RTP Dump Script
File: rtp_dump.pl
Contributor: James Cloos
Description:
There is a Perl module (Net::Pcap) that can decode pcap files; it makes it easy to grab the payload of RTP packets.
This script uses Net::Pcap to do the heavy lifting. It drops the first 54 octets of each packet (Ethernet frame headers, IPv4 headers, UDP headers and RTP headers) and writes the rest to a target file.
This is a simple example that requires significant work to become a generally useful application.
Get Net::Pcap from cpan.org if it is not included in your distribution. (It is in FreeBSD's ports, gentoo's portage, probably others.)
To use this script:
- Use TShark first to isolate just the (unidirectional) RTP packets
- Save the data into a pcap file
- Run this script on the dump file
The resulting file is a raw dump of whatever codec the RTP uses. You can use e.g., sox(1) to encapsulate or convert that to something your audio-playing apps understand.
If it is a codec that sox(1) doesn't understand, you'll need to get the reference code for the codec to convert it to something sox(1) understands. I.e., the ref code for G.729 from the ITU-T, the code in the iLBC draft/RFC, speexdec(1), etc.
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