Since its release on the market in 2003, HDMI has grown in popularity because it has made the digital devices connection process significantly simpler, as you only need to use one cable. In its essence, the HDMI is an intelligent signal linking technology that enables devices to discover each other and recognize the proper formats and resolutions. Thanks to its capabilities of delivering real time data, many people make the assumption the signal received by the source is going to be unaltered and will not suffer any degradation. While this is perfectly true for compressed formats, it is important to note that the HDMI does not use the same conversion and encoding methods.
First of all, the HDMI cables consist of twisted pair wires that have the role of sending the signal to the source and making an exact inverse copy of the data it transmits at the same time. The purpose of creating the copy is to help compensate for data that is lost whilst transmitting, and to enhance the current full signal to its maximum capacity. By measuring the differences between the two signals, the device will automatically add more pixels that fill in the missing or non-existent ones, by using known data points.
The match and increase of the resolution from the output to the one of the viewing area is also known as upscaling. The main benefit that results from HDMI upscaling is an overall better picture for non Blue-ray DVDs. Truth be told, the quality of that image will not be as clear or have the same quality to the display of a HDMI compatible device. Keep in mind that the picture will usually need to be stretched several times beyond its initial resolution and the original signal will go through an encoding and conversion to another format process.
Overall, nobody can deny the fact that outputting an upscaled high definition resolution via an HDMI cable is not a digital to digital signal chain process. However, considering that it needs to pass through different encoding and conversions steps, an upscaling digital to analogue is sometimes preferred. It is important to note that an error free and perfectly inherited display depends on a plethora of factors, both for digital to digital, or digital to analogue. Therefore, it would a mistake to simply assume that a digital to digital data conversion is superior in all circumstances to its counterpart.