RTPTranslatorImpl.java

/*
 * Jitsi, the OpenSource Java VoIP and Instant Messaging client.
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package org.jitsi.impl.neomedia;

import java.io.*;
import java.lang.reflect.*;
import java.util.*;

import javax.media.*;
import javax.media.format.*;
import javax.media.protocol.*;
import javax.media.rtp.*;
import javax.media.rtp.event.*;
import javax.media.rtp.rtcp.*;

import org.jitsi.impl.neomedia.protocol.*;
import org.jitsi.service.neomedia.*;
import org.jitsi.util.*;

import com.sun.media.rtp.*;

/**
 * Implements <tt>RTPTranslator</tt> which represents an RTP translator which
 * forwards RTP and RTCP traffic between multiple <tt>MediaStream</tt>s.
 *
 * @author Lyubomir Marinov
 */
public class RTPTranslatorImpl
    implements ReceiveStreamListener,
               RTPTranslator
{
    /**
     * The <tt>Logger</tt> used by the <tt>RTPTranslatorImpl</tt> class and its
     * instances for logging output.
     */
    private static final Logger logger
        = Logger.getLogger(RTPTranslatorImpl.class);

    /**
     * The indicator which determines whether the method
     * {@link #createFakeSendStreamIfNecessary()} is to be executed by
     * <tt>RTPTranslatorImpl</tt>.
     */
    private static final boolean CREATE_FAKE_SEND_STREAM_IF_NECESSARY = false;

    /**
     * An array with <tt>long</tt> element type and no elements explicitly
     * defined to reduce unnecessary allocations.
     */
    private static final long[] EMPTY_LONG_ARRAY = new long[0];

    /**
     * The <tt>RTPConnector</tt> which is used by {@link #manager} and which
     * delegates to the <tt>RTPConnector</tt>s of the <tt>StreamRTPManager</tt>s
     * attached to this instance.
     */
    private RTPConnectorImpl connector;

    /**
     * The <tt>SendStream</tt> created by the <tt>RTPManager</tt> in order to
     * ensure that this <tt>RTPTranslatorImpl</tt> is able to disperse RTP and
     * RTCP received from remote peers even when the local peer is not
     * generating media to be transmitted.
     */
    private SendStream fakeSendStream;

    /**
     * The <tt>RTPManager</tt> which implements the actual RTP management of
     * this instance.
     */
    private final RTPManager manager = RTPManager.newInstance();

    /**
     * The <tt>SendStream</tt>s created by the <tt>RTPManager</tt> and the
     * <tt>StreamRTPManager</tt>-specific views to them.
     */
    private final List<SendStreamDesc> sendStreams
        = new LinkedList<SendStreamDesc>();

    /**
     * The list of <tt>StreamRTPManager</tt>s i.e. <tt>MediaStream</tt>s which
     * this instance forwards RTP and RTCP traffic between.
     */
    private final List<StreamRTPManagerDesc> streamRTPManagers
        = new ArrayList<StreamRTPManagerDesc>();

    /**
     * Initializes a new <tt>RTPTranslatorImpl</tt> instance.
     */
    public RTPTranslatorImpl()
    {
        manager.addReceiveStreamListener(this);
    }

    public synchronized void addFormat(
            StreamRTPManager streamRTPManager,
            Format format, int payloadType)
    {
        manager.addFormat(format, payloadType);

        getStreamRTPManagerDesc(streamRTPManager, true)
            .addFormat(format, payloadType);
    }

    public synchronized void addReceiveStreamListener(
            StreamRTPManager streamRTPManager,
            ReceiveStreamListener listener)
    {
        getStreamRTPManagerDesc(streamRTPManager, true)
            .addReceiveStreamListener(listener);
    }

    public void addRemoteListener(
            StreamRTPManager streamRTPManager,
            RemoteListener listener)
    {
        manager.addRemoteListener(listener);
    }

    public void addSendStreamListener(
            StreamRTPManager streamRTPManager,
            SendStreamListener listener)
    {
        // TODO Auto-generated method stub
    }

    public void addSessionListener(
            StreamRTPManager streamRTPManager,
            SessionListener listener)
    {
        // TODO Auto-generated method stub
    }

    /**
     * Closes {@link #fakeSendStream} if it exists and is considered no longer
     * necessary; otherwise, does nothing.
     */
    private synchronized void closeFakeSendStreamIfNotNecessary()
    {
        /*
         * If a SendStream has been created in response to a request from the
         * clients of this RTPTranslator implementation, the newly-created
         * SendStream in question will disperse the received RTP and RTCP from
         * remote peers so fakeSendStream will be obsolete.
         */
        try
        {
            if ((!sendStreams.isEmpty() || (streamRTPManagers.size() < 2))
                    && (fakeSendStream != null))
            {
                try
                {
                    fakeSendStream.close();
                }
                catch (NullPointerException npe)
                {
                    /*
                     * Refer to MediaStreamImpl#stopSendStreams(
                     * Iterable<SendStream>, boolean) for an explanation about
                     * the swallowing of the exception.
                     */
                    logger.error("Failed to close fake send stream", npe);
                }
                finally
                {
                    fakeSendStream = null;
                }
            }
        }
        catch (Throwable t)
        {
            if (t instanceof ThreadDeath)
                throw (ThreadDeath) t;
            else if (logger.isDebugEnabled())
            {
                logger.debug(
                        "Failed to close the fake SendStream of this"
                            + " RTPTranslator.",
                        t);
            }
        }
    }

    private synchronized void closeSendStream(SendStreamDesc sendStreamDesc)
    {
        if (sendStreams.contains(sendStreamDesc)
                && (sendStreamDesc.getSendStreamCount() < 1))
        {
            SendStream sendStream = sendStreamDesc.sendStream;

            try
            {
                sendStream.close();
            }
            catch (NullPointerException npe)
            {
                /*
                 * Refer to MediaStreamImpl#stopSendStreams(
                 * Iterable<SendStream>, boolean) for an explanation about the
                 * swallowing of the exception.
                 */
                logger.error("Failed to close send stream", npe);
            }
            sendStreams.remove(sendStreamDesc);
        }
    }

    /**
     * Creates {@link #fakeSendStream} if it does not exist yet and is
     * considered necessary; otherwise, does nothing.
     */
    @SuppressWarnings("unused")
    private synchronized void createFakeSendStreamIfNecessary()
    {
        /*
         * If no SendStream has been created in response to a request from the
         * clients of this RTPTranslator implementation, it will need
         * fakeSendStream in order to be able to disperse the received RTP and
         * RTCP from remote peers. Additionally, the fakeSendStream is not
         * necessary in the case of a single client of this RTPTranslator
         * because there is no other remote peer to disperse the received RTP
         * and RTCP to.
         */
        if (CREATE_FAKE_SEND_STREAM_IF_NECESSARY
                && (fakeSendStream == null)
                && sendStreams.isEmpty()
                && (streamRTPManagers.size() > 1))
        {
            Format supportedFormat = null;

            for (StreamRTPManagerDesc s : streamRTPManagers)
            {
                Format[] formats = s.getFormats();

                if ((formats != null) && (formats.length > 0))
                {
                    for (Format f : formats)
                    {
                        if (f != null)
                        {
                            supportedFormat = f;
                            break;
                        }
                    }
                    if (supportedFormat != null)
                        break;
                }
            }
            if (supportedFormat != null)
            {
                try
                {
                    fakeSendStream
                        = manager.createSendStream(
                                new FakePushBufferDataSource(supportedFormat),
                                0);
                }
                catch (Throwable t)
                {
                    if (t instanceof ThreadDeath)
                        throw (ThreadDeath) t;
                    else
                    {
                        logger.error(
                                "Failed to create a fake SendStream to ensure"
                                    + " that this RTPTranslator is able to"
                                    + " disperse RTP and RTCP received from"
                                    + " remote peers even when the local peer"
                                    + " is not generating media to be"
                                    + " transmitted.",
                                t);
                    }
                }
            }
        }
    }

    public synchronized SendStream createSendStream(
            StreamRTPManager streamRTPManager,
            DataSource dataSource, int streamIndex)
        throws IOException,
               UnsupportedFormatException
    {
        SendStreamDesc sendStreamDesc = null;

        for (SendStreamDesc s : sendStreams)
            if ((s.dataSource == dataSource) && (s.streamIndex == streamIndex))
            {
                sendStreamDesc = s;
                break;
            }
        if (sendStreamDesc == null)
        {
            SendStream sendStream
                = manager.createSendStream(dataSource, streamIndex);

            if (sendStream != null)
            {
                sendStreamDesc
                    = new SendStreamDesc(dataSource, streamIndex, sendStream);
                sendStreams.add(sendStreamDesc);

                closeFakeSendStreamIfNotNecessary();
            }
        }
        return
            (sendStreamDesc == null)
                ? null
                : sendStreamDesc.getSendStream(streamRTPManager, true);
    }

    /**
     * Releases the resources allocated by this instance in the course of its
     * execution and prepares it to be garbage collected.
     */
    public synchronized void dispose()
    {
        manager.removeReceiveStreamListener(this);
        try
        {
            manager.dispose();
        }
        catch (Throwable t)
        {
            if (t instanceof ThreadDeath)
                throw (ThreadDeath) t;
            else
            {
                /*
                 * RTPManager.dispose() often throws at least a
                 * NullPointerException in relation to some RTP BYE.
                 */
                logger.error("Failed to dispose of RTPManager", t);
            }
        }
    }

    public synchronized void dispose(StreamRTPManager streamRTPManager)
    {
        Iterator<StreamRTPManagerDesc> streamRTPManagerIter
            = streamRTPManagers.iterator();

        while (streamRTPManagerIter.hasNext())
        {
            StreamRTPManagerDesc streamRTPManagerDesc
                = streamRTPManagerIter.next();

            if (streamRTPManagerDesc.streamRTPManager == streamRTPManager)
            {
                RTPConnectorDesc connectorDesc
                    = streamRTPManagerDesc.connectorDesc;

                if (connectorDesc != null)
                {
                    if (this.connector != null)
                        this.connector.removeConnector(connectorDesc);
                    connectorDesc.connector.close();
                    streamRTPManagerDesc.connectorDesc = null;
                }

                streamRTPManagerIter.remove();

                closeFakeSendStreamIfNotNecessary();

                break;
            }
        }
    }

    private synchronized StreamRTPManagerDesc
        findStreamRTPManagerDescByReceiveSSRC(
            long receiveSSRC,
            StreamRTPManagerDesc exclusion)
    {
        for (int i = 0, count = streamRTPManagers.size(); i < count; i++)
        {
            StreamRTPManagerDesc s = streamRTPManagers.get(i);

            if ((s != exclusion) && s.containsReceiveSSRC(receiveSSRC))
                return s;
        }
        return null;
    }

    public Object getControl(
            StreamRTPManager streamRTPManager,
            String controlType)
    {
        return manager.getControl(controlType);
    }

    public GlobalReceptionStats getGlobalReceptionStats(
            StreamRTPManager streamRTPManager)
    {
        return manager.getGlobalReceptionStats();
    }

    public GlobalTransmissionStats getGlobalTransmissionStats(
            StreamRTPManager streamRTPManager)
    {
        return manager.getGlobalTransmissionStats();
    }

    public long getLocalSSRC(StreamRTPManager streamRTPManager)
    {
        return ((RTPSessionMgr) manager).getLocalSSRC();
    }

    public synchronized Vector<ReceiveStream> getReceiveStreams(
            StreamRTPManager streamRTPManager)
    {
        StreamRTPManagerDesc streamRTPManagerDesc
            = getStreamRTPManagerDesc(streamRTPManager, false);
        Vector<ReceiveStream> receiveStreams = null;

        if (streamRTPManagerDesc != null)
        {
            Vector<?> managerReceiveStreams = manager.getReceiveStreams();

            if (managerReceiveStreams != null)
            {
                receiveStreams
                    = new Vector<ReceiveStream>(managerReceiveStreams.size());
                for (Object s : managerReceiveStreams)
                {
                    ReceiveStream receiveStream = (ReceiveStream) s;

                    if (streamRTPManagerDesc.containsReceiveSSRC(
                            receiveStream.getSSRC()))
                        receiveStreams.add(receiveStream);
                }
            }
        }
        return receiveStreams;
    }

    public synchronized Vector<SendStream> getSendStreams(
            StreamRTPManager streamRTPManager)
    {
        Vector<?> managerSendStreams = manager.getSendStreams();
        Vector<SendStream> sendStreams = null;

        if (managerSendStreams != null)
        {
            sendStreams = new Vector<SendStream>(managerSendStreams.size());
            for (SendStreamDesc sendStreamDesc : this.sendStreams)
                if (managerSendStreams.contains(sendStreamDesc.sendStream))
                {
                    SendStream sendStream
                        = sendStreamDesc.getSendStream(streamRTPManager, false);

                    if (sendStream != null)
                        sendStreams.add(sendStream);
                }
        }
        return sendStreams;
    }

    private synchronized StreamRTPManagerDesc getStreamRTPManagerDesc(
            StreamRTPManager streamRTPManager,
            boolean create)
    {
        for (StreamRTPManagerDesc s : streamRTPManagers)
            if (s.streamRTPManager == streamRTPManager)
                return s;

        StreamRTPManagerDesc s;

        if (create)
        {
            s = new StreamRTPManagerDesc(streamRTPManager);
            streamRTPManagers.add(s);
        }
        else
            s = null;
        return s;
    }

    public synchronized void initialize(
            StreamRTPManager streamRTPManager,
            RTPConnector connector)
    {
        if (this.connector == null)
        {
            this.connector = new RTPConnectorImpl();
            manager.initialize(this.connector);
        }

        StreamRTPManagerDesc streamRTPManagerDesc
            = getStreamRTPManagerDesc(streamRTPManager, true);
        RTPConnectorDesc connectorDesc = streamRTPManagerDesc.connectorDesc;

        if ((connectorDesc == null) || (connectorDesc.connector != connector))
        {
            if (connectorDesc != null)
                this.connector.removeConnector(connectorDesc);
            streamRTPManagerDesc.connectorDesc
                = connectorDesc
                    = (connector == null)
                        ? null
                        : new RTPConnectorDesc(streamRTPManagerDesc, connector);
            if (connectorDesc != null)
                this.connector.addConnector(connectorDesc);
        }
    }

    /**
     * Logs information about an RTCP packet using {@link #logger} for debugging
     * purposes.
     *
     * @param obj the object which is the source of the log request
     * @param methodName the name of the method on <tt>obj</tt> which is the
     * source of the log request
     * @param buffer the <tt>byte</tt>s which (possibly) represent an RTCP
     * packet to be logged for debugging purposes
     * @param offset the position within <tt>buffer</tt> at which the valid data
     * begins
     * @param length the number of bytes in <tt>buffer</tt> which constitute the
     * valid data 
     */
    private static void logRTCP(
            Object obj, String methodName,
            byte[] buffer, int offset, int length)
    {
        /*
         * Do the bytes in the specified buffer resemble (a header of) an RTCP
         * packet?
         */
        if (length > 8)
        {
            byte b0 = buffer[offset];
            int v = (b0 & 0xc0) >>> 6;

            if (v == 2)
            {
                byte b1 = buffer[offset + 1];
                int pt = b1 & 0xff;

                if (pt == 203 /* BYE */)
                {
                    int sc = b0 & 0x1f;
                    long ssrc = (sc > 0) ? readInt(buffer, offset + 4) : -1;

                    logger.trace(
                            obj.getClass().getName() + '.' + methodName
                                + ": RTCP BYE v=" + v + "; pt=" + pt + "; ssrc="
                                + ssrc + ';');
                }
            }
        }
    }

    /**
     * Notifies this instance that an RTP or RTCP packet has been received from
     * a peer represented by a specific <tt>PushSourceStreamDesc</tt>.
     *
     * @param streamDesc a <tt>PushSourceStreamDesc</tt> which identifies the
     * peer from which an RTP or RTCP packet has been received
     * @param buffer the buffer which contains the bytes of the received RTP or
     * RTCP packet
     * @param offset the zero-based index in <tt>buffer</tt> at which the bytes
     * of the received RTP or RTCP packet begin
     * @param length the number of bytes in <tt>buffer</tt> beginning at
     * <tt>offset</tt> which are allowed to be accessed
     * @param read the number of bytes in <tt>buffer</tt> beginning at
     * <tt>offset</tt> which represent the received RTP or RTCP packet
     * @return the number of bytes in <tt>buffer</tt> beginning at
     * <tt>offset</tt> which represent the received RTP or RTCP packet 
     * @throws IOException if an I/O error occurs while the method processes the
     * specified RTP or RTCP packet
     */
    private int read(
            PushSourceStreamDesc streamDesc,
            byte[] buffer, int offset, int length,
            int read)
        throws IOException
    {
        boolean data = streamDesc.data;
        StreamRTPManagerDesc streamRTPManagerDesc
            = streamDesc.connectorDesc.streamRTPManagerDesc;
        Format format = null;

        if (data)
        {
            /*
             * Do the bytes in the specified buffer resemble (a header of) an
             * RTP packet?
             */
            if ((length >= 12)
                    && (/* v */ ((buffer[offset] & 0xc0) >>> 6) == 2))
            {
                long ssrc = readInt(buffer, offset + 8);

                if (!streamRTPManagerDesc.containsReceiveSSRC(ssrc))
                {
                    if (findStreamRTPManagerDescByReceiveSSRC(
                                ssrc,
                                streamRTPManagerDesc)
                            == null)
                        streamRTPManagerDesc.addReceiveSSRC(ssrc);
                    else
                        return 0;
                }

                int pt = buffer[offset + 1] & 0x7f;

                format = streamRTPManagerDesc.getFormat(pt);
            }
        }
        else if (logger.isTraceEnabled())
            logRTCP(this, "read", buffer, offset, read);

        createFakeSendStreamIfNecessary();

        OutputDataStreamImpl outputStream
            = data
                ? connector.getDataOutputStream()
                : connector.getControlOutputStream();

        if (outputStream != null)
        {
            outputStream.write(
                    buffer, offset, read,
                    format,
                    streamRTPManagerDesc);
        }

        return read;
    }

    /**
     * Reads an <tt>int</tt> from a specific <tt>byte</tt> buffer starting at a
     * specific <tt>offset</tt>. The implementation is the same as
     * {@link DataInputStream#readInt()}.
     *
     * @param buffer the <tt>byte</tt> buffer to read an <tt>int</tt> from
     * @param offset the zero-based offset in <tt>buffer</tt> to start reading
     * an <tt>int</tt> from
     * @return an <tt>int</tt> read from the specified <tt>buffer</tt> starting
     * at the specified <tt>offset</tt>
     */
    public static int readInt(byte[] buffer, int offset)
    {
        return
            ((buffer[offset++] & 0xff) << 24)
                | ((buffer[offset++] & 0xff) << 16)
                | ((buffer[offset++] & 0xff) << 8)
                | (buffer[offset] & 0xff);
    }

    public synchronized void removeReceiveStreamListener(
            StreamRTPManager streamRTPManager,
            ReceiveStreamListener listener)
    {
        StreamRTPManagerDesc streamRTPManagerDesc
            = getStreamRTPManagerDesc(streamRTPManager, false);

        if (streamRTPManagerDesc != null)
            streamRTPManagerDesc.removeReceiveStreamListener(listener);
    }

    public void removeRemoteListener(
            StreamRTPManager streamRTPManager,
            RemoteListener listener)
    {
        manager.removeRemoteListener(listener);
    }

    public void removeSendStreamListener(
            StreamRTPManager streamRTPManager,
            SendStreamListener listener)
    {
        // TODO Auto-generated method stub
    }

    public void removeSessionListener(
            StreamRTPManager streamRTPManager,
            SessionListener listener)
    {
        // TODO Auto-generated method stub
    }

    /**
     * Notifies this <tt>ReceiveStreamListener</tt> about a specific event
     * related to a <tt>ReceiveStream</tt>.
     *
     * @param event a <tt>ReceiveStreamEvent</tt> which contains the specifics
     * of the event this <tt>ReceiveStreamListener</tt> is being notified about
     * @see ReceiveStreamListener#update(ReceiveStreamEvent)
     */
    public void update(ReceiveStreamEvent event)
    {
        /*
         * Because NullPointerException was seen during testing, be thorough
         * with the null checks.
         */
        if (event != null)
        {
            ReceiveStream receiveStream = event.getReceiveStream();

            if (receiveStream != null)
            {
                StreamRTPManagerDesc streamRTPManagerDesc
                    = findStreamRTPManagerDescByReceiveSSRC(
                            receiveStream.getSSRC(),
                            null);

                if (streamRTPManagerDesc != null)
                    for (ReceiveStreamListener listener
                            : streamRTPManagerDesc.getReceiveStreamListeners())
                        listener.update(event);
            }
        }
    }

    private static class OutputDataStreamDesc
    {
        public RTPConnectorDesc connectorDesc;

        public OutputDataStream stream;

        public OutputDataStreamDesc(
                RTPConnectorDesc connectorDesc,
                OutputDataStream stream)
        {
            this.connectorDesc = connectorDesc;
            this.stream = stream;
        }
    }

    private static class OutputDataStreamImpl
        implements OutputDataStream,
                   Runnable
    {
        private static final int WRITE_QUEUE_CAPACITY
            = RTPConnectorOutputStream
                .MAX_PACKETS_PER_MILLIS_POLICY_PACKET_QUEUE_CAPACITY;

        private boolean closed;

        private final boolean data;

        private final List<OutputDataStreamDesc> streams
            = new ArrayList<OutputDataStreamDesc>();

        private final RTPTranslatorBuffer[] writeQueue
            = new RTPTranslatorBuffer[WRITE_QUEUE_CAPACITY];

        private int writeQueueHead;

        private int writeQueueLength;

        private Thread writeThread;

        public OutputDataStreamImpl(boolean data)
        {
            this.data = data;
        }

        public synchronized void addStream(
                RTPConnectorDesc connectorDesc,
                OutputDataStream stream)
        {
            for (OutputDataStreamDesc streamDesc : streams)
                if ((streamDesc.connectorDesc == connectorDesc)
                        && (streamDesc.stream == stream))
                    return;
            streams.add(new OutputDataStreamDesc(connectorDesc, stream));
        }

        public synchronized void close()
        {
            closed = true;
            writeThread = null;
            notify();
        }

        private synchronized void createWriteThread()
        {
            writeThread = new Thread(this, getClass().getName());
            writeThread.setDaemon(true);
            writeThread.start();
        }

        private synchronized int doWrite(
                byte[] buffer, int offset, int length,
                Format format,
                StreamRTPManagerDesc exclusion)
        {
            int write = 0;

            for (int streamIndex = 0, streamCount = streams.size();
                    streamIndex < streamCount;
                    streamIndex++)
            {
                OutputDataStreamDesc streamDesc = streams.get(streamIndex);
                StreamRTPManagerDesc streamRTPManagerDesc
                    = streamDesc.connectorDesc.streamRTPManagerDesc;

                if (streamRTPManagerDesc != exclusion)
                {
                    if (data)
                    {
                        if ((format != null) && (length > 0))
                        {
                            Integer payloadType
                                = streamRTPManagerDesc.getPayloadType(format);

                            if ((payloadType == null) && (exclusion != null))
                                payloadType = exclusion.getPayloadType(format);
                            if (payloadType != null)
                            {
                                int payloadTypeByteIndex = offset + 1;

                                buffer[payloadTypeByteIndex]
                                    = (byte)
                                        ((buffer[payloadTypeByteIndex] & 0x80)
                                            | (payloadType & 0x7f));
                            }
                        }
                    }
                    else if (logger.isTraceEnabled())
                    {
                        logRTCP(
                                this, "doWrite",
                                buffer, offset, length);
                    }

                    int streamWrite
                        = streamDesc.stream.write(buffer, offset, length);

                    if (write < streamWrite)
                        write = streamWrite;
                }
            }
            return write;
        }

        public synchronized void removeStreams(RTPConnectorDesc connectorDesc)
        {
            Iterator<OutputDataStreamDesc> streamIter = streams.iterator();

            while (streamIter.hasNext())
            {
                OutputDataStreamDesc streamDesc = streamIter.next();

                if (streamDesc.connectorDesc == connectorDesc)
                    streamIter.remove();
            }
        }

        public void run()
        {
            try
            {
                while (true)
                {
                    int writeIndex;
                    byte[] buffer;
                    StreamRTPManagerDesc exclusion;
                    Format format;
                    int length;

                    synchronized (this)
                    {
                        if (closed
                                || !Thread.currentThread().equals(writeThread))
                            break;
                        if (writeQueueLength < 1)
                        {
                            boolean interrupted = false;

                            try
                            {
                                wait();
                            }
                            catch (InterruptedException ie)
                            {
                                interrupted = true;
                            }
                            if (interrupted)
                                Thread.currentThread().interrupt();
                            continue;
                        }

                        writeIndex = writeQueueHead;

                        RTPTranslatorBuffer write = writeQueue[writeIndex];

                        buffer = write.data;
                        write.data = null;
                        exclusion = write.exclusion;
                        write.exclusion = null;
                        format = write.format;
                        write.format = null;
                        length = write.length;
                        write.length = 0;

                        writeQueueHead++;
                        if (writeQueueHead >= writeQueue.length)
                            writeQueueHead = 0;
                        writeQueueLength--;
                    }

                    try
                    {
                        doWrite(buffer, 0, length, format, exclusion);
                    }
                    finally
                    {
                        synchronized (this)
                        {
                            RTPTranslatorBuffer write = writeQueue[writeIndex];

                            if ((write != null) && (write.data == null))
                                write.data = buffer;
                        }
                    }
                }
            }
            catch (Throwable t)
            {
                logger.error("Failed to translate RTP packet", t);
                if (t instanceof ThreadDeath)
                    throw (ThreadDeath) t;
            }
            finally
            {
                synchronized (this)
                {
                    if (Thread.currentThread().equals(writeThread))
                        writeThread = null;
                    if (!closed
                            && (writeThread == null)
                            && (writeQueueLength > 0))
                        createWriteThread();
                }
            }
        }

        public int write(byte[] buffer, int offset, int length)
        {
            return doWrite(buffer, offset, length, null, null);
        }

        public synchronized void write(
                byte[] buffer, int offset, int length,
                Format format,
                StreamRTPManagerDesc exclusion)
        {
            if (closed)
                return;

            int writeIndex;

            if (writeQueueLength < writeQueue.length)
            {
                writeIndex
                    = (writeQueueHead + writeQueueLength) % writeQueue.length;
            }
            else
            {
                writeIndex = writeQueueHead;
                writeQueueHead++;
                if (writeQueueHead >= writeQueue.length)
                    writeQueueHead = 0;
                writeQueueLength--;
                logger.warn("Will not translate RTP packet.");
            }

            RTPTranslatorBuffer write
                = writeQueue[writeIndex];

            if (write == null)
                writeQueue[writeIndex] = write = new RTPTranslatorBuffer();

            byte[] data = write.data;

            if ((data == null) || (data.length < length))
                write.data = data = new byte[length];
            System.arraycopy(buffer, offset, data, 0, length);

            write.exclusion = exclusion;
            write.format = format;
            write.length = length;

            writeQueueLength++;

            if (writeThread == null)
                createWriteThread();
            else
                notify();
        }
    }

    private static class PushSourceStreamDesc