HDMI FAQs - The Differences Between HDMI Cables

What is an HDMI Connection? Understanding How to Choose the Right Cable...

HDMI is a digital signal which transmits sound and video from one device to another. Look at the table below to work out which is the best HDMI cable for you. Depending on your TVs and source device resolution capability, will determine which HDMI cable will be best to choose.

A standard HDMI connection is known as Type A but other HDMI connection types have also been developed. These are type C and type D connections.

Type C and D connectors are smaller in size than the Type A and are usually found on smaller portable devices such as camcorders, tablets & smart phones. If you are wondering what a HDMI connection looks like, we have a picture below to help.

What is HDMI with Ethernet and What is ARC?

The ethernet channel within a "HDMI cable with ethernet" allows multiple devices to share an internet connection when only one of the devices is connected to the internet.

Many people think that a special HDMI Cable is required to provide an ARC (audio return channel) and somehow differ in construction because of this. This is incorrect as only the pieces of equipment that you are connecting to need to have the ARC facility (usually version 1.4 equipment), not the cable.

Does the quality of an HDMI cable make a difference?

There has been plenty of debate and controversy in both the press and on internet forums in recent years about whether a digital HDMI cable can really make a difference to the quality of the picture and sound achieved. We are not going to even attempt to argue either way, the only real evidence we have is what our customers have told us about our previous award winning HDMI cables.

Overall our customers have reported that they think our HDMI cables do make a difference. We've always taken the stance that sourcing quality materials such as oxygen free copper (not CCA copper clad aluminium which is usually found in cheaper cables) will make a difference to signal quality & bandwidth achieved, along with a well made durable cable that will stand the test of time. The main issue we find is manufacturers making claims about cable speed across all their lengths, for example quite often a 1m cable will work at the 4K@30Hz, whereas a 5m or 10m cable in the same range will not due to attenuation (more information below).

HDMI Cross Compatibility & Older Cables

You may see cables being sold as a version number, for example HDMI V1.4 but what this actually means is that the cable is compatible with v1.4 equipment, i.e. the HDMI cable is ‘high speed’. HDMI cables that were produced when HDMI was in its infancy will still work with V1.4 equipment today as the only thing that has actually changed about the construction of the HDMI cables is their ability to carry an ethernet signal and the amount of data they are capable of handling (the lower the data, the lower the achievable resolution). You may even find that an older cable can carry a higher resolution such as 4K@60Hz, the only way to find out is to try. As outlined in the next paragraph, the 'speed' (data transfer ability) of the cable determines its ability to perform at a particular resolution, colour depth and frame rate.

If you're looking for an Ultra High Speed HDMI Cable, view our range here.

How Is The Speed Achieved? Additional Technical Information

HDMI is very different to previous consumer devices that originally ran on analogue signals such as SCART, S-Video, Component, etc. HDMI is digital and therefore is far more similar to digital data cables usually associated with PCs such as USB and CAT5.

Within an HDMI cable there are 19 conductors, four of these are twisted pair lines which are what the HDMI signal mainly relies upon to transfer the signal. Three of them carry the colour components and sync information and one of them carries the clock pulses. The signal as you would expect is carried in ones and zeros (which is the digital format), when the signal is decoded by a TV, the values of the red, green and blue components are used to create the colours of the image/video signal.

Before the 'speed rating' of HDMI cables was introduced, V1.3 cables were segregated into categories 1 and 2. Category 1 has the 3 signal pairs running at 742.5 Mbps, category 2 has the 3 signal pairs running at 1.65Gbps and then again with equalization running at 3.4Gbps. As there are 3 signal pairs, the 3.4Gbps can be multiplied by 3 making 10.2Gbps.

You may have seen data transfer values such as 10.2Gbps on certain specifications. If the 3 mains pairs of an HDMI signal can only carry 742.5Mbps each and a higher data value is required, the cable will not work. The are 3 main properties that change the data requirement of an HDMI signal, colour depth, resolution and frame rate. A 480 x 720 resolution (480i), with 8 bit colour running at 30 frames per second is likely to use about 135Mbps per each signal pair. 1080i and 720P use similar amounts of data; 1080x1920, 30 frames, 8 bit & 720Px1280, 60 frames, 8 bit will use 742.5Mbps. A 1080P signal will double the frame rate and therefore double the data used to 1.485Gbps. Deep colour which is a feature within some HDMI equipment can increase the bit rate from 8 to 12 or 16. At 12 bit, the data used will increase by 50% and at 16 bit the data used will double. Therefore a 1080p signal; 1920x1080, 60 frames, 16 bit will use 2.97Gbps.

A 3D signal has the information for each eye built into alternate frames. So for example (as above) a 1080p signal; 1920x1080, 60 frames, 16 bit will still use 2.97Gbps, 30 of the frames will be for the left eye and 30 of the frames will be for the right eye.

Some popular data speeds certain signals use is below;

2.25 Gbps - The minimum bandwidth required to transmit a 720p/1080i signal at 60Hz with 8-bit per channel colour depth is 0.75 Gbps per channel, or 2.25 Gbps total.

4.95 Gbps - The minimum bandwidth required to transmit a 1080p signal at 60Hz with 8-bit per channel colour depth is 1.65 Gbps per channel, or 4.95 Gbps total.

6.75 Gbps - The minimum bandwidth required to process a Full High Definition 3D signal (1920x1080 resolution for each eye at 24 Hz refresh rate) is 2.25 Gbps per channel, or 6.75 Gbps total.

As the length of the cable increases the attenuation of the signal becomes so high that the ones and zeros become difficult to determine. For example, using a cable over 10 metres could result in the cable only being able to run at 720p rather than 1080p at shorter distances. Therefore, if you intend to use a longer cable it is very important to check (with the manufacturer or retailer) that it will work with the resolution, frame per second and bit rate (outlined above) that you intend to use it at. For example, a very short HDMI cable (10cm) which is very poorly made from poor quality metal will more than likely work at 2.97Gbps, however the same cable at 20cm in length would probably not work.