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In DVD technology, files are burnt to a disc and read by a laser eye inside the player. The eye decodes the information and displays it on a monitor. At home, this is generally accomplished with a TV and DVD player. It can also be done with a desktop or laptop computer. In an automobile, the player is mounted either in dash or in the ceiling of the car's back seat. Cables feed the signal to monitors mounted to the ceiling of the cabin or in the headrests of the front seats.
DVD players installed by the factory are tied into the car's stereo system and project audio into the car's speakers. Aftermarket units also can tie into the car's speaker systems, but may have their own independent speakers. Many units come with wireless or wired headphones so that passengers in the back seat can watch a DVD without disturbing other riders.
Potholes, graded pavement, train tracks and a host of other bumps and dips in a moving vehicle can cause skipping and jumping of the video. While players often lock the disc in, sudden movement can jar the laser and interrupt the reading of the disc. An important feature of car units is buffering. Sometimes referred to as "anti-shock memory," the DVD actually operates on a seconds delay, storing video in its memory in the event that playback is interrupted. The buffering provides continuous video while the laser resets itself.
Factory-installed players are tied into the electrical system of your car and derive power just as any other component would. Aftermarket units can also get their power in this fashion, although many rely on rechargeable batteries and converters that plug into dashboard outlets that used to power cigarette lighters.