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TarsosDSP library
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/*
*      _______                       _____   _____ _____  
*     |__   __|                     |  __ \ / ____|  __ \ 
*        | | __ _ _ __ ___  ___  ___| |  | | (___ | |__) |
*        | |/ _` | '__/ __|/ _ \/ __| |  | |\___ \|  ___/ 
*        | | (_| | |  \__ \ (_) \__ \ |__| |____) | |     
*        |_|\__,_|_|  |___/\___/|___/_____/|_____/|_|     
*                                                         
* -------------------------------------------------------------
*
* TarsosDSP is developed by Joren Six at IPEM, University Ghent
*  
* -------------------------------------------------------------
*
*  Info: http://0110.be/tag/TarsosDSP
*  Github: https://github.com/JorenSix/TarsosDSP
*  Releases: http://0110.be/releases/TarsosDSP/
*  
*  TarsosDSP includes modified source code by various authors,
*  for credits and info, see README.
* 
*/


package be.tarsos.dsp;


/**
 * The continuing silence detector does not break the audio processing pipeline when silence is detected.
 */
public class SilenceDetector implements AudioProcessor {
	
	public static final double DEFAULT_SILENCE_THRESHOLD = -70.0;//db
	
	private final double threshold;//db
	
	private final boolean breakProcessingQueueOnSilence;
	
	/**
	 * Create a new silence detector with a default threshold.
	 */
	public SilenceDetector(){
		this(DEFAULT_SILENCE_THRESHOLD,false);
	}
	
	/**
	 * Create a new silence detector with a defined threshold.
	 * 
	 * @param silenceThreshold
	 *            The threshold which defines when a buffer is silent (in dB).
	 *            Normal values are [-70.0,-30.0] dB SPL.
	 * @param breakProcessingQueueOnSilence 
	 */
	public SilenceDetector(final double silenceThreshold,boolean breakProcessingQueueOnSilence){
		this.threshold = silenceThreshold;
		this.breakProcessingQueueOnSilence = breakProcessingQueueOnSilence;
	}

	/**
	 * Calculates the local (linear) energy of an audio buffer.
	 * 
	 * @param buffer
	 *            The audio buffer.
	 * @return The local (linear) energy of an audio buffer.
	 */
	private double localEnergy(final float[] buffer) {
		double power = 0.0D;
		for (float element : buffer) {
			power += element * element;
		}
		return power;
	}

	/**
	 * Returns the dBSPL for a buffer.
	 * 
	 * @param buffer
	 *            The buffer with audio information.
	 * @return The dBSPL level for the buffer.
	 */
	private double soundPressureLevel(final float[] buffer) {
		double value = Math.pow(localEnergy(buffer), 0.5);
		value = value / buffer.length;
		return linearToDecibel(value);
	}

	/**
	 * Converts a linear to a dB value.
	 * 
	 * @param value
	 *            The value to convert.
	 * @return The converted value.
	 */
	private double linearToDecibel(final double value) {
		return 20.0 * Math.log10(value);
	}
	
	double currentSPL = 0;
	public double currentSPL(){
		return currentSPL;
	}

	/**
	 * Checks if the dBSPL level in the buffer falls below a certain threshold.
	 * 
	 * @param buffer
	 *            The buffer with audio information.
	 * @param silenceThreshold
	 *            The threshold in dBSPL
	 * @return True if the audio information in buffer corresponds with silence,
	 *         false otherwise.
	 */
	public boolean isSilence(final float[] buffer, final double silenceThreshold) {
		currentSPL = soundPressureLevel(buffer);
		return currentSPL < silenceThreshold;
	}

	public boolean isSilence(final float[] buffer) {
		return isSilence(buffer, threshold);
	}


	@Override
	public boolean process(AudioEvent audioEvent) {
		boolean isSilence = isSilence(audioEvent.getFloatBuffer());
		//break processing chain on silence?
		if(breakProcessingQueueOnSilence){
			//break if silent
			return !isSilence;
		}else{
			//never break the chain
			return true;
		}
	}


	@Override
	public void processingFinished() {
	}
}