AACADTSPacketizer.java

/*
 * Copyright (C) 2011-2014 GUIGUI Simon, fyhertz@gmail.com
 * 
 * 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;
	}

}