HDMI stands for high definition multimedia interface. It is actually a standard that gives a set of guidelines for making connections between digital devices with emphasis on high bandwidth. The standard is for either audio or video interfaces and the data sent is uncompressed. This standard is known as the EIA/CEA-861. HDMI was started in 2003 and exists up to date.
HDMI uses transition minimized differential signaling (TMDS) to move a digital signal from one place to another. The sending device first has to encode the signal that it is sending. This helps to preserve signal quality since it will degrade when it makes many transitions from 1 to 0. The cable usually has two pairs of twisted cables. One pair carries the actual encoded signal while the other pair carries an inverse of the original signal. When the signal reaches the receiver, the original signal and the inverse are compared to derive a differential. The receiver then makes compensations for signal loss using this differential.
The main advantage of HDMI is its security. It protects data from piracy using HDCP (high bandwidth digital copy protection). In this protocol, the sender generates a key and shares the key with the intended receiver. The sender then repeatedly sends more keys to the receiver as it sends more data. If the receiver fails to be authenticated at any point, it stops sending. If an unauthorized user tries to intercept the data, the sender will easily notice and will not send any information.
HDMI devices are also known to have a wider screen, usually an aspect ratio of 16:9. The televisions using this protocol are also faster refreshing and have more pixels compared with the older NTSC televisions. The resolution reaches 1920 by 1080 pixels. The main disadvantage with HDMI is that both the sender and the receiver must be compatible. HDMI protocol is mainly used in tablet computers, mobile phones and blu-ray dvd.