session-android/app/src/main/java/org/thoughtcrime/securesms/audio/AudioCodec.java

package org.thoughtcrime.securesms.audio;

import android.annotation.TargetApi;
import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.MediaRecorder;
import android.os.Build;
import org.session.libsignal.utilities.Log;

import org.session.libsession.utilities.Util;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;

@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
public class AudioCodec {

  private static final String TAG = AudioCodec.class.getSimpleName();

  private static final int    SAMPLE_RATE       = 44100;
  private static final int    SAMPLE_RATE_INDEX = 4;
  private static final int    CHANNELS          = 1;
  private static final int    BIT_RATE          = 32000;

  private final int         bufferSize;
  private final MediaCodec  mediaCodec;
  private final AudioRecord audioRecord;

  private boolean running  = true;
  private boolean finished = false;

  public AudioCodec() throws IOException {
    this.bufferSize  = AudioRecord.getMinBufferSize(SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
    this.mediaCodec  = createMediaCodec(this.bufferSize);
    try {
      this.audioRecord = createAudioRecord(this.bufferSize);
      this.mediaCodec.start();
      audioRecord.startRecording();
    } catch (Exception e) {
      Log.w(TAG, e);
      mediaCodec.release();
      throw new IOException(e);
    }
  }

  public synchronized void stop() {
    running = false;
    while (!finished) Util.wait(this, 0);
  }

  public void start(final OutputStream outputStream) {
    new Thread(new Runnable() {
      @Override
      public void run() {
        MediaCodec.BufferInfo bufferInfo         = new MediaCodec.BufferInfo();
        byte[]                audioRecordData    = new byte[bufferSize];
        ByteBuffer[]          codecInputBuffers  = mediaCodec.getInputBuffers();
        ByteBuffer[]          codecOutputBuffers = mediaCodec.getOutputBuffers();

        try {
          while (true) {
            boolean running = isRunning();

            handleCodecInput(audioRecord, audioRecordData, mediaCodec, codecInputBuffers, running);
            handleCodecOutput(mediaCodec, codecOutputBuffers, bufferInfo, outputStream);

            if (!running) break;
          }
        } catch (IOException e) {
          Log.w(TAG, e);
        } finally {
          mediaCodec.stop();
          audioRecord.stop();

          mediaCodec.release();
          audioRecord.release();

          Util.close(outputStream);
          setFinished();
        }
      }
    }, AudioCodec.class.getSimpleName()).start();
  }

  private synchronized boolean isRunning() {
    return running;
  }

  private synchronized void setFinished() {
    finished = true;
    notifyAll();
  }

  private void handleCodecInput(AudioRecord audioRecord, byte[] audioRecordData,
                                MediaCodec mediaCodec, ByteBuffer[] codecInputBuffers,
                                boolean running)
  {
    int length                = audioRecord.read(audioRecordData, 0, audioRecordData.length);
    int codecInputBufferIndex = mediaCodec.dequeueInputBuffer(10 * 1000);

    if (codecInputBufferIndex >= 0) {
      ByteBuffer codecBuffer = codecInputBuffers[codecInputBufferIndex];
      codecBuffer.clear();
      codecBuffer.put(audioRecordData);
      mediaCodec.queueInputBuffer(codecInputBufferIndex, 0, length, 0, running ? 0 : MediaCodec.BUFFER_FLAG_END_OF_STREAM);
    }
  }

  private void handleCodecOutput(MediaCodec mediaCodec,
                                 ByteBuffer[] codecOutputBuffers,
                                 MediaCodec.BufferInfo bufferInfo,
                                 OutputStream outputStream)
      throws IOException
  {
    int codecOutputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);

    while (codecOutputBufferIndex != MediaCodec.INFO_TRY_AGAIN_LATER) {
      if (codecOutputBufferIndex >= 0) {
        ByteBuffer encoderOutputBuffer = codecOutputBuffers[codecOutputBufferIndex];

        encoderOutputBuffer.position(bufferInfo.offset);
        encoderOutputBuffer.limit(bufferInfo.offset + bufferInfo.size);

        if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != MediaCodec.BUFFER_FLAG_CODEC_CONFIG) {
          byte[] header = createAdtsHeader(bufferInfo.size - bufferInfo.offset);


          outputStream.write(header);

          byte[] data = new byte[encoderOutputBuffer.remaining()];
          encoderOutputBuffer.get(data);
          outputStream.write(data);
        }

        encoderOutputBuffer.clear();

        mediaCodec.releaseOutputBuffer(codecOutputBufferIndex, false);
      }  else if (codecOutputBufferIndex== MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
        codecOutputBuffers = mediaCodec.getOutputBuffers();
      }

      codecOutputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
    }

  }

  private byte[] createAdtsHeader(int length) {
    int    frameLength = length + 7;
    byte[] adtsHeader  = new byte[7];

    adtsHeader[0]  = (byte) 0xFF; // Sync Word
    adtsHeader[1]  = (byte) 0xF1; // MPEG-4, Layer (0), No CRC
    adtsHeader[2]  = (byte) ((MediaCodecInfo.CodecProfileLevel.AACObjectLC - 1) << 6);
    adtsHeader[2] |= (((byte) SAMPLE_RATE_INDEX) << 2);
    adtsHeader[2] |= (((byte) CHANNELS) >> 2);
    adtsHeader[3]  = (byte) (((CHANNELS & 3) << 6) | ((frameLength >> 11) & 0x03));
    adtsHeader[4]  = (byte) ((frameLength >> 3) & 0xFF);
    adtsHeader[5]  = (byte) (((frameLength & 0x07) << 5) | 0x1f);
    adtsHeader[6]  = (byte) 0xFC;

    return adtsHeader;
  }

  private AudioRecord createAudioRecord(int bufferSize) throws SecurityException {
    return new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE,
                           AudioFormat.CHANNEL_IN_MONO,
                           AudioFormat.ENCODING_PCM_16BIT, bufferSize * 10);
  }

  private MediaCodec createMediaCodec(int bufferSize) throws IOException {
    MediaCodec  mediaCodec  = MediaCodec.createEncoderByType("audio/mp4a-latm");
    MediaFormat mediaFormat = new MediaFormat();

    mediaFormat.setString(MediaFormat.KEY_MIME, "audio/mp4a-latm");
    mediaFormat.setInteger(MediaFormat.KEY_SAMPLE_RATE, SAMPLE_RATE);
    mediaFormat.setInteger(MediaFormat.KEY_CHANNEL_COUNT, CHANNELS);
    mediaFormat.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, bufferSize);
    mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, BIT_RATE);
    mediaFormat.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);

    try {
      mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
    } catch (Exception e) {
      Log.w(TAG, e);
      mediaCodec.release();
      throw new IOException(e);
    }

    return mediaCodec;
  }

}