Digital Age

The use of digital video storage over analog videotape is preferred by many security dealers and end users for the following reasons:

• Digital video storage uses magnetism or optics to store video images. This greatly reduces the wear and tear of tapes and other mechanical problems related to VCR storage mediums.
• Digital storage systems " digitize" their images. This means that they are generally better in quality with time saving functions of retrieval, transport, and image enhancement.
• Image integrity is never compromised with the digital storage systems.
• The use of digital media eliminates the need to maintain a large videotape library.

Digital Storage vs. Analog Videotape

By its very nature, stored digitized images are usually better in quality than analog images stored on magnetic videotape. Digitization also makes it possible to more easily transport and enhance images.

The use of digital storage also makes it possible to continuously record video without interruption during playback, archiving, image searches, or other operations. By contrast, when a conventional videotape machine is employed, recording stops when the user places the unit in playback mode, unless a second recorder is used.

Digital storage units also are more convenient than conventional time-lapse videotape recorders because searches are faster and easier to perform. In addition, digital storage does not necessitate the constant changing of the magnetic storage media, as do systems that use videotape, other than for archiving.

Another reason for the excitement about digital video storage is its durability: these systems require little or no maintenance. For instance, because there is no contact between the recording stylus and a hard disk, very little wear-and-tear takes place on the disk's surface.

Videotape is different in that the tape is in constant contact with the video heads, which revolve at a speed of 1,800 rpm each. Thus, excessive use can result in abnormal wear-and tear on the videotape, the tape heads, and the mechanical transport. Thus, the user must rotate videotapes on a routine basis.

Most of the digital video storage systems now on the market operate using four basic record modes:

* continuous
* event
* scheduled
* time-lapse

In the continuous mode, images from one or more cameras are recorded continuously at a rate of 2 to 30 frames per second (fps). Using this mode requires a relatively large memory device. Unless the system is operated in loop mode, where images are written over others on a first-in, first-out basis. Some systems also operate so images are captured and saved when an event takes place, thus lowering storage requirements.

As is the case with conventional time-lapse recorders, most of the digital video storage systems on the market will accommodate the event-recording mode. Here, recording does not begin until an event takes place.The catalyst for recording in this case can be a PIR, doo switch, dry-contact output from a relay inside an alarn control panel, or a vide motion detection circuit, either built within the storage system itself or external to it.

Many of the digital video storage units on the market also can be programmed to record according to time and date. This feature is especially helpful in multiple-camera storage systems. The resolution, frame rate, and color criteria can be adjusted on a camera-by-camera basis. Another benefit to many digital video storage systems on the market is that they can be accessed through a local area network (LAN) or wide area network (WAN). This means that stored images can be viewed from any workstation on the network.

Digital signal processing and new, improved compression techniques have propelled today's digital storage systems into the 21st Century. Although price now stands between some consumers and these phenomenal products, once manufacturers recoup their initial investment, this picture will change. In the next few years, security dealers are likely to hear more and more clients ask for digital video storage.