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6.4.5 Multi-Channel Ambisonic Inputs

As we have mentioned a few times already, High Order Ambisonics is a technology that encodes sound sources along with full sphere positional information, as complex interleaved audio files that need decoding before they can be listened to on speakers. The lowest order of 3D Ambisonics requires 4 channels, conventionally named as;

This is the conventional B-Format also known as First Order Ambisonics. Some Ambisonic microphones record into a very similar four-channel format called AFormat, which ideally needs transcoding into B-Format. You can use the Input Transcoder Module to do that (see next section). There are a number of options that some Ambisonic encoders set differently to others, and these are sometimes concerned with the actual order of the WXYZ - for example a format called Ambix has a different order of channels that carry the spherical components, compared to FuMa. It is possible to configure channel sorting and normalisation options in the Input and Input Transcoder modules, and at any point where Ambisonic streams are decoded to a channel based stream. Please contact Flux:: support if you need expert guidance in the area of Ambisonic decoding options, as the topic is very large, and is beyond the scope of this guide.

High Order Ambisonics ( HOA ) needs more channels to contain the complex interleaved Ambisonic domain information. High Orders encode and decode into sharper and more accurate spatial information as the Order gets higher - but the number of channels needed to hold all the ‘spherical harmonics’ along with the serious computation involved, becomes very complicated very quickly. Fortunately….

★ Spat Revolution makes it easy to work with High Order Ambisonics

Just dial up the Higher Orders using the pulldown menu of an Ambisonic Input module, Transcoder or Ambisonic Room. The output stream will then expand its channels internally to accommodate the higher channel count needed. 3D full sphere HOA channel counts are defined by the function (n+1)^2 (where n = Ambisonic Order)

B-Format can also be encoded without elevation - this is called 2D horizontal and is quite suitable for decoding to configurations that do not have speakers on elevated planes. The 2 dimensional Ambisonic data is encoded in multichannel files with a channel count defined by the function 2n+1