Video signals have always depended on precise synchronization along the entire delivery chain from camera to consumer display, whether in analog, digital or compressed formats. Timing drives every aspect of signal delivery, particularly synchronizing video to audio to achieve “lip sync.”
With the transition to IP networks for all aspects of the signal processing path, IEEE 1588 Precision Time Protocol (PTP) has become required by a variety of standards used throughout the media production industry, including SMPTE ST 2110:2017 “Professional Media over Managed IP Networks” and AES67 “High-performance streaming audio-over-IP interoperability.” The primary use of PTP in these standards is to provide a stable time base that can be used to synchronize video, audio and other signals so that they can be processed easily and delivered to local and remote audiences.
Consider the needs of an audio production within a live concert venue. Many times, several sets of speakers need to be coordinated, so that their sound outputs reach all members of the audience without annoying echoes or, worse, canceling each other out due to phase mismatch. Achieving the best sound for the largest portion of the audience requires adding delay to some of the speaker outputs so that their sounds are in phase with those emitted by other speakers in the venue. Speaker arrays can also be adjusted to maximize their “sound field” output in specific directions by adjusting the timing of the audio signals fed into each speaker element. PTP provides a stable timebase that allows accurate synchronization of all the speakers.
Remote video production can also benefit from PTP, which enables every camera, microphone and signal processing device to be tied to a common clock. When these signals are transported across a long-haul link back to the television production facility, the timing relationships between the signals are used to allow accurate switching between video signals and proper video/audio signal alignment. Because PTP clocks are used to generate the timestamps within each video and audio data packet, these embedded timing relationships can be used wherever the IP media signals are delivered.
There are other applications beyond the media space that will benefit from IP routers and Ethernet switches that support PTP. For example, financial services firms and markets need accurate timestamps for securities trading and record keeping. Factory automation systems often need to have machines working in lockstep for a variety of tasks. Electric power utilities need to accurately control the phases of high voltage sources and signals across their networks, to avoid damaging current surges. Many other applications, including automobile systems, will benefit from accurate, reliable PTP-enabled networks.
For additional information about precision timing, its benefits, and system components download It’s About (Precision) Time white paper
Related Solutions: Quarra PTP Ethernet switches