[Ethereal-users] how does ethereal determine whether RTP or not?

["darren" <teodarren@xxxxxxxxxxxxx>]

Hi all,

I did some capture of a Video stream with ethereal on my own
computer...after which ethereal correctly identified the UDP packets as
being RTP.

After I did a filter on all the RTP packets (filter RTP) and save the
filtered packets in a separate file, I reopened the file in another ethereal
session...but this time...it was identified as simply UDP...

Any ideas?