With the transition to IP networks for all aspects of the signal processing path, accurate timing becomes more difficult, due to the fundamentally asynchronous, non-deterministic nature of packet-based networks. Fortunately, a solution is available, in the form of IEEE 1588 Precision Time Protocol (PTP). When used properly, this technology can provide a very accurate and stable time base for all types of signals within modern media operations.
Much like systems that run NTP, only significantly more accurate, with precise time distribution the need for setting clocks across multiple devices is eliminated. In addition, PTP provides a number of other benefits that are extremely advantageous for media networks, including:
- Multiple Media Formats – Using the clock/epoch system described above, any device can accurately calculate the precise current phase of any media signal (video, audio, etc.) – even signals with different time bases (such as 50 and 59.94 Hz video). There is no requirement to have one flavor of PTP for U.S. media networks and a different flavor for European media networks – both systems can work from the same precision timing signal.
- No Sync Overlay Network – Since the PTP clock signals are distributed over Ethernet connections that can also be used for media signals, there is no longer any need to install an overlay network to distribute synchronization. This can greatly reduce the complexity of cabling systems, particularly ones that connect cameras to their control units.
- Suitable for any IP-connected Device – Interface cards and modules that provide the time stamping function required for PTP are widely available on the market. As PTP becomes entrenched in other markets (financial services, electric power distribution, and factory automation, for example) the availability of these components and the appropriate network infrastructure devices will continue to increase.
- Accurate for Media Applications – With accuracy levels better than 1 microsecond, PTP offers much better precision than what is required to support video synchronization, and plenty of margin for audio applications. For example, PTP can provide accuracy better than one-tenth of a sampling period for a 96 kHz audio signal, which is suitable for any known practical application.
- Synchronize Multiple Locations – PTP grandmasters are commonly tied to GPS signals, making it possible to deliver accurate clock signals to multiple locations – even ones separated by hundreds of miles. Since each location can use the same SMPTE Epoch and a clock locked to the same GPS reference, each location can share precisely synchronized video and audio signals with other locations, eliminating the need to distribute a sync signal from one location to another.
For additional information about precision timing download It’s About (Precision) Time white paper
Related Solutions: Quarra PTP Ethernet switches