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 just a quick and simple example. It needs a lot of work to be 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:

  1. Use TShark first to isolate just the (unidirectional) RTP packets
  2. Save the data into a pcap file
  3. Run this script on the dump file

The resulting file is a raw dump of whatever codec the RTP was using. You can use eg sox(1) to encapsulate or convert that to something that your audio-playing apps understand.

If it is a codec sox(1) doesn't understand, you'll need to get the reference code for the codec to convert it to something sox(1) does grok. 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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RtpDumpScript (last edited 2008-04-12 17:51:37 by localhost)