HDMI FAQs - Differences Between HDMI Cables

What is an HDMI Connection?

HDMI is a digital signal which transmits sound and vision from one device to another, however, the latest HDMI cables also feature an Ethernet capability whereby an internet connection can also be broadcast.

 

All new TV’s, Blu-ray and most laptops have an HDMI connection built in. Older equipment may also have an HDMI connection.

 

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 and mobile phones.

What is HDMI with Ethernet and What is ARC?

HDMI cables are used to transfer the signal from one device to another. The newest HDMI cable available to buy is a ‘High Speed HDMI cable with Ethernet’. It has an additional channel within the cable which allows multiple devices to share an internet connection when only one of the devices is connected to the internet.

 

Many people think that ‘High Speed HDMI Cables’ have 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. We have found in our experience that most people are prepared to pay an extra £3-4 for an HDMI cable, as they do desire a well built quality product that will hopefully not cause them problems or issues in the future. And after all, if there is a difference between the signal produced from HDMI cables, £3-4 isn't going to break the bank where as £60-70 from other manufacturers may do!

Which HDMI Cable Do I Need for 3D?

At Thatcable all our HDMI cables are 'High Speed' and therefore capable of 1080P resolution, 3D and 4x2k resolutions as a minimum, see all our 'HDMI Speed HDMI Cables' now. The seller should tell you whether the cable they are selling is suitable or not. If you want to future proof yourself the best you can, a ‘High Speed HDMI Cable with Ethernet’ would be the best cable to buy as it is suitable for all the newest features and is certified to cope with a minimum of 10.2Gbps across all lengths. Some of the shorter lengths of our ‘High Speed HDMI Cable with Ethernet’ are capable of data transfer rates in excess of 17.8Gbps, therefore if there are any advancements in the HDMI technology, our cable should still be suitable.

What is HDMI Version 1.4 and Version 1.3B?

How to differentiate between HDMI cables has become very confusing. To rectify this HDMI cables do not now have a version, i.e. v1.3 or v1.3b. The version, i.e. v1.4 refers to the equipment being used and not the HDMI cable itself. You may see cables being sold as 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 equiment today as the only thing that has actually changed about the construction of the HDMI cables is their ability to carry an ethernet signal. 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.

What does 'High Speed' really mean?

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. To give some manufacturing play, the HDMI specification states that a tested cable should be suitable for up to 3.4Gbps per signal pair or 10.2Gbps (for the three signal pairs). QFHD commonly known as 4kx2k resolution or 3840x2160 and 3D can also be run over cables that are certified to 10.2Gbps. A 2160p signal run at the following: 3840x2160, 24 frames, 8 bit will use 2.376Gbps per signal pair which is still well within the 3.2Gbps that 'High Speed HDMI cables' are certified up to.

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.

One important factor which is often overlooked is the ability of an HDMI cable to carry a particular data speed over a longer length. A lot of cables are tested at 2 metres and state that they can perform at a certain speed but what they don't say is that they may not be as fast over longer distances.  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 that  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.