 46 is a memory, 47 is a D/A converter, and 48
is a switch, and 49 is a video output terminal. Other parts are the same as those in FIG. 1 and are designated by the same reference numerals. In this embodiment, for example, audio heads 2, 5 and video heads 22, 25,
The rotary transformer (not shown) that connects 24, 25 and the circuit system is shared by the audio system and video system (the same core is used)
This relates to a case where mutual interference between the audio system and the video system becomes an interlayer through each channel of the rotary transformer.

That is, during post-recording, in a field in which a PCM signal time-base compressed on T is supplied to the audio head 2, the crosstalk component of the rotary transformer is superimposed on the video head output, and the reproduced image is greatly disturbed.

Therefore, in the embodiment shown in FIG. 8, the post-recording switch 48 is switched by the head switching pulse (B) for the audio head, and the portion where normal output cannot be obtained due to crosstalk is replaced by the 45
The field memory consisting of .about.47 is used to replace the signal of one field before, so that one monitor image equivalent to that during normal playback can be obtained.

As explained above, in this embodiment, in a VTR having a double azimuth 4-head configuration, only P mode is used for that day.
It realizes CM dubbing, and here especially VH
Although the explanation has been given using an F3 standard VTR as an example, it is obvious that the present invention can be applied to other home VTRs.

〔Effect of the invention〕

According to the present invention, a double azimuth 4-head configuration VTR
In the EJP mode, PCM audio signals can be after-recorded, the field opening of the playback head output after after-recording is minimized, and the flicker in the playback image is 87m.

This has the effect of minimizing deterioration, and also has the effect of obtaining a high-quality monitor image during after-recording.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recording/reproducing circuit showing an embodiment of the present invention, FIG. 2 is a layout diagram of the head configuration, FIG. 5 is an explanatory diagram showing the level difference between heads, and FIG. 4 is a track diagram on a magnetic tape. FIG. 5 and FIG. 6 are frequency spectrum diagrams of recording signals, FIG. 7 is a plan view showing an example of a track pattern on a magnetic chip, and FIG. 8 is an explanatory diagram showing a pattern and its cross section. This is a block diagram of a recording/reproducing circuit showing one embodiment of the present invention. 13... Time axis compression/expansion circuit, 16... I'CM signal processing circuit, 19... FM audio signal processing circuit, 2.3... Audio head. 45... A/D converter, 46... Field memory. 47...D/A converter. and 1st Prisoner 2 and Calamity 5 Enclosure Light 60 0 / 2 5
4, inverse number around f (a, hh) 70th, 8! l! l

Claims (1)

[Claims] Two pairs of adjacent video heads with different azimuth angles are installed on a rotating cylinder at 180 degree intervals, and two audio heads for recording audio signals in the deep part of the magnetic tape are installed on the rotating cylinder. In a magnetic recording/reproducing device installed above at 180 degree intervals, recording and reproduction are performed at at least two tape speeds, and the two video heads used in the faster tape speed mode are made to have different head widths. Only in the mode where the speed is faster, 1/2
2. A magnetic recording and reproducing device characterized in that it performs after-recording of a time-base compressed PCM audio signal (PCM audio signal).