Dear H323plus Team members,
 
   Recently, I have done H.323 testing (simple conference without presentation channel opened) and captured the video packets using wireshark.
 
 I found that when both endpoints are polycom PVX system, there are extra video packets (ie. coded slice data partition A, coded slice of an IDR picture, and subsequent ..,) with difference with dynamic payload type value (eg. actual video payload type is 109, it has payload type 99)  tranferring to each other site during conference.
 
    It will not happened if either site using other H.323 system(not polycom system). 
 
    What is the purpose of this packet as It seems like the received site can form even a complete picture?
   
Thanks.