For almost ten years now, HDMI has established itself as a universal connection for pictures and sound. The abbreviation stands for High Definition Multimedia Interface, i.e. an audio and video connection that transmits high resolutions. HDMI connections are found on televisions and monitors on the one hand and on TV receivers, DVD and Blu-ray players, game consoles and notebooks on the other. This makes it easy to transmit pictures and sound in the best possible quality with just one cable. In practice, it is not always quite so uncomplicated because there are different HDMI versions with different possibilities – and low-performance cables.
HDMI 1.4, 2.0 and 2.1: good to know
HDMI comes in different versions. From the beginning, all of them transmit videos in normal standard resolution as well as in HD resolution with 1920×1080 pixels. Ultra HD with 3840×2180 pixels (also called 4K) has long been possible. Up to version HDMI 1.4, UHD with up to 30 frames per second was possible, and HDMI 2.0 manages 60 frames per second. HDMI 2.1 is even more powerful, so even 8K resolution (7680×4320 pixels) can run up to 60 frames per second. Gamers benefit from variable frame rates, which have been possible since HDMI 2.0 and are firmly anchored in the standard with HDMI 2.1. Important: The version numbers always indicate only the principal capabilities of the connections. The actual capabilities of the device often only include a part of them. For example, HDMI 2.0 enabled Ultra HD resolution and increased colour depth with HDR, but a TV with HDMI 2.0 can also only handle Ultra HD and no HDR. In other words, a TV with HDMI 2.1 does not necessarily handle the variable frame rates of the new game consoles.
AV receiver and HDMI switch: more connections
Older or very inexpensive TVs and projectors often have too few HDMI connections for HDTV receivers, game consoles, streaming boxes and similar players. Switches provide the remedy with several HDMI inputs and one output, which are available for about 35 euros. It is important to pay attention to the specifications so that UHD and HDR videos or certain sound formats pass through the HDMI switcher unharmed. The same applies to AV receivers. Their HDMI inputs offer space for several players and forward the images to the TV via HDMI. Soundbars in higher price ranges also have corresponding connections, even if they rarely offer more than two or three HDMI inputs. But only the latest and high-quality models, such as Dolby Vision, are suitable for UHD and HDR in all its forms.
The HDMI connection on the TV for a soundbar or for an AV receiver carries the suffix ARC. Some TVs have more powerful HDMI connections: On older ones, 4K-capable HDMI inputs are labelled HDMI 2.0 or with the suffix 4K/UHD; on current ones, special inputs for game consoles are labelled with an icon or HDMI 2.1/2160p120.
HDMI and home cinema surround sound
Blu-ray discs and UHD Blu-rays, as well as many streaming players, deliver high-resolution home cinema sound with Dolby Digital Plus, Dolby True HD and DTS-HD Master as well as Dolby Atmos and DTS:X. No special HDMI cable is required for this. And a new AV receiver is not necessarily required:
- Blu-ray players and game consoles always output stereo sound for TV sets and the proven home cinema sound formats Dolby Digital and DTS for previous AV receivers. The corresponding setting is made in the player menu.
- Some players output the new sound formats converted via HDMI – in PCM format with up to eight channels. Many older AV receivers with HDMI connections can also handle this format. However, the new DTS:X and Dolby Atmos surround sound formats cannot be transmitted in this way; they must be sent from the player to the AV receiver or soundbar as a so-called bitstream without conversion.
Connecting an AV receiver with HDMI
If your home cinema boxes remain mute on the AV receiver, the receiver may not be using the HDMI sound itself but sending it onto the TV set or leaving it unused. In this case, set the receiver so that it receives the picture and the sound from the HDMI input. You can find out how to do this in the operating instructions of the AV receiver. Also, check that the HDMI output of all external players is set to bitstream or raw for the sound so that not an only stereo sound is transmitted. Alternatively, PCM multichannel is permissible.
If desired, televisions output the TV sound from one of their HDMI connections to AV receivers and sound bars. This HDMI connection is additionally marked on the TV set with the abbreviation ARC (Audio Return Channel). The matching counterpart on the AV receiver or soundbar is the HDMI connection for the TV, i.e. HDMI Out or TV Out. To ensure that the TV set does not reproduce the sound via its loudspeakers but lets it out via the HDMI connection, a corresponding setting is required in the sound menu of the TV set. New televisions have a higher bandwidth audio return channel, abbreviated eARC. This can output high-resolution surround sound, including Dolby Atmos. The corresponding sound formats do not arrive at the AV receiver. Often the extension is deactivated in the TV menu at the factory. In such cases, switch on eARC in the TV menu under Connections or Sound.
TVs output the sound to sound bars and AV receivers via the HDMI-ARC connection, including Dolby Atmos on models with eARC. Users must activate Dolby Atmos pass-through.
How to recognise good HDMI cables
Especially with longer HDMI cables, problems with pictures and sound sometimes occur. The cause can be poor cable quality or insufficient bandwidth. Good cables can be bought cheaply, but here the specifications for HDMI versions such as HDMI 2.0 or HDMI 2.1 are nonsense. Only the standardised bandwidth classes guarantee interference-free operation:
- HDMI High Speed safely transmits 10 gigabits per second (Gbps). This is scarce for 4K with 60 Hz, but it can work.
- HDMI Premium guarantees 18 Gbps, enough for 4K with 60 Hertz and HDR.
- HDMI Ultra High Speed identifies cables with a guaranteed 48 Gbps. That’s also enough for 4K at 120 hertz and 8K.
Strips with these designations guarantee that error-free picture and sound transmission is possible over the cable length offered. If this does not work, exchange the cable for another brand. For even longer distances, divide the distance into two strands of equal length. And connect an HDMI repeater in between: This boosts the signal so that 20 metres is no problem, at least for UHD pictures.
Select the correct HDMI picture setting
Various settings can be selected for picture resolution and display on devices with HDMI output. For example, older TV sets and beamers do not process the resolutions 576p or 1080p and therefore do not show any pictures. In such cases, connect the external player via an analogue video cable so you can see its menu. You can select a resolution that matches the TV or projector, such as 576i, 720p or 1080i. Then set the TV back to the HDMI input. HDR is also tricky: For example, you have to activate UHD and HDR playback in the menu of the PS4 Pro and enable the corresponding HDMI inputs of the TV for HDR on the other side.