JPH0652942B2 - Magnetic recording / reproducing device - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus (hereinafter referred to as a VTR), and particularly to a reproducing signal recording standard suitable for a VTR having a plurality of video luminance signal recording standards. It relates to a circuit for automatically determining.

[Conventional technology]

Currently, in a home VTR, a video signal is recorded by a luminance signal FM-modulated chromaticity signal low frequency conversion method. VH
In the S standard, the luminance signal has a carrier frequency of 3.4MHz to 4.4MHz.
FM modulation is performed and the chromaticity signal is low-pass converted from 3.58MHz to 0.629MHz and recorded on the magnetic tape. Therefore, the transmission band of the luminance signal is about 3MHz, and the horizontal resolution is about 240 lines.

As a means to improve the horizontal resolution and improve the image quality,
As described in "1 / 2-inch high-band VTR" in P36-39, May 1986, issue of the Television Society, there is a high-band recording method in which the carrier frequency of the luminance signal is shifted to a high frequency side. In this method, it is necessary to partially change the characteristics of the luminance signal processing circuit with the carrier frequency shift of the luminance signal, and in order to enable recording and reproduction of both the conventional method and the high band method with one VTR. The user switches a part of the luminance signal processing circuit according to the recording method with a switch.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, the user switches the luminance signal processing circuit according to the recording system of the reproduced signal at the time of reproduction by the operation of the manual switch, and the recording system is discriminated by the visual confirmation of the user looking at the monitor screen. It was done by judgment. That is, the switching of the luminance signal processing circuit at the time of reproduction is not automated, and the operation is troublesome.

An object of the present invention is to provide a means for automatically discriminating a recording method at the time of reproduction in a VTR capable of recording and reproducing both the conventional method and the high band method.

[Means for solving problems]

The above-mentioned object is to provide a luminance signal processing circuit whose characteristics are switched according to the recording system at the time of reproduction, and a discriminating circuit for discriminating the recording system by using the reproduced FM signal before reaching the luminance signal processing circuit. The signal to be used is the signal after passing through the FM automatic gain adjustment circuit (hereinafter referred to as the FMAGC circuit), and if necessary, the timing is used to determine using the rotation phase signal of the head drum, and based on the determination result of the determination circuit This is achieved by switching the reproduction luminance signal processing circuit.

[Action]

In the discriminating circuit, the reproduction FM before reaching the luminance signal processing circuit whose characteristics are switched according to the recording system during reproduction
By discriminating the recording method using the signal, it is possible to perform a reliable discrimination process even when the recording method is changed at the start of reproduction or in the middle of the tape. Further, by discriminating the recording method by using the reproduced FM signal after passing through the FMAGC circuit, the discriminating process can be surely carried out regardless of the variation in the reproducing level of the tape and the head. Further, by using the rotation phase signal of the head drum and the like to determine the timing of determination, it is possible to perform a reliable determination process even during special reproduction such as search.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows frequency allocation of a video signal recorded on a magnetic tape. Figure 2 (a) shows VH
In the conventional S standard, the luminance signal (Y signal) is a carrier wave 3.
It is FM-modulated to 4 to 4.4 MHz, and the subcarrier of the chromaticity signal (C signal) is low-pass converted from 3.58 MHz to 0.629 MHz. The band of the Y signal is about 3 MHz. In addition to this, the VTR to which the present invention is applied also performs recording / reproduction according to the new high band standard in which the carrier wave of the Y signal is set to 5.5 to 6.5 MHz, as shown in FIG. 2 (b). However, the C signal is subjected to low frequency conversion similar to the conventional method. Due to this high band, Y
The low frequency band of the signal is expanded by about 2MHz, and the resolution can be improved by about 160 lines.

FIG. 3 is a block diagram showing an embodiment of the recording system circuit of the present invention. The NTSC video signal input from terminal 14 is BPF1
Only the C signal component is taken out at 5, and the recorded C signal processing circuit 1
The low-frequency conversion is performed at 6, the unnecessary high-frequency component is removed at LPE 17, and the result is input to the adder 18. In addition, the input signal from the terminal 14 is also applied to the C signal removing circuit 19, where only the Y signal is extracted and is FM-modulated by the recording Y signal processing circuit 20, and HP
In F22, the frequency component that overlaps with the low-pass converted C signal is removed and added to the adder 18. Where Y signal and C
The signals are frequency-multiplexed, and the video signal is recorded on the magnetic tape 1 via the recording amplifier 23 and the head 2. In addition, record Y
LPF in signal processing circuit 20, pre-emphasis circuit, FM
The characteristics of the modulation circuit or the like can be switched to the conventional system or the high band system by a signal input from the terminal 21 from a recording system selection switch which can be arbitrarily switched by the user.

Next, FIG. 1 shows a circuit block diagram of the embodiment as a circuit for reproducing the signal recorded by the above circuit.

The signal read from the magnetic tape 1 by the head 2 passes through the preamplifier 3 and is input to the LPE 4, the switch 8 and the discrimination circuit 12, respectively. First, in the LPF 4, only the C signal component is extracted, and the reproduced C signal processing circuit 5 extracts the subcarrier from the original signal.
The frequency is set to 3.58 MHz, unnecessary frequency components are removed by the BPF 6, and the result is input to the adder 7. Next, in the switch 8, when the reproduction signal is conventionally recorded by the output of the discrimination circuit 12 which will be described later, it is sent to the peaking circuit 9 having a frequency characteristic such as the characteristic 24 of FIG. In the case of,
For example, it is sent to the peaking circuit 10 having a frequency characteristic such as the characteristic 25 shown in FIG. After this, the signal passes through the reproduction Y signal processing circuit 11, is input to the adder 7, frequency-multiplexed with the above-mentioned C signal, and is output from the terminal 13 as the original NTSC video signal. The characteristics of the FM demodulation circuit, the de-emphasis circuit, etc. in the reproduction Y signal processing circuit 11 are also switched by the output of the discrimination circuit 12 in accordance with the recording system of the reproduction signal.
The discriminating circuit 12 discriminates the recording system of the reproduced signal as described above, and the result is determined by the switch 8 and the reproduced Y signal processing circuit 11.
The characteristics of the signal processing circuit of the playback system are automatically switched according to the recording method. The reason why the reproduction signal before passing through the peaking circuit is used to determine the recording method is as follows. The peaking circuits 9 and 10 are FMs for compensating the transmission characteristics of low-frequency emphasis and high-frequency suppression that occur in tape and head systems.
It functions as an equalizer, and as shown in FIG. 4, it has the characteristic of emphasizing the vicinity of the highest frequency of the FM carrier and suppressing the lower sideband. Therefore, in this embodiment, the peaking circuit 10 has a peaking center frequency of about 2 MHz as compared with the peaking circuit 9.
It is on the high frequency side. It is assumed that a signal that has passed through the peaking circuit, such as an input signal of the reproduction Y signal processing circuit 11, is used to determine the recording method. When the switch 8 is connected as shown in FIG. 1 at the time of starting the reproduction and the signal recorded by the high band method is reproduced, the input signal of the reproduction Y signal processing circuit 11 is the lower sideband component about 2 MHz away from the carrier wave. Is abnormally emphasized with respect to the carrier wave, so that the determination circuit determines that the lower sideband is the carrier wave and erroneously determines that the reproduction signal is recorded by the conventional method. The same thing can happen when the recording method of the reproduction signal is changed from the conventional method to the high band method in the middle of the tape. In order to prevent such erroneous discrimination of the discriminating circuit, the present invention discriminates the recording system by using the reproduced signal before passing through the peaking circuit, as shown in FIG. As a result, it is possible to make a reliable judgment regardless of the operating states of the peaking circuit and the reproduction Y signal processing circuit of the reproduction system.

Next, in the reproduction system circuit, the FMA is applied to the input signal to the discrimination circuit.
An embodiment using the output of the GC circuit is shown in FIG.

The signal read by the head 2 is amplified by the preamplifier 3 and then input to the LPF 4 at this point in the same manner as in the above-described embodiment, but the switch 8 and the discrimination circuit 12 are fed to the FMAGC.
It is input after the amplitude is made constant by the circuit 26. This allows
Even if the sensitivity of the tape and the head changes and the amplitude of the reproduction signal changes, the input amplitude to the discriminating circuit becomes constant and reliable discrimination is possible.

Further, although the input to the peaking circuit is switched by the switch 8 in the above-described embodiment, the output of the peaking circuit may be switched by the switch 8 as shown in FIG.

Next, a specific configuration of the discrimination circuit 12 will be described. FIG. 7 is a circuit block diagram showing an embodiment of the discrimination circuit. The reproduction signal is input from the terminal 27 and sent to the BPF 28 and BPF 30.
These BPFs extract the vicinity of the carrier of the FM luminance signal in each recording method.

The output of each BPF is sent to a signal level detection circuit (hereinafter referred to as AMDET) 29, 31. In AMDET, a detection voltage proportional to the signal level passing through the BPF is output.

The output of the signal level detection circuit (AMDET) 29, 31 is applied to the comparator 32, and the terminal 33 outputs the high level when the reproduction signal is the high band method and the low level when the reproduction signal is the conventional method. It becomes the output of the circuit and is sent to the switch 8 and the reproduction Y signal processing circuit 11.

In the case of the embodiment shown in FIG. 6, since the switch 8 is arranged after the peaking circuit, even if the configuration of the discriminating circuit is as shown in the circuit block diagram of FIG. The function of is obtained. This is because the peaking circuit substitutes the function of the BPF in the discrimination circuit shown in FIG. 7, and the configuration of the discrimination circuit can be simplified.

Next, FIG. 9 shows an embodiment in which a malfunction is prevented in the discrimination circuit. The hold timing circuit 34 is
Generates a control signal that turns on the switches 36 and 38 for the vertical synchronization or horizontal synchronization period based on the head drum rotation phase signal (hereinafter referred to as SW30 signal) or horizontal synchronization signal input from the terminal 35. . This allows the switches 36,38
The capacitors 37 and 39 connected to the output of are connected to the signal level detection circuit (AMDET) 2 for the vertical synchronization or horizontal synchronization period.
9,31 output voltage is retained. This enables stable determination without being affected by the video content of the video signal.

Further, in the case of searching (high-speed reproduction) the tape recorded in the card band, the hold timing circuit 34 controls the switches 36 and 38 to be in the off state based on the SW30 signal during the noise band in one video field. Generate a signal. This prevents malfunction of the control circuit (such as chattering) during the noise band period during the search.

The malfunction of the control circuit during the noise band period during the search can be prevented also by the embodiment shown in FIG. The reproduced signal input from the terminal 27 has its amplitude attenuated to almost the noise level during the noise band period during the search.
Therefore, the signal level detection circuit (AMDET) 40 outputs a detection voltage proportional to the amplitude of this reproduction signal, and the hold timing circuit 34 detects the noise band period based on this detection voltage, and the noise band period is switched by the switch 36. A control signal for turning off the switches 38 and 38 is generated. Therefore the capacitor
Even in the noise band period, 37 and 39 hold the detection voltage of the AMDETs 29 and 31 immediately before becoming the noise band, so that malfunction of the control circuit can be prevented. In this embodiment, even if the noise band period in one field of the image is not fixed at the time of search, the malfunction of the control circuit can be prevented.

〔The invention's effect〕

According to the present invention, when reproducing a signal recorded in a conventional system or a high band system in a VHS VTR, a reproduced FM signal before reaching a luminance signal processing circuit whose characteristics are switched according to the recording system is used, By performing the automatic determination of the recording method, the automatic determination of the recording method can be surely performed without being affected by the characteristics of the circuit at the time of starting the reproduction.

Further, by substituting the peaking circuit for performing FM equalization, the BPF required in the discrimination circuit,
The configuration of the discrimination circuit can be simplified.

[Brief description of drawings]

1, 5 and 6 are block diagrams showing an embodiment of a reproducing system circuit according to the present invention, and FIG. 2 is an explanatory diagram showing a conventional standard of a VHS system VTR and frequency allocation of a recording signal according to the present invention. FIG. 3 is a block diagram showing an embodiment of a recording system circuit according to the present invention, FIG. 4 is an explanatory diagram showing characteristics of a peaking circuit in a conventional system and a high band system, FIG. 7, FIG. 8, FIG. FIG. 10 and FIG. 10 are block diagrams showing an embodiment of the discrimination circuit in the present invention. 8 ... Switch, 9,10 ... Peaking circuit, 11 ... Playback Y signal processing circuit, 12 ... Discrimination circuit, 19 ... C signal removal circuit, 20 ... Recording Y signal processing circuit, 26 ... FM automatic Gain adjustment circuit, 28,30 …… BPF, 29,31 …… Signal level detection circuit, 32 …… Comparator, 34 …… Hold timing circuit, 36,38 …… Switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Michio Masuda Inventor Michio Masuda 292 Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture Home Appliances Research Laboratories (72) Inventor Kuniaki Miura 1410 Inada, Katsuta, Ibaraki Hitachi, Ltd. (56) References JP 62-293896 (JP, A) JP 59-81989 (JP, A) JP 61-281687 (JP, A) Actual development 62-5775 (JP) , U)

Claims (1)

[Claims] 1. A first recording mode for recording at least a video luminance signal on a magnetic tape as an FM modulated signal having a certain carrier frequency (hereinafter referred to as a first FM modulated signal), and at least a video luminance signal. An FM modulated signal having a carrier frequency higher than that of the first recording mode (hereinafter referred to as the second FM
A second recording mode for recording on a magnetic tape as a modulated signal) and reproducing the FM modulated signal recorded in these recording modes from the magnetic tape. A magnetic recording / reproducing apparatus adapted to change the characteristics of a part of the circuit for reproducing luminance signal processing of the FM modulated signal according to a recording mode at the time of recording, wherein the reproduced FM signal is reproduced. For the modulated signal, the first FM
A first peaking circuit for performing FM equalization according to a modulated signal and outputting the same, and an FM equalization according to the second FM modulated signal for the reproduced FM modulated signal and outputting The second peaking circuit, the level of the signal output from the first peaking circuit and the level of the signal output from the second peaking circuit are compared, and the reproduced FM-modulated signal is reproduced. A discriminating circuit for discriminating between the first FM modulated signal and the second FM modulated signal; and F outputted from the first peaking circuit.
Selection for inputting the M modulated signal and the FM modulated signal output from the second peaking circuit, selecting either one according to the discrimination result by the discrimination circuit, and outputting to the reproduction luminance signal processing circuit The magnetic recording / reproducing apparatus is characterized in that a characteristic of a part of the reproduction luminance signal processing circuit is changed according to a result of the judgment by the judging circuit.