JPS6076045A - Discriminating circuit for reproduction mode of video tape recorder - Google Patents

Abstract

PURPOSE:To obtain the 2nd reproduction mode discriminating signal which is free from noise signals even though the noise signal is superposed on the 1st reproduction mode discriminating signal, by using the 1st and 2nd D flip-flops which contain an input terminal, an output terminal, a reverse output terminal and a clock terminal respectively. CONSTITUTION:The outputs given from output terminals Q of the 1st and 2nd flip-flops 10 and 20 are supplied to both input terminals of the 1st AND circuit 30. While the outputs given from reverse output terminals Q' of the flip-flop 10 are applied to the 2nd AND circuit 40. Therefore the noise signal corresponding to a cycle of a control signal S1 which is applied to every clock terminals C and C of flip-flops 10 and 20 as a clock signal never appears at the output terminal of the circuit 30. As a result, an accurate 2nd mode discriminating signal S3' can be obtained despite irregular control signals S1.

Description

[Detailed description of the invention] The present invention relates to a reproduction mode determination circuit for a VTR.

Conventional VTRs have two types: the Standard Play (SP) method, in which the videotape is played back by running it at normal speed, and the Long Play (LP) method, in which the videotape is played back by running it at 1/3 times the normal speed. There are some that have both types. In such a VTR, it is necessary to determine which playback mode is used to perform playback. Some devices have made it easier to perform playback operations by automatically performing this discrimination, but conventional playback mode discrimination circuits
Video signal track 2 on videotape 1 as shown in the figure
,2. , , , on the Huntroll track 3 in correspondence with Huntroll (W No. S1.Sl, , , ).

NS is used to record the video tape 1 and to detect the rotation speed of the motor 5 of the capstan 4 that drives the video tape 1 to run.
Some motors are equipped with a magnetic pole 6 and a detection coil 7 that generates an FG signal S2 corresponding to the rotational speed by the magnetic flux of the magnetic pole 6. This reproduction mode discrimination circuit outputs, for example, a low level signal number in response to the large number of FG signals S2 in the standard play mode, and outputs a low level signal number in response to the large number of FG signals S2 in the long play mode. Correspondingly, a high level signal is output, and in synchronization with the control signal S1, it is automatically determined whether the long play mode or the standard play mode is selected depending on whether the signal level is low level or high level. However, even if the playback mode is the same, for example, the long play playback mode, when switching from the normal playback mode to a special playback mode such as reverse playback or still image playback, the control signal S1 may become irregular during the transition period. This tends to cause noise signals to be superimposed, which tends to cause misjudgment of the playback mode.

SUMMARY OF THE INVENTION An object of the present invention is to ensure that noise signals are removed from a reproduction mode determination signal so that the reproduction mode can be accurately determined.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings. FIG. 2 is a circuit diagram of this embodiment. This example uses VH3 system, Beta 7 Ohma.

This applies to any type of VTR (video tape recorder). The reproduction mode discrimination circuit of this embodiment has an input terminal, an output terminal Q, an inverted output terminal Q', and a clock terminal C.
and the first. A second D7 lip-flop 10.20 is provided. The output terminal Q of the first D flip 70 block 10 is connected to the input terminal of the second D flip 70 block 20 and one input terminal of the first AND circuit 30. The inverted output terminal Q' of the first D flip 70 tube 10 is connected to the second AND circuit 4.
Connected to one input terminal of 0. 2nd D flip 70
The output terminal Q of the tube 20 is connected to the other input terminal of the first AND circuit 30, and the inverted output terminal Q' of the second D flip-flop 20 is connected to the other input terminal of the second AND circuit 40. Each output terminal of the AND circuits 30 and 40 is connected to the set input terminal S and the reset input terminal R of the R87 lip 70 tube 50, respectively.

Figure 3 (b)
) is given as a first reproduction mode determination signal S3. This first playback mode determination signal S3 is applied to the motor 5 of the capstan 4 that drives the videotape 1 in the same way as in FIG.
An NS magnetic pole 6 is provided to detect the rotation speed, and the magnetic flux from this magnetic pole 6 generates an FG signal S corresponding to the rotation speed.
2 is provided, and in the standard play mode, the signal becomes low level corresponding to the large number of FG signals S2, and in the long play mode, the answer is that of the FG signal S2. This is a signal that becomes high level in response to a small number of signals. Both D7 lip 10
An inverted signal of the control signal S1 on the video tape 1 of the VTR shown in FIG.

Next, the operation will be explained.

A first reproduction mode discrimination signal S3 corresponding to the rotational speed of the capstan 4 is applied to the input terminal of the seventeenth lip 70 and the knob 10. When the rotation speed is low, for example, in the long play mode, the first reproduction mode discrimination signal S3 becomes high level as shown in FIG. Similarly, the first reproduction mode discrimination signal $3 becomes low level as shown in FIG. 3(b). As shown in FIG. 3(b), in this first reproduction mode discrimination signal S3, times t1 and t2
, a noise signal is superimposed between times L3 and t4, and when the first reproduction mode discrimination signal S3 is between times t5 and t6, the output of the R87 lip-flop 50 in the circuit of the embodiment is Only the second reproduction mode discrimination signal S3' from which the noise signal has been removed is applied to the terminal Q. This applies the output from the output terminal Q of the 17th lip 70 tube 10 and the output from the output terminal Q of the 27th lip 70 tube 20 to both input terminals of the first AND circuit 30, and also the output from the output terminal Q of the 27th lip flop 10. The output from the inverted output terminal Q' and the second
Since the output from the inverting output terminal Q' of the 7-rip 70-tube 20 is applied to the second AND circuit 40,
1.127 rip 70 rip 10 as clock signal
．． The noise signal corresponding to one cycle of the control signal S1 applied to each of the 20 clock terminals C1C is the first
This is because the output terminal of the AND circuit 30 is not affected.

Therefore, only the first reproduction mode discrimination signal S3 between time L5 and t7 in FIG. 3(b) is transmitted at time [
The second playback mode discrimination signal 83' between the output terminals 6 and L8 is applied to the output terminal Q of the R37 lip 70 tube 50, and the VTR switches from the normal playback mode to the special playback mode and outputs the mount roll signal. Even when S1 becomes irregular as described above, an accurate second reproduction mode discrimination signal S3' can be obtained. As a result, in this embodiment, both the long play mode and the standard play mode can be accurately discriminated without being affected by noise signals.

As described above, according to the present invention, the first pA2D7 having an input terminal, an output terminal, an inverted output terminal, and a clock terminal
Equipped with 70 lips, the input terminal of the 1st D7 lip and the 1st
Connected to one input terminal of the AND circuit, and also connected to the first D7
The inverting output terminal of the flip-flop is connected to one input terminal of the second AND circuit, the output terminal of the second D flip-flop 70 is connected to the other input terminal of the first AND circuit, and the inverting output terminal of the second D flip-flop is connected to the other input terminal of the first AND circuit. The output terminals of both AND circuits are connected to the set input terminal and reset input terminal of the R371J tube 70, respectively, and the first D7 lip 70 is connected to the other input terminal of the second AND circuit.
Apply the first reproduction mode discrimination signal to the input terminal of the knob, and
The control signal on the video tape of the VTR is applied to the clock terminal of the R87 lip-flop, and the second reproduction mode discrimination signal is obtained from the output terminal of the R87 lip-flop, so that the noise signal becomes the first reproduction mode discrimination signal. Even if the noise signal is superimposed, the noise signal is reliably removed from the second reproduction mode discrimination signal, so that the reproduction mode can be accurately determined.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a VTR video tape and a capstan that drives the video tape, Fig. 2 is a circuit diagram of an embodiment of the present invention, and Fig. 3 is an explanation of the operation of the circuit of Fig. 2. This is a time chart of the signals for. 161. Videotape, 410. Capstan, 10.
20. ,, 17th lip flop, 27th lip 70 knobs, 30.40. , , first AND circuit, second AND circuit, 50. ,, R37 lip 70. . Bu, Si, , control signal, 83. ,,first reproduction mode determination signal, 33'. 60. 2nd playback mode discrimination signal Applicant: ROHM Co., Ltd. Agent Patent attorney: Oka 1) Partner Figure 1: 7

Claims (1)

[Claims] (1) A first terminal having an input terminal, an output terminal, an inverted output terminal, and a clock terminal. The output terminal of the first D7 lip is connected to the second D7 lip 70.
The input terminal of the knob is connected to one input terminal of the first AND circuit, and the inverted output terminal of the first D flip 70 knob is connected to one input terminal of the second AND circuit. terminal is connected to the other input terminal of the first AND circuit, and the inverted output terminal of the second D7 lip-flop is connected to the other input terminal of the second AND circuit, and each output terminal of both said AND circuits is connected to the other input terminal of the first AND circuit.
Connect to the set input terminal and reset input terminal of the knob,
The tJtJ1 playback mode discrimination signal is applied to the input terminal of the first D flip-flop 70, the control signal on the video tape of the VTR is applied to the clock terminals of both D7 flip-flops, and the second playback mode discrimination signal is applied from the output terminal of the R37 flip-flop 70. A reproduction mode determination circuit for a VTR.