On Tue, 01 Oct 2002, PC Drew <[EMAIL PROTECTED]> wrote: > The problem that you're facing is that RTP doesn't define a very > "unique" way to determine that this UDP data actually is RTP. So, as > far as I know, the only way you can automagically dissect UDP data as > RTP is by capturing the control packets as well (i.e. SIP/SDP, IPDC, > MGCP, RTCP, etc).
Drew, what you say is correct, and I wrote exactly the same in my email. Now I start to think my english skills are lower than I thought ;-) I do get a RTSP packet containing SDP informations, that allow me to map the RTP payload type to the actual protocol. I actually don't need automagic dissect, it is enough for me to be able to use "Tools|Decode As" (obviously automagic would be cool). I will have a look at your pointers for the code, thanks :-) Marco > I haven't worked with RTP in about a year, so I'm a little rusty, but > as I recall, you can determine the IP:Port information from the > session control packets (if they're captured as well) in the form of > SIP/SDP packets for example. I wrote some code a while back to decode > define the conversation from an SDP packet, but I don't think it ever > got checked in (as I recall, it had a bunch of memory leaks and > general "not good code" problems). > > Here's my original post: > > http://marc.theaimsgroup.com/?l=ethereal-dev&m=99184276504320&w=2 > > And here was Guy Harris's response. I never took the patch any > further than my original post because I didn't have time: > > http://marc.theaimsgroup.com/?l=ethereal-dev&m=99292667406710&w=2 > > Hope it helps! > > Marco Molteni wrote: > > Hi, > > > > first of all, I would like to say a big THANK YOU to all the people > > involved in Ethereal :-) > > > > The following comes from a MPEG-4 streaming dump but the question is > > more generic. > > > > Real Time Protocol (RTP) has a dynamic range of payload types, from > > 96 to 127. Ethereal shows (obviously) such RTP packets as payload > > type=Unknown. > > > > One way to know the payload type is from a RTSP/SD packet. > > > > Now, let's say I know the payload type, how do I tell ethereal to > > use that payload type to dissect the RTP packet? Do I just write the > > dissector and then use "Tools|Decode Packet As" to map the RTP > > protocol type to my dissector? > > > > Also, it seems to me that the "Decode Packet As" doesn't have the > > granularity that I want, because it allows me to map, for example, > > UDP plus a source/destination port to a protocol, while what I would > > like to do is to map the RTP (contained in UDP) type field to a > > protocol. Any suggestions? > > > > thanks for your help > > Marco > > _______________________________________________ > > Ethereal-dev mailing list > > [EMAIL PROTECTED] > > http://www.ethereal.com/mailman/listinfo/ethereal-dev > > > -- Computers are like air conditioners. They stop working when you open Windows.
