Network synchronisation is crucial for professional broadcast, both for traditional aspects such as audio alignment and lip-sync, and especially as tasks such as high quality live event broadcasting, becomes more prevalent.
Ethernet + PTP for network synchronisation
Ethernet + Precision Time Protocol (PTP) is fast becoming the most popular method of delivering network synchronisation in a broad range of environments. Ethernet-based networks have the benefits of high bandwidth, joint infrastructure for file-based and A/V signals, and access to advanced network management functions.
PTP, as a message-based time transfer protocol, ensures different points in the network are precisely synchronised to the reference (master) clock, allowing the network as a whole to meet specific performance limits. As an integral part of the ITU-T standards for packet transport networks, it allows for different profiles in order to meet the needs of various applications, for example, industrial and financial networks, and automotive systems.
ST 2059-2 is commonly referred to as the Broadcast profile. Defined by the Society of Motion Picture and Television Engineers (SMPTE), this profile proposes a timing requirement of 1 µs (±500ns) across the network. Most of the available options from the PTP “default profile” can be used: IPv4/IPv6 encapsulations, multicast or unicast transmission, using ordinary, boundary or transparent clock devices.