Documentation/Engine/Sound/Mixer

Audio buses, routing and mixer

The definition of the sound buses and their routing is a very important part of the Master Bank.

• Master Bus
  The master bus creates the final submix of all buses routed to it before outputting audio to the speaker channels.
  All buses, return buses, and events not assigned to a group are routed into the master bus.
• Bus
  The bus is an object which helps to collect specific sounds to groups and centrally control their volume or mute state.
  Any sound event in the game should be assigned to the corresponding prepared audio bus.
• Routing
  Routing the events and buses by the mixer helps to control specific sounds in groups and applying effects (as a reverb) for the whole group of the sounds together.

Current table describes mixer principles in our Master Bank:

Bus	Routing to...	Using for sounds...	Remark
master		- none -	Target for the central mixing of all other audio buses. "Master" volume and mute state (from application settings) is applied to the bus.
<--- cabin	master	- none -
.....<--- interior	cabin	Individual truck interior sounds as for example: air warning, blinkers, sticks, park brake, wipers, windows, seat noise...
.....<--- window_left	cabin	- none -
.....<--- window_right	cabin	- none -
.....<--- window_out	cabin	- none -
<--- outside	master	- none -	The bus should not contents any sounds. It is only technically group to collect all sounds from the outer world.
...<--- exterior	outside	- none -	The bus should not contents any sounds. It is only technically group to collect all exterior sounds.
.....<--- traffic	exterior	Sounds of the traffic system.
.....<--- trailer	exterior	Player's trailer sounds.
.....<--- truck_effects	exterior	Player's truck effects (air cutoff, air gear, hook, horns, reverse, ...).
.....<--- truck_engine	exterior	Player's truck engine. (see: Sounds - Truck Engine)
.....<--- truck_exhaust	exterior	Player's truck exhaust. (see: Sounds - Truck Engine)
.....<--- truck_turbo	exterior	Player's truck turbo. (see: Sounds - Truck Engine)
.....<--- truck_noise	exterior	Player's truck noise (aero noise, suspension noise, ...).
.....<--- world	exterior	Prefab sounds, sounds of animations...
...<--- unprocessed	outside	- none -	The bus should not contents any sounds. It is only technically group to collect all exterior sounds which are not affected by sound processing (like reverb).
.....<--- ambient	unprocessed	Ambient and environmental sounds and effects.
<--- game	master	- none -
.....<--- music	game	In-game music (as a 'hurry up' melody).
.....<--- navigation	game	Voice navigation output.
.....<--- ui	game	Sounds of the user interface (click, mail, reward, camera, ...).
.....<--- ui_music	game	Music for UI (menu, garage, service, ...).
.....<--- voiceover	game	Reserved for the future use.
<--- radio	master	Output for the in-game radio (user music) player.