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/*
* Copyright (C) 2016 Andrew Comminos <andrew@comminos.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.morlunk.jumble.audio.inputmode;
/**
* An input mode that sends audio if the amplitude exceeds a certain threshold.
* Created by andrew on 13/02/16.
*/
public class ActivityInputMode implements IInputMode {
// Continue speech for 250ms to prevent dropping.
private static final int SPEECH_DELAY = (int) (0.25 * Math.pow(10, 9));
private final float mVADThreshold;
private long mVADLastDetected;
public ActivityInputMode(float detectionThreshold) {
mVADThreshold = detectionThreshold;
}
@Override
public boolean onInputReceived(short[] pcm, int length) {
// Use a logarithmic energy-based scale for VAD.
float sum = 1.0f;
for (int i = 0; i < length; i++) {
sum += pcm[i] * pcm[i];
}
float micLevel = (float) Math.sqrt(sum / (float)length);
float peakSignal = (float) (20.0f * Math.log10(micLevel / 32768.0f)) / 96.0f;
boolean talking = (peakSignal + 1) >= mVADThreshold;
talking |= (System.nanoTime() - mVADLastDetected) < SPEECH_DELAY;
// Record the last time where VAD was detected in order to prevent speech dropping.
if(talking) {
mVADLastDetected = System.nanoTime();
}
return talking;
}
}
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