R&D - Precision Time Protocol (PTP)

For traditional SDI-based production, the question of synchronisation is relatively simple, since SDI is an inherently synchronous communication medium. Sync pattern generators are used within the broadcast facility to provide an absolute reference for frequency and time, delivered over every SDI link.

However, as the industry is taking its first steps away from SDI, looking to use IP networks for production, the task of synchronizing a multitude of elements connected via Ethernet is no longer as straightforward.

PTP in an SMPTE ST 2110 environment

As explained in an article, written by Thomas Kernen (Mellanox) and Nikolaus Kerö (Oregano Systems), media organizations have turned to PTP to solve the timing challenge. The IEEE protocol is already used extensively in telecommunications and industrial applications. It was specified in a generic manner so that its performance could be adjusted to suit the requirements of a specific application, via PTP profiles.

There two PTP profiles that are relevant for broadcast production are AES67 – for audio – and SMPTE ST 2059-2. The latter, for video applications, is an important element of the SMPTE ST 2110 suite of specifications for professional media over managed IP networks (see tech-i 34, pages 8-9).