Advanced AudioBIFS: virtual acoustics modeling in MPEG-4 scene description

We present the virtual acoustics modeling framework that is a part of the MPEG-4 standard. A scene description language called the binary format for scenes (BIFS) is defined within MPEG-4 for making multimedia presentations that include various types of audio and visual data. BIFS also provides means for creating three-dimensional (3-D) virtual worlds or scenes, where visual and sound objects can be positioned and given temporal behavior. Local interaction between the user and the scene can be added to MPEG-4 applications. Typically the user can navigate in a 3-D scene so that it is viewed from different positions. In case that there are sound source objects in a scene, the sounds may be spatialized so that they are heard coming from the positions defined for them. A subset of BIFS, called the advanced AudioBIFS aims at enhanced modeling of 3-D sound environments. In this framework, sounds can be given positions, and also the virtual environment where they appear can be associated with acoustic properties that allow modeling of phenomena such as air absorption, Doppler effect, sound reflections, and reverberation. These features can be used for adding room acoustic effects to sound in the MPEG-4 terminal, and for creating immersive 3-D audiovisual scenes.