MPEG-FAQ 4.1:

How can I do RTP encapsulation of MPEG1/MPEG2 ?

There is a Internet Draft about that. It is usally called:

    draft-hoffman-rtp-mpeg-encap-01.txt

Here's the excerpt:

This draft describes a packetization scheme for MPEG video and audio
streams.  The scheme proposed can be used to transport such a video or audio
flow over the transport protocols supported by RTP.  Two profiles are
described. The first is designed to support maximum interoperability with
MPEG2 System environments.  The second is designed to maximize simplicity of
implementation and to leverage other efforts within IETF.