Keeping Time: How NTP Keeps Broadcast Contribution Streams Synchronized
In our previous blog post about synchronization for broadcast video, we reviewed why it is so critical to keep your streams in sync, and how genlock can ensure that your streams start from synchronized sources. However, once your streams have begun their journey from a remote location to a central broadcast production facility, keeping them synchronized along the way can become another challenge.
The Challenges of Maintaining Synchronization in the First Mile
Your video streams, once they leave their video encoder, will have to travel over a variety of networks to reach their destination video decoder. With different video encoders used for processing your streams, which may travel over different networks, and be fed into studios using different video decoders, there are many opportunities for your streams to fall out of sync.
To make things rather simplified: genlock ensures that your video sources leave at the same time, but they are travelling different routes before arriving at different points of entry within the same destination. And we want to ensure that these video sources arrive at the same time.
How can we ensure our streams are synchronized through the first mile?
NTP: Network Time Protocol
As genlock synchronizes the feeds from your cameras, NTP works to keep your streams synchronized through your video encoders and video decoders. NTP is the acronym for Network Time Protocol, an internet standard that functions by syncing your servers and devices to coordinated universal time (UTC).
NTP works by synchronizing your devices, (in this case encoders and decoders,) to an NTP server, which in turn, is synchronized to a “grandmaster” clock (often one of the atomic clocks, or a GPS clock.)
NTP is precise to within tens of milliseconds over the internet, and under ideal circumstances, can be precise to sub-millisecond levels. And this precision is from the grandmaster clock to your device. So your devices (which should all be connected to the same NTP server), will be very close to each other in terms of time precision.
How NTP Contributes to Remote Production
For NTP to work, all of your video encoders will need to be synchronized to the same server. All of your video decoders will also need to be synchronized to a single server. However, your encoders do not necessarily need to be synchronized to the same server as your decoders. This makes NTP ideal for remote production contribution feeds for broadcast. When using NTP, you can connect your encoders and decoders to servers that are the best for each of them, as opposed to finding a server somewhere in the middle of your encoders and decoders.
With NTP, the distance between your video encoders and video decoders will not hinder the quality of your synchronization.
Moving Forward; Together
Genlock and NTP work hand in hand to ensure that your video streams leave their cameras synchronized, and arrive at your video decoders still synchronized. Possibly even more importantly, genlock and NTP are needed together to keep all video streams (camera angles) synchronized to your audio source.
Keeping your audio and video feeds synchronized through this “first mile” of remote production is critical, and will help to ensure your team can create smooth, timely broadcast video, with your viewers getting all the best angles, with perfectly synchronized audio and visuals.
Want to learn more about how you can keep your live video streams synchronized? Read our white paper, Synchronizing Video Sources Over the Internet for Live Event Coverage.