JPH0614732B2 - Superimpose circuit - Google Patents

Description

The present invention relates to a superimposing circuit of a video tape recorder.

(B) Prior art A superimposing circuit for displaying a pattern by multiplexing it on an image is disclosed in JP-A-62-140565 (H).
04N5 / 278) and JP-A-62-203489 (H04N5 / 278). These superimposing methods include a method of synchronizing the video signal source and the pattern signal source with respect to the reference synchronization signal and combining both signals, and a method of synchronizing the pattern signal source with the synchronization signal obtained from the video signal source. The method of synthesizing

(C) Problems to be Solved by the Present Invention However, in the case of superimposing a reproduced video signal of a portable video tape recorder, a circuit for externally driving the video tape recorder is not provided. The reference signal for reproduction in the tape recorder is I for servo.
In many cases, the structure is formed in C but is not led to the external terminal. Therefore, the pattern signal source cannot be driven by the reference signal.

Therefore, it is conceivable to drive the pattern signal source in synchronization with the reproduced video signal of the video tape recorder. However, like the video tape recorder for field still reproduction, the same recording track is formed by the main head and sub head that share the same azimuth. When performing reproduction scanning, when the sub head is not at a position where the sub head faces 180 degrees from the main head but is at a position that precedes the position where the sub head faces 180 degrees by 25H, the reproduction in the still reproduction video signal is performed. The cycle of the vertical synchronizing signal has an imbalance of 5H. When still reproduced video signals having different vertical synchronization periods are monitored on the monitor screen as described above, the reproduced screen vertically shakes. Therefore, the sync re-insertion process is performed for the purpose of changing the timing of the vertical sync signal in order to prevent the vertical shaking of the monitor screen. The timing of this synchronous reinsertion must be changed according to the characteristics of the monitor TV.

As described above, in the video signal subjected to the synchronous re-insertion processing, the vertical sync signal timing and the video information do not have a common phase relationship in each field, and the pattern signal source is driven based on the re-inserted vertical sync signal. If so, the pattern signal will fluctuate up and down in the playback screen.

(D) According to the present invention, according to the present invention, a pattern signal source that is synchronized with a reproduction synchronization signal or a synchronization pulse having the same phase as that of a reproduction synchronization signal in a video tape record that is subjected to synchronous reinsertion processing during special reproduction. It is characterized by arranging.

(E) Operation Therefore, according to the present invention, the combined phase of the reproduced video information and the pattern information matches.

(F) Example Hereinafter, the present invention will be described in accordance with an illustrated example. In the present embodiment, the present invention is applied to an 8 mm video in which azimuth recording is performed by shifting recording tracks by 1H (H is a horizontal synchronization period) in the scanning direction. Further, in the 8 mm video of the present embodiment, a pair of main heads having different azimuths is 180 °.
It is obtained by arranging the main head and the sub head having the same azimuth as one main head in advance of the other main head by 2.5H, and alternately scanning the main head and the sub head. The reproduced FM video signal is input to the video processing circuit (1).

As a result, the playback video signal obtained in the still playback mode is
One frame is composed of 527 (= 525 + 2) H, the main head output side field is 266H, and the sub head side field is 261H. Further, the reproduction vertical synchronizing signal in the reproduction video signal is delayed by 11H on the main head side and 8.5H on the sub head side with respect to the head output switching pulse (RF) (see FIG. 2).

If there is a difference of 5H between the fields, the monitor screen will pitch vertically. In order to prevent this pitching, the sync reinsertion circuit (8) performs a sync reinsertion process. In this sync re-insertion, a new vertical sync signal is inserted prior to the reproduction vertical sync signal timing. This new vertical synchronizing signal (VD1) is derived from the microcomputer (7), and the microcomputer (7) changes the formation timing of the vertical synchronizing signal on the main head side in accordance with the synchronizing adjustment signal. The microcomputer (7) forms a new vertical synchronization signal according to the mode designation signal and the synchronization adjustment signal, using the rotation speed signal and the rotation phase signal of the drum on which the video head is arranged as timing inputs.

In this embodiment, the pattern signal is combined with the reproduced video signal in the preceding stage of the synchronous reinsertion circuit (8). This synthesis circuit
The operation of (6) is controlled by the microcomputer (7), and the pattern signals generated by the pattern signal source (5) are multiplexed by switching. Also, the pattern signal source
In (5), the pattern signal is formed and derived in synchronization with the reproduction horizontal synchronization signal from the reproduction vertical synchronization signal in the reproduction video signal as a starting point. Therefore, in this embodiment, the horizontal sync signal obtained by inputting the reproduced video signal to the horizontal sync separation circuit (2) is P
The continuous horizontal synchronizing signal obtained by inputting to the LL circuit (3) is used as the count input of the pattern signal source (5). Further, the vertical synchronizing signal forming circuit (4) for inputting the horizontal synchronizing signal uses the reproduced vertical synchronizing signal (VD) obtained by the sync separation as the reference input of the pattern signal source (5).

Therefore, the pattern signal is formed in phase synchronization with the reproduced synchronization signal, and the phases of the reproduced video information and the pattern information match.

In the above-described embodiment, the reproduction vertical synchronization signal obtained by the sync separation is directly input to the pattern signal source.However, when noise occurs in the reproduction vertical synchronization signal, the reproduction vertical synchronization signal is reproduced by the microcomputer (7). It is also possible to form a sync pulse that coincides with the signal timing and input the sync pulse to the pattern signal source instead of the reproduced vertical sync signal obtained by synchronously separating the sync pulse. It is said that such a configuration is included in the present invention. Not even.

Further, in this embodiment, a microcomputer is used during normal reproduction.
It is assumed that a new sync signal is not derived from (7), and that a new sync signal is formed at the timing different from that at the time of still reproduction during double speed reproduction.

Further, the derivation of the pattern signal is controlled by an ON / OFF signal input to the microcomputer (7).

Furthermore, in the present embodiment, stable pattern information can be displayed on the motor screen even during intermittent slow playback.

(G) According to the present invention, according to the present invention, a stable pattern can be displayed on the monitor screen without causing vertical pitching in the pattern information despite re-insertion of the vertical synchronization signal during still reproduction or slow reproduction. Can be formed and its effect is great.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention, FIG. 1 is a circuit block diagram, and FIG. 2 is a signal waveform diagram of essential parts. (5) …… Pattern signal source, (6) …… Synthesis circuit.

Claims (1)

[Claims] 1. A still image is provided which comprises a pair of main heads which are arranged opposite to each other by 180 ° with different azimuths, and a sub head which is arranged in proximity to the other main head with one main head in common. In the video tape recorder, which prevents vertical pitching of the monitor screen by performing re-insertion processing on the playback video signal obtained by continuously scanning the same recording track by one of the main head and sub head during playback, playback vertical synchronization A superimposing circuit comprising a pattern signal source for generating a pattern signal in synchronization with a sync pulse having the same phase as a signal or a reproduction vertical synchronizing signal, and a synthesizing circuit for synthesizing the pattern signal with a reproduced video signal. .