plectrum

Plectrum: instrument tuner for Android
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DTMF.java (4402B)

      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 /**
     28  * Utility class to generate Dual-tone multi-frequency (DTMF) signaling tones.
     29  * This class also contains a list of valid DTMF frequencies and characters.
     30  * 
     31  * See the <a href="http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling"
     32  * >WikiPedia article on DTMF</a>.
     33  * 
     34  * @author Joren Six
     35  */
     36 public class DTMF {
     37 
     38 	/**
     39 	 * The list of valid DTMF frequencies. See the <a
     40 	 * href="http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling"
     41 	 * >WikiPedia article on DTMF</a>.
     42 	 */
     43 	public static final double[] DTMF_FREQUENCIES = { 697, 770, 852, 941, 1209,
     44 			1336, 1477, 1633 };
     45 
     46 	/**
     47 	 * The list of valid DTMF characters. See the <a
     48 	 * href="http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling"
     49 	 * >WikiPedia article on DTMF</a> for the relation between the characters
     50 	 * and frequencies.
     51 	 */
     52 	public static final char[][] DTMF_CHARACTERS = { { '1', '2', '3', 'A' },
     53 			{ '4', '5', '6', 'B' }, { '7', '8', '9', 'C' },
     54 			{ '*', '0', '#', 'D' } };
     55 
     56 	/**
     57 	 * Generate a DTMF - tone for a valid DTMF character. 
     58 	 * @param character a valid DTMF character (present in DTMF_CHARACTERS}
     59 	 * @return a float buffer of predefined length (7168 samples) with the correct DTMF tone representing the character.
     60 	 */
     61 	public static float[] generateDTMFTone(char character){
     62 		double firstFrequency = -1;
     63 		double secondFrequency = -1;
     64 		for(int row = 0 ; row < DTMF_CHARACTERS.length ; row++){
     65 			for(int col = 0 ; col < DTMF_CHARACTERS[row].length ; col++){
     66 				if(DTMF_CHARACTERS[row][col] == character){
     67 					firstFrequency = DTMF_FREQUENCIES[row];
     68 					secondFrequency = DTMF_FREQUENCIES[col + 4];
     69 				}
     70 			}
     71 		}
     72 		return DTMF.audioBufferDTMF(firstFrequency,secondFrequency,512*2*10);
     73 	}
     74 	
     75 	/**
     76 	 * Checks if the given character is present in DTMF_CHARACTERS.
     77 	 * 
     78 	 * @param character
     79 	 *            the character to check.
     80 	 * @return True if the given character is present in
     81 	 *         DTMF_CHARACTERS, false otherwise.
     82 	 */
     83 	public static boolean isDTMFCharacter(char character){
     84 		double firstFrequency = -1;
     85 		double secondFrequency = -1;
     86 		for(int row = 0 ; row < DTMF_CHARACTERS.length ; row++){
     87 			for(int col = 0 ; col < DTMF_CHARACTERS[row].length ; col++){
     88 				if(DTMF_CHARACTERS[row][col] == character){
     89 					firstFrequency = DTMF_FREQUENCIES[row];
     90 					secondFrequency = DTMF_FREQUENCIES[col + 4];
     91 				}
     92 			}
     93 		}
     94 		return (firstFrequency!=-1 && secondFrequency!=-1);
     95 	}
     96 
     97 	/**
     98 	 * Creates an audio buffer in a float array of the defined size. The sample
     99 	 * rate is 44100Hz by default. It mixes the two given frequencies with an
    100 	 * amplitude of 0.5.
    101 	 * 
    102 	 * @param f0
    103 	 *            The first fundamental frequency.
    104 	 * @param f1
    105 	 *            The second fundamental frequency.
    106 	 * @param size
    107 	 *            The size of the float array (sample rate is 44.1kHz).
    108 	 * @return An array of the defined size.
    109 	 */
    110 	public static float[] audioBufferDTMF(final double f0, final double f1,
    111 			int size) {
    112 		final double sampleRate = 44100.0;
    113 		final double amplitudeF0 = 0.4;
    114 		final double amplitudeF1 = 0.4;
    115 		final double twoPiF0 = 2 * Math.PI * f0;
    116 		final double twoPiF1 = 2 * Math.PI * f1;
    117 		final float[] buffer = new float[size];
    118 		for (int sample = 0; sample < buffer.length; sample++) {
    119 			final double time = sample / sampleRate;
    120 			double f0Component = amplitudeF0 * Math.sin(twoPiF0 * time);
    121 		    double f1Component = amplitudeF1 * Math.sin(twoPiF1 * time);
    122 		    buffer[sample] = (float) (f0Component + f1Component);
    123 		}
    124 		return buffer;
    125 	}
    126 }