JPS6338156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device, and relates to a magnetic recording and reproducing device that is improved to eliminate disturbances in reproduced images during special playback such as high-speed playback in, for example, a video tape recorder (hereinafter referred to as VTR). Regarding.

As is well known, in a system that uses a helical scanning mechanism to perform tilted azimuth recording, such as in a cassette VTR, the playback output from the video head in special playback modes such as still, slow, and high-speed playback is based on the azimuth of the head gap matching. It depends on how much of the track you want to trace. That is, reproduction output is obtained from the portion where the video signal recorded on the track and the azimuth of the head match, but there is no reproduction output from the portion where the azimuth does not match, resulting in only noise. For example, in the special playback mode in the VHS 4-hour mode or the β-system 2-hour mode with a format that does not satisfy the H arrangement conditions,
There has been a problem in that discontinuities occur in the intervals of the horizontal synchronizing signals in between the noise parts, making the reproduced image look dull. Here, the H arrangement condition refers to a state in which the recording positions of horizontal synchronizing signals are adjacent to each other between adjacent video tracks. For this reason, conventionally, the playback video signal and the playback video signal delayed by a delay time twice the recording position shift of the horizontal synchronization signal between adjacent video tracks are switched based on a switching detection signal, and the horizontal synchronization signal interval is continuity was maintained. However, this switching detection signal is obtained by installing an oscillator with a frequency twice the horizontal synchronizing frequency synchronized with the horizontal synchronizing signal, and comparing the signal obtained by dividing this output by 1/2 with the horizontal synchronizing signal using a flip-flop circuit. Ta. As a result, the switching detection method described above has the disadvantage that the circuit becomes complicated and the cost becomes high.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a magnetic recording and reproducing apparatus which can prevent image distortion during special reproduction in a format that does not satisfy the H alignment condition, with a simple circuit configuration and at low cost.

To summarize, this invention delays the reproduced video signal based on a delay means (hereinafter referred to as delayed reproduced video signal) during special playback in a format that does not satisfy the H alignment condition, and in fast forward mode, the field is delayed based on the vertical synchronization signal. At the time of switching, a predetermined one of the delayed playback video signal and the playback video signal is commanded to be output, and in the rewind mode, the playback video signal and the delayed playback video signal are alternately commanded to be output. .

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. In construction, the magnetic recording/reproducing apparatus is comprised of a delay circuit 10 as an example of delay means, a switching detection generation circuit 20 as an example of switching detection signal generation means, and a video switch circuit 30 as an example of video switching means.

The delay circuit 10 includes a modulator 11 and a glass delay line 12
, an oscillator 13 and a demodulator 14 . Input terminal 4
A reproduced video signal is input to 1. This reproduced video signal is applied to a modulator 11 and a video switch circuit 30. The modulator 11 is for converting a reproduced video signal to the center frequency of a glass delay line 12, which will be described later.
An oscillation output signal is given from 3. The delay time of the delay line 12 is selected to be twice the recording position shift of the horizontal periodic signal between adjacent tracks in a format that does not satisfy the H arrangement condition. The reproduced video signal delayed by the delay line 12 is given to a demodulator 14 and demodulated by the oscillation output signal of the oscillator 13. The delayed reproduced video signal and the undelayed reproduced video signal are applied to the video switch circuit 30. The video switch circuit 30 switches between the aforementioned two reproduced video signals in response to a switching detection signal applied from the switching detection generating circuit 20.

The switching detection generation circuit 20 includes an amplitude phase (hereinafter referred to as AM) detection circuit 21 which is an example of a detection means, a 1/2 frequency divider circuit 22 which is an example of a frequency divider, and a preset pulse generator circuit 23 which is an example of a control means. include. A reproduced frequency modulated wave of a reproduced video signal is applied to the AM detection circuit 21 from an input terminal 42 . AM detection circuit 21
detects this reproduced frequency modulated wave and supplies it to the 1/2 frequency divider circuit 22. Further, a high level pulse for determining fast forward mode is inputted to the 1/2 frequency divider circuit via the input terminal 43, and a low level pulse for determining rewind mode is inputted thereto. The 1/2 frequency divider circuit 22 divides the detected reproduced frequency modulated wave into 1/2, discriminates between fast-forward mode and rewind mode, and provides a frequency-divided output signal to the video switch circuit 30. The preset pulse generation circuit 23 has an input terminal 44 to prevent image disturbance at the top of the screen.
A vertical synchronization signal synchronously separated from the reproduced video signal is provided. For this reason, the preset pulse generation circuit 23 gives a pulse to the 1/2 frequency divider circuit 22 so as to always output either the delayed playback video signal or the playback video signal at the top of the screen when switching fields in fast forward mode. . Also,
The preset pulse generating circuit 23 applies a pulse to the 1/2 frequency divider circuit 22 so as to always alternately output a delayed reproduction video signal and a reproduction video signal at the top of the screen when switching fields in the rewind mode.

FIG. 2 shows waveform diagrams of each circuit in this embodiment in the 9x fast forward mode.

FIG. 3 shows waveform diagrams of each part of this embodiment in the 9x high speed rewind mode.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 to 3.

(1) Operation in high-speed fast forward mode.

In this case, the trajectory of the recorded video track and the head will be as shown in FIG. 2a. At this time, the reproduced video signal is recorded in the shaded area as shown in FIG. 2a. When this reproduced video signal is given to the input terminal 41, this reproduced video signal is transmitted to the modulator 11, the delay line 12, the oscillator 13, and the demodulator 14.
As a result, the delay time is twice as long as the difference in recording position of the horizontal synchronizing signal between adjacent tracks in a format that does not satisfy the H arrangement condition. This delayed video signal is applied to a video switch circuit 30. On the other hand, a reproduced video signal that is not delayed is also provided to the video switch circuit 30. The reproduced video signal recorded in the shaded area becomes a reproduced frequency modulated wave in the magnetic head as shown in FIG. 2b. When this reproduced frequency modulated wave is applied to the input terminal 42, the reproduced frequency modulated wave is converted into an AM signal by the AM detection circuit 21 as shown in FIG.
Detected. This detection signal is transmitted to the 1/2 frequency divider circuit 22
The frequency is divided by 1/2 as shown in FIG. 2e.
Further, the 1/2 frequency divider circuit 22 detects the fast forward mode based on a high level pulse from the input terminal 43. The output signal of the 1/2 frequency divider circuit 22 is given to the video switch circuit 30 as a switching signal. Accordingly, the video switch circuit 30 outputs a delayed playback video signal when the switching signal is at a high level, and outputs a playback video signal when the switching signal is at a low level.

On the other hand, when a vertical synchronizing signal is applied to the input terminal 44, the preset pulse generating circuit 23 determines the head switching timing (hereinafter referred to as field switching time) as shown in FIG. 2c based on this vertical synchronizing signal. ), a pulse as shown in FIG. 2f is output. That is, the preset pulse generating circuit 23 applies a pulse to the 1/2 frequency divider circuit 10 when the field is switched, and presets the output of the 1/2 frequency divider circuit 10 to be at a high level when the field is switched. For this reason,
The video switch circuit 30 outputs a delayed playback video signal when switching fields. Therefore, in a magnetic recording/reproducing device, the horizontal synchronization signal is continuous,
This prevents image distortion at the top of the screen.

(2) Operation in fast rewind mode.

In this case, the trajectory of the recorded video track and the head is as shown in FIG. 3a. At this time, the reproduced video signal is recorded in the shaded area as shown in FIG. 3a. The reproduced video signal recorded in the shaded area becomes a reproduced frequency modulated wave in the magnetic head as shown in FIG. 3b. The reproduction frequency modulation wave is AM
As shown in FIG. 3d by the detection circuit 21,
AM is detected. This detected signal is frequency-divided by 1/2 by the 1/2 frequency divider circuit 22 as shown in FIG. 3e. Furthermore, the 1/2 frequency divider circuit 22 is connected to the input terminal 43.
Rewind mode is detected based on a low level pulse from.

On the other hand, the preset pulse generating circuit 23 outputs a pulse as shown in FIG. 3f at the time of field switching, as shown in FIG. 3c, based on the vertical synchronizing signal. That is, the preset pulse generation circuit 23 gives a pulse to the 1/2 frequency divider circuit 22 when the field is switched, and the output of the 1/2 frequency divider circuit 22 alternates between low level and high level when the field is switched. Preset as follows. Therefore, the video switch circuit 30 alternately outputs a reproduced video signal and a delayed reproduced video signal when switching fields. Therefore, in a magnetic recording/reproducing device, the horizontal synchronization signal is continuous,
This prevents image distortion at the top of the screen.

In the above embodiment, the video switch circuit 30 outputs a delayed playback video signal when the output of the 1/2 frequency divider circuit 22 is at a high level, and outputs a playback video signal when the output is at a low level. However, the present invention is not limited to this, and the reproduced video signal may be output when the signal is at a high level, and the delayed reproduced video signal may be output when the signal is at a low level. In addition, in the above embodiment, the fast forward mode and the rewind mode are distinguished by using high level and low level pulses, but the invention is not limited to this. You can do it by any method.

As described above, according to the present invention, the reproduced video signal is delayed by a delay time twice the recording position shift of the horizontal synchronization signal between adjacent video tracks,
Since it uses an inexpensive and simple circuit configuration to switch between the playback video signal and the delayed playback video signal, it is possible to prevent image disturbances during special playback in formats that do not satisfy the H-alignment conditions. Effects can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a schematic block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. FIG. 2 shows a waveform diagram of each part of FIG. 1 in the high-speed fast-forward reproduction mode. Figure 3 shows the first
The waveform diagram of each circuit part of the figure is shown. In the figure, 11 is a modulator, 12 is a glass delay line, 13 is an oscillator, 14 is a demodulator, 21 is an AM detection circuit, 22 is a 1/2 frequency divider circuit, 23 is a preset pulse generation circuit, and 30 is a video switch. Shows the circuit.

Claims (1)

[Scope of Claims] 1. In a magnetic recording and reproducing apparatus during special playback in a format in which the recording positions of horizontal synchronizing signals between adjacent video tracks are not adjacent to each other, A delay means for delaying the playback video signal by a delay time twice as long as the recording position shift, based on a vertical synchronization signal when switching fields in a fast forward mode, among the playback video signal or the playback video signal delayed by the delay means. generates a switching signal that commands the output of one of the predetermined signals, and alternates between the reproduced video signal and the reproduced video signal delayed by the delay means based on a vertical synchronization signal when switching fields in rewind mode; a switching detection signal generating means for generating a switching signal for instructing output to the switching detection signal generating means; switching between the reproduced video signal and the reproduced video signal delayed by the delay means in accordance with the switching signal output from the switching detection signal generating means; A magnetic recording and reproducing device equipped with video switching means. 2. The switching detection signal generating means includes a detection means for amplitude and phase detection of the reproduction frequency modulated wave of the reproduction video signal, and a detection signal detected by the detection means by 1/
Claim 1, comprising a frequency dividing means that performs two rounds; and a control means that causes the frequency dividing means to output a pulse when switching the field based on a vertical synchronization signal to prevent disturbances in the upper part of the screen. The magnetic recording and reproducing device described above. 3. The magnetic recording and reproducing apparatus according to claim 2, wherein the control means outputs the pulse in synchronization with the high level of the output of the frequency dividing means when switching the field in the fast forward mode. . 4. Claim 2, wherein the control means outputs the pulses in synchronization with alternating low and high levels of the output of the frequency dividing means when switching the fields in the rewind mode. Or the magnetic recording and reproducing device according to item 3.