RaopServer.java

package de.debugco.jairport;

import com.beatofthedrum.alacdecoder.AlacDecodeUtils;
import com.beatofthedrum.alacdecoder.AlacFile;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.SourceDataLine;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketAddress;

public class RaopServer extends Thread {
  private RaopSession session;
  private int port;
  private DatagramSocket receiveSocket;
  private Cipher aesCipher;
  private SecretKeySpec secretKey;
  private IvParameterSpec keySpec;
  private SocketAddress clientSocketAddress;
  private AlacFile alac;
  private SourceDataLine line;
  private int[] outbuffer;
  private byte[] outbufferBytes;

  public RaopServer(RaopSession session) {
    super("RaopServer " + session.getId());

    this.port = session.getControlPort() - 1;
    this.session = session;
    try {
      this.aesCipher = Cipher.getInstance("AES/CBC/NOPADDING");
      receiveSocket = new DatagramSocket(port);

      DataLine.Info info = new DataLine.Info(SourceDataLine.class, new AudioFormat(session.getFormat().getSampleRate(), session.getFormat().getSampleSize(), 2, true, true));
      line = (SourceDataLine) AudioSystem.getLine(info);
      line.open();
      line.start();
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
    secretKey = new SecretKeySpec(session.getAesKey(), "AES");
    secretKey = new SecretKeySpec(session.getAesKey(), "AES");
    keySpec = new IvParameterSpec(session.getAesIv());

    int frameSize = session.getFormat().getFrameSize();
    alac = AlacDecodeUtils.create_alac(session.getFormat().getSampleSize(), 2);
    alac.setSetinfo_max_samples_per_frame(frameSize);
    alac.setSetinfo_rice_historymult(session.getFormat().getRiceHistoryMult());
    alac.setSetinfo_rice_initialhistory(session.getFormat().getRiceInitialHistory());
    alac.setSetinfo_rice_kmodifier(session.getFormat().getRiceKModifier());
    alac.setSetinfo_sample_size(session.getFormat().getSampleSize());

    outbuffer = new int[frameSize * 4];
    outbufferBytes = new byte[outbuffer.length * 2];
  }

  public void requestRtpResend(int first, int last) throws IOException {
    if(first > last) {
      System.out.println(first + " > " + last);
      return;
    }

    int len = last - first + 1;
    byte[] b = new byte[] { (byte) 0x80, (byte) (0x55|0x80), 0x01, 0x00, (byte) ((first & 0xFF00) >> 8), (byte) (first & 0xFF), (byte) ((len & 0xFF00) >> 8), (byte) (len & 0xFF)};
    DatagramPacket packet = new DatagramPacket(b, 0, b.length, clientSocketAddress);
    receiveSocket.send(packet);
  }

  private int lastSeqNo = 0;

  private int convertSampleBufferToByteBuffer(int[] sampleBuffer, int len, byte[] outbuffer) {
    int j = 0;
    for (int i = 0; i < len; ++i) {
      int sample = sampleBuffer[i];
      outbuffer[j++] = (byte) (sample >> 8);
      outbuffer[j++] = (byte) sample;
    }
    return j;
  }

  private void putDataInBuffer(int seqNo, byte[] data, int offset, int len) {
    byte[] out = new byte[len];
    decryptAes(data, offset, len, out);
    int samplesInBytes = AlacDecodeUtils.decode_frame(alac, out, outbuffer, outbuffer.length);
    assert(samplesInBytes == session.getFormat().getFrameSize() * 4);

    int lenBytes = convertSampleBufferToByteBuffer(outbuffer, samplesInBytes >> 1, outbufferBytes);
    line.write(outbufferBytes, 0, lenBytes);

    if(seqNo + 1 < lastSeqNo) {
      System.out.println(seqNo  + " " + lastSeqNo);
    }
    lastSeqNo = seqNo;
  }

  @Override
  public void run() {
    byte[] b = new byte[2048];
    DatagramPacket packet = new DatagramPacket(b, b.length);
    while(!Thread.interrupted()) {
      try {
        receiveSocket.receive(packet);
      } catch (IOException e) {
        e.printStackTrace();
        this.interrupt();
        continue;
      }
      if(clientSocketAddress == null) {
        clientSocketAddress = packet.getSocketAddress();
      }

      int offset = packet.getOffset();
      int length = packet.getLength();
      byte[] data = packet.getData();
      byte type = (byte)(data[offset + 1] & ~0x80);
      if(type == 0x60 || type == 0x56) { // audio data / resend
        if(type == 0x56) {
          offset = offset + 4;
          length = length - 4;
        }
        int seqno = (data[offset + 2]  << 8) | data[offset + 3];
        putDataInBuffer(seqno, data, offset + 12, length - 12);
      }
    }
  }

  public int getPort() {
    return port;
  }

  private int decryptAes(byte[] inbuf, int offset, int len, byte[] outbuffer) {
    int decodeLen = len - (len % 16);
    try {
      aesCipher.init(Cipher.DECRYPT_MODE, secretKey, keySpec);
      int ret = aesCipher.doFinal(inbuf, offset, decodeLen, outbuffer);
      System.arraycopy(inbuf, offset + decodeLen, outbuffer, decodeLen, len % 16);
      return ret;
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }
}