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 AC 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.
Mobile High Definition Link (MHL) is a logical progression of HDMI. It has three channels multiplexed into one. Each channel acts for an HDMI channel. It needs only five pins instead of 19 pins.