Spatial Audio System for Surround Video

Abstract

In this paper we present the design processes of a spatial audio system for Surround Video. Surround Video is a method of reproducing two simultaneous video streams captured by two cameras onto a main television screen and onto the walls of a room via a projector. Through the use of distortion software to correctly map the surround image to the geometry of the viewing room, the user experiences 180 degrees of video reproduction, immersing them in the content. The design of a spatial audio system was necessary to give 360 degree coverage of audio so that, like for the video, the viewer is immersed into the programme world. We discuss the design process and decisions made that concluded in using a mixed reproduction system of Vector Base Amplitude Panning with Ambisonics to match the audio localisation precision with the video precision; high localisation around the main monitor image whilst the surrounding audio is immersive, but with less localisation. Attributes associated with objects in the real world are discussed and methods for recreating the effect of distance, in-head panning, sound scene rotations, reverberation and movement that alter the reverberation placement are presented. The end result is an immersive video and audio system that can be used by the BBC Research & Development department to demonstrate the potential of such technologies where the audio system uses 14 loudspeakers, a subwoofer signal and a discrete ‘4D’ type effects channel.