Wireshark-dev: Re: [Wireshark-dev] Feature Request for EDITCAP - Selecting by IP Address and Po
From: Bill Meier <[email protected]>
Date: Wed, 30 Jan 2008 11:33:13 -0500
 What I need to do is to be able to extract out a specific VoIP call using
UNISTIM that spans multiple capture files based on IP Address and
Source and/or Destination Port and possible a within a specific time frame.

Altho I haven't tried this, I think the following should work:

tshark -r <input file> -R <read filter> -f <output file>

(You might need to write a script to run tshark on each of multiple files and then use mergecap to combine the output files).
See the tshark help or manpage for additional information.