AudioCue

AudioCue is a Java resource for playing sound files, designed for use with game programming.

Why?

Java's Clip class (javax.audio.sampled.Clip) was not designed with the special needs of game audio in mind. The class has a tricky, non-intuitive syntax and a limited feature set. A Clip cannot be played concurrently with itself, can only be played at its recorded pitch, and the Control class provided for real time changes such as panning and volume is system-dependent and limited to only allowing changes at buffer increments.

AudioCue addresses these issues:

• Easy to Use

  • Very light: Download or copy/paste five class files from GitHub directly into your project.
  • Syntax is simpler than Java's Clip class.
  • API and demonstration programs provided.

• Powerful

  • Runs directly on Java's SourceDataLine.
  • Supports playback of PCM (signed, stereo floats) and WAV (16-bit, 44100 fps, stereo, little-endian)
  • Allows concurrent playback of cues.
  • Allows playback at varying speeds.
  • Supports real-time volume, panning and frequency changes.
  • Highly configurable.
  • Includes messaging system for coordination with graphics.

• BSD License (open source, free)

• Now includes AudioMixer for consolidating AudioCues into a single output line.

NOTE: AudioCue may not be the best choice for your project if one of the following limitations apply:

• AudioCue only supports one output format: 16-bit, 44100fps, stereo, little-endian (aka CD Quality).
• Compressed audio formats are not currently supported. As a work-around, if you are able to use another library to decompress your audio to PCM data as normalized stereo floats (data range -1 to 1, left then right), AudioCue will accept that array as input.
• This is not a 3D audio system. Major elements like delay-based panning, distance attenuation, Doppler effects, are not implemented.

Comparison of Clip Alternatives

Demo Jars (including source code):

SlidersDemo allows you three concurrent playbacks of a .wav of a bell. Sliders provided alter pitch, volume and panning in real time. A playback using Java Clip is provided for comparison purposes. FrogPondDemo creates a soundscape of many frogs from a single croak I recorded at nearby El Cerrito Creek. BattleFieldDemo creates a soundscape of fighting in a war zone, from a wav of a single gunshot (slight cheat: the machine gun uses an Audacity edit of the same gunshot that trims the decay a bit).

Installation via Gradle

Gradle (Maven, Sbt, Leiningen)

• Add in your root build.gradle at the end of repositories:

  allprojects {
   repositories {
       ...
       maven { url 'https://jitpack.io' }
   }
  }
  

• Add the dependency

  dependencies {
   compile 'com.github.philfrei:AudioCue:-SNAPSHOT' 
  }
  

Manual Installation

AudioCue requires five files:

• AudioCue.java
• AudioCueInstanceEvent.java
• AudioCueListener.java
• AudioMixer.java
• AudioMixerTrack.java

In addition, there are two optional file folders with demo content and resources used by the demo programs:

• supportpack
• supportpack.res

Manual installation involves copying and pasting the five files into your project.

• Method 1) navigate to, then copy and paste the five files directly into your program.
• Method 2) download audiocue.jar, which includes source code, the "supportpack" and "res" content, and import into your IDE. [NOTE: I'm not clear if the .jar file, which I generated from Eclipse on 11/10/2017, can be imported into other IDEs. If run, the .jar file executes a program that demonstrates the real time capabilities.]

Maven alternative

A Maven-based alternative is now available. The project has been split into two parts. For the core tool, see AudioCue-maven, and for the supporting demonstration code, see audiocue-demo.

Usage

// Simple case example ("fire-and-forget" playback):
// assumes sound file "myAudio.wav" exists in same file folder,
// we will allow up to four concurrent instances.

// Preparatory steps (do these prior to playback): 
URL url = this.getClass().getResource("myAudio.wav");
AudioCue myAudioCue = AudioCue.makeStereoCue(url, 4); //allows 4 concurrent
myAudioCue.open();  // see API for parameters to override "sound thread" configuration defaults

// For playback, normally done on demand:
myAudioCue.play();  // see API for parameters to override default vol, pan, pitch 

// release resources when sound is no longer needed
myAudioCue.close();

Usage: real time controls

An important feature of AudioCode is the the ability to drill down to individual playing instances of a cue and alter properties in real time. To drill down to a specific instance, we can use one of two methods to capture an int handle that will identify the instance. The first is to capture the return value of the play method, as follows:

int handle = myAudioCue.play(); 

Another way is to directly poll a handle from the pool of available instances, as follows:

int handle = myAudioCue.obtainInstance(); 

An instance that is obtained in the second manner must be directly started, stopped, and released (returned to the pool of available instances).

myAudioCue.start(handle); // to start an instance
myAudioCue.stop(handle);  // to stop an instance
myAudioCue.release(handle); // to return the instance to available pool

An important distinction between an instance handle gotten from a play() method and the obtainInstance() method is that the default value of a boolean field recycleWhenDone differs. An instance arising from play() has this value set to true, and an instance arising from obtainInstance() has this value set to false. When an instance finishes playing, if the boolean recycleWhenDone is true, the instance is automatically returned to the pool of available instances and no longer available for updating. If the value is false, properties of the instance can continue to be updated, and the instance can be repositioned and restarted.

Properties that can be altered for an instance include the following:

//*volume*: 
myAudioCue.setVolume(handle, value); // double ranging from 0 (silent)
                                     // to 1 (full volume)
//*panning*: 
myAudioCue.setPan(handle, value); // double ranging from -1 (full left)
                                  // to 1 (full right)
//*speed of playback*: 
myAudioCue.setSpeed(handle, value); // value is a factor, 
                  // multiplied against the normal playback rate, e.g.,
                  // 2 will double playback speed, 0.5 will halve it 
//*position*:
myAudioCue.setFramePosition(handle, frameNumber);
myAudioCue.setMillisecondPosition(handle, int); // position in millis
myAudioCue.setsetFractionalPosition(int, double); // position as a fraction of whole cue,
                                                // where 0 = first frame, 1 = last frame

Usage: output configuration

Output configuration occurs with the AudioCue's open() method. The default configuration will use Java AudioSystem's (javax.sound.sampled.AudioSystem) default Mixer and SourceDataLine, a 1024 frame buffer, and the highest available thread priority. (A high thread priority should not affect performance of the rest of an application, as the audio thread should spend the vast majority of its time in a blocked state.) The buffer size can be set to optimize the balance between latency and dropouts. For example, a longer cue, used to play many concurrent instances might require a larger buffer in order to minimize dropouts.

You can override the output line defaults via using an alternate form of the open() method. For example:

myAudioCue.open(mixer, bufferFrames, threadPriority); // where mixer is javax.sound.sampled.Mixer

Each AudioCue can have its own optimized configuration, and will be output on its own SourceDataLine line, similar to the way that each Java Clip consumes an output line.

Usage: Outputting via AudioMixer

Alternatively, the output of an AudioCue can be directed to an AudioMixer, which is part of this package. All inputs to an AudioMixer are merged and sent out on a single SourceDataLine. This can be especially helpful for systems that have a limited number of output lines.

myAudioCue.open(myAudioMixer); 

The AudioMixer can also be configured for javax.sound.sampled.Mixer, buffer size (the default is 8192 frames), and thread priority. Any AudioCue routed through an AudioMixer will automatically be use the AudioMixer's configuration properties. AudioCues can be added or removed from the AudioMixer while the AudioMixer is playing. Pending track additions and removals are handled at the start of each iteration of the buffer.

In the following example, we create and start an AudioMixer, add an AudioCue track, play the cue, then shut it all down.

AudioMixer audioMixer = new AudioMixer();
audioMixer.start();
// At this point, AudioMixer will create and start a runnable and will
// actively output 'silence' (zero values) on its SourceDataLine. 

URL url = this.getClass().getResource("myAudio.wav");
AudioCue myAudioCue = AudioCue.makeStereoCue(url, 1); 
myAudioCue.open(mixer); 
// The open method will handle adding the AudioCue to
// the AudioMixer.

myAudioCue.play(); 
Thread.sleep(2000); // Allow cue to finish (assuming
                    // cue is shorter than 2 seconds)
myAudioCue.close(); // will remove AudioCue from the mix                    
audioMixer.stop();  // AudioMixer will stop outputting and will
                    // close the runnable in an 'orderly' manner.

Usage: Additional examples and test files

Additional examples and test files can be found in the supportpack package. The SlidersTest demonstrates real time controls, via GUI sliders. The BattleField and FrogPond show techniques for building rich soundscapes from a minimum of resources, by taking advantage of the volume, pitch, and pan parameters to make a single cue provide the illusion of many individual entities. The AudioCueListener, which broadcasts events such as starting, looping or stopping, is also demonstrated.

These demo programs can be downloaded and run via the following jar files:

• SlidersTest.jar showing real-time controls, alongside a Clip for comparison
• FrogPond.jar built from a single frog.wav file
• Battlefield.jar built from two gunshot wavs

DONATE

It would be great to hear (by email or by donation) if AudioCue has been helpful. Positive feedback is very motivating, and much appreciated!

I'm happy to list links to games or game-makers using AudioCue.

Contact Info

Programmer/Sound-Designer/Composer: Phil Freihofner

URL: http://adonax.com

Email: phil AT adonax.com

Recommended forum: https://jvm-gaming.org/c/java-sound-amp-openal/12

If using StackOverflow for a question about this code, chances are highest that I will eventually see it if you include the tag "javasound".