JPS6347117Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a dropout compensation circuit in a magnetic recording/reproducing device such as a VTR.

(b) Prior Art FIG. 1 shows a block diagram of a conventional dropout compensation circuit. After passing through the limiter 1, the reproduced FM luminance signal passes through the terminal a of the first switch circuit 2 and is FM demodulated by the FM demodulation circuit 3.

Dropout of the output of the limiter 1 is detected by a dropout detection circuit 4 by envelope detection. The first switch circuit 2 is controlled by this dropout detection output. That is, the first switch circuit is normally tilted toward the terminal a side, but when the dropout detection output occurs, it is tilted toward the terminal b side. terminal b
is connected to a 1H delay circuit 5 that delays the output of the first switch circuit by 1H (one horizontal synchronizing signal period), and when a dropout occurs, the output of the 1H delay circuit 5 is sent to the FM demodulation circuit 3 instead of the output of the limiter 1. Dropout compensation is performed.

According to the dropout compensation circuit described above, when a dropout occurs, the output is taken out from the closed loop consisting of the first switch circuit 2 and the 1H delay circuit 5, so that the compensation operation can be performed effectively even for a dropout of 2H or more. be done.

On the other hand, during special playback such as still playback and slow playback, the video head traces across adjacent tracks, resulting in noise bands. Since the reproduction output level decreases at and before the occurrence of this noise band, the dropout detection circuit 4 issues a detection output. Therefore, even though it is not a true dropout, a compensation operation is performed, making the reproduced image even harder to see.

For this reason, in the past, during special playback, the drop-out compensation operation was not performed to prevent malfunction. Although this method did not cause malfunction due to noise bands, when a real drop-out occurred, deterioration of the picture quality was unavoidable.

(c) Purpose of the invention This invention was created in view of the above points,
The present invention provides a dropout compensation circuit that effectively compensates only for the original dropout during special playback.

(D) Structure of the invention The present invention includes means for detecting a dropout in a reproduced video signal, means for delaying the reproduced video signal by 1H (one horizontal synchronizing signal period), and when a dropout is detected by the dropout detection means, the reproduction a first switch means for selecting and outputting the 1H delay means output in place of the video signal; and a 1H delay means for selecting the first switch means output during normal playback and selecting the first switch means input during special playback. and a second switch means for supplying a dropout compensation circuit.

(e) Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of the circuit of this embodiment, and the same parts as in FIG. 1 are given the same reference numbers and their explanation will be omitted.

The feature of this embodiment is that a second switch circuit 6 controlled by a special reproduction command signal is provided, and the signals supplied to the 1H delay circuit 5 are extracted from different parts during normal reproduction and during special reproduction. It is.

That is, during normal playback, the second switch circuit 6 is tilted toward the terminal NP side, and dropout compensation is performed in the same manner as in FIG.

Also, during special playback, the terminal SP is turned to the side, and the limiter 1 output is supplied to the 1H delay circuit 5.

Therefore, during special playback, the first switch circuit 2
and 1H delay circuit 5 do not form a closed loop,
Even if a dropout detection output is output when a noise band occurs, only a 1H compensation operation is performed, so image quality deterioration due to malfunction when a noise band occurs can be minimized. Furthermore, if the original dropout occurs, at least 1H
Compensation is fully performed for dropouts within the range.

(f) Effects of the invention As described above, according to the invention, during special playback, image deterioration due to malfunction of the dropout detection circuit when a noise band occurs can be minimized, and dropouts within 1H can be suppressed. Since the dropout compensation operation is completely performed, the image quality during special playback is improved and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional dropout compensation circuit, and FIG. 2 is a block diagram of a dropout compensation circuit according to an embodiment of the present invention. Explanation of main drawing numbers, 2, 6...first and second switch circuits, 4...dropout detection circuit, 5...
1H delay circuit.

Claims (1)

[Scope of utility model registration request] means for detecting a dropout in the reproduced video signal; means for delaying the reproduced video signal by 1H (one horizontal synchronizing signal period); and when the dropout detection means detects a dropout, the 1H delay means replaces the reproduced video signal. a first switch means for selecting and outputting an output; and a first switch means for selecting and outputting an output; and a first switch means for selecting and outputting an output;
a second switch means for selecting the switch means input and supplying it to the 1H delay means.