RTP Clock Source Signalling

Abstract

NTP format timestamps are used by several RTP protocols for synchronisation and statistical measurements. This memo specifies Session Description Protocol (SDP) signalling that identifies timestamp reference clock sources and SDP signalling that identifies the media clock sources in a multimedia session.

RTP Payload for Society of Motion Picture and Television Engineers (SMPTE) ST 291-1 Ancillary Data

“…Note that techniques described in RFC 7273 [RFC7273] can provide a common reference clock for multiple RTP streams intended for synchronized presentation.…”

How to Write an RTP Payload Format

“…The important factor is that all media streams from a particular source that are being synchronized use the same reference clock to derive their relative RTP timestamp time scales. The type of reference clock and its timebase can be signaled using RTP Clock Source Signaling [RFC7273].…”

A Taxonomy of Semantics and Mechanisms for Real-Time Transport Protocol (RTP) Sources

“…As indicated in [RFC7273], despite using NTP format timestamps, it is not required that the clock be synchronized to an NTP source.…”