+ Go beyond with HDR!
After exploring Side-Chaining for giving space to certain elements of your soundscape and help them cut through the mix, there is one more big-budget workflow left to discuss. You are not going to implement this in the Plaformer Game, but it is necessary that you’ve heard about it for your future career in Game Audio. The Beyond in the title of this chapter hints at High Dynamic Range, or HDR. HDR is a new mixing paradigm available within Wwise to augment the already existing suite of dynamic mixing tools. HDR allows for authoring a system that responds to the dynamic loudness of sounds by giving priority to sounds that are authored the loudest. With this relativistic mixing system, the clarity of intention from the authoring perspective is ensured to make appropriate space in the mix for important sounds to be heard.
Think of a big budget AAA game like EA Dice’s Battlefield for a moment. As the sounds of battle ensue, you instinctively focus on the loudest sounds (combat), and quieter sounds (footsteps) are ignored. In an HDR system, these loud sounds represent the top of a user-defined window that moves dynamically to ensure that the loudest sounds are in focus. As this window moves upward, sounds below the window bottom are removed or culled from the mix. When one side emerges triumphant in an one-on-one brawl with machine guns and grenades, the sound of footsteps pounding the earth suddenly swell with renewed amplitude, becoming the loudest, and most focused sounds again. As the HDR window threshold returns to its rest position, the original amplitude of the footsteps is represented.
This example perfectly demonstrates how the soundscape is being mixed with an HDR system. On the battlefield there are lots of sound effects with rather drastic Dynamic Range, one that could never be played back on a speaker system. You may notice that the HDR system is culling less important sound effects like footsteps or foley sounds of the Player Character as louder, more important sound effects are being played back. This creates a great focus and feedback for the player.
Recently, also Rocket League offers an HDR setting. Although the soundscape is not as dense as in Example01, it made sense for the developers to focus the players attention on sound effects with a higher priority. These are sounds of the interaction with the ball, such as enemy vehicle over the player’s own vehicle sounds. It is also noticeable when listening to crowd chants, which alter its volume depending on the current gameplay situation and prioritization of other sound effects.
To be brief, HDR in Wwise can be enabled for any parent Audio Bus in the in the Master-Mixer Hierarchy. Once enabled, the Audio Bus acts as converter between Sound Object volumes at the input of the HDR Bus and full (device) scale at the Output of the same Bus. All sounds that are routed to it are handled relative to each other within the HDR Bus, with the Output of quieter sounds constantly modified according to the Properties of the system. The controls of an HDR Bus are similar to that of a Dynamic Compressor. The Properties of Threshold, Ratio, and Release Time are used to modify the behavior of the project-specified Dynamic Range window. At run-time, the authored system dynamically maps this wide range of levels to a volume range that is more suited to your system's sound output.
In real life, the audible Dynamic Range, defined by the loudest possible sound and the threshold of human hearing is several times wider than the Dynamic Range offered by speakers at gameplay levels. The role of the HDR system is to collapse or compress this real life Dynamic Range into roughly 40 dBSPL (70 dBSPL for TV/Music listening minus 30 dBSPL for the room noise level). The process is a sort of Behavioral Compression. It affects your mix by making soft sounds inaudible as soon as loud sounds play, and then making them audible again when the soft sounds play alone. The relative levels of sounds between one another remain intact and add clarity to the mix by playing fewer sounds.