WHAM – Webcam Head-track AMbisonics

The restrictions imposed by the pandemic thwarted the continuation of ‘in-person’ listening tests into Ambisonic Order and transparency over head-tracked headphones in 2020/21, which is an ongoing project using Very High Order Ambisonics (up to 35th) and hardware head-tracking. It raised the question, “How do we maintain our essential test features using remote systems?”. Many people had access to webcams, laptops and headphones due to remote working, so we sought to leverage this, with the results being WHAM!

The WHAM (Webcam Head-tracked Ambisonics) website (www.brucewiggins.co.uk/WHAM) takes the approach of using a webcam to measure head rotation via the browser to provide the dynamic cues necessary for a convincing room auralisation using Binaural Room Impulse Response (BRIR) data. Visitors to the site can experience up to 17th Order Ambisonics over headphones which incorporate asymmetric binaural filtering of captured room responses that reacts to the rotation of the head.

This approach is only able to model a single source position, but with the associated room response captured to a much higher order than is currently possible using Ambisonic microphones (which max out at 5th order) and allowing for accurate dynamic head movement cues to be processed in real-time in the browser.

The project has added extra functions to the JS Ambisonics library, to enable asymmetrical filtering (left/right symmetry is a common method for increasing the efficiency of Ambisonics to Binaural processing, but isn’t valid if room responses are to be used). The forked JSAmbisonics can be found at: https://github.com/DrWig/JSAmbisonics

If you have a webcam and headphones, do give it a try!

New AmbiX WigWare Plugins Available

After some time, I decided to both update my Ambisonic tools to support the AmbiX standard (now widely used for immersive audio, 360 videos and VR) and rework my speaker array decoders using JSFX to make them a little more powerful and with a better workflow for me to quickly create new ones! My plug-ins implement near-field compensation, distance filtering and a few other things that other Ambisonic tools don’t, hence why I decided to bite the bullet and update them all. My 3D Ambisonic Reverb (AmbiXFreeverb) is also available in the bundle.

An example of one of the decoders is shown below. Dual-band decoding is available, and you’re able to tweak the overall gain of the low frequency vs high frequency decodes too (as energy optimised ones tend to be a little quieter). They’ll default to all sensible options, so if you don’t know what some of the controls do, just don’t change them 😉

Screenshot of a 3rd order Octagon Ambisonic Decoder

Both the platform-dependent VSTs (for Mac and PC) and the platform-independent decoders are available for download on the WigWare page, or below:

The VST plugins can be placed in the usual folders for Mac and PC, and a guide to installing JSFX plugins can be found at: https://reaperblog.net/2015/06/quick-tip-how-to-install-js-plugins/

The folder JSFX plugins go in is (Mac)
~/Library/Application Support/REAPER/Effects/WigWare/Amb Dec AmbiX/
or (PC)
%USERPROFILE%\AppData\Roaming\REAPER\Effects\WigWare\Amb Dec AmbiX\

You’ll need to create the WigWare folders. You can get to this quickly from Reaper by selecting Options->Show Resource Path in Explorer/Finder…

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