The High Definition Multimedia Interface (HDMI) is a digital
substitute for analog video standards. It is a compact interface for
audio and visual electronic exchange. It transfers uncompressed and
compressed digital audio files and uncompressed video output files from
an HDMI-compliant source device to a compatible computer monitor,
digital audio device, video projector, digital television etc.
There
are a variety of HDMI cables uniquely suitable for uncompressed PC or
TV video format, enhanced high-definition and 3D video signals, 8
channels of uncompressed and compressed digital audio data, a Consumer
Electronics Control (CEC) connection and Ethernet connected data. HDMI
executes Consumer Electronics Association (CEA) and Electronic
Industries Alliance (EIA) -861 standards.
HDMI connectors are of five types: A/B (defined in 1.0 specifications), C (defined in 1.3), and D/E defined in 1.4).
The type A HDMI connector has 19 pins. Its bandwidth supports SDTV, HDTV and EDTV modes. It is electrically matched to single-link digital visual interface- digital (DVI-D).
The type B
HDMI connector has 29 pins. It can carry 6 differential pairs tailored
for future high-resolution displays. It electrically complies with DVI-D
with dual link.
The type C is a mini connector. It has 19 pins. It is smaller than type A. The basic difference is that its positive signals of differential pairs are traded with corresponding shields. The type C may be used as a type A using a type A-C cable.
The type D is a micro connector with 19 pins just like type A and C. It is very small. Again the pin assignment is slightly different from A and C.
The automotive system uses type E
HDMI connector. It has a locking stub so that it does not become loose
due to a vibrating machine. There is a shell that shields it from
moisture and dust. It needs a relay connector for getting connected to
the automotive.
There are two categories of cables defined by HDMI 1.3. The
category 1 is a standard cable. It is tested at 74.5 MHz. The category 2
cables are high-speed cables. It is tested at 40 MHz. It gives a higher
resolution. The length of such cables depends on conducting materials
and construction quality. These characteristics affect attenuation.
Category 1 cables with 5 meter length use thinner conductors. A longer
cable needs a thicker connector with better quality construction.
