JPH01291591A - Pal/ntsc system discriminator - Google Patents

Abstract

PURPOSE:To perform the discrimination of a system correctly even when a pose operation is performed by connecting a one-shot multivibrator which expands the pulse width of a vertical synchronizing signal, and eliminating a pose signal included just before the vertical synchronizing signal. CONSTITUTION:A signal inputted to an input terminal 3 to which the vertical synchronizing signal waveform-arranged already is inputted turns ON and OFF a transistor Q1. And the signal from the transistor Q1 is inputted to an integration circuit 4 consisting of resistors R1 and R2, a diode D1, and a capacitor C1. The signal expands the pulse width of the vertical synchronizing signal integrated at the circuit 4 to prescribed pulse width. Therefore, by setting the discharge time constant of the signal at a value over an interval T1 between the pose signal A and the vertical synchronizing signal B, the signal obtained from the collector of a transistor Q2 goes to a unified pulse signal C when two pulses A and B are inputted successively, and by sending the signal to a system discrimination circuit, the decision of a PAL system can be performed normally without being affected by the pose signal A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a system discrimination device for recording a playback signal of a PALJllIvTR (video tape recorder) with a PAL/NTSCJ111VTR.

[Conventional technology]

As shown in FIG. 3, when recording, or dubbing, an image being played back on a PAL VTR 1 on a PAL/NTSC VTR 2, a PAL/NTSC VTR 1 is used.
R2 automatically determines that a PAL system video signal is being input, switches the internal mode to PAL mode, and performs a recording operation.

This system determination is performed when the number of horizontal synchronization signals between adjacent vertical synchronization signals (between fields) is 625/
2. Taking advantage of the fact that NTSC is smaller than 525/2, if the horizontal synchronizing signal count is larger than a preset value, it is judged as PAL, and if it is less, it is judged as NTSC.

[Problem to be solved by the invention]

However, when the pause button is operated on the PAL VTR 1, the pause signal A resulting from the pause button operation is inserted immediately before the original vertical synchronization signal B and sent to the PAL/NTSC VTRZ side. Sent.

In this case, the system determination on the PAL/NTSC VTRZ side is performed based on the number of horizontal synchronization signals T1 and T2 between the rising edges of the signals A and H. However, the number of horizontal synchronization signals T1 and T2 counted here is smaller than the number of horizontal synchronization signals counted in the absence of signal A (=T I +T 2), and therefore, it is misidentified as an NTSC signal, resulting in normal recording. The problem is that it will no longer be done.

The present invention has been made in view of these points, and the purpose is to
The purpose is to ensure that correct system discrimination is performed.

[Means to solve the problem]

To this end, the present invention provides a discrimination device that automatically discriminates between PAL signals and NTSC signals based on the number of horizontal synchronization signals included between vertical synchronization signals, in which a one-shot multiplier for expanding the pulse width of the vertical synchronization signal is connected, The pause signal included immediately before the vertical synchronization signal was removed.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing a one-shot multi circuit according to one embodiment. 3
is an input terminal to which a vertical synchronizing signal that has already been waveform-shaped is input, and the signal input here turns on/off the transistor Q1. Then, the signal from the transistor Ql is transmitted through the resistors R1, R2, the diode D1, and the capacitor C1.
The signal is input to an integrating circuit 4 consisting of the following. Then, the output from the integrating circuit 4 is inverted by the transistor Q2 and transferred to the system discrimination circuit.

Now, when a pulse of the vertical synchronizing signal A is input from the input terminal 3, this signal is integrated by the integrating circuit 4, and this integrating circuit 4 has a charging time constant Ta and a discharging time constant Tb, Ta = R1xCI Tb = R2XC1, R1<R2, and Ta<Tb. That is, the one-shot multiplexer shown in FIG. 1 expands the pulse width of the input vertical synchronizing signal to a predetermined pulse width.

Therefore, if the above-mentioned discharge time constant Tb is set to the interval T1 or more between the pause signal A and the vertical synchronization signal B, then when two pulses A and B are continuously applied manually, the transistor Q2
The signal obtained from the collector becomes an integrated pulse signal C as shown in FIG.

This pulse signal C has the same period as the vertical synchronizing signal B, so if this signal is sent to the system discrimination circuit, PAL determination will be performed normally without being affected by the pause signal A.

〔Effect of the invention〕

As described above, according to the present invention, when recording a playback signal from a PAL VTR with a PAL/NTSC VTR, the PAL
Even if a pause is applied to a PAL/NTSC VTR, the PAL/NTSC VTR automatically discriminates the PAL signal normally without being affected by the pause operation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a one-shot multi-circuit according to an embodiment of the present invention, FIG. 2 is an operation timing chart, FIG. 3 is an explanatory diagram of dubbing, and FIG. 4 is an explanatory diagram of occurrence of misjudgment. 1...VTR for PAL, 2...VTR13 for PAL/NTSC...Vertical synchronization signal input terminal, 4...Integrator circuit. Agent Patent Attorney Tsuneaki Nagao

Claims (2)

[Claims] (1) In a discrimination device that automatically discriminates PAL signals and NTSC signals based on the number of horizontal synchronization signals included between the vertical synchronization signals, a one-shot multiplier that expands the pulse width of the vertical synchronization signal is connected, and the vertical synchronization signal is A PAL/NTSC system discriminator characterized in that a pause signal included immediately before a signal is removed. (2) The PAL/NTSC system discriminator according to claim 1, wherein the one-shot multi output pulse width is longer than the period from the generation of the pause signal to the end of the vertical synchronization signal. .