plectrum

Plectrum: instrument tuner for Android
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Goertzel.java (4535B)

      1 /*
      2 *      _______                       _____   _____ _____  
      3 *     |__   __|                     |  __ \ / ____|  __ \ 
      4 *        | | __ _ _ __ ___  ___  ___| |  | | (___ | |__) |
      5 *        | |/ _` | '__/ __|/ _ \/ __| |  | |\___ \|  ___/ 
      6 *        | | (_| | |  \__ \ (_) \__ \ |__| |____) | |     
      7 *        |_|\__,_|_|  |___/\___/|___/_____/|_____/|_|     
      8 *                                                         
      9 * -------------------------------------------------------------
     10 *
     11 * TarsosDSP is developed by Joren Six at IPEM, University Ghent
     12 *  
     13 * -------------------------------------------------------------
     14 *
     15 *  Info: http://0110.be/tag/TarsosDSP
     16 *  Github: https://github.com/JorenSix/TarsosDSP
     17 *  Releases: http://0110.be/releases/TarsosDSP/
     18 *  
     19 *  TarsosDSP includes modified source code by various authors,
     20 *  for credits and info, see README.
     21 * 
     22 */
     23 
     24 
     25 package be.tarsos.dsp.pitch;
     26 
     27 import be.tarsos.dsp.AudioEvent;
     28 import be.tarsos.dsp.AudioProcessor;
     29 
     30 /**
     31  * Contains an implementation of the Goertzel algorithm. It can be used to
     32  * detect if one or more predefined frequencies are present in a signal. E.g. to
     33  * do DTMF decoding.
     34  * 
     35  * @author Joren Six
     36  */
     37 public class Goertzel implements AudioProcessor {
     38 
     39 	/**
     40 	 * If the power in dB is higher than this threshold, the frequency is
     41 	 * present in the signal.
     42 	 */
     43 	private static final double POWER_THRESHOLD = 35;// in dB
     44 
     45 	/**
     46 	 * A list of frequencies to detect.
     47 	 */
     48 	private final double[] frequenciesToDetect;
     49 	/**
     50 	 * Cached cosine calculations for each frequency to detect.
     51 	 */
     52 	private final double[] precalculatedCosines;
     53 	/**
     54 	 * Cached wnk calculations for each frequency to detect.
     55 	 */
     56 	private final double[] precalculatedWnk;
     57 	/**
     58 	 * A calculated power for each frequency to detect. This array is reused for
     59 	 * performance reasons.
     60 	 */
     61 	private final double[] calculatedPowers;
     62 
     63 	private final FrequenciesDetectedHandler handler;
     64 
     65 	public Goertzel(final float audioSampleRate, final int bufferSize,
     66 			double[] frequencies, FrequenciesDetectedHandler handler) {
     67 
     68 		frequenciesToDetect = frequencies;
     69 		precalculatedCosines = new double[frequencies.length];
     70 		precalculatedWnk = new double[frequencies.length];
     71 		this.handler = handler;
     72 
     73 		calculatedPowers = new double[frequencies.length];
     74 
     75 		for (int i = 0; i < frequenciesToDetect.length; i++) {
     76 			precalculatedCosines[i] = 2 * Math.cos(2 * Math.PI
     77 					* frequenciesToDetect[i] / audioSampleRate);
     78 			precalculatedWnk[i] = Math.exp(-2 * Math.PI
     79 					* frequenciesToDetect[i] / audioSampleRate);
     80 		}
     81 	}
     82 
     83 	/**
     84 	 * An interface used to react on detected frequencies.
     85 	 * 
     86 	 * @author Joren Six
     87 	 */
     88 	public static interface FrequenciesDetectedHandler {
     89 		/**
     90 		 * React on detected frequencies.
     91 		 * 
     92 		 * @param frequencies
     93 		 *            A list of detected frequencies.
     94 		 * @param powers
     95 		 *            A list of powers of the detected frequencies.
     96 		 * @param allFrequencies
     97 		 *            A list of all frequencies that were checked.
     98 		 * @param allPowers
     99 		 *            A list of powers of all frequencies that were checked.
    100 		 */
    101 		void handleDetectedFrequencies(final double timestamp,final double[] frequencies,
    102 				final double[] powers, final double[] allFrequencies,
    103 				final double allPowers[]);
    104 	}
    105 
    106 	@Override
    107 	public boolean process(AudioEvent audioEvent) {
    108 		float[] audioFloatBuffer = audioEvent.getFloatBuffer();
    109 		double skn0, skn1, skn2;
    110 		int numberOfDetectedFrequencies = 0;
    111 		for (int j = 0; j < frequenciesToDetect.length; j++) {
    112 			skn0 = skn1 = skn2 = 0;
    113 			for (int i = 0; i < audioFloatBuffer.length; i++) {
    114 				skn2 = skn1;
    115 				skn1 = skn0;
    116 				skn0 = precalculatedCosines[j] * skn1 - skn2
    117 						+ audioFloatBuffer[i];
    118 			}
    119 			double wnk = precalculatedWnk[j];
    120 			calculatedPowers[j] = 20 * Math.log10(Math.abs(skn0 - wnk * skn1));
    121 			if (calculatedPowers[j] > POWER_THRESHOLD) {
    122 				numberOfDetectedFrequencies++;
    123 			}
    124 		}
    125 
    126 		if (numberOfDetectedFrequencies > 0) {
    127 			double[] frequencies = new double[numberOfDetectedFrequencies];
    128 			double[] powers = new double[numberOfDetectedFrequencies];
    129 			int index = 0;
    130 			for (int j = 0; j < frequenciesToDetect.length; j++) {
    131 				if (calculatedPowers[j] > POWER_THRESHOLD) {
    132 					frequencies[index] = frequenciesToDetect[j];
    133 					powers[index] = calculatedPowers[j];
    134 					index++;
    135 				}
    136 			}
    137 			handler.handleDetectedFrequencies(audioEvent.getTimeStamp(),frequencies, powers,
    138 					frequenciesToDetect.clone(), calculatedPowers.clone());
    139 		}
    140 
    141 		return true;
    142 	}
    143 
    144 
    145 
    146 	@Override
    147 	public void processingFinished() {
    148 	}
    149 
    150 }