RFC 4040 · PROPOSED STANDARD · 2005
SUN · 14 JUN 2026
RTP Payload Format for a 64 kbit/s Transparent Call
Overview
RFC 4040, “RTP Payload Format for a 64 kbit/s Transparent Call”, is a Proposed Standard document published in April 2005 by R. Kreuter. The canonical text is published by the RFC Editor.
Abstract
This document describes how to carry 64 kbit/s channel data transparently in RTP packets, using a pseudo-codec called "Clearmode". It also serves as registration for a related MIME type called "audio/clearmode".
"Clearmode" is a basic feature of VoIP Media Gateways. [STANDARDS-TRACK]
What “Proposed Standard” means
An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.
Read this RFC
The canonical text of RFC 4040 is hosted at rfc-editor.org. Available in TXT,HTML.
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