diff --git a/src/zm_rtp_source.cpp b/src/zm_rtp_source.cpp
index a61bfffe3..a4dfcd5d7 100644
--- a/src/zm_rtp_source.cpp
+++ b/src/zm_rtp_source.cpp
@@ -262,6 +262,11 @@ bool RtpSource::handlePacket( const unsigned char *packet, size_t packetLen )
 	int rtpHeaderSize = 12 + rtpHeader->cc * 4;
     // No need to check for nal type as non fragmented packets already have 001 start sequence appended
     bool h264FragmentEnd = (mCodecId == AV_CODEC_ID_H264) && (packet[rtpHeaderSize+1] & 0x40);
+    // M stands for Market, it is the 8th bit
+    // The interpretation of the marker is defined by a profile. It is intended
+    // to allow significant events such as frame boundaries to be marked in the
+    //  packet stream. A profile may define additional marker bits or specify
+    //  that there is no marker bit by changing the number of bits in the payload type field.
     bool thisM = rtpHeader->m || h264FragmentEnd;
 
     if ( updateSeq( ntohs(rtpHeader->seqN) ) )
@@ -275,15 +280,18 @@ bool RtpSource::handlePacket( const unsigned char *packet, size_t packetLen )
             if( mCodecId == AV_CODEC_ID_H264 )
             {
                 int nalType = (packet[rtpHeaderSize] & 0x1f);
+                Debug( 3, "Have H264 frame: nal type is %d", nalType );
                 
                 switch (nalType)
                 {
-                    case 24:
+                    case 24: // STAP-A
                     {
                         extraHeader = 2;
                         break;
                     }
-                    case 25: case 26: case 27:
+                    case 25: // STAP-B
+                    case 26: // MTAP-16
+                    case 27: // MTAP-24
                     {
                         extraHeader = 3;
                         break;
@@ -304,6 +312,9 @@ bool RtpSource::handlePacket( const unsigned char *packet, size_t packetLen )
                         extraHeader = 2;
                         break;
                     }
+                    default: {
+                        Debug(3, "Unhandled nalType %d", nalType );
+                    }
                 }
                 
                 // Append NAL frame start code
@@ -311,6 +322,8 @@ bool RtpSource::handlePacket( const unsigned char *packet, size_t packetLen )
                     mFrame.append( "\x0\x0\x1", 3 );
             }
             mFrame.append( packet+rtpHeaderSize+extraHeader, packetLen-rtpHeaderSize-extraHeader ); 
+        } else {
+            Debug( 3, "NOT H264 frame: type is %d", mCodecId );
         }
 
         Hexdump( 4, mFrame.head(), 16 );