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HDMI FAQ

On this page we have listed many of the common questions related to HDMI cables and connectors, and provided simple answers to each.

There are many problems that you might get when wiring up your system, and these days most people will use an HDMI cable as the main way of connecting everything together.

Unfortunately it can get complicated, as there have been quite a few updates to the technology over recent years - HDMI 1.3, 1.4, 2.0 - the list seems endless.

So if you are feeling confused, take a look below and hopefully you'll find the answer to your questions.

Close up of HDMI cable connector

What does HDMI stand for?

HDMI stands for High-Definition Multimedia Interface.

What are the different versions?

Version 1.0:

The release version of the HDMI standard. An audio and video interface which allowed the transfer of standard and high-definition video - and up to 8 channels of uncompressed digital audio.

Maximum data transfer of 4.9 Gb per second.

Version 1.1:

  • Support for DVD Audio.

Version 1.2 and 1.2a:

  • Support for the One Bit Audio format such as SACD (up to 8 channels).
  • Fully specified support for CEC.

Version 1.3:

  • Increased bandwidth to 10.2 Gb per second.
  • Improved colour - support for Deep Colour and x.v.Colour. These provide increased colour depths and the ability to reproduce any colour the eye can see.
  • Lip sync - allows devices to automatically synchronise the picture and sound.
  • Support for streaming high-definition Dolby TrueHD and DTS-HD Master Audio to an AV receiver for decoding.
  • Defined two standards for HDMI cables - category 1 and 2 (see below).

Version 1.4:

  • Support for increased resolutions - up to 3840 x 2160p at 25/30Hz and 4096 x 2160p at 24Hz.
  • Support for an audio return channel - allows the TV to send audio from an internal tuner to the AV receiver - therefore allowing an easy way to send this audio to a home theater sound system.
  • Support for an ethernet connection over HDMI - therefore allowing an internet or home network connection through the cables.
  • Support for 3D TV signals.

Version 2.0:

  • supported bandwidth increased to 18Gb per second
  • added support for 4K Ultra HD resolutions at 60 frames per second
  • added support for 21:9 aspect ratios

Version 2.0a:

  • added support for HDR (high dynamic range) video

Do I need HDMI 1.3 devices to hear HD audio?

No. The versions of HDMI before 1.3 fully supported the transfer of HD audio. However, this required the HD audio to be decoded by the playback device and then sent across the cable to the amplifier as a Linear PCM signal (LCPM). The amplifier/receiver also needed to support HDMI audio (not all did).

What was added by HDMI 1.3 was the ability to to bitstream the HD audio to the amplifier/receiver. This means the HD audio signal is sent ('streamed') directly to the amplifier/receiver without being decoded first, and the decoding is done by the receiver instead.

For this to work, all of the parts of the chain must be HDMI 1.3 compliant.

What is a category 1 HDMI cable?

A 'standard speed' category 1  cable has been tested at speeds of 75 MHz.

An HDMI cable has 3 data pairs of wire that transmit the signal. The two different categories of HDMI cable are speed tested using just one data pair - however the bitrate you see quoted will often be the combined total for all three (to get a higher number to impress you with).

This means a 'standard speed' category 1 cable has been tested to transfer data at 742 Mb per second for a single data pair - or 2.2 Gb per second for the three combined. This is seen as the equivalent of a 720p or 1080i video signal.

What is a category 2 HDMI cable?

A 'high speed' cable that has been tested at speeds of 340 MHz. This is up to 3.4 Gb per second for each data pair of wires - or a maximum of 10.2 Gb per second for the three pairs combined.

This is usually seen as the equivalent of a 1080p signal at 60 frames per second - or a 2160p signal at 30 frames per second. This would also include 3D video and any increased colour depth signals.

There is a new certification for a 'Premium HDMI Cable'. This is a category 2 cable that has been tested up to the theoretical maximum of 18 Gb per second - and should support any devices that operate under the HDMI 2.0 specification.

Do I need an HDMI 1.4 cable?

Cables shouldn't be defined by the version numbers of the HDMI specification -  1.2, 1.3 etc. These numbers refer to the capabilities of the hardware connections in your devices.

To transfer 1080p video and 3DTV signals you should make sure you buy a category 2 'high speed' cable to ensure it will transfer the high data rates required. If you aren't sending the highest resolution signals, then a standard category 1 cable should be sufficient.

What is an Ultra Speed HDMI cable?

It is just marketing speak. The actual cable specifications are either category 1 (standard speed) or category 2 (high speed).

What is the maximum cable length?

There is no defined maximum cable length for HDMI cables - only a required performance. The ability of a cable to accurately reproduce signals over a long distance is very much dependant on the build quality of the cable - and the quality of the circuits in the devices. However, in practice, a high quality cable should be able to transfer data successfully over about 10 metres before a repeater or amplifier is required to boost the signal.

Over a short distance, like less than 3 meters, almost any cable should be able to transfer the required data. Don't be fooled into buying over-priced HDMI cables.

Are the new versions compatible with the old versions?

Yes. HDMI is fully backwards compatible with older versions.

What is the difference between HDMI and DVI?

They are essentially the same, except HDMI has:

  • Support for 8 channels of audio
  • Support for the YUV colour space
  • CEC (wiring to enable remote control between devices)
  • A different connector

Is HDMI compatible with DVI?

Yes - although not DVI-A. You can buy DVI to HDMI cables and send video signals between devices. However, the DVI device must be HDCP enabled for this to work.

What is the difference between HDMI and component video cables?

HDMI cables are audio/video interconnects that send digital signals between AV devices. Component video cables send component analog signals between devices and are restricted to video only - they do not send audio signals.

Can I convert a component video output to HDMI?

Not easily/cheaply. You cannot simply have a component video to HDMI cable/adaptor as one is an analog signal and the other is digital. You can buy converter boxes but these can be expensive. Many AV receivers have the ability to upconvert a component input to an HDMI output.

Do I need to buy a new cable for my 3D TV?

Probably not. If you already have a 'high speed' category 2 HDMI cable then this will support all the requirements of HDMI 1.4 and 3DTV signals (with one exception - see below). A standard category 1 cable hasn't been tested to support the higher data rates, and so may not be reliable enough. However, before you buy a new cable, give it a try and you find it will work.

One part of the new HDMI 1.4 specification will require a new cable. The 1.4 update supports an ethernet connection through HDMI. To utilize this in your equipment, you will need a category 1 or 2 HDMI cable 'with ethernet'.

Do I need to buy a new cable for my HDMI 2.0 device?

Maybe, but probably not. An interesting point has been reached where the maximum data rate specification of the HDMI 2.0 specification has overtaken that of the 'fastest' HDMI cable.

HDMI 2.0 devices are designed to transfer data up to 18 Gb per second, whereas a 'high speed' category 2 cable is only designed to support a maximum  of 10.2 Gb per second.

However, a well made category 2 cable will probably handle data rates far higher than it has actually been tested to. To be sure, the HDMI licensing authority have introduced an optional 'Premium HDMI Cable' certification, which is allowed to be used on category 2 cables which have been tested up to 18 Gb per second.

The same rule applies to that mentioned above. Try the cable you have already, and if you get picture drop-outs or interference, then maybe look into getting a 'Premium HDMI Cable'.


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