JPH01201870A - Recording mode discriminator - Google Patents

Abstract

PURPOSE:To increase the allowance of discrimination and to reduce the possibility of malfunction in mode discrimination by performing the peak detection of both format signals of S-VHS and VHS outputted from a FM demodulator at the forefront part of synchronization. CONSTITUTION:A reproducing FM signal is inputted from an input terminal 1 to a reproducing amplifier 2, and its output is inputted to the FM demodulator 3. The output of the demodulator 3 is inputted to a peak detector 4, and the allowance of discrimination is increased by setting a level difference between the synchronization forefront demodulation output of the VHS signal and that of the S-VHS signal at around 2MHz, then, it is inputted to a comparator 6. It is compared with DC potential generated by a reference potential source 5, and an output in which a recording mode is detected based on the difference of the frequency allocation of the reproducing signals is outputted from a recording mode detection output terminal 7. In such a way, the discrimination of both signals can be performed with simple constitution easy to be made into an integrated circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video signal recording and reproducing device for recording and reproducing video signals on a recording medium such as a magnetic tape. This relates to means for automatically determining whether something is recorded in a high-band format or not.

Conventional technology In recent years, television broadcasting and video tape recorders (V
With the spread of video discs (VD), etc., there is a growing demand for higher quality video information media.

Even in home VTRs, the S/N ratio and resolution are improved by increasing the FM recording frequency of the video signal to a higher band. However, a large change in frequency allocation causes a loss of compatibility with conventional formats, and if multiple formats can be recorded on a recording medium of the same shape, it becomes necessary to determine the recording format from the reproduced signal.

Problems to be Solved by the Invention In the VHS format, the FM carrier frequency during recording is 3.4 MHz at the beginning of synchronization and 4.4 MHz at the white level.
.

5-VHS format, 5.4MHz at the beginning of synchronization
, the white level is 7.0 MHz. FIG. 2 shows the signal waveform when this is demodulated by an FM demodulator with the same characteristics. From Figure 2, if nothing is done, VHS format and 5-V
The discrimination margin between HS formats is IMHxL.

This leaves little room for setting the reference potential for discrimination, and increases the possibility of malfunctions due to FM modulator frequency deviation, ambient temperature, power supply fluctuations, etc.

In the recording mode determination described above, the present invention provides FM
The demodulated signal is peak-detected to increase the discrimination margin.

Means for Solving the Problems In the present invention, in order to solve the problems mentioned above, FM
It has an added function to peak detect the demodulated signal.

According to the present invention, the discrimination margin can be increased to about 2 MHz by peak-detecting the synchronization head of VH3, 5-VH3.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, a reproduced FM signal is input to a reproduction amplifier 2 from an input terminal 1, and the output of the reproduction amplifier 2 is input to an FM demodulator 3. The output of the FM demodulator 3 is input to the peak detector 4, the discrimination margin is increased by the peak detector 4, and the output is input to the comparator 6.
is input. DC generated by this and the reference potential source 5
By inputting the potential to the comparator 6, the recording mode detection output terminal 7 outputs an output that detects the recording mode based on the difference in frequency allocation of the reproduced signal.

FIG. 2 shows the characteristics of the device according to the embodiment of the present invention, that is, the output characteristics when peak detection is performed. As is clear from this characteristic diagram, the synchronous leading demodulator output of the VH8 signal and the 5-
There is a level difference equivalent to 2 MHz between the VH8 signal and the VH8 signal, making it easy to distinguish between the two signals.

As described in detail, according to the present invention, the discrimination margin is increased by performing peak detection at the beginning of synchronization for both the 5-VH8 and VH8 format signals output from the FM demodulator. , the possibility of mode discrimination malfunction can be reduced. Further, according to the present invention, the configuration is simple;
Integrated circuits can also be easily realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing each output characteristic of the embodiment of the present invention and a conventional example. 1... Reproduction FM input signal, 2... Reproduction amplifier, 3... FM demodulator, 4... Peak detector, 5...・Reference potential source, 6...
・Comparator, 7... Recording mode detection output terminal. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1°2nd library student FM'! ! 5 frequencies

Claims (1)

[Claims] 1. A recording mode discriminating device, characterized in that a recording mode detecting section that converts an FM signal recorded on a recording medium into a DC potential using an FM demodulator is provided with peak detection.