Android Open Source - APSK Audio Input Thread

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Back to project page APSK.

License

The source code is released under:

GNU General Public License

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Java Source Code

package net.thinkindifferent.apsk;
/*from ww  w. j a  v  a2  s  .  com*/
import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder.AudioSource;
import android.os.Process;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

import org.wa5znu.znuradio.dsp.Subsampler;
import org.wa5znu.znuradio.receiver.WaveHandler;

public class AudioInputThread extends Thread {
  private static AudioRecord audioRecord;
  private static int frameSize;
  private static boolean stopRequested = true;
  private static WaveHandler waveHandler;
  private int deviceSampleRate;
  private byte frameBytes[];
  private double data[];
  private int frame = 0;
  private ByteBuffer frameByteBuffer;
  private Subsampler subsampler;
  private static final int OUTPUT_SAMPLES = 2048;
  
  public AudioInputThread(int outputSampleRate, int deviceSampleRate) {
    this.deviceSampleRate = deviceSampleRate;
    int oversampleRate = deviceSampleRate / outputSampleRate;
    if (outputSampleRate > 1) {
      subsampler = new Subsampler(oversampleRate);
    }
    else if (oversampleRate < 1) {
      throw new RuntimeException("AudioInputThread cannot interpolate: outputSampleRate=" + outputSampleRate + " deviceSampleRate=" + deviceSampleRate);
    }
    frameSize = OUTPUT_SAMPLES * oversampleRate;
    frameBytes = new byte[frameSize * 2];
    frameByteBuffer = ByteBuffer.wrap(frameBytes).order(ByteOrder.LITTLE_ENDIAN);
    data = new double[OUTPUT_SAMPLES * oversampleRate];
    Process.setThreadPriority(Process.THREAD_PRIORITY_AUDIO);
  }
  
  public void start() {
    stopRequested = false;
    audioRecord.startRecording();
    super.start();
  }
  
  public void run() {
    int nInputSamples = data.length;
    while (!stopRequested) {
      frameByteBuffer.clear();
      int bytesRead = audioRecord.read(frameBytes, 0, frameBytes.length);
      if (bytesRead == frameBytes.length) {
        double data[] = new double[nInputSamples];
        for (int n = 0; n < nInputSamples; n++) {
          data[n] = (double)(frameByteBuffer.getShort()) / 32768.0;
        }
        if (subsampler != null)
            data = subsampler.subsample(data, nInputSamples);
        waveHandler.handleWave(frame, data, OUTPUT_SAMPLES);
      }
      frame++;
    }
  }
  
  public boolean startAudio(WaveHandler waveHandler) {
    stopAudio();
    {
      int mono = Integer.parseInt(android.os.Build.VERSION.SDK) < 5 ? AudioFormat.CHANNEL_CONFIGURATION_MONO : AudioFormat.CHANNEL_IN_MONO;
      audioRecord = new AudioRecord(AudioSource.DEFAULT, deviceSampleRate, mono, AudioFormat.ENCODING_PCM_16BIT, 2 * frameBytes.length); // AudioRecord.getMinBufferSize(deviceSampleRate, mono, AudioFormat.ENCODING_PCM_16BIT)
    }
    if (audioRecord == null) {
      return false;
    }
    AudioInputThread.waveHandler = waveHandler;
    start();
    return true;
  }
  
  public void stopAudio() {
    if (stopRequested || audioRecord == null) return;
    stopRequested = true;
    interrupt();
    try {
      join();
    } catch (InterruptedException exp) { }
    audioRecord.stop();
    audioRecord = null;
  }
}

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