Event and SoundBank callbacks are exposed to Blueprint. In both cases, they are implemented using custom Events.

Event callbacks

Most callbacks exposed in the C++ sound engine API are exposed to Blueprint. For more information on what the various callback types accomplish, please refer to the SDK documentation.

Note: Because Blueprint graphs need to be executed on the game thread, callbacks requiring you to modify the AkCallbackInfo structure (AK_SpeakerVolumeMatrix, for example) cannot be exposed to Blueprint. Please implement them using C++ code.

Using Event callbacks

To subscribe to an Event callback, you first need to select it in the Callback Mask input pin dropdown. Then you can implement the Blueprint graph you wish to execute in the selected callback using a custom Blueprint Event:

Subscribing to multiple callback types

If you wish to subscribe to more than one callback type, you can simply select multiple values in the Callback Mask input pin dropdown:

Then, in your Custom Event graph, you can use a Switch on the Callback Type variable to determine what the current callback type is. You should then cast the Callback Info class to the appropriate type:

Using MIDI callbacks

The contents of a MIDI Event callback info class can be interpreted differently depending on the current MIDI Event type. In order to simplify parsing the MIDI callback info, a Blueprint macro, SwitchOnMidiType, is provided. It will automatically parse the callback info object and trigger the correct execution pin:

Note: The Chan member of the MIDI Callback Info class refers to the MIDI channel. Its range is from 1 to 16.

SoundBank callbacks

Much like Event callbacks, SoundBank callbacks are implemented using custom Events. The LoadBankAsync and UnloadBankAsync nodes will queue a bank load request to the sound engine and continue graph execution immediately. Once the SoundBank is loaded (or unloaded), a custom Event will be triggered: