Section: Software and Platforms

Mobile Audio Language

Participants : Yohan Lasorsa, Jacques Lemordant.

MAUDL library

The MAUDL library (Mobile AUDio Language) is an evolution of the ARIA library whose primary target was games on mobile devices.

Augmented Reality Audio applications use sound objects to create a soundscape. A sound object is a time structure of audio chunks whose duration is on the time scale of 100 ms to several seconds. These sound objects have heterogeneous and time-varying properties. In order to describe Interactive Audio (IA) contents, we created MAUDL, an XML language inspired by iXMF that is well adapted to the design of dynamic soundtracks for navigation systems.

MAUDL prevents audio information overwhelming through categorization at the declarative level and the use of priority queues at the execution level. This takes account of speed when walking, and of rapid hand gestures when interrogating the environment, for example. MAUDL can be used as an authoring time interchange file format for interactive mobile applications or as a runtime file format that is actually loaded through the web and played directly in the device. MAUDL is a cue-oriented interactive audio system, where audio services are requested using named events and the system's response to each event is determined by the audio artist.

The library has been implemented in C++ and now supports different mobile operating systems such as Android and iOS. MAUDL has been widely used in the first demonstrator of the VENTURI project consisting of a mobile augmented reality game.

3D Audio Pointer

A virtual 3D audio pointer provides an intuitive guide to the user of a mobile navigation application, reducing the need for cognitive work when compared to vocal instructions. We have built such a pointer using the MAUDL language. It gives the user the azimuth using HRTF spatialized audio cues, with additional hints taking the form of variations in the sound used. It allows superposing other kinds of audio contents, such as voice while the pointer is active, to indicate distance for example. This audio object is suitable for different sorts of navigation systems, such as POI browsers, self-guided audio tours, or applications for following predefined routes.

As the 3D audio pointer is based on MAUDL this technology is also available for both platforms, iOS and Android. It has been used by Metaio for the micro-navigation which is part of the second VENTURI demonstrator. The use case was to help a visually impaired person to find a box on a shelf with computer vision and 3D audio rendering.