What does the pure uncompressed HD signal of the HDMI refer to?

Whilst it is true that the audio and video HD signal transmission of the HDMI is considered the most advanced cable technology at the moment, most people have a hard time understanding what this feature refers to. The uncompressed signal implies that the transmission signal will not be compressed any further when it passes from its source and into the HDMI cable. For the vast majority of tech fans, this analogue to digital conversion translates into a pure and undamaged signal on the HDTV or other electronic devices.

However, it seems that the encoding step of the signal seems to be left out of this equation.
The way the HDMI cables manage to transfer information from one location to the other one is by employing an innovative method of encoding known as TMDS. The TMDS encoding method can reduce the number of transitions because it only uses a single clock channel and an advanced data-encoding algorithm via its three data channels. It is important to note that while one of the twisted pair cables carries the actual signal to the source, the other cable will transmit an inverse copy of it. Consequently, when the electronic device decodes the signal, it will simply measure the difference between the input signal and its inverse and use that data to compensate for any information loss along the transmission.

One of the advantages of using an uncompressed HD signal on a HDTV or a home cinema, for instance, is that the images will be real-time. Real-time imaging is usually preferred to a compressed format mainly because there is no more delay between what the camera sees and what you receive on the TV monitor. Moreover, even though compressed files require a smaller digital bit-rate ratio, there is always the risk of adding artefacts during the compression process that will translate in a lower quality image perceived on a TV. However, in order to enjoy the clarity and quality of real-time imaging you need to ensure that all the components of the home cinema and the TV are HDMI compatible.
From a certain perspective, the high quality sound and picture displays over the regular copper wires are the result of minimized electro-magnetic interferences. However, even though they do not employ the exact mechanism of data transfer, some source-to-display baseband video formats, such as the RGB analogue component or the video component, for example, use encoding and stop compressing the signals even further.

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