The central controller as well as the storage for a digital video security system is the security camera DVR or Digital Video Recorder. The DVR coordinates and controls the actions of the system as well as provides a central location for quick access of the recorded digital video files. In this article, we will talk about the functions of the DVR and how it works.
A typical digital video security and surveillance system consists of up to three types of components; the digital video camera, the security camera DVR, and the system or spot camera monitor. The camera’s main function is to capture light images and convert them into electronic images that can be sent to the DVR to be compiled, stored, and viewed. The monitor’s function is to provide the display mechanism for viewing the electronic video.
But it is the security camera DVR that is responsible for tying all this together. The DVR is basically a specialized computer with its video processing services on steroids. The DVR has a central processor much like a personal computer, however the DVRs processor is specifically designed to deal with the data that is used to make video images, control cameras, store files, and display the images.
Most cameras have a special Integrated Circuit or IC chip called a Digital Signal Processor or DSP that is used to convert the electronic impulses sent by the sensor chip into video data. However, the DVR also has its own dedicated DSP and central processing unit to handle the tasks needed to produce security video images.
First, the DVR must be able to accept multiple video data streams or bits simultaneously. For example, most digital video security systems have more than one camera. The DVR must be able to handle the video information being sent by as many cameras as it is designed for. Think of the complexity involved when a personal computer uses a Webcam. Many personal computers, until recently, didn’t have the computing resources to do anything else when the Webcam was in operation. Now imagine using 4, 8, 16 or even 32 cameras at one time!
Further, the DVR doesn’t just receive the video data, but it must do something with it as well. In fact, it must compile it, compress it, decompress it (for viewing) and store it all in just a few milliseconds. It’s no wonder then, why a DVR is far superior to processing digital security video than say, a typical personal computer.
A security camera DVR creates a digital video file out of the data sent to it by the digital video camera. The data that is created for just one camera is enormous. For example, a digital video is actually in a simpler form, a series of digital photographs all stitched together. When these photographs are played in front of the human eye at a fast enough rate, they fool the human eye and brain into thinking it is seeing fluid, motion video.
Typically, a security camera DVR produces high quality video at a rate of 30 frames per second or 30 fps. That is 30 digital photographs taken within the time span of 1 second. The information that is processed by the DVR at this rate just for one camera in one hour is 30 fps x 60 seconds x 60 minutes or 108,000 times the size of one digital photograph; if the DVR is a 16 channel DVR that jumps to 1,728,000 times.
The security camera DVR uses a utility called a CODEC which stands for COmpression/DECompression to shrink the digital file to a fraction of its original size while maintaining a minimal loss of quality. This makes the file easier for the DVR to handle and requires less storage space to hold. All of Security Camera King’s featured DVRs use the latest, most efficient CODEC known as H.264.
Once the file is compressed it is then made available by the DVR for viewing (live) or storing on the hard drive for future use. Not until you consider all of the activity that is involved in creating digital video files for security systems can you really appreciate the high speed, intensive work performed by the security camera DVR.
In addition, the security camera DVR also acts as a fine tuner, relay station for other inputs, audio processor, and networking server. The more channels a DVR processes the more expensive the unit because of the hardware and technology that is required to handle the job.