Event Callbacks with FMOD in Godot 4

If you have set up tempo markers in your FMOD Event or set up normal destination markers you can get time related information about the Event or a trigger when the cursor reaches a marker in the Timeline by using event callbacks.

Here is an example the prints prints “beat!” on every beat of the Event:

extends Node3D

var callable: Callable = Callable(self, "beat_callback")

@export var event: EventAsset
var instance: EventInstance

func _ready():
	instance = FMODRuntime.create_instance(event)
	instance.start()
	instance.set_callback(callable, FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_BEAT)

func beat_callback(args):
	if args.properties.beat:
		print("beat!")

To stop the callback from running you would pass null to set_callback:

instance.set_callback(null, FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_ALL)

For markers the process is the same, but you would pass FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_MARKER to set_callback:

extends Node3D

var callable: Callable = Callable(self, "marker_callback")

@export var event: EventAsset
var instance: EventInstance

func _ready():
	instance = FMODRuntime.create_instance(event)
	instance.start()
	instance.set_callback(callable, FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_MARKER)

func marker_callback(args):
	print("Marker: " + args.properties.name + " at position: " + str(args.properties.position))

Naturally, you can both get information about the timeline beats and markers by passing FMOD_STUDIO_EVENT_CALLBACK_ALL or both callback types to set_callback:

extends Node3D

var callable: Callable = Callable(self, "callback")

@export var event: EventAsset
var instance: EventInstance
var type = FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_BEAT | FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_MARKER

func _ready():
	instance = FMODRuntime.create_instance(event)
	instance.start()
	instance.set_callback(callable, type)

func callback(args):
	if args.type == FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_BEAT:
		print(args.properties.beat)
	elif args.type == FMODStudioModule.FMOD_STUDIO_EVENT_CALLBACK_TIMELINE_MARKER:
		print("Marker: " + args.properties.name + " at position: " + str(args.properties.position))