O7A Decoder - Quad Binaural

Host Support

Audio

Controls

• Head

Description

This plugin takes a seventh order ambisonic (O7A) mix and decodes it to synthetic "Quad Binaural".

Quad Binaural is a format used in some Virtual Reality (VR) applications. It uses four binaural stereo recordings for pairs of ears at ninety degree angles (so eight audio channels in total). The stereo recordings are mixed together during playback in a way that can give the impression of a horizontal scene rotation, typically in response to head-tracking.

We do not particularly recommend the Quad Binaural format for VR applications. If your VR audio engine supports ambisonics properly then better rotational results can be achieved using ambisonic formats directly (for example, in Rapture3D Universal).

The decoder plugin assumes that at any one time during playback, two of the four binaural stereo recordings will be mixed together to produce the final binaural output, using sine and cosine gains (i.e. an equal-power crossfade). This can cause various artefacts which the binaural processing used in this plugin attempts to compensate for. Because of this, when only one head is being used, the results are typically not as good as when using the standard headphone decoder directly.

We recommend use of the standard binaural headphone decoder (O7A Decoder - Headphones) instead of this plugin when Quad Binaural is not in use.

The plugin is available in the O7A Decoding plugin library.

Controls

Control: Head

This control identifies which of the four binaural stereo recordings should be synthesized. They are:

For instance, the "Right" head corresponds to the case where the head is looking 90 degrees to the right. The scene is thus rotated 90 degrees to the left, so a sound that was previously at the front will be heard on the left.

Technical Notes

This plugin is based on the Blue Ripple Sound Amber HRTF (see the O7A Decoder - Headphones plugin). However, it has been simplified and modified to improve results with Quad Binaural rotation.

The plugin compensates assuming a sine and cosine equal-power crossfade during rotation. Results with linear crossfades are not expected to be as good.