DVR - Digital Video Recorders

Video cassete recorders( VCRs) were all the rage half a decade ago. They allowed people to record TV programmes, watch them when they felt like it and skip through the commercials.

Now, recording the television programmes has become even more convenient with digital video recorders(DVRs), also called personal video recorders(PVRs). The predominant DVR types on the market are TiVo, Replay TV and Ultimate TV with TiVo being the current market leader.

The basics Simply put, a DVR is a hard drive inside a fancy box. The hard drive is connected to the outside world through a variety of jacks on the back of the box, usually the typical RCA connections that you would use to hook up, say a cable box or a VCR.

The television signal comes into the DVR's built in tuner through antenna, cable or satellite. If the signal comes from antenna or cable, it goes into an MPEG-2 encoder or MPEG-4 encoder, which converts the data from analogue into digital . From the encoder, the signal is sent to two different places: first to the hard drive for storage, and second to an MPEG-2 decoder, which converts the signal back into analogue and sends it to the television for viewing.

The device is driven by a customised operating system- for instance, in the case of TiVo, the machine runs on a highly modified Linux installation. The operating system resides on the hard disk, along with the recording space, a buffer for live broadcasts, and in some cases a space for future expansion.