By Joel Guilbert, Technology Development Manager, Dale Pro Audio
As audio and video over IP networks grow ever larger (and excitement builds over successful implementation of SMPTE 2110 networks that marry the audio and video) the topic of network timing and synchronization is set to become a new stumbling block in these installations.
In a nutshell, just like an audio/video production facility would have a house master clock with very high precision to make sure all the equipment is synchronized, the same is needed in computer networks when they are starting to handle the same type of signals/data that require precise synchronization.
In a computer network used for audio/video, the timing scheme is called “Precision Time Protocol” or PTP. All of the equipment in the network needs to be able to accept these timing signals - this is called being “PTP AWARE” This is a term that will be coming up more and more in the future!
PTP is the master clock that keeps a network tightly synchronized. Outside of its burgeoning use in broadcast IP networks, it has been utilized heavily in industrial automation, power grids and the stock market trading infrastructure. It’s really fast synchronization. For example, Blackburst, a common master synchronization method for analog video, the sync was in the 1 millionth of a second range (NTSC at 3.58Mhz) PTP aims to be in the BILLIONTH and TRILLIONTH of a second range. That’s fast!
Speaking of SMPTE 2110 - one really cool thing about 2110 is that the audio, video, and metadata are separate essences. Unlike SDI, where the audio was embedded into the video, with 2110 if you only want the audio, you can just grab that. The method that these essences are kept synchronized is via PTP.
Even as recently as a year ago switches that were PTP aware were incredibly costly, but these days companies like Extreme and Brocade have products in the $2-4000 range.
As far as the PTP master clocks, known and trusted audio companies like Studio Technologies and Sonifex are offering PTP models.
Some more light reading on this topic can be had HERE and HERE.
Joel Guilbert is Dale Pro Audio's Technology Development Manager, and assists on technical support inquiries, system design and integration, and much more for our company. He can be reached at joel@daleproaudio.com.
