Digital Video Recorders

A digital video recorder (DVR) or personal video recorder (PVR) is a device that records video in a digital format to a disk drive or other memory medium within a device. Some consumer electronic manufacturers have started to offer televisions with DVR hardware and software built in to the television itself. In 1985, while working at Honeywell’s Physical Sciences Center, David Rafner first described a drive-based DVR designed for home TV recording, time-slipping, and skipping commercials. Most DVRs use the MPEG format for compressing the digitized video signals. At the 1999 CES show Dish Network demonstrated the hardware that would later have DVR capability with the assistance of Microsoft software. Also LG Group offers a television with DVR functions built in. The DVR simply stores the digital stream directly to disk. In 2003 many Satellite and Cable providers introduced dual-tuner DVRs.

The main use for this feature is the capability to record a live program while watching another live program simultaneously or to record two programs at the same time while watching a previously recorded one. Elgato makes a series of DVR devices called EyeTV. SageTV provides DVR software for the Mac with built in place shifting for watching TV remotely and sells and supports the Hauppauge HVR-950, myTV.PVR and HDHomeRun hardware with its DVR software. To record an analog signal a few steps are required. Digital television contains audio/visual signals that are broadcast over the air in a digital rather than analog format. Recording digital TV is generally a straightforward capture of the binary MPEG-2 data being received. The MythTV DVR supports both international DVB signals and American ATSC signals while the TiVo Series 3 supports only the ATSC signals. Recording satellite or digital cable signals on a digital video recorder is more complex than recording analog signals or broadcast digital signals. The satellite or cable set-top box does two things. Digital video recorders configured for physical security applications record video signals from closed circuit television cameras for detection and documentation purposes. A PC based DVR’s architecture is a classical personal computer with video capture cards designed to capture video images. Looping video outputs for each input which duplicates the corresponding input video signal and connector type. You can have the features of the controlled outputs to external video display monitors. 

Moreover, the network connections consistent with the network type and utilized to control features of the recorder and to send and/or receive video signals are also available. Internal CD, DVD, VCR devices typically for archiving video. Alarm event inputs from external security detection devices, usually one per video input are also there. User selectable image capture rates either on an all input basis or input by input basis. Routing of input video to video monitors based on user inputs or automatically on alarms or events. The facility of the input, time and date stamping are also available. These work through the alarm and event logging on appropriate video inputs. The digital video recorders can record through one or more sound recording channels. Digital video recorders cannot record from a high definition digital audio/video source such as HDMI or DVI, due to restrictions imposed by High Definition Content protection (hdcp). The latest development was recorded when on July 14, 2005, Forgent Networks filed suit against various companies alleging infringement on U.S. Patent 6,285,746 , entitled "Computer controlled video system allowing playback during recording.