Digital security cameras offer a number of advantages over videotape based security systems. First, let's define some terms: when we refer to ‘digital security cameras', the difference is not in the actual camera, but rather in the way that the image is recorded.
Videotapes use analog recording in which data is written by the device onto a physical medium - the cassette tape. Once the tape is recorded, every time it is played there is a chance of the media degrading.
Digital recording, on the other hand, records the image as a series of numbers in a file. This is called encoding. The information in the file is unencoded to display it on a video monitor of some sort. The encoded file is usually saved to a computer hard drive or similar device for later retrieval. No matter how many times the data is accessed, there's no degradation. Digital security camera systems have the capability of much higher resolution - which means more detailed security tapes.
There are two main types of DVR technology for use with digital security cameras.
Embedded DVR Devices with Digital Security Cameras
An embedded DVR is a device that has been manufactured for the specific purpose of recording digital images. Many of the ‘digital security cameras' sold today include an embedded DVR system. They can provide continuous monitoring of an area, or use a stop-sequence to record a certain number of scheduled frames per second or per minute. Many can also be set up with a motion sensor, or alarm trigger which starts the DVR recording when it senses motion. Embedded DVR security devices have a high degree of reliability, and are generally capable of recording higher quality images than a PC based DVR. The amount of video surveillance that you can store is dependent on the hard drive space available on the unit, and less expensive DVRs may not allow you to upgrade the hard drive space.
PC Based DVRs with Digital Security Cameras
A PC based DVR is essentially a personal computer that includes the hardware and software needed to record video input from one or more digital security cameras. The needed hardware includes a video capture card and a CD burner to save the images. PC-based DVR's generally will work with any analog security cameras that you have. The software converts the analog signal to an encoded digital stream and saves it to the hard drive. The advantages of a PC based DVR are many. With included software - or software enhancements purchased separately - you can monitor as many cameras as you can fit on your screen. Each camera can be set up separately for frame rate, speed of pan, tilt or zoom. You can control the camera from the PC to pan, tilt or zoom, or set up digital tracking to allow the camera to follow certain types of movement. Digital security camera systems make it much easier to find particular times and sequences of recording, and it's far easier to store recorded CDs than it is to store recorded videotapes.