JPH0740403B2 - Recording mode detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for a video signal recorded on a recording medium such as a magnetic tape, and in particular, information recorded on a recording medium having the same shape is converted into a high band. The present invention relates to a recording mode detection device for automatically discriminating whether a recording mode or not.

2. Description of the Related Art In recent years, with the spread of television tapes, video tape recorders, video discs, and the like, there has been a strong demand for higher-quality video information media. In the home VTR (abbreviation of video tape recorder), S / N improvement and high resolution have been realized in various forms. Of these, increasing the FM recording frequency to the higher band is the most effective method, and it is about to be used.

Problems to be Solved by the Invention A large change in frequency band due to high band loss of compatibility under the conventional format, and when recorded on a recording medium of the same shape, the same reproduction processing as the recorded format is performed. If this is not done, a preferable reproduction signal cannot be obtained, but there has been no such processing device in the past.

The present invention automatically detects the recording format by discriminating the signals of different recording formats recorded on the recording medium of the same shape from the difference of the reproduced FM signals from the low-frequency signal level after FM demodulation, The purpose is to automate the reproduction process that matches the recording format.

Therefore, the recording mode detecting apparatus of the present invention includes a reproducing amplifier that amplifies a signal recorded on a recording medium, a limiter circuit that makes an output signal of the reproducing amplifier a constant amplitude, and An FM demodulator that FM demodulates the output signal of the limiter circuit and outputs FM demodulation outputs from multiple output terminals, respectively, and the FM demodulation output from one output terminal of the same FM demodulator is input and multiple mode reproduction is performed. A reproduction processing circuit capable of switching and operating the processing, an integrator for extracting a low frequency component from the FM demodulation output output to the other output terminal of the FM demodulator, an output voltage of the integrator and a reference potential And a comparator for comparing the two, and the operation mode of the reproduction processing circuit is set by the output signal of the comparator.

According to the recording mode detection device of the present invention, the FM of the reproduction processing system is
The demodulator and the FM demodulator of the recording mode detection system can be shared, and by only adding an integrator and a comparator to one of the two output terminals of the FM demodulator in the luminance signal reproducing device. , The recording mode can be detected accurately, and 2
It is possible to automatically switch to the required reproduction processing according to the reproduction luminance signal of the type, and it is possible to reduce the overlapping portions in the entire circuit configuration.

Embodiment An embodiment of the recording mode detecting device of the present invention will be described with reference to the block diagram shown in FIG.

In the present invention, the FM signal recorded on the magnetic tape 1 is transmitted to the head 2
Detected by the reproduction amplifier 3, this FM signal is amplified and input to the limiter 4, the output of the limiter 4 is demodulated by the FM demodulator 5, and the demodulated signal is averaged to some extent via the integrator 6. Then, this signal is compared with the signal of the reference power source 7 set to an appropriate value in advance by the comparator 8,
Recording mode detection device 10 including a circuit that outputs a recording mode detection signal to the recording mode detection output terminal 9
Is. The FM demodulated signal is input to the reproduction processing circuit 11 as the original video signal and processed for reproduction.
It is output to 12 as a video signal. Here, the recording mode detection signal is input to the reproduction processing circuit 11 and used as information necessary for automating the reproduction processing, a signal for display, and the like.

Next, the principle of the present invention will be described with reference to FIG. 2 showing the relationship between the characteristics of the FM demodulator and the demodulated waveform.

The VHS format FM signal used conventionally is
The carrier frequency is 3.4 MHz at the synchronization start and 4.4 MHz at the white level. Here, the output level on the vertical axis in FIG. 2 (a) is an arbitrary level, but now when the FM signal of VHS format is demodulated by the FM demodulator by showing the relative level corresponding to the FM frequency (MHz) and 1: 1. It is demodulated as a signal of 3.4 at the sync head level and 4.4 at the white level. In the high-band format SVHS of VHS, the sync head is 5.4 MHz, white level is 7.0M.
Since it is Hz, the sync head level after demodulation is 5.4 and the white level is 7.0. As can be seen from the above, when the FM demodulator with the same characteristics is used, the white level of the VHS format is sufficiently lower than the sync head level of the SVHS format, and between the VHS white level and the SVHS sync head level. VHS format and SVHS format can be easily distinguished by setting a reference level and comparing with a comparator. However, in recording both VHS and SVHS, emphasis is applied to improve S / N before FM modulation, and as shown in the demodulated video signal waveform shown in FIG. In some cases, a large whisker-like peak waveform appears on the white level side and the black level side of the component. In these peak waveforms, the white side level of VHS and the black side level of SVHS intersect each other, so that the above-mentioned simple level comparison of the FM demodulated signal level cannot be correctly discriminated. Therefore, an accurate format can be detected by passing the output signal from the FM demodulator 5 to the integrator 6 and averaging the peak waveforms so that they do not intersect each other.

Next, referring to FIG. 3, a circuit configuration diagram of one embodiment showing the configuration of the limiter circuit 4, FM demodulator 5, integrator 6, comparator 8 and reference power source 7 in FIG. 1 more specifically. And explain. First, the output of the limiter 4 is input to the FM demodulator 5. The FM demodulator 5 is a pulse count type current output type, and current outputs are taken out from the collectors of the PNP transistor Q ₁ and the PNP transistor Q ₂ . The output of the transistor Q ₁ is processed by the resistor R and the low pass filter (LPF) 13 and taken out to the FM demodulation output terminal 14 as the original FM demodulation video signal. The output of the transistor Q ₂ is integrated with the capacitor C while being compared with the current value I ₀ of the constant current source 15. When the average value of the output current of the FM demodulator 5 is larger than the current value I ₀ of the constant current source 15, the integrating capacitor C is charged to a high potential and the comparator 8 compares it with the voltage of the reference power source 7. Then, the potential is detected, and the recording mode signal is output to the recording mode detection output terminal 9. Further, when the average output current of the FM demodulator 5 is smaller than the current value I ₀ of the constant current source 15, the electric charge of the capacitor C is discharged and becomes a low potential,
A recording mode signal opposite to the above is output from the comparator to the recording mode detection output terminal 9.

According to the recording mode detection device of the present invention, the FM of the reproduction processing system is
The demodulator and the FM demodulator of the recording mode detection system can be shared, and only the integrator and the reference voltage source are added to one of the two output terminals of the FM demodulator in the luminance signal reproducing device. Thus, it is possible to accurately detect the recording mode, and it is possible to automatically switch to the required reproduction processing according to the two types of reproduction luminance signals. Further, there are few overlapping parts of the circuit configuration, and a circuit configuration suitable for integration into an integrated circuit can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a recording mode detecting device of the present invention, and FIG. 2 is a diagram for explaining the operating principle of the present invention.
FIG. 3 is a diagram showing the relationship between the characteristics of the FM demodulator and the demodulated waveform, and FIG. 3 is a configuration diagram of an embodiment more specifically showing the present invention. 1 ... Magnetic tape, 2 ... Head, 3 ... Playback amplifier,
4 ... Limiter, 5 ... FM demodulator, 6 ... Integrator, 7 ...
... reference power source, 8 ... comparator, 9 ... recording mode detection output terminal, 10 ... recording mode detection device, 11 ... reproduction processing circuit, 12 ... video output terminal, 13 ... low pass filter,
14 …… FM demodulation terminal, 15 …… constant current source, Q ₁ , Q ₂ …… PNP transistor, R …… resistor, C …… capacitor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 5/93

Claims (1)

[Claims] 1. A reproduction amplifier for amplifying a signal recorded on a recording medium, a limiter circuit for making the output signal of the reproduction amplifier a constant amplitude, and FM demodulation of the output signal of the limiter circuit for FM output from a plurality of output terminals. FM demodulator that outputs demodulation output respectively,
The FM demodulation output from one output end of the same FM demodulator is input, and a reproduction processing circuit that can operate by switching the reproduction processing of a plurality of modes and output to the other output end of the FM demodulator Equipped with an integrator that extracts low-frequency components from the FM demodulated output and a comparator that compares the output voltage of the integrator with a reference potential, and set the operation mode of the reproduction processing circuit with the output signal of the comparator. A recording mode detection device characterized by: