diff --git a/src/net/java/sip/communicator/impl/neomedia/MediaStreamImpl.java b/src/net/java/sip/communicator/impl/neomedia/MediaStreamImpl.java
index 16f97feb6..2d02d5bed 100644
--- a/src/net/java/sip/communicator/impl/neomedia/MediaStreamImpl.java
+++ b/src/net/java/sip/communicator/impl/neomedia/MediaStreamImpl.java
@@ -17,6 +17,8 @@
 import javax.media.rtp.*;
 import javax.media.rtp.event.*;
 
+import com.sun.media.rtp.*;
+
 import net.java.sip.communicator.impl.neomedia.device.*;
 import net.java.sip.communicator.impl.neomedia.format.*;
 import net.java.sip.communicator.impl.neomedia.transform.*;
@@ -129,12 +131,18 @@ public class MediaStreamImpl
     /**
      * The SSRC identifier of the party that we are exchanging media with.
      */
-    private String remoteSourceID = null;
+    private long remoteSourceID = -1;
 
     /**
      * Our own SSRC identifier.
      */
-    private String localSourceID = null;
+    private long localSourceID = -1;
+
+    /**
+     * The list of CSRC IDs that the remote party reported as contributing to
+     * the media they are sending toward us.
+     */
+    private long[] remoteContributingSourceIDList = new long[0];
 
     /**
      * The indicator which determines whether this <tt>MediaStream</tt> is set
@@ -164,6 +172,8 @@ public MediaStreamImpl(StreamConnector connector, MediaDevice device)
         setDevice(device);
 
         this.rtpConnector = new RTPTransformConnector(connector);
+
+
     }
 
     /**
@@ -419,8 +429,7 @@ public MediaDirection getDirection()
 
         MediaDeviceSession deviceSession = getDeviceSession();
 
-        return
-            (deviceSession == null)
+        return (deviceSession == null)
                 ? MediaDirection.INACTIVE
                 : deviceSession.getDevice().getDirection();
     }
@@ -445,8 +454,7 @@ public Map<Byte, MediaFormat> getDynamicRTPPayloadTypes()
     {
         synchronized (dynamicRTPPayloadTypes)
         {
-            return
-                new HashMap<Byte, MediaFormat>(dynamicRTPPayloadTypes);
+            return new HashMap<Byte, MediaFormat>(dynamicRTPPayloadTypes);
         }
     }
 
@@ -465,16 +473,15 @@ public MediaFormat getFormat()
 
     /**
      * Gets the synchronization source (SSRC) identifier of the local peer or
-     * <tt>null</tt> if it is not yet known.
+     * <tt>-1</tt> if it is not yet known.
      *
      * @return  the synchronization source (SSRC) identifier of the local peer
-     * or <tt>null</tt> if it is not yet known
+     * or <tt>-1</tt> if it is not yet known
      * @see MediaStream#getLocalSourceID()
      */
-    public String getLocalSourceID()
+    public long getLocalSourceID()
     {
-        // TODO Auto-generated method stub
-        return null;
+        return this.localSourceID;
     }
 
     /**
@@ -486,8 +493,7 @@ public String getLocalSourceID()
      */
     public InetSocketAddress getRemoteControlAddress()
     {
-        return
-            (InetSocketAddress)
+        return (InetSocketAddress)
                 rtpConnector.getControlSocket().getRemoteSocketAddress();
     }
 
@@ -500,20 +506,19 @@ public InetSocketAddress getRemoteControlAddress()
      */
     public InetSocketAddress getRemoteDataAddress()
     {
-        return
-            (InetSocketAddress)
+        return (InetSocketAddress)
                 rtpConnector.getDataSocket().getRemoteSocketAddress();
     }
 
     /**
      * Get the synchronization source (SSRC) identifier of the remote peer or
-     * <tt>null</tt> if it is not yet known.
+     * <tt>-1</tt> if it is not yet known.
      *
      * @return  the synchronization source (SSRC) identifier of the remote
-     * peer or <tt>null</tt> if it is not yet known
+     * peer or <tt>-1</tt> if it is not yet known
      * @see MediaStream#getRemoteSourceID()
      */
-    public String getRemoteSourceID()
+    public long getRemoteSourceID()
     {
         return remoteSourceID;
     }
@@ -579,9 +584,7 @@ private RTPManager getRTPManager()
 
             //JMF inits the local SSRC upon initialize(RTPConnector) so now's
             //the time to ask:
-            setLocalSourceID(Long.toHexString(
-                (((com.sun.media.rtp.RTPSessionMgr)
-                                rtpManager).getLocalSSRC())));
+            setLocalSourceID(((RTPSessionMgr)rtpManager).getLocalSSRC());
 
             createSendStreams();
         }
@@ -1256,7 +1259,7 @@ public void update(ReceiveStreamEvent event)
                     logger.trace("Received new ReceiveStream with ssrc "
                                 + receiveStream.getSSRC());
 
-                setRemoteSourceID( Long.toHexString( receiveStream.getSSRC() ));
+                setRemoteSourceID( receiveStream.getSSRC() );
 
                 synchronized (receiveStreams)
                 {
@@ -1326,9 +1329,9 @@ public void update(SessionEvent event)
      * @param ssrc the SSRC identifier that this stream will be using in
      * outgoing RTP packets from now on.
      */
-    private void setLocalSourceID(String ssrc)
+    private void setLocalSourceID(long ssrc)
     {
-        String oldValue = this.localSourceID;
+        Long oldValue = this.localSourceID;
         this.localSourceID = ssrc;
 
         firePropertyChange(PNAME_LOCAL_SSRC, oldValue, ssrc);
@@ -1341,11 +1344,64 @@ private void setLocalSourceID(String ssrc)
      * @param ssrc the SSRC identifier that this stream will be using in
      * outgoing RTP packets from now on.
      */
-    private void setRemoteSourceID(String ssrc)
+    private void setRemoteSourceID(long ssrc)
     {
-        String oldValue = this.remoteSourceID;
+        Long oldValue = this.remoteSourceID;
         this.remoteSourceID = ssrc;
 
         firePropertyChange(PNAME_REMOTE_SSRC, oldValue, ssrc);
     }
+
+    /**
+     * Returns the list of CSRC identifiers for all parties currently known
+     * to contribute to the media that this stream is sending toward its remote
+     * counter part. In other words, the method returns the list of CSRC IDs
+     * that this stream will include in outgoing RTP packets. This method will
+     * return an empty <tt>List</tt> in case this stream is not part of a mixed
+     * conference call.
+     *
+     * @return a <tt>List</tt> of CSRC IDs for parties that are currently known
+     * to contribute to the media that this stream is currently streaming or
+     * an empty <tt>List</tt> in case this <tt>MediaStream</tt> is not part of
+     * a conference call.
+     */
+    public List<String> getLocalContributingSourceIDs()
+    {
+        List<String> csrcList = new ArrayList<String>();
+
+        MediaDeviceSession deviceSession = getDeviceSession();
+        if( this.deviceSession != null)
+            csrcList.addAll( deviceSession.getRemoteSSRCList() );
+
+        Iterator<String> csrcIter = csrcList.iterator();
+
+        //in case of a conf call the mixer would return all SSRC IDs that are
+        //currently contributing including this stream's counterpart. This
+        //method is about
+        while(csrcIter.hasNext())
+        {
+            String csrc = csrcIter.next();
+
+            if (csrc.equals(getRemoteSourceID()))
+                csrcIter.remove();
+        }
+
+        return csrcList;
+    }
+
+    /**
+     * Returns the <tt>List</tt> of CSRC identifiers representing the parties
+     * contributing to the stream that we are receiving from this
+     * <tt>MediaStream</tt>'s remote party.
+     *
+     * @return a <tt>List</tt> of CSRC identifiers representing the parties
+     * contributing to the stream that we are receiving from this
+     * <tt>MediaStream</tt>'s remote party.
+     */
+    public List<String> getRemoteContributingSourceIDs()
+    {
+        List<String> csrcList = new ArrayList<String>();
+
+        return csrcList;
+    }
 }
diff --git a/src/net/java/sip/communicator/impl/neomedia/RawPacket.java b/src/net/java/sip/communicator/impl/neomedia/RawPacket.java
index d46d5d2d8..d374bd5c6 100755
--- a/src/net/java/sip/communicator/impl/neomedia/RawPacket.java
+++ b/src/net/java/sip/communicator/impl/neomedia/RawPacket.java
@@ -6,6 +6,9 @@
  */
 package net.java.sip.communicator.impl.neomedia;
 
+import java.math.*;
+import java.util.*;
+
 /**
  * When using TransformConnector, a RTP/RTCP packet is represented using
  * RawPacket. RawPacket stores the buffer holding the RTP/RTCP packet, as well
@@ -19,6 +22,7 @@
  *
  * @author Werner Dittmann (Werner.Dittmann@t-online.de)
  * @author Bing SU (nova.su@gmail.com)
+ * @author Emil Ivov
  */
 public class RawPacket
 {
@@ -39,6 +43,11 @@ public class RawPacket
      */
     protected int length;
 
+    /**
+     * The size of the fixed part of the RTP header as defined by RFC 3550.
+     */
+    public static final int FIXED_HEADER_SIZE = 12;
+
     /**
      * Construct a RawPacket using specified value.
      *
@@ -237,4 +246,100 @@ public void shrink(int len)
             this.length = 0;
         }
     }
+
+    /**
+     * Returns the number of CSRC identifiers currently included in this packet.
+     *
+     * @return the CSRC count for this <tt>RawPacket</tt>.
+     */
+    public int getCsrcCount()
+    {
+        return (buffer[offset] & 0x0fb);
+    }
+
+    /**
+     * Replaces the existing CSRC list (even if empty) with <tt>newCsrcList</tt>
+     * and updates the CC (CSRC count) field of this <tt>RawPacket</tt>
+     * accordingly.
+     *
+     * @param newCsrcList the list of CSRC identifiers that we'd like to set for
+     * this <tt>RawPacket</tt>.
+     */
+    public void setCsrcList(long[] newCsrcList)
+    {
+        int newCsrcCount = newCsrcList.length;
+        byte[] csrcBuff = new byte[newCsrcCount * 4];
+        int csrcOffset = 0;
+
+        for(long csrc : newCsrcList)
+        {
+            csrcBuff[csrcOffset] = (byte)(csrc >> 24);
+            csrcBuff[csrcOffset+1] = (byte)(csrc >> 16);
+            csrcBuff[csrcOffset+2] = (byte)(csrc >> 8);
+            csrcBuff[csrcOffset+3] = (byte)csrc;
+
+            csrcOffset += 4;
+        }
+
+        int oldCsrcCount = getCsrcCount();
+
+        byte[] oldBuffer = this.getBuffer();
+
+        //the new buffer needs to be bigger than the new one in order to
+        //accommodate the list of CSRC IDs (unless there were more of them
+        //previously than after setting the new list).
+        byte[] newBuffer
+            = new byte[oldBuffer.length + csrcBuff.length - oldCsrcCount*4];
+
+        //copy the part up to the CSRC list
+        System.arraycopy(
+                    oldBuffer, 0, newBuffer, 0, offset + FIXED_HEADER_SIZE);
+
+        //copy the new CSRC list
+        System.arraycopy( csrcBuff, 0, newBuffer,
+                        offset + FIXED_HEADER_SIZE, csrcBuff.length);
+
+        //now copy the payload from the old buff and make sure we don't copy
+        //the CSRC list if there was one in the old packet
+        int payloadOffsetForOldBuff
+            = offset + FIXED_HEADER_SIZE + oldCsrcCount*4;
+
+        int payloadOffsetForNewBuff
+            = offset + FIXED_HEADER_SIZE + newCsrcCount*4;
+
+        System.arraycopy( oldBuffer, payloadOffsetForOldBuff,
+                          newBuffer, payloadOffsetForNewBuff,
+                          csrcBuff.length - payloadOffsetForOldBuff);
+
+        //set the new CSRC count
+        newBuffer[offset] = (byte)((newBuffer[offset] & 0xF0b)
+                                    & newCsrcCount);
+    }
+
+    /**
+     * Returns the list of CSRC IDs, currently encapsulated in this packet.
+     *
+     * @return an array containing the list of CSRC IDs, currently encapsulated
+     * in this packet.
+     */
+    public long[] extractCsrcList()
+    {
+        int csrcCount = getCsrcCount();
+        byte[] buffer = getBuffer();
+
+        long[] csrcList = new long[csrcCount];
+
+        int csrcStartIndex = offset + FIXED_HEADER_SIZE;
+        for (int i = 0; i < csrcCount; i++)
+        {
+            csrcList[i] =   buffer[csrcStartIndex]     << 24
+                          & buffer[csrcStartIndex + 1] << 16
+                          & buffer[csrcStartIndex + 2] << 8
+                          & buffer[csrcStartIndex + 3];
+
+            csrcStartIndex += 4;
+        }
+
+        return csrcList;
+    }
 }
diff --git a/src/net/java/sip/communicator/impl/neomedia/transform/TransformEngineChain.java b/src/net/java/sip/communicator/impl/neomedia/transform/TransformEngineChain.java
index 2c545c32c..f77470783 100644
--- a/src/net/java/sip/communicator/impl/neomedia/transform/TransformEngineChain.java
+++ b/src/net/java/sip/communicator/impl/neomedia/transform/TransformEngineChain.java
@@ -116,7 +116,10 @@ public RawPacket transform(RawPacket pkt)
                     ? engine.getRTPTransformer()
                     : engine.getRTCPTransformer();
 
-                pkt = pTransformer.transform(pkt);
+                //the packet transformer may be null if for example the engine
+                //only does RTP transformations and this is an RTCP transformer.
+                if( pTransformer != null)
+                    pkt = pTransformer.transform(pkt);
             }
 
             return pkt;
@@ -144,7 +147,10 @@ public RawPacket reverseTransform(RawPacket pkt)
                 ? engine.getRTPTransformer()
                 : engine.getRTCPTransformer();
 
-                pkt = pTransformer.reverseTransform(pkt);
+                //the packet transformer may be null if for example the engine
+                //only does RTP transformations and this is an RTCP transformer.
+                if( pTransformer != null)
+                    pkt = pTransformer.reverseTransform(pkt);
             }
 
             return pkt;
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/OperationSetTelephonyConferencingSipImpl.java b/src/net/java/sip/communicator/impl/protocol/sip/OperationSetTelephonyConferencingSipImpl.java
index 83346ada1..c4b202ea9 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/OperationSetTelephonyConferencingSipImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/OperationSetTelephonyConferencingSipImpl.java
@@ -626,7 +626,7 @@ private void getMediaXML(CallPeerSipImpl callPeer, StringBuffer xml)
                 // </type>
                 append(xml, "</", ELEMENT_TYPE, ">");
 
-                String srcId = stream.getRemoteSourceID();
+                String srcId = Long.toString(stream.getRemoteSourceID());
 
                 if (srcId != null)
                 {
diff --git a/src/net/java/sip/communicator/service/neomedia/MediaStream.java b/src/net/java/sip/communicator/service/neomedia/MediaStream.java
index c5fa7fde2..1b93e04a7 100644
--- a/src/net/java/sip/communicator/service/neomedia/MediaStream.java
+++ b/src/net/java/sip/communicator/service/neomedia/MediaStream.java
@@ -97,25 +97,25 @@ public interface MediaStream
 
     /**
      * Returns the synchronization source (SSRC) identifier of the remote
-     * participant or <tt>null</tt> if that identifier is not yet known at this
+     * participant or <tt>-1</tt> if that identifier is not yet known at this
      * point.
      *
      * @return  the synchronization source (SSRC) identifier of the remote
-     * participant or <tt>null</tt> if that identifier is not yet known at this
+     * participant or <tt>-1</tt> if that identifier is not yet known at this
      * point.
      */
-    public String getRemoteSourceID();
+    public long getRemoteSourceID();
 
     /**
      * Returns the synchronization source (SSRC) identifier of the local
-     * participant or <tt>null</tt> if that identifier is not yet known at this
+     * participant or <tt>-1</tt> if that identifier is not yet known at this
      * point.
      *
      * @return  the synchronization source (SSRC) identifier of the local
-     * participant or <tt>null</tt> if that identifier is not yet known at this
+     * participant or <tt>-1</tt> if that identifier is not yet known at this
      * point.
      */
-    public String getLocalSourceID();
+    public long getLocalSourceID();
 
     /**
      * Returns the address that this stream is sending RTCP traffic to.