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HD CCTV » What Is
SDI? |
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Serial Digital Interface (SDI) refers to a family
of video interfaces standardized by SMPTE. It is a
standard in the broadcast Industry for digital
video transmission over coaxial cable. For
example, ITU-R BT.656 and SMPTE 259M define
digital video interfaces used for broadcast-grade
video. A related standard, known as
high-definition serial digital interface (HD-SDI),
is standardized in SMPTE 292M; this provides a
nominal data rate of 1.485 Gbit/s.
The most common data speed is 270 megabits per
second (Mbps). However, speeds of up to 540 Mbps
are theoretically possible. Standard 75-ohm cable
is used. This is the same type of coaxial cable
used in most home television (TV) installations.
The SDI standard uses data words that are 8 or 10
bits in length. Signals are uncompressed and are
self-synchronizing between the source
(transmitter) and destination (receiver). Most
errors caused by noise or interference can be
detected, and the lost data recovered by means of
a specialized code called the Hamming code. A
signal in SDI can contain up to four independent
digital audio signals along with the video signal.
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