Recorders: Recording CCTV video

Most CCTV systems use video cassette recorders (VCRs) to record video images from the monitors.  Recordings make it possible to view events that may have gone unnoticed at the time they occurred or that may require close investigation later.  Technological advances now make it possible to record images in digital form on a computer disk.  This new type of recorders is called digital video recorders (DVRs).
 

There are 2 types of DVRs:

• Standalone DVRs:
  This type of DVRs look similar to a standard VCRs. It's connected to the CCTV monitor for video capturing and display. A computer disk inside the DVR will be used to store the video footage. Some comes with built it CD-RW to enable video footage to be stored in CDs.

• Computer based DVRs:
  Computer based DVR system makes use of frame grabber cards such as the Geovision DVR cards to capture video. The DVR card is plugged into the computer’s motherboard and receives video input from the CCTV cameras. The video input will then be displayed onto the computer's monitor or stored into the computer's hard disk.

Standalone DVRs offers more video input channels as compared to computer based DVR systems. A standalone DVR can be connected up to 64 cameras!

VCRs are still presently the most common recording method but the number of current systems upgrading to digital is rapidly increasing due to the advanced features available and the increased recorded image quality. When digital systems are compared side-by-side to VHS format TLRs most clients opt for the superior quality and features of today’s DVRs. The latest DVRs are now able to record up to 480 frames per second divided by the number of cameras used in the system.

VCRs designed for CCTV can record video images in either real-time or time-lapse modes.  In the real-time recording mode, the tape moves at the same speed as home VCRs (2 to 6 hours) and captures 30 pictures per second.  This produces high quality recordings, but requires operators to change tapes every two to six hours.  The 24-hour real time VCR will record 24 hours of video on a single tape at 20 pictures per second. It is considered a real time recorder because 20 pictures per second approximate the ability of the human eye to easily distinguish moving images.

Time-lapse recording makes it possible to record video over long periods of time on a relatively small amount of videotape.  Time-lapse recording can capture from 12 to 960 hours of video on one T-120 tape.  However, the number of pictures recorded per second in time-lapse mode decreases significantly as the recording time increases.  As fewer pictures are recorded per second, critical images may not appear on tape, and movement may appear jerky.

Both the DVRs and VCRs offer video capturing through alarm recording. With this method, the VCR usually runs in time-lapse mode until an alarm occurs. This would enable the VCRs to record for a longer period of time without having to change tape. As for the DVRs, some DVRs come with built in Motion detection technology. This means that digital footage is only recorded when the motion sensor is triggered.

With the maximum storage space of computer disk increasing rapidly, it has enables DVRs to record long hours of non stop video footage. It can be left recording without being attended to as opposed to VCRs whereby you will need to change the tape after hours of recording. This is where the DVRs gain the edge over the VCRs. Computer based DVRs also offers the ability to search for scenes with just a drag of the mouse button.