1. Field of the Invention
The present invention relates to an apparatus and method for preserving/recording video signals in a video recording/reproducing apparatus such as a video cassette recorder (VCR). More specifically, the present invention relates to an apparatus and method for preserving/recording video signals to be recorded in a time-lapse VCR that makes it possible to preserve video signals written in a memory before a recording medium is forcibly ejected or ejected without proper authorization, and to record the preserved video signals on a recording medium inserted thereafter.
2. Brief Description of the Prior Art
Unlike an ordinary continuous VCR which records every frame of video signals, a time-lapse VCR records intermittently records frames of video signals from several video cameras or the like on a recording medium, e.g., a magnetic tape with a pre-selected regular interval. The time-lapse VCR is often used in security applications requiring long-time recording such as the monitoring of a bank or a museum. As shown in FIG. 9, a time-lapse VCR comprises a switching unit 10 which selects a video signal from among video signals received from several video cameras; a control unit 20 which extracts one frame intermittently from the continuous video signal received from the switching unit 10; and a recording unit 30 which records the video signal received from the control unit 20 on tracks on a magnetic tape. The recording unit 30 comprises a video signal processing unit and mechanical elements such as a loading motor which moves a loading post to load/unload the magnetic tape; a drum motor which rotates a head drum onto which video heads are mounted to record/reproduce a video signal on the magnetic tape; a capstan motor which rotates a capstan shaft to move the magnetic tape at a designated tape running speed.
For example, if a tape of 2 hours running time is used for recording during 48 hours, then the switching unit 10 switches to connect to the next video camera at an interval of 24 frames (=48 hours/2 hours), receives a video signal from the connected video camera, and sends the received video signal to the control unit 20. Then, the control unit 20 extracts one frame out of the video signal being received from the switching unit 10 at a specific point in time, and the extracted frame is recorded on the tape while the tape is advanced one frame by the capstan motor.
A time-lapse VCR has been one of the important components in most security monitoring systems because it enables recordation of video signals received from video cameras installed in several sites over a long time on one recording medium.
In the prior art, however, if an intruder destroys or takes out the recording medium having the recorded video signals thereon, the time-lapse VCR loses the capability to monitor the intrusion or emergency.