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Implementation of generative audio for haxe/NME3/android
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README.md

nme-android-dynamicsound

Implementation of generative audio for haxe+NME3+android

Current version: 0.1.0

This native extension for haxe NME implements generative audio for android target by wrapping AudioTrack API.

Curent limitations

  • only one DynamicSound object at a time (don't sure if an issue, AudioTrack API is rather slow)
  • listener is called from separate thread, writing a thread safe code could be tricky
  • android only ;) flash is rather an inconsistent model for unified generative sound api
  • example application doesn't implement fade out to zero volume on note release, so it has clicks and sounds unconvincing.

Known issues

  • synchronization error with following thread crash on slow devices and/or low buffer sizes (typical for Acer Liquid) possibly API should have ability to change sample rate or auto-downsample

Usage

Reference the extension in your .nmml:

<extension name="DynamicSound" path="path/to/nme-android-dynamic/Extension" />

Add imports:

import com.github.scythianfuego.DynamicSound;
import com.github.scythianfuego.DynamicSoundDataEvent;

Create a new DynamicSound object:

var s = new DynamicSound();

Request a minimal buffer size (device dependent) or set your own. The buffer must be set before starting playback.

var buffer_size = s.getBufferSize();  // minimal possible buffer

or

var buffer_size = 2400;               //should be greater than the minimal one
s.setBufferSize(buffer_size); 

Buffer size is set in samples, for one out of two channels. Real buffer size on the android device will be buffer_size * 2 (16bit) * 2 (stereo) bytes.

Add a listener of DynamicSoundDataEvent (it is NOT a subclass of nme.Event) The event.data property is an Array, because current ByteArray implementation in haxe NME is too slow to use original SampleDataEvent:

var listener = function(event : DynamicSoundDataEvent) {
  for ( i in 0...buffer_size ) {  
    event.data.push(...);   //left  channel, float -1.0 to 1.0
    event.data.push(...);   //right channel, float -1.0 to 1.0
  }
}
s.listen(listener);  

Note that the listener will be called from a separate thread, so you will have to use synchronization primitives, mutex for example (have a look at http://haxe.org/api/cpp/vm/thread API) to pass data between render thread and sound generator thread. The listener should process a chunk of data faster than playback consumes it, underruns (and rather possibly crashes) could be expected otherwise.

Control playback:

s.play();
s.stop();

The stop() function makes sound threads wait in thread lock instead of stopping them. If you want to stop API completely, release threads and resources using

s.shutdown();	

Note that DynamicSound object is not valid after this action, you'll have to recreate it to use again.

Running the test application

build.bat on Windows

or

cd Project
haxelib run nme test soundupdate.nmml android

Recompiling the extension

cd Extension\project
haxelib run hxcpp Build.xml -Dandroid

License:

This extension and example provided under the main haxe NME project license.

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