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b-format to binaural

September 4, 2005

The common way of transforming an ambisonic b-format audio signal to binaural signal seems to be by first decoding the signal for a number of loudspeakers and then use convolution with head-related transfer-functions to transform those signals into binaural signals.

The Bformat2Binaural VST plug-in (PC only) use this approach:

In this plug-in four speaker feeds are derived from an Ambisonic sound field and those feeds are convolved with the corresponding HRTF for those speaker positions. The speaker positions are 0 90 180 and 270 degrees. Since the left and right ear HRTF are the same at 0 degrees there is one less convolution required. Same applies for the rear 180 degree position avoiding a total of two convolutions as opposed to eight required if the speakers were positioned at 45 135 225 and 315 degrees.

The Ircam Spat library have externals for transaural to binaural conversion: trans~ and trans4~.