Aura is a fast and lightweight 3D audio engine for Kha to ease creating realistic sound atmospheres for your games and applications.

Table of Content

• Features
• Setup
• Usage
• Platform Support
• License

Features

• Multiple attenuation models for 3D sound
• Mix channels for modifying groups of sounds together
• Doppler effect
• Noise generator channels
• Built-in DSP filters:
  • High-/band-/lowpass filter
  • Haas effect
  • Per-channel source effects, e.g. to generate variations using Velvet noise (original paper)
• Extendable DSP system – easily write your own filters
• [Experimental] Support for HRTFs (head-related transfer functions)

Setup

1. In your project directory, create a folder called Subprojects.

2. Open a command line in that folder and execute the following command (Git must be installed on your machine):

   git clone https://github.com/MoritzBrueckner/aura.git

3. Add the following line to your project's khafile.js (if you're using Armory 3D, you can skip this step):

   await project.addProject("Subprojects/aura");

4. [Optional] If you're using Iron, but not Armory 3D, please also add the following to your Khafile to be able to use Iron's vector classes with Aura:

   project.addDefine("AURA_WITH_IRON");

Usage

• Load sounds (and automatically uncompress them when needed):

  import aura.Aura;
  
  ...
  
  Aura.init(); // <-- Don't forget this!
  
  var loadConfig: AuraLoadConfig = {
      // List of sounds to uncompress
      uncompressed: ["MySoundFile"],
  
      // List of sounds to remain compressed
      compressed: ["AnotherSoundFile"],
  
      // List of .mhr HRTF files for the HRTFPanner, if used (empty lists can be omitted)
      hrtf: ["myHRTF_mhr"],
  };
  
  Aura.loadSounds(loadConfig, () -> {
      // Access a loaded sound
      var mySound: kha.Sound = Aura.getSound("MySoundFile");
  });

  Note
  Instead of referencing sounds by hard-coded names (like it is done in the above example), you can also rely on Kha's asset system and use the IDE's autocompletion for assistance:

  kha.Assets.sounds.MySoundFileName; // Note the "Name" ending. This will give you the ID name for this sound
  kha.Assets.blobs.myHRTF_mhrName;   // The same works for blobs and all other asset types

  As a positive side effect, there will be errors during compile time if an asset does not exist.

• Play a sound:

  // Plays the uncompressed sound `mySound` without repeat on the master channel
  Aura.createUncompBufferChannel(mySound).play();
  
  // Plays the uncompressed sound `mySound` with repeat on the master channel
  Aura.createUncompBufferChannel(mySound, true).play();
  
  // Plays the uncompressed sound `mySound` without repeat on the predefined fx channel
  Aura.createUncompBufferChannel(mySound, false, Aura.mixChannels["fx"]).play();

  You can also play audio from compressed sounds without having to uncompress them first (Kha calls this "streaming"). This is useful for longer sounds such as background music, they need less memory and load faster if they do not need to be uncompressed, but on the other side this is more computationally demanding than playing uncompressed sounds. Whether a sound can be streamed highly depends on the target, please consult the Kha sources if in doubt.

  Aura.createCompBufferChannel(mySound, false, Aura.mixChannels["music"]).play();

  Both Aura.createUncompBufferChannel() and Aura.createCompBufferChannel() return so-called handle objects with which you can control channel playback and relevant parameters.

• Create a MixChannelHandle to control a group of sounds:

  // Create a channel for all voices for example and store a handle to it in `voiceChannel`.
  // The channel can also be accessed with `Aura.mixChannels["voice"]`
  var voiceChannel = Aura.createMixChannel("voice");
  
  // Mix the output of `voiceChannel` into the master channel
  voiceChannel.setMixChannel(Aura.masterChannel);
  
  // Create a new channel handle for `mySound` and mix the output of that channel into the voice mix channel
  Aura.createUncompBufferChannel(mySound, false, voiceChannel).play();

• Add a lowpass filter to the master channel:

  import aura.dsp.Filter;
  
  ...
  
  Aura.createUncompBufferChannel(mySound).play();
  
  var lowPass = new Filter(LowPass);
  lowPass.setCutoffFreq(1000); // Frequency in Hertz
  
  // Aura.masterChannel is short for Aura.mixChannels["master"]
  Aura.masterChannel.addInsert(lowPass);
  

• 2D sound:

  import aura.dsp.panner.StereoPanner;
  
  ...
  
  var mySoundHandle = Aura.createUncompBufferChannel(mySound);
  var panner = StereoPanner(mySoundHandle);
  
  // Some utility constants
  panner.setBalance(LEFT);
  panner.setBalance(CENTER); // Default
  panner.setBalance(RIGHT);
  
  // Set angle in degrees between -90 (left) and 90 (right)
  // You can also use Rad(value) for radians in [-pi/2, pi/2]
  panner.setBalance(Deg(30));

• 3D sound:

  import aura.dsp.panner.HRTFPanner;
  import aura.dsp.panner.StereoPanner;
  
  ...
  
  var mySoundHandle = Aura.createUncompBufferChannel(mySound);
  
  // Create a panner for the sound handle (choose one)
  new StereoPanner(channel); // Simple left-right panner
  new HRTFPanner(channel, Aura.getHRTF("myHRTF_mhr"));  // More realistic panning using head-related transfer functions, but slower to calculate
  
  // Set the 3D location and view direction of the listener
  var cam = getCurrentCamera(); // <-- dummy function
  Aura.listener.set(cam.worldPosition, cam.look, cam.right);
  
  // Set the 3D location of the sound independent of the math API used
  mySoundHandle.panner.setLocation(new kha.math.FastVector3(-1.0, 1.0, 0.2));
  mySoundHandle.panner.setLocation(new iron.math.Vec3(-1.0, 1.0, 0.2));
  mySoundHandle.panner.setLocation(new aura.math.Vec3(-1.0, 1.0, 0.2));
  
  // Apply the changes to the sound to make them audible (!)
  mySoundHandle.panner.update3D();
  
  // Switch back to 2D sound. The sound's saved location will not be reset, but
  // you won't hear it at that location anymore. The panner however still exists
  // and can be re-enabled via update3D().
  mySoundHandle.panner.reset3D();

  Aura's own Vec3 type can be implicitly converted from and to Kha or Iron vectors (3D and 4D)!

Platform Support

Thanks to Haxe and Kha, Aura runs almost everywhere!

The following targets were tested so far:

Target	Tested environments	Supported	Notes
Armorcore (Krom)	Windows 10	✔
HTML5	Electron, Firefox	✔	- No dedicated audio thread for non-streaming playback - If kha.SystemImpl.mobileAudioPlaying is true, streamed playback is not included in the Aura mix pipeline (no DSP etc.)
Hashlink/C	Windows 10	✔
hxcpp	Windows 10	✔

License

This work is licensed under multiple licences, which are specified at .reuse/dep5 (complying to the REUSE recommendations). The license texts can be found in the LICENSES directory, or in case of submodules in their respective repositories.

Short summary:

• The entire source code in Sources/aura is licensed under the Zlib license which is a very permissive license also used by Kha and Armory at the time of writing this. This is the important license for you if you include Aura code in your project.
• This readme file and other configuration files are licensed under CC0-1.0.
• All files in .img/ are licensed under CC-BY-4.0.