As surveillance technologies drop in price and setup complexity, increasing numbers of businesses, schools and residences buy and install security cameras themselves to monitor their premises and record the results. The resulting footage can offer a reference to events, individuals and potential liabilities. PC- and DVR-based surveillance systems both rely on hard drives to retain security video, but connecting cameras to a PC limits the amount of specialized hardware required for a workable system design.
Turnkey surveillance systems often include a DVR, similar to the equipment used in home theater systems, instead of a conventional computer. Although you can't use a DVR as a PC, it's actually a special-purpose computer based on an embedded processor, with software set up specifically for the task of recording stills or video, and an off-the-shelf internal hard drive as a storage medium. The biggest drawbacks of DVR-based surveillance systems lie in their inflexible configurations. Upgrading a DVR hard drive means voiding its warranty to take apart its case. The procedure poses a greater challenge than swapping out a PC drive. Finally, upgrading DVR software may be difficult or even impossible on a unit designed to function like a video appliance.
You can attach surveillance cameras to a regular PC equipped with a PCI capture card or USB input device and the specialized software necessary to record time-lapse or motion-activated footage. Because a capture card installs in a PCI expansion slot, it requires a desktop tower or minitower system with a motherboard that accepts add-on cards. USB camera-footage input devices can plug in to any CPU with an available port and the ability to run the software required by the surveillance system. Using a PC broadens the range of hard drive types and sizes you can use over the options available for DVRs. You can set up a single-camera configuration or attach up to 32 networked sensors.
The hard drive capacity you need for a surveillance system depends on the frame size your cameras' capture, the type and amount of compression applied to the footage, the duration of recordings, the number of cameras and the amount of time for which the system must run without purging its stored footage. Some surveillance cameras capture HD footage that measures up to 1,920 by 1,080 pixels per video frame. Because even a simple security setup can accrue multiple gigabytes of data in a single day and may store its footage for 30 days at a time, choose your drive capacities and configurations to match the maximum amount of input you need to store.
Surveillance systems that record footage around the clock can push hard drive durability to its limits. Some drive manufacturers make storage devices designed specifically for this application. These mechanisms combine high capacities with power-management features that limit the amount of electricity required to keep an always-on system running. Drives with special-purpose features can command a higher price than standard off-the-shelf choices, but depending on the amount of information your system must store and the application in which you use it, the investment may pay off.
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