JPS6051381A - Magnetic picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To stabilize a horizontal synchronization of the time of reproducing at a varying speed, and to raise a picture quality by detecting a noise bar of a reproducing signal of the time of reproducing at a varying speed, and inserting a pseudo horizontal synchronizing signal into the part of the noise bar. CONSTITUTION:A horizontal synchronizing signal VH is separated from a reproducing video signal VD by a synchronizing separating circuit 1, a further stabilized horizontal synchronizing signal VH' is outputted by an automatic frequency control circuit 2, and as a result, a pseudo horizontal synchronizing signal VHA is generated by a pseudo synchronizing signal generating circuit 3. On the other hand, the drop-out of a reproducing signal PA of the time of reproducing at a varying speed is detected by a drop-out detecting circuit 4, a drop-out pulse DP is outputted, a noise bar is detected from this output by a noise bar detecting circuit, and a noise bar detecting signal NA is outputted. A switching circuit 6 is switched to a terminal (b) by the noise bar detecting signal, and the pseudo horizontal synchronizing signal is inserted.

Description

[Detailed Description of the Invention] This invention provides a VT for recording and playing back using magnetic tape.
This invention relates to magnetic recording and reproducing devices such as R.

In general, in magnetic recording and playback devices such as helical scan VTRs, the width of the head is wider than the recording track in order to prevent disturbances in image quality due to noise bars during variable-speed playback, such as high-speed playback. I am using a video head.

In other words, when a wide video head is used for high-speed playback, the trajectory of the head will be as shown in Figure 1 (A), and the envelope waveform of the playback signal will have a narrow noise bar as shown in Figure 1 (B). Therefore, the playback screen is hardly affected.

However, in the case of a pattern method in which the SECAM method does not have H alignment (the recording positions of horizontal synchronization signals are adjacent to each other between adjacent tracks), for example, the L of the VH8 method
In the P (long play) mode, the width of the video head cannot be made wider than the width of the track because the influence of picking up signals from adjacent tracks is large.

When high-speed playback is performed using such a narrow video head, the trajectory of the head becomes as shown in Figure 2 (A), and the envelope waveform of the playback signal has a wider noise bar as shown in Figure 2 (B). Therefore, distortion occurs on the playback screen.

By the way, in conventional magnetic recording/playback devices, in order to compensate for dropouts in playback signals, dropouts are detected and the playback output from one horizontal period (144) before is inserted into the dropout portion. An out compensation circuit is provided.

However, such a dropout compensation circuit
Although this method is effective against narrow dropouts, it cannot be used to deal with wide signal dropouts during high-speed playback because the horizontal synchronization signal before IH is also lost.

1-Hiroshi This invention has been made in view of the above points, and an object thereof is to improve the image quality of reproduced images during variable speed reproduction in a magnetic recording and reproducing apparatus.

For this reason, the magnetic recording and reproducing apparatus according to the present invention detects the noise bar of the reproduction signal during variable speed reproduction, and inserts a pseudo-horizontal synchronizing signal into the noise bar.

Embodiments of the present invention will be described below with reference to FIG. 3 and subsequent figures of accompanying drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention.

In the figure, a synchronization signal separation circuit 1 is configured to handle a reproduced video signal V
A horizontal synchronizing signal VH is separated from D and outputted.

The AFC (automatic frequency control) circuit 2 outputs a horizontal synchronization signal V I-1′ obtained by stabilizing the horizontal synchronization signal V H from the synchronization signal separation circuit 1 .

The pseudo sync signal generation circuit 3 generates a pseudo horizontal sync signal VIIA from the horizontal sync signal vIr' from the AFC circuit 2 and outputs it.

These synchronization signal separation circuit i, AFC circuit 2, and pseudo synchronization signal generation circuit B constitute a pseudo horizontal synchronization signal generation circuit that generates a pseudo horizontal synchronization signal synchronized with the reproduced video signal.

The drop-out detection circuit 4 outputs a drop-out pulse DP when detecting a drop-out of the reproduced signal PA during variable-speed reproduction.

3- The noise bar detection circuit 5 detects a noise bar from the dropout pulse DP from the dropout detection circuit 4 and outputs a noise bar detection signal NA.

The switch circuit 6 is a selection circuit, and is a selection circuit that selects the reproduced video signal VD.
When the pseudo horizontal synchronizing signal V If A from the pseudo synchronizing signal generation circuit 3 is input to the terminal a, and the noise bar detection signal NA from the noise bar detection circuit 5 is not input, the signal is switched to the terminal a side. When the noise bar detection signal NA is inputted, the terminal switches to the terminal side and outputs the pseudo horizontal synchronization signal VHA as the video signal VDD.

Next, the operation of this embodiment constructed in this manner will be explained with reference to FIG. 4 as well.

First, in a helical scan type magnetic recording/playback device,
When recording and high-speed playback are performed using a narrow video head, the envelope waveform of the playback signal PA becomes as shown in FIG. However, as shown in FIG. 3C, the noise bar becomes unstable in a part.

By inputting this reproduced video signal vn to the synchronization signal separation circuit 1, an unstable horizontal synchronization signal VH as shown in FIG. 4(d) is output, and the AFC circuit 2 controls the frequency of this horizontal synchronization signal VH As shown in FIG.

Then, the pseudo synchronization signal generation circuit 3 generates and outputs a pseudo horizontal synchronization signal V HA as shown in FIG.

On the other hand, the dropout detection circuit 4 outputs a dropout pulse Dr at the noise bar portion of the reproduced signal PA, and the noise bar detection circuit 5 outputs a noise bar detection signal NA at the noise bar portion as shown in FIG. 4(b). Output.

As a result, the switch circuit 6 detects that the noise bar detection signal NA from the noise bar detection circuit 5 is not output (
When NA is at low level), it switches to the terminal a side, so except for the noise bar part of the reproduced signal PA, the reproduced blowing acid signal VII) is output as it is as the video signal VDD,
When the noise bar detection signal NA is output (N8 is high level), it switches to the terminal side, so the playback signal P
In the noise bar portion of A, the pseudo horizontal synchronizing signal VHA is output as the video signal VDD.

Therefore, from this switch circuit 6, as shown in FIG.
), the reproduced signal 1) is a video signal V in which a pseudo horizontal synchronizing signal V II A is inserted into the noise bar part of A.
DD is output.

In this way, in this magnetic recording and reproducing apparatus, the pseudo horizontal synchronization signal is inserted into the noise bar portion of the reproduction signal, so synchronization is stable and distortion on both sides is eliminated.

In addition, in the second embodiment, a dropout pulse was used to detect the noise bar, but the invention is not limited to this.
Any signal that can distinguish between noise and signal may be used.

In addition, in the second embodiment, high-speed playback has been described as an example of variable-speed playback, but similar effects can be obtained in still playback, slow playback, fine slow playback, etc.

As explained above, according to the present invention, horizontal synchronization during variable speed playback in a magnetic recording/playback device is stabilized, distortion of the television screen is eliminated, and image quality is improved.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing an example of the trajectory of the head and the envelope waveform of the reproduction signal during high-speed reproduction by a wide video head and a narrow video head, respectively. FIG. 3 is an embodiment of the present invention. Block diagram showing 4th
The figure is a waveform diagram of each part used for explanation of FIG. 3. 1... Synchronous signal separation circuit 2... AFC circuit 3...
- Pseudo synchronous signal generation circuit 4... Dropout detection circuit 5... Noise bar detection circuit 6... Switch circuit =
7- Figure 1 Figure 2 8- 〉

Claims (1)

[Claims] 1. In a magnetic recording and playback device, a noise bar detection circuit that detects noise bars in a playback signal during variable speed playback, a pseudo horizontal synchronization signal generation circuit that generates a pseudo horizontal synchronization signal synchronized with a playback video signal, and the noise bar detection circuit. 1. A magnetic recording and reproducing apparatus comprising: a selection circuit that selects and outputs either the reproduced video signal or the pseudo-horizontal synchronization signal from the pseudo-horizontal synchronization signal generation circuit according to the detection signal of the magnetic recording/reproduction device.