The ADMix tool suite, developed during the research project ORPHEUS (European Union’s Horizon 2020 research and innovation program), can be used for recording (ADMix Recorder) and reproduction (ADMix Renderer) of objectbased audio contents.
The object-based format follows the audio definition model (ADM) defined by international standardization bodies (European Broadcast Union and International Telecommunication Union). ADM data is typically stored in .wav audio files (BW64) in which a <axml> chunk embeds the metadata. The association of audio channels and the metadata is defined in the <chna> chunk.
ADM elements can be of different types: DirectSpeakers, HOA, binaural, Matrix, or Objects. DirectSpeakers elements make it possible to create a multi-channel bed for standard loudspeaker setup (stereo, 5.1, etc.). HOA elements are used to store a sound scene encoded as High Order Ambisonics. Object elements are the most generic and are defined by their location, as well as a their gain. These positions and gain values can vary over time.
An ADM file can further contain multiple audio “programs” that each exploit all, or a part, of the audio tracks and are associated with different metadata sets. This functionality can e.g. be used to transmit contents in different languages, where only the dialogues in the selected language are played while the musical components and ambient sounds are shared by all programs. Another application of multi-program contents could consist of transmitting a single sound scene, mixed and rendered according to different listening positions.
In practice, the ADMix Recorder can connect with any digitalaudio work station in order to convert automation tracks to ADM metadata. Communication between the DAW and ADMix is established via the ToscA plugin, and relies on the OSC communication protocol. ADMix Renderer is based on the Spat~ library and makes it possible to render contents on 2-or-3D reproduction systems, over headphones or any loudspeaker setup.
The ADMix tool suite, downloadable from the IRCAM Forum website, is available for Mac OSX and Windows.
Main window of ADMix Renderer.
1) Meters corresponding to different objects in the audio file;
2) Meters of different output channels created depending on the rendering mode;
3) Choice rendering system (binaural with headphones or standard or ad hoc
4) Instantaneous visualization of the position of different objects;
5) Graph of the sound scene and activation of objects (mute/solo).