O3A Decoder - Headphones

Host Support

Audio

Description

This plugin takes a third order ambisonics (O3A) mix and decodes it to 3D stereo suitable for use with headphones. The results are similar to a binaural recording and can be used to place sounds behind, around, above and below the listener.

This plugin uses Blue Ripple Sound's ground-breaking "Amber" HRTF technology. This is also available in the Rapture3D game engines and O3A View plugin library.

Real-time plots are shown of the peak frequency content of the output left and right channels, using half-octave frequency bands centred from about 62Hz to 11kHz.

If you are targeting stereo speakers, the output of this plugin may be passed through the Stereo Crosstalk Cancellation plugin, which uses the same HRTF data. Under highly controlled conditions, this can be used with the stereo output from this plugin to produce 3D sound from stereo speakers.

The plugin is available in the O3A Decoding plugin library.

Technical Notes

The Blue Ripple Sound Amber HRTF uses data from the IRCAM LISTEN HRTF data set, available at http://recherche.ircam.fr/equipes/salles/listen/index.html.

The HRTF data for each head in the data set is cleaned and converted into a suitable parameterised model. The parameter space is explored to find an "average" head model which works on a wide range of heads. This is then used to build a higher order ambisonics (HOA) decoder.

This results in smooth HRTF-based decoders which work on a wide range of heads and do not suffer from the high frequency phasing artefacts common with some other headphone decoders and binaural panners, particularly when sounds are moving. The decoder is able to synthesise ITD (inter-aural time difference) cues at low frequencies and ILD (inter-aural level differences) throughout the frequency range. This plugin uses the third order (O3A) version of the decoder.