HD-SDI or High Definition Serial Digital Interface is a newer kind of video interface run by SMPTE (Society of Motion Picture and Television Engineers) and an upgrade to the current SD-SDI (Standard Definition Serial Digital Interface).  An HD-SDI camera allows you the ability to have megapixel in a standalone DVR.  HD-SDI also gives you the ability to upgrade your system without rerunning coax cables. 

 

Gowell group HD-SDI, just like SD Serial Digital Interface, uses coax cable with impeded BNC connection with standard nominal impedance of 75 ohms.  For surveillance systems, this means you could use RG-59 or coax and a BNC connector to run your cable.  The main difference with HD-SDI vs. the standard analog is that HD-SDI cameras will have to be connected to a DVR with an HD-SDI video input.  Due to the higher video transmission, a DVR with the ability to read HD-SDI video signal will require dedicated channels that cannot be used with your average analog camera.  HD-SDI can transmit video signals of at least 100 m with RG-59 cable before requiring repeaters to boost its signal.

 

HD-SDI video signal has a few advantages over IP and analog cameras.  For an analog camera, as you might have guessed, HD-SDI has improved video quality.  Normally, analog cameras transmit their video footage in an electric signal which is then decoded to digital data in the video recorder.  This essentially means that the video footage will lose some quality as it is processed and displayed on your LCD monitor. It further loses quality as the digital video recorder compresses and saves the video as MPEG4 on your hard drive.
 

Unlike analog cameras, HD-SDI does not lose video footage quality as the electrical signal is transmitted through the BNC cable, as it uses Non-Return to Zero Inverted (or NRZI) to encode the video signal.  NRZI helps facilitate the transmission of the encoded video back to its original data form.  In a way, HD-SDI and IP cameras are both very similar in the way that they both transmit video digitally.  Unlike IP cameras however, HD-SDI has better zero recovery and lower latency when zooming in digitally, as the video is processed digitally at the DVR.