HDMI, or High-Definition Multimedia Interface, is a common interface for transmitting uncompressed digital video and audio streams. The HDMI system provides an extremely high data quality of both video and audio in a single cable, and is therefore rapidly becoming the standard for many different devices, including Blu-ray players, gaming consoles, and LCD and Plasma Televisions; HDMI ports also exist on some newer computer multimedia cards.
Like many other computer cables, manufacturers produce HDMI cables to an increasingly strigent level of specifications. Newer cables have even more bandwidth than their predecessors, but are backwards compatible, meaning they can work with older HDMI-capable devices. The newest widely-available HDMI cables meet the 1.3b standard, and it’s best to purchase HDMI 1.3b cables if possible.
HDMI cables feature connectors with 19 pins on both ends of the cable. These pins allow for both High Definition video and audio to be transmitted at very high speeds.
Sustainability being recently of more importance to the well being of our planet HDMI cables can be found on the used market. As long as they aren’t damaged recycled cables work just as well.
To understand the working principle of an HDMI cable, we need to penetrate what’s inside an HDMI cable. Once we understand the building blocks of the HDMI cable and devices, then we can technically analyze the function of each cable that resides within an HDMI cable.
Media standard before HDMI
First of all, the technology HDMI stands for High definition media interface. Before it surfaced back in 2013, TVs used ‘standard definition’ media playing technology. The output of that standard was pretty feeble with an almost square aspect ratio of 4:3 and a resolution of 704 x 480 pixels. Further, that analog media system which used to run on varying levels of electrical current as inputs also used picture interlacing feature in which every moving image frame contained only half of its full picture.
Gone are those days. Now the media ecosystem has walked into a digital age and HDTVs are the new ‘regular thing’. Technically, this digital media rendering system feeds on information packets in binary forms(1s and 0s). Further, these binary values snake through the HDMI cables as electrical pulses, and they are considered as media inputs at the signal receiving ends.
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Now. Coming to the features of the HDMI cable, it spews the media signal to HDTVs that render a picture having a rectangular (16:9) aspect ratio with high definition resolutions of up to 1920 x 1080 pixels. Added to this, HDMI signals are progressive. It means that while travelling through the HDMI cable, each frame of the image is a whole picture.
More pixels. Wider TV screens and beefy sound systems. Now, an HDMI connection needs more data and that too in a thick and fast way to maintain all of these. The existing standard of HDMI cables is equipped to carry a 1080p video signal with a whooping 8 channel wide audio signals that are good enough to handle up to 7.1 channel home theater.
Moreover, HDMI cable has two categories based on the speed of the signal processing. Category 1 has 74.25 MHz speed where the category 2 delivers 340 MHz speed. Statistically, most of the HDMI smart consumer electronics use category 2 cables.
There are also two distinct categories of HDMI cables based on the number of pins in their connectors. Now, the category A-type HDMI cables have 19 pin connectors where category B-type cables come with 29 pin connectors. Statistically, most of the existing HDMI world uses the type A connection and smaller digital electronic devices use the type B connection.
Data/Signal Flow & Encryption in HDMI Age
Further, HDMI technology is also good at data protection during the transfer of data. It uses an authentication protocol namely, DHCP or high-bandwidth digital copy protection, and the whole process of this data security layer is widely known as ‘Handshake’.
This entire, end to end, data encryption process is coupled with two data sets that are common with each HDMI device – Identification data and encryption data. And, both of these are stored in the device’s EDID or the ‘extended device identification data’ chip.
Now, the data source point or a sender device(like blu-ray cd player) automatically check for the authentication key of the receiver device(like a home theater or an HDTV ), when they are previously connected with an HDMI cable. If there’s a match, then the sending device moves on to generate a unique encryption key and share the same with the receiving device.
Yes, It’s a secret key that is shared within the source to end. Thus, it’s called an end to end data security standard and this entire process gets completed within a blade of time.
Ok. Now, it’s time to shed some light on the HDMI signal processing.
HDMI technology uses a unique process for moving the information in the form of binary or digital signals – TMDS or ‘’ transition minimized differential signalling. This is a digital signal encoding technique that prevents the corrosion of signals during their travel through HDMI cables.
What happens is:
- The sending device encodes the signal heads, curbs down the number of transitions or simply, the number of changes between 0 and 1 to preserve the quality of the generated signals. Now, a pair of twisted cables also carry the ‘inverse’ or the exact opposites of the core signals.
- At the receiving end, decodes the signals. Further, it also measures the difference between the original signal with its inverse value. Now, the value of this differential is used to recoup the losses of the signal heads.
Lastly, I bet, there are other deep technical issues coupled with the functioning HDMI cables. But, for sure, this article is going to help you to understand the whole technology easily.
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