HDMI Signal Distribution

HDMI Signal Distribution

Ever wondered what HDMI actually is? CIE’s HowToAV.tv explains the facts and fiction in this in-depth guide to HDMI...


Since the introduction of HDMI enabled devices over a decade ago, many myths and misconceptions have developed surrounding the technology and how to use it. Knowing which piece of AV equipment you need for a particular purpose can be difficult; in this blog we explain some of the technology available and answer some of the most frequent issues regarding HDMI, discussing what you can do to get the most out of your AV system.


What Is HDMI?

HDMI stands for High Definition Multimedia Interface. It was developed by a group of major electronics manufacturers, with the first HDMI based products released at the end of 2003. It was developed as an alternative to analog standards such as Radio Frequency (RF), Coaxial Cable, S-Video and VGA. Since then it has gone on to become the most frequently used signal interface, as it’s the first which can handle both HD video and audio over a single cable.

HDMI is now used for a huge variety of different products which connect to a screen/TV and can be controlled or manipulated through innovative equipment such as HDMI switchers, converters, scalers and many more – all of which perform specific tasks like duplicating an image to multiple screens or changing its format.

It is used for both commercial AV applications as well as for home entertainment purposes, from connecting security camera feeds to a monitor, through to the devices in our homes such as DVD players, games consoles and Sky boxes. The flexibility and simplicity of HDMI is what has made it such a great success, leading to its use in all corners of society including education, retail, home entertainment and public spaces.


HDMI Cabling – What’s The Truth?

HDMI cables are designed as a simple one connector cable which has a ‘male’ input at both ends that connects to devices through their inbuilt ‘female’ HDMI port. Despite being one of the most frequently used cables in homes and businesses nationwide; there are still a number of myths which persist around them which won’t go away.

While there are different types of HDMI cable on the market, knowing which one is needed for a particular application requires an understanding of the equipment. High-speed HDMI cables are only needed for HD 1080p, 3D TV and deep colour. All other applications can be accomplished with standard HDMI cables.


Are Expensive HDMI Cables Better Quality?

Of all the misconceptions, the price and quality of HDMI cables is one of the most common. Their price ranges considerably, from around £5 right up to £450. However, it is a fact that the price and quality of a HDMI cable makes absolutely no difference to the picture and sound quality on the output screen/TV.

This is because the technology behind HDMI is digital. So unlike previous analogue devices such as DVI or VGA where the quality of cable can affect signal performance, HDMI cable signals are made up of digital code (1’s and 0’s), meaning that better materials or a cable made by a particular brand is not going to improve the quality of the signal.

The picture and sound quality you get is solely based on the quality of your source device and the media it is playing. The screen/TV you are using can also have an effect, but with an HDMI cable it either works or it doesn’t.


What Are The Different Types Of HDMI Cable?

There are five HDMI connector types, with each one designed for a slightly different purpose. Type A/B are defined in the HDMI 1.0 specification, type C is defined in the HDMI 1.3 specification, and type D/E are defined in the HDMI 1.4 specification.

HDMI Connector Type Physical Size Used For
Type A 13.90 mm wide Standard HDMI connector for use in digital AV applications.
Type B 21.20 mm wide A 29-pin version of the Type A HDMI connector.
Type C 10.42 mm wide Designed specifically for use with portable equipment.
Type D 6.40 mm wide Designed specifically for use in compact portable equipment, such as mobile phones.
Type E 13.90 mm wide Designed for automotive applications. Adds a latching shell to the standard connector, helping to prevent vibration-caused disconnects.


How Can I Make My HDMI Signal Travel Over 5 Metres?

There are a variety of ways to extend an HDMI signal, each dependant on how far you need it to reach. A reasonably priced 3 metre HDMI cable will easily the cover the distance between your TV and any device you have connected to it, giving you a perfect picture. If you are looking to carry the signal between 5 and 10 metres, then a higher quality category 2 HDMI cable is the best option.

An HDMI Repeater can take the signal from a source over a 10m cable into the repeater, then boost the signal a further 10m over a standard HDMI cable. But sometime it is necessary to transmit the signal a little further.

For these instances it is necessary to add an HDMI extender in order to effectively carry the signal further than 10 metres. These work by having two extender devices at each end which converts the HDMI signal so that it can travel on Cat 5/Cat 6 cables, allowing longer runs around different floors or rooms of a house, office or shop.


Most HDMI extenders will usually amplify the signal as well, ensuring that the signal level received at the end will be sufficient. When using HDMI extenders with a Cat 5/Cat 6 cable, runs of up to 100 meters can be made without any loss in signal strength or quality.


Can I Add More Inputs To My Screen Or TV?

As we are using an increased number of devices, the lack of outputs in which to connect them all has become a problem, resulting in an unsightly mess of tangled wires and awkward cable switches behind the TV every time you want to watch a DVD.

In order to effectively control and switch between different sources, without changing any wires around, the best option is an HDMI switcher. These allow you to switch between sources without the need to turn each one on or off, giving you a quick and easy method to go between your TV, games console and any other HDMI device you have connected.

An HDMI switcher adds on to your AV system, giving you a number of extra HDMI inputs along with a single HDMI output. They range from 2, 3, 4 or even 8 inputs, significantly increasing the flexibility of your TV and allowing you to have all your devices connected at any given time.

There are various switcher types, however they all generally have buttons on the front and an infrared remote control, allowing the user to switch from source to source without the need to unplug and re-plug the required device.

Professional switchers will also contain RS-232 connectivity, which is a standard used to integrate third-party control systems such as Crestron, Control4 or Savant. These allow for full smart control of your connected device from handheld applications on your smart phone or tablet.

What Do I Do If I Need To Extend My Signal AND Add Inputs?

If you are creating an AV system which can be used for a variety of purposes including extending, amplifying and switching, the best option is an HDMI matrix. These are designed to be multi-purpose, giving you complete freedom to manipulate the HDMI matrix’s inputs and outputs.

An HDMI Matrix allows simultaneous connectivity of anything from 4, 8, 16 or even 32 devices to a similar amount of output displays, meaning the user can send each input signal to either a single or multiple output displays.

Some also have special features such as ‘Video Wall' mode, which extends one of the selected HDMI sources to cover all 4 displays. This is commonly used in large stores, airports and office receptions to create one large screen to display information.



How Can I Play Different Audio Over An HDMI Signal?

There are a number of commercial applications for HDMI which require separate audio to play over the top of a video source. Examples of this include waiting rooms which may have a news channel on the TV with the radio playing over the top or a sports bar which wants to switch between the audio from a football match and another music source.

The best option for this is an audio embedder, which is able to embed a separate audio source into an HDMI signal that has been connected through the input. It then sends out a combined signal via the device’s HDMI Out which can then be connected to the screen/TV. It is a great way to add value to your AV system, providing a function which is frequently used for both commercial and home entertainment purposes.

If you are looking to do the opposite of this and split the audio source from the HDMI signal in order to play it through a separate audio system, then you will need an audio de-embedder. These are ideal for distributing the audio from an HDMI signal to an independent speaker/PA system.


Why Is My HDMI Signal Dropping Out On My TV?

There’s nothing worse than connecting up your new TV and discovering that you have a bad picture or other signal related issues. Here are a few common causes which could be causing the problem:

  • Take a look at the cabling and ensure everything is connected properly
  • Check your source is switched on and working
  • Ensure there are no broken or frayed wires which could be affecting the signal
  • If all of these are okay, then restart the device and change the input channel

Some of these may seem obvious, but often it is the simple issues which are the root cause of the problem. These are great if you have had your system working previously, but if you are having trouble with the initial set up of the source and screen, try investigating:

  • Whether you have a faulty HDMI cable
  • If the cable is too long for your system
  • HDCP – Is you source and display/sink HDCP compliant
  • You have the resolution setting correct for the TV

If none of these steps work, then you will need to begin troubleshooting each element of your AV system one at a time until you can locate the source of the problem.

Is HDMI Going To Remain The Best AV Option In Years To Come?

HDMI is expected to remain our number one choice for digital AV for the short term, but in the long term there are already new technologies which are attempting to replace it. These include HDBaseT, which has been developed to operate as a single cable for everything a device needs, including audio, video, power and internet. Click here to read our guide on HDBaseT.

Also hot on HDMI’s heels are internet based technologies. High speed WiFi and 4G are enabling more devices to become wireless, however so far this has been predominantly for web connected devices, rather than AV. However as technologies such as iPlayer and Netflix begin to blend the two together, interfaces which combine both are expected to become standard in the future.


Got a question for the HowToAV Team?

Thank you for reading our guide on HDMI. We’ve looked into HDMI technology and some of the products which can enable you to create the entertainment system you require in your home or work environment, as well as discussing ways in which you can troubleshoot problems with your HDMI signal. If you have any further questions regarding HDMI then please don’t hesitate to get in touch with our team of AV experts. Email us at findout@howtoav.tv

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