Android Open Source - spydroid-ipcamera A A C A D T S Packetizer

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * Copyright (C) 2011-2014 GUIGUI Simon, fyhertz@gmail.com
 * //from w  w w .java  2 s .c om
 * This file is part of libstreaming (https://github.com/fyhertz/libstreaming)
 * 
 * Spydroid 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 source code 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 source code; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package net.majorkernelpanic.streaming.rtp;

import java.io.IOException;

import net.majorkernelpanic.streaming.audio.AACStream;
import android.os.SystemClock;
import android.util.Log;

/**
 *   
 *   RFC 3640.  
 *
 *   This packetizer must be fed with an InputStream containing ADTS AAC. 
 *   AAC will basically be rewrapped in an RTP stream and sent over the network.
 *   This packetizer only implements the aac-hbr mode (High Bit-rate AAC) and
 *   each packet only carry a single and complete AAC access unit.
 * 
 */
public class AACADTSPacketizer extends AbstractPacketizer implements Runnable {

  private final static String TAG = "AACADTSPacketizer";

  private Thread t;
  private int samplingRate = 8000;

  public AACADTSPacketizer() {
    super();
  }

  public void start() {
    if (t==null) {
      t = new Thread(this);
      t.start();
    }
  }

  public void stop() {
    if (t != null) {
      try {
        is.close();
      } catch (IOException ignore) {}
      t.interrupt();
      try {
        t.join();
      } catch (InterruptedException e) {}
      t = null;
    }
  }

  public void setSamplingRate(int samplingRate) {
    this.samplingRate = samplingRate;
    socket.setClockFrequency(samplingRate);
  }

  public void run() {

    Log.d(TAG,"AAC ADTS packetizer started !");

    // "A packet SHALL carry either one or more complete Access Units, or a
    // single fragment of an Access Unit.  Fragments of the same Access Unit
    // have the same time stamp but different RTP sequence numbers.  The
    // marker bit in the RTP header is 1 on the last fragment of an Access
    // Unit, and 0 on all other fragments." RFC 3640

    // Adts header fields that we need to parse
    boolean protection;
    int frameLength, sum, length, nbau, nbpk, samplingRateIndex, profile;
    long oldtime = SystemClock.elapsedRealtime(), now = oldtime;
    byte[] header = new byte[8]; 

    try {
      while (!Thread.interrupted()) {

        // Synchronisation: ADTS packet starts with 12bits set to 1
        while (true) {
          if ( (is.read()&0xFF) == 0xFF ) {
            header[1] = (byte) is.read();
            if ( (header[1]&0xF0) == 0xF0) break;
          }
        }

        // Parse adts header (ADTS packets start with a 7 or 9 byte long header)
        fill(header, 2, 5);

        // The protection bit indicates whether or not the header contains the two extra bytes
        protection = (header[1]&0x01)>0 ? true : false;
        frameLength = (header[3]&0x03) << 11 | 
            (header[4]&0xFF) << 3 | 
            (header[5]&0xFF) >> 5 ;
        frameLength -= (protection ? 7 : 9);

        // Number of AAC frames in the ADTS frame
        nbau = (header[6]&0x03) + 1;

        // The number of RTP packets that will be sent for this ADTS frame
        nbpk = frameLength/MAXPACKETSIZE + 1;

        // Read CRS if any
        if (!protection) is.read(header,0,2);

        samplingRate = AACStream.AUDIO_SAMPLING_RATES[(header[2]&0x3C) >> 2];
        profile = ( (header[2]&0xC0) >> 6 ) + 1 ;

        // We update the RTP timestamp
        ts +=  1024L*1000000000L/samplingRate; //stats.average();

        //Log.d(TAG,"frameLength: "+frameLength+" protection: "+protection+" p: "+profile+" sr: "+samplingRate);

        sum = 0;
        while (sum<frameLength) {

          buffer = socket.requestBuffer();
          socket.updateTimestamp(ts);

          // Read frame
          if (frameLength-sum > MAXPACKETSIZE-rtphl-4) {
            length = MAXPACKETSIZE-rtphl-4;
          }
          else {
            length = frameLength-sum;
            socket.markNextPacket();
          }
          sum += length;
          fill(buffer, rtphl+4, length);

          // AU-headers-length field: contains the size in bits of a AU-header
          // 13+3 = 16 bits -> 13bits for AU-size and 3bits for AU-Index / AU-Index-delta 
          // 13 bits will be enough because ADTS uses 13 bits for frame length
          buffer[rtphl] = 0;
          buffer[rtphl+1] = 0x10; 

          // AU-size
          buffer[rtphl+2] = (byte) (frameLength>>5);
          buffer[rtphl+3] = (byte) (frameLength<<3);

          // AU-Index
          buffer[rtphl+3] &= 0xF8;
          buffer[rtphl+3] |= 0x00;

          send(rtphl+4+length);

        }

      }
    } catch (IOException e) {
      // Ignore
    } catch (ArrayIndexOutOfBoundsException e) {
      Log.e(TAG,"ArrayIndexOutOfBoundsException: "+(e.getMessage()!=null?e.getMessage():"unknown error"));
      e.printStackTrace();
    } catch (InterruptedException ignore) {}

    Log.d(TAG,"AAC ADTS packetizer stopped !");

  }

  private int fill(byte[] buffer, int offset,int length) throws IOException {
    int sum = 0, len;
    while (sum<length) {
      len = is.read(buffer, offset+sum, length-sum);
      if (len<0) {
        throw new IOException("End of stream");
      }
      else sum+=len;
    }
    return sum;
  }

}

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