AmbiGrainer - A Higher Order Ambisonic Granulator in Pd

AmbiGrainer is a sound file granulator implemented in Pd that is capable of spatializing individual grains in azimuth and elevation using IEM Higher Order Ambisonics (HOA) encoding objects.

This paper presents AmbiGrainer - a higher order Ambisonic granulator developed in the Pure Data signal processing environment. AmbiGrainer is capable of performing granular synthesis with individual grains spatialised in two dimensions, in spherical coordinates, using the IEM higher order Ambisonics encoding objects. Individual grain positions in the sound-field can be controlled directly or the meta-characteristics of the grain cloud could be controlled separately using an algorithm of choice. For example, the grain cloud could be directed to a single direction and distance, randomised according to a chosen probability distribution, or driven by a particle swarming or flocking model. This functionality enables the spatial shape of the generated grain cloud to be manipulated as desired to truly incorporate space as a musical parameter. AmbiGrainer outputs audio as Ambisonic channels that may then be decoded to a speaker array or binaural audio for headphones. Other features of AmbiGrainer are its capacity for real-time variable polyphony (numbers of simultaneous grains), synchronous or asynchronous sound-file granulation, and external control via OSC. In synchronous mode, playback rate is prioritised so that timbre may be altered by varying other parameters (such as grain size) while preserving tempo.

Key words: Higher-Order Ambisonics, Granular Synthesis, Sound Granulation