JPH0587900B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a magnetic playback device such as a videotape player including a magnetic recording and playback device typified by a VTR (video tape recorder). It is possible to reproduce multiple types of video signals with different values. Incidentally, if such a device also has a recording function, it is possible to record a plurality of types of video signals. [Conventional technology] Conventionally, PAL was used as a helical scan type VTR.
Some devices are capable of recording and reproducing two types of video signals with different field frequencies, such as a video signal and an NTSC video signal. By the way,
The field frequency for PAL video signals is 50Hz, and for NTSC video signals it is 59.94Hz. In such a VTR, it is necessary to change the rotational speed of a rotating drum having a magnetic head depending on the field frequency of the video signal to be recorded or reproduced. To automatically switch this rotation speed during playback, a synchronization signal such as a horizontal synchronization signal is obtained from the reproduced video signal, and the field frequency of the reproduced video signal is determined based on the frequency of this synchronization signal. It is known to switch the rotational speed of a drum motor that drives the rotating drum based on the rotation speed. In a device that switches the rotational speed of the drum motor in this way, the magnetic tape is run during playback, the frequency of the synchronization signal of the reproduced video signal obtained from the magnetic head of the rotating drum is detected, and the rotational speed of the rotating drum is changed. Switch the rotation speed of the drum motor and lock the servo of the motor. If this servo is not locked, the rotational speed of the motor will not be stabilized, and the playback screen cannot be displayed until the rotational speed is stabilized. Therefore, a predetermined time is required from the reproduction operation until the reproduction screen is obtained, although it is a short time. Separately, in general, in a VTR, when a playback operation key is operated during playback, the magnetic tape is pulled out from the loaded cassette, wound around the circumference of a rotating drum having a magnetic head (loading), and then A playback screen is obtained. In such a VTR, the time required for loading is required from the time a playback operation is performed until a playback screen is obtained. In order to eliminate such drawbacks and to immediately obtain a playback screen upon playback operation, that is, without requiring the above-mentioned loading time during playback operation, the magnetic tape is loaded immediately after loading the cassette. There are also some that are loaded. In this device, even when the magnetic tape is stopped, the magnetic tape is loaded and is in contact with a rotating drum having a magnetic head. [Problem to be Solved by the Invention] In a VTR in which a magnetic tape is loaded by the above-described playback operation, it is possible to play back two types of video signals having different field frequencies, and the rotational speed of the rotating drum is If the rotation speed of the drum motor is changed automatically during playback, the time required from the playback operation to switch the rotation speed of the drum motor to obtain the playback screen, that is, the time until the rotation of the drum motor stabilizes, is as described above. Since the time required for loading the magnetic tape is sufficiently short, the time required for the rotation of the drum motor to stabilize does not matter much. However, in VTRs in which the magnetic tape is loaded when the cassette is loaded,
When it is possible to reproduce two types of video signals having different field frequencies, and when the rotational speed of the rotary drum is automatically switched during reproduction, loading time of the magnetic tape is required during reproduction operation. Therefore, the time from the playback operation until the playback screen is obtained is only the time required for the rotation of the rotating drum to stabilize as described above, which is necessary when the rotational speed of the rotating drum is automatically switched during playback. However, this time starts to feel like a long time to the person operating it. The present invention is a VTR or the like in which a magnetic tape is loaded when the cassette is loaded, and which is capable of reproducing two types of video signals having different field frequencies, and in which the rotational speed of the rotating drum is adjusted. In a magnetic playback device that automatically switches the rotation speed during playback, the playback operation can be performed without requiring time for the rotation of the rotating drum to stabilize when switching the rotation speed of the rotating drum as in the conventional example. This makes it possible to immediately obtain a playback screen. [Means for Solving the Problems] In order to solve the above problems, in this invention,
When the magnetic tape is stopped running, the magnetic tape is loaded and is in contact with a rotating drum having a magnetic head.The helical scan type magnetic reproducing device reproduces a plurality of types of video signals having different field frequencies. so that you can
means for obtaining a synchronization signal from a reproduced video signal; means for determining a field frequency of the reproduced video signal from the obtained synchronization signal; and a rotation speed of the rotary drum in accordance with the field frequency determined by the means. The apparatus is characterized in that the synchronization signal is obtained from a reproduced video signal reproduced by the magnetic head from the magnetic tape in the stopped state. [Function] In the magnetic playback device configured as described above, the magnetic tape is loaded when the cassette is loaded, so even when the magnetic tape is stopped running, the magnetic tape is loaded and the rotating drum having the magnetic head is connected to the magnetic tape. are in contact. The synchronization signal is obtained from the reproduced video signal reproduced by the magnetic head of the rotating drum from the magnetic tape in the stopped state. The field frequency of the reproduced video signal is determined from the frequency of the obtained synchronization signal. The rotational speed of the rotary drum is changed according to the determined field frequency. [Examples] Examples of the present invention will be described below with reference to the drawings. The figure is a block diagram showing only the portions of a helical scan type magnetic reproducing device related to the present invention. Although the cassette loading mechanism and loading mechanism are not shown in this magnetic playback device, the magnetic tape is loaded when the cassette is loaded, and even when the magnetic tape is stopped running, the magnetic tape is loaded and the magnetic tape is It is in contact with a rotating drum having a head. A video signal can be reproduced from the magnetic tape in the stopped state by the magnetic head of the rotating drum. In the figure, reference numeral 1 denotes a terminal, to which a video signal reproduced from the magnetic head is supplied. The reproduced video signal from this terminal is input to the synchronization separation circuit 2, and the horizontal synchronization signal of the reproduced video signal is separated. This separated synchronization signal is input to an AFC (automatic frequency control circuit) to obtain a horizontal synchronization signal with a stable frequency. The synchronous separation circuit 2
The frequency of the horizontal synchronizing signal from AFC3 is shown in the table below, and field frequency discrimination circuit 4
The frequency of the signal from is 15.625KHz or
Detect whether it is 15.734KHz.

[Table] The frequency of the signal from AFC3 is 15.625KHz
When the frequency is not 15.734KHz, switch 5 is switched to the opposite side. That is, when this switch 5 is in the state shown in the figure, the frequency of the signal from the AFC 3 is 15.625KHz, and when the switch 5 is in the state opposite to that shown in the figure, the frequency of the signal from the AFC3 is 15.734KHz. Switch 5 so that Reference numeral 6 is a drum motor that drives a known rotary drum (not shown) having a magnetic head. The PG signal and FG signal from a phase detector that detects the phase of rotation of the motor 5 and a frequency detector that detects the frequency (both not shown) are amplified by amplifiers 7 and 8, respectively, and are sent to a servo circuit as is well known. 9
is supplied to The output of the servo circuit 9 controlled by the PG signal and the FG signal is supplied to the driver circuit 10, and the drum motor 6 is driven by the output of the driver circuit. 11 and 12 are oscillators, respectively 25Hz and 29.97
Outputs a reference signal with a frequency of Hz. The outputs from these oscillators 11 and 12 are supplied via the switch 5 to the servo circuit 9 as a reference signal. In the magnetic playback device described above, a magnetic tape (not shown) that has been loaded and is in a stopped state.
A video signal is reproduced from the magnetic head. This reproduced video signal is input from terminal 1 to a synchronization separation circuit 2, where the horizontal synchronization signal is separated. This horizontal synchronizing signal is stabilized by the AFC 3, and its frequency is detected by a field frequency determining circuit 4 to determine the field frequency of the reproduced video signal. Based on this determination result, the switch 5 is switched, and the reference signal having a frequency corresponding to the field frequency of the reproduced video signal is transmitted to the oscillators 11 and 1.
2 to the servo circuit 9. The drum motor 6 is rotationally driven via the servo circuit 9 in response to a reference signal from the oscillator 11 or 12, thereby rotating the rotating drum. Note that when the magnetic tape is stopped, the AFC3 described above may have a pattern that generates noise due to the relationship between the track width of the magnetic tape and the width of the magnetic head.
AFC is performed using the horizontal synchronization signal so that the field frequency can be determined even if the horizontal synchronization signal is lost due to this noise.
However, it is not necessary to provide the magnetic head by appropriately selecting the width of the magnetic head. [Effects of the Invention] As described above, the present invention obtains a synchronization signal from a reproduced video signal reproduced by a magnetic head from a magnetic tape that is not running, and determines the field of the reproduced video signal from the obtained synchronization signal. Since the frequency is determined and the rotational speed of the rotary drum is switched in accordance with the determined field frequency, the time from reproduction operation to obtaining the reproduction screen can be extremely shortened.

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. 2...Synchronization separation circuit, 4...Field frequency discrimination circuit, 5...Switch, 6...Drum motor.

Claims (1)

[Claims] 1. When the magnetic tape is stopped running, the magnetic tape is loaded and is in contact with a rotating drum having a magnetic head.It is a helical scan type magnetic reproducing device that reproduces multiple types of video signals with different field frequencies. means for obtaining the synchronization signal from the reproduced video signal, means for determining the field frequency of the reproduced video signal from the obtained synchronization signal, and a means for determining the field frequency of the reproduced video signal according to the field frequency determined by the means. and a means for switching the rotational speed of the rotating drum, characterized in that the synchronization signal is obtained from a reproduced video signal reproduced by the magnetic head from the magnetic tape in a stopped state. playback device.