Understanding HDMI, Optical, and Analog Audio Outputs & Connections

Understanding HDMI, Optical, and Analog Audio Outputs

Different audio connections support different audio formats and channel counts. Understanding these differences is especially important when using an audio extractor with more than one audio device.

HDMI Audio

HDMI provides the highest audio bandwidth of the common audio connections and may support stereo, multichannel PCM, Dolby Digital, Dolby TrueHD, Dolby Atmos, DTS, DTS-HD Master Audio, DTS:X, and other formats depending on the OREI product and the connected equipment.

HDMI ARC and HDMI eARC are also different. eARC provides significantly more audio bandwidth and can support higher-bandwidth formats that may not be available through standard ARC.

Always check the specifications of the individual OREI model to confirm which HDMI audio formats it supports.

Optical / TOSLINK / S/PDIF Audio

Optical audio can carry both 2-channel and multichannel audio.

A common misconception is that an Optical output supporting 5.1 audio cannot provide stereo. This is incorrect.

For example, an Optical port may support:

The actual supported formats depend on the specific OREI product.

If the connected Optical device only supports stereo, set the source, TV, or audio extractor to PCM or Stereo when required.

Optical does not automatically convert a surround-sound signal to stereo. The OREI product must specifically support audio decoding or downmixing for this to happen automatically.

Analog L/R, RCA, or 3.5mm Audio

Analog L/R audio is normally limited to 2-channel stereo.

It does not carry Dolby Atmos, Dolby Digital 5.1, DTS 5.1, or other encoded surround-sound formats.

If a product does not have built-in downmixing, the incoming audio normally needs to be set to PCM/Stereo for the analog output to work.

Products with built-in downmixing may accept certain multichannel formats and convert them internally to 2-channel stereo.

Why Does Audio Stop When I Connect a Second Output?

When multiple audio outputs are being used simultaneously, the audio format must be compatible with the connected devices.

For example, consider an eARC soundbar that supports Dolby Atmos and a pair of stereo headphones connected through an analog output.

The soundbar may accept Dolby Atmos, but the headphones can only accept stereo. If the audio extractor cannot independently downmix the secondary output, setting the source to Dolby Atmos may result in audio only from the soundbar.

Changing the source to PCM/Stereo allows both devices to receive audio, but the soundbar will then also receive stereo.

This is known as a common audio format limitation.

Passthrough vs. Downmixing

These two functions are different.

Audio passthrough sends the original audio format to the connected device without changing it.

Audio downmixing converts a multichannel format into a lower-channel format, such as converting Dolby Digital 5.1 to 2-channel stereo.

A product that supports Dolby Atmos passthrough does not necessarily support converting Dolby Atmos to stereo at the same time.

When you need one audio device to receive surround sound while another receives stereo simultaneously, look for a product that specifically supports independent audio decoding or downmixing.

Important

The connection type alone does not determine the exact audio format.

For example:

Optical does not always mean 5.1. It can also carry 2-channel PCM.

HDMI does not always mean Dolby Atmos. The source, OREI device, and receiving audio equipment must all support the requested format.

Analog does not mean the device automatically converts surround sound to stereo. The product must support downmixing, or the source must be configured for stereo.

When selecting an OREI audio product, always consider both the connection type and the audio formats required by each connected device.