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HDMI audio

Overview

The miniDSP Flex HTx supports HDMI eARC – enhanced Audio Return Channel – for multichannel audio. Up to eight channels of lossless PCM audio can be sent to the Flex HTx over eARC.

The Flex HTx is backwards compatible with the older ARC standard, although in that case there will be only two channels of audio over HDMI. (The rest of this page will assume eARC is available.)

Info

The HDMI port on the Flex HTx is an output. It must be connected to the eARC-compatible HDMI input port of a modern TV or similar device. The audio goes in the return direction (hence the name). You can not connect an HDMI output from (for example) a computer or blu-ray player to the HDMI port of the Flex HTx.

For multichannel audio, the connected TV must support eARC and not just ARC. In addition, the source device connected to the TV must be able to output audio as multichannel linear PCM, as the Flex HTx can not decode bitstream audio (e.g. Dolby/DTS). Finally, the connected TV must support pass-through of audio from connected source devices to its eARC port.

Tip

For information on using HDMI CEC for remote control of the miniDSP Flex HTx, see HDMI CEC.

Connections

To use eARC, connect the HDMI port of the Flex HTx to the eARC-compatible HDMI port on the TV.

Info

If your TV does not have an eARC-compatible HDMI input, then you may be able to use an external eARC convertor. See the next section.

Here is a typical connection:

Illustrating eARC connection to the miniDSP Flex HTx

Illustrating eARC connection to the miniDSP Flex HTx

Info

Note that the eARC port on the Flex HTx is an output that connects to the eARC-enabled HDMI input on the TV. The audio goes in the return direction (hence the name). If using a directional HDMI cable (e.g. fibre optic), connect the "Source" end to the Flex HTx and the "Display" end to the TV.

Using an eARC adapter

To use a display that does not have eARC – such as a computer monitor, projector or older TV – an external adapter such as those made by HDFury can be used. We have partnered with HDFury to provide a selection of these devices as a bundled purchase with the Flex HTx.

More detailed information on the devices is available on the HDFury website. See also the application note Using the HDFury Arcana or VRROOM with Flex HT.

HDFury Arcana 4k or 8k

The HDFury Arcana comes in two versions:

The figure below shows how to connect the Arcana with the Flex HTx:

  • Connect an HDMI source to the HDMI IN port. If there is more than one source, an external HDMI switch is needed.

  • Connect the display to the HDMI OUT port.

  • Connect the miniDSP Flex HTx to the eARC OUT port.

Illustrating connections for the miniDSP Flex HTx and HDFury Arcana

Illustrating connections for the miniDSP Flex HTx and HDFury Arcana

HDFury VRROOM

The HDFury VRROOM supports 8k video and many other features. It has four HDMI inputs, so an external HDMI switch is usually not needed.

The figure below shows how to connect the VRROOM with the Flex HTx:

  • Connect HDMI sources to ports HDMI 0 through HDMI 3.

  • Connect the display to the HDMI TX0 or HDMI TX1 port (consult the VRROOM manual).

  • Connect the miniDSP Flex HTx to the eARC AUDIO port.

Illustrating connections for the miniDSP Flex HTx and HDFury VRROOM

Illustrating connections for the miniDSP Flex HTx and HDFury VRROOM

TV settings

The connected TV will need to have the correct settings for multichannel audio over eARC. The exact method of configuration and the naming will vary between brands, but the key items to check for are:

  • Enable HDMI-CEC. CEC stands for "Consumer Electronics Control." It allows HDMI devices to send each other control commands.

  • Enable eARC. This may not enabled by default, so be sure to locate the setting and enable eARC. You may also need to set the eARC port as the audio destination.

  • Set the audio mode for external devices to Passthrough. This is so that multichannel PCM from external devices will be forwarded to the Flex HTx over eARC. (The external devices will also need to be set to output multichannel PCM – see the next section.)

  • Set the input mode of connected sources. In some cases, the TV will need to be told to not convert the input audio signal. Setting the mode to "PCM" may not work, as this actually means "Stereo PCM". A setting such as "Pass through" will have the effect of disabling format conversion.

See the application note Apple TV 4k with miniDSP Flex HT/HTx for a concrete example of the settings.

Audio sources and formats

The Flex HTx only supports linear PCM (LPCM) audio. It does not support encoded bitstream audio e.g. Dolby/DTS. This means that any source device must be capable of generating multichannel LPCM audio. Typically, a setting will need to be changed to tell it to do so.

Unfortunately, not all devices support multichannel LPCM and manufacturers generally do not provide this information in their specifications. We cannot test every piece of hardware but from the limited testing we have been able to do we have these observations:

Streaming boxes

The Apple TV 4k generates multichannel linear PCM for streaming apps such as Netflix and Prime. With the youtube app, we got multichannel linear PCM with 5.1 audio but not with Atmos. The Amazon Fire devices that we tried were not able to generate multichannel LPCM.

Blu-ray players

High end players such as Panasonic DP-UB820 and the (discontinued) Oppo players were able to generate multichannel LCPM.

Gaming consoles

The Nintendo Switch and Sony Playstation 5 were able to generate multichannel LCPM.

HTPC

If you have a Windows PC connected to your TV, the capability to generate multichannel LCPM depends on the application. We found that we had success with the native Netflix app but not with Prime Video. Browser-based playback does not play multichannel audio.

TV internal apps

The internal apps on the TV (e.g. streaming apps) may or may not be able to output multichannel LCPM over eARC. Unfortunately, this capability does not seem to be documented in the TV manuals.

HDMI status

The HDMI status screen provides information about the eARC connection:

HDMI status in miniDSP Flex HTx

HDMI status in miniDSP Flex HTx