JPS6053996B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video recording and reproducing device, particularly a video recording and reproducing machine (V
TR) relates to a video recording and reproducing apparatus that can determine whether a signal is an NTSC signal or a PAL signal and obtain a regular reproduction signal.

In conventional VTRs, when a cassette is loaded, it is impossible to automatically determine the television system recorded on the tape of the loaded cassette and to obtain a regular reproduction signal.
In view of the above points, the present invention provides a VTR equipped with a discrimination circuit that automatically discriminates whether the system is NTSC or PAL.

Hereinafter, this invention will be explained in detail using an embodiment of the invention shown in the drawings.

In the figure, 1 is a reference oscillator, 1a is a tuning fork which is an oscillation source for the tape speed Vp of the PAL system, and lb is an NTSC
2 is a tape speed control circuit that controls a servo system (not shown) based on the reference oscillation frequency of the reference oscillator 1; 3 is a tape speed control circuit that controls the oscillation frequency of the reference oscillator 1; A frequency dividing circuit that divides the frequency, 4 an amplifier that amplifies the control signal recorded on the tape, and 5 a comparison between the frequency of the output of the frequency dividing circuit 3 and the frequency of the output of the control signal amplifier 4, and outputs a discrimination signal. Comparator, 6
8 is a gate circuit that selects a color signal from the color signal input 7 in accordance with the discrimination signal of the comparator 5; 8 is an NTSC color circuit 9 that operates in accordance with the discrimination signal of the comparator 5; is a phase detector for PAL signals; , 10 is a switch circuit that performs switching depending on the presence or absence of the output of the phase detector 9, and 11 is a switch circuit 1.
This is a PAL color circuit that operates according to 0.

In this configuration, the first tape speed 9 corresponds to the PAL system, and the second tape speed 9 corresponds to the NTSC system.
The relationship between the vertical frequency, control signal frequency, and tape speed for both methods is as follows.
Shown in the table.

Now, focusing on the control signals recorded on the tape, if a tape recorded in the PAL system is played back at the first tape speed ■P (23.39Ti1&/S), it will be 2! according to the system! Obtain the control signal for Sanda.

However, when a tape recorded in the PAL system is reproduced at the second tape speed VN (33.35T1f!11/S), the control signal becomes.

Next, the tape recorded at the second tape speed VN is
When played at tape speed ■N, it is 29.97Hz according to the method.
control signal.

However, when a tape recorded using the N'VSC method is reproduced at the first tape speed 9, the control signal becomes .

On the other hand, at the first tape speed Vp, the oscillation frequency of the reference oscillator 1 is 1867Hz1 at the second tape speed. When the oscillation frequency at the time is 26 molar pressure, when the frequency divider circuit 3 performs a lucky division, the frequencies obtained from the frequency divider circuit 3 are the first and the first, respectively.
Second tape speed ■,, 23.04Hz depending on VN,
It becomes 32.87Hz.

This relationship is shown in Table 2. As is clear from Table 2,
If the output frequency of the frequency divider circuit 3 is set as above, the PA
The control signal frequency of a tape recorded in the L method is always reproduced higher than the output frequency of the frequency dividing circuit 3 when reproduced at the first or second tape speed VPl or VN.

Conversely, the control signal frequency of the tape recorded at the second tape speed ■N is always lower than the output frequency of the frequency divider circuit 3 when played back at the first or second tape speed ■9 or VN. will be played.

Therefore, depending on whether the frequency of the reproduced control signal is higher or lower than the frequency of the frequency dividing circuit 3, it is possible to determine by which system the reproduced tape is recorded. When this determination result is expressed in a truth table as shown in Table 3, it can be seen that regardless of whether the tape speed is the first or second tape speed, the tape being played back is at the first tape speed Vp.
If the tape was recorded at the second tape speed VN, the output of the comparator 5 will be at the L level, and if the tape was recorded at the second tape speed VN, the output from the comparator 5 will be at the H level.

If it is determined that the tape was recorded using the formula,
The NTSC color circuit 8 is activated via the gate circuit 6.

As a means of activation, for example, when the H level is not present, NTS
A configuration may also be used in which the power supply circuit of the C color circuit 8 is turned off and turned on when it is at H level. Next, when the output of the comparator 5 is at the L level, it is assumed that the television system of the recorded tape is the PAL system, and the color signal from the color signal input 7 is sent to the gate circuit 6 to the PAL phase detector 9. Supplied via

For PAL signals, 4.43 times per horizontal period of the video signal.
Since the 36m× subcarrier is inserted as a burst signal, this burst signal is phase-detected to obtain a detection output signal.

The switch circuit 10 is turned on according to this output signal, and P
Activate the AL color circuit. As explained above, the present invention detects the phase of the control signal and input signal recorded on the tape to determine whether it is a PA signal or not.
It is possible to distinguish between the C system and the PAL system, and because the PAL system is phase-detected to obtain a discrimination signal,
This prevents malfunctions caused by noise or interference signals contained in the signal, and allows normal images to be reproduced.

- A simple explanatory diagram of the drawing is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention.

In the figure, 1 is the reference oscillator, 5 is the comparator, and 8 is the NTSC
9 is a phase detector, and 11 is a PAL color circuit.

Claims (1)

[Claims] 1 The first reference oscillation frequency is lower than the frequency of the control signal recorded at the first tape speed obtained when played back at the first tape speed, and the second reference oscillation frequency obtained when played back at the first tape speed is The second reference oscillation frequency is set higher than the frequency of the control signal recorded at the tape speed, and is lower than the frequency of the control signal recorded at the first tape speed obtained when the second reference oscillation frequency is reproduced at the second tape speed.
and a reference oscillator set higher than the frequency of the control signal recorded at the second tape speed obtained when playing back at the second tape speed, and the reference oscillator frequency set higher than the frequency of the control signal recorded at the second tape speed when playing back at the first tape speed. The frequency of the control signal recorded on the tape is compared, and when reproducing at the second tape speed, the second reference oscillation frequency is compared with the frequency of the control signal recorded on the tape, and the NTSC A comparator that determines whether the video signal was recorded in the PAL format or another format, and a PAL that determines whether or not it was recorded in the PAL format by phase-detecting the video signal recorded on the tape and extracting the subcarrier. A magnetic recording/reproducing device comprising a method determining means.