JPS6219880U

JPS6219880U -

Info

Publication number: JPS6219880U
Application number: JP11115985U
Authority: JP
Priority date: 1985-07-20
Filing date: 1985-07-20
Publication date: 1987-02-05

Description

[Brief explanation of the drawing]

第１図はこの考案のドロツプアウト補償回路の
１実施例のブロツク図、第２図は第１図の補償パ
ルス出力回路の一部の結線図、第３図ａ〜ｃは第
２図の動作説明用のタイミングチヤート、第４図
ａは第１図の復調欠落補償用制御回路の詳細な結
線図、第４図ｂ，ｃはそれぞれ復調欠落補償制御
回路の他の例の結線図、第５図ａ，ｂはそれぞれ
従来のドロツプアウト補償回路のブロツク図であ
る。１……ビデオテープ、４……欠落検出回路、５
……ＦＭ欠落補償用スイツチ、６……遅延回路、
８……ＦＭ復調器、１０……比較器、１３……補
償パルス出力回路、１５……復調欠落補償用制御
回路。 Fig. 1 is a block diagram of one embodiment of the dropout compensation circuit of this invention, Fig. 2 is a wiring diagram of a part of the compensation pulse output circuit of Fig. 1, and Figs. 3 a to c are explanations of the operation of Fig. 2. Figure 4a is a detailed wiring diagram of the control circuit for demodulation loss compensation shown in Figure 1, Figures 4b and c are wiring diagrams of other examples of the demodulation loss compensation control circuit, respectively, and Figure 5 Figures a and b are block diagrams of conventional dropout compensation circuits, respectively. 1... Videotape, 4... Missing detection circuit, 5
...FM loss compensation switch, 6...Delay circuit,
8...FM demodulator, 10...Comparator, 13...Compensation pulse output circuit, 15...Control circuit for compensating for demodulation loss.

Claims

[Scope of utility model registration request]

In a dropout compensation circuit that is provided in a video tape recorder having a standard playback function and a special playback function and compensates for a drop in a demodulated brightness signal formed by FM demodulating a reproduced FM brightness signal of a videotape, the dropout compensation circuit compensates for the loss of the demodulated brightness signal formed by FM demodulating the reproduced FM brightness signal of the videotape. a loss detection circuit that detects a loss in the reproduced FM brightness signal and outputs an FM loss detection pulse having a pulse width of a detection period; an FM loss compensation switch that supplies the reproduced FM brightness signal of 1 to the FM demodulator, and supplies the reproduced FM brightness signal delayed by the delay circuit to the demodulator during the output period of the FM loss detection pulse; A comparator that outputs a demodulated loss detection signal when the level of the output demodulated luminance signal is equal to or higher than a predetermined loss reference level, and a playback mode is determined based on the presence or absence of a special playback mode signal that is output only during special playback. and the leading edge of the FM missing detection pulse during standard playback when the mode signal is not output;
A compensation pulse is output at each timing of the trailing edge, and a compensation pulse having the pulse width of the demodulation loss detection signal is output only when the FM loss detection pulse during the special playback in which the mode signal is output is input. A dropout compensation circuit comprising: a compensation pulse output circuit; and a demodulation loss compensation control circuit that reduces and outputs the level of the demodulated luminance signal only during the input period of the compensation pulse.