The System Audio Device is the only type of built-in Wwise Audio Device that supports Audio Objects. The System Audio Device determines which combination of outputs is delivered to the endpoint based on the endpoint's capabilities and the System Audio Device settings.
The System Audio Device routes Audio Objects to either the Main Mix, Passthrough Mix, or System Audio Objects, according to the following rules:
An Audio Object is routed to the endpoint as System Audio Object(s) only if it meets all of the following requirements:
It has a 3D position.
Its Speaker Panning / 3D Spatialization Mix is set to 100%.
All of its channels are located on the listener plane.
There are enough available System Audio Objects to accommodate all of its channels. In other words, the number of System Audio Objects Used would not exceed the number of Available System Audio Objects as shown in the Audio Device Editor when profiling.
It is good practice to avoid exceeding the maximum number of Available System Audio Objects. Surplus Audio Objects routed to the Main Mix might be processed differently, resulting in perceptible variation. System Audio Objects are allocated using first-in, first-out prioritization.
An Audio Object that does not meet the above requirements is routed to the Passthrough Mix only if it meets all of the following requirements:
It has a mono or stereo channel configuration.
It does not have a 3D position.
Audio Objects that do not meet the above requirements are routed to the Main Mix. Audio routed to the Main Mix is rendered to the output configuration of the Main Mix of the System Audio Device. This configuration is defined using either the Main Mix for Binauralization or the Main Mix for Home Theater setting in the Audio Device Editor, or if both of these are set to Use Game-Defined Settings, the Main Mix configuration is initialized by the endpoint. In this case, the Main Mix configuration can adapt to various listening scenarios.
The Mix Behavior defined in the plug-in Metadata of an Audio Object can override the default behavior described above. Refer to Metadata for details.
When an Audio Object with a 3D position and multiple channels is received by the System Audio Device, it's split into multiple mono System Audio Objects, one for each channel, and then delivered to the endpoint. For example, an Audio Object with a stereo configuration is split into two System Audio Objects. Note that LFE channels are discarded. For example, a 5.1 channel configuration is split into five System Audio Objects, discarding the LFE.
Refer to Understanding the Voice Pipeline for further details.