Abstract: This document contains information on how to best write an RTP payload format. Reading tips, design practices, and practical tips on how to quickly and with good results produce an RTP payload format specification. A template is also included with instructions that can be used when writing an RTP payload format.
If you're looking forward to write an RTP payload format, I guess this document may be helpful unless you're an IETF RTP playload format guru ;-) If you're not sure, here's the definition of an RTP playload format:
"The RTP Payload format specifies how a specific media format is put into the RTP Payloads. Thus enabling the format to be used in RTP sessions."Overall, a useful document and check out the references section for a list of existing payload formats.