This document specifies a real-time transport protocol (RTP) payload format to be used for the Variable-Rate Multimode Wideband (VMR-WB) speech codec. The payload format is designed to be able to interoperate with existing VMR-WB transport formats on non-IP networks. In addition, a file format is specified for transport of VMR-WB speech data in storage mode applications such as email. A MIME type registration is included, for VMR-WB, specifying use of both the RTP payload and the storage formats that has a number of operating modes, one of which is interoperable with AMR-WB (i.e., RFC 3267) audio codec at certain rates. Therefore, provisions have been made in this draft to facilitate and simplify data packet exchange between VMR-WB and AMR-WB in the interoperable mode with no transcoding function involved.