RTP Engine creates PCAP files for recorded calls on offer answer instead
of initial offer.
We make up bogus values for the nonessential parts of the PCAP, UDP, and
IP headers. We might be able to pull these from other parts of the RTP
Engine, but that information was unnecessary for recording calls so they
can be recorded to audio files.
If you change the packet headers, be really careful about byte order and
datatype size!