Karl Kuhn making his presentation.
At the Wednesday, January 24, 2018 meeting...
Implementation Realities of SMPTE 2110 and PTP
With Karl Kuhn, Tektronix’s Senior Video Applications Engineer
Tektronix’s Senior Video Applications Engineer, Karl Kuhn was the guest speaker at the SMPTE New England Section’s January 24th meeting held at WGBH in Boston. Kuhn’s presentation was on the topic of “Implementation Realities of SMPTE 2110 and PTP.”
Kuhn, who is also SMPTE’s North American Section’s Director and Past SMPTE Eastern Region Governor, was also a contributing author for the 11th Edition of the NABHandbook , covering Digital Video Standards and Practices.
In 2015 Karl was raised to SMPTE Fellow.
Kuhn is a noted demystifier of highly technical topics. That’s exactly what he set out to do as he took on the challenge of covering this very wide-ranging and complex topic.
The purpose of Kuhn’s presentation was to examine the basic structure of the packets for ST 2022 and ST 2110 and see how variable delay across a network introduces jitter at the receiver and how measurements can be made on the stream.
Kuhn explained how network traffic can produce out of order packets or corruption of the data causing packets to be dropped and how important it is to monitor the stream to ensure error free transmission of high bit rate media.
Unlike the earlier ST 2022-6, SMPTE ST 2110 splits essences (video, audio and metadata) into separate and independent signals. This produces benefits such as eliminating the need to embed and de-embed audio. It also increases bandwidth efficiency by not sending the HANC and VANC as part of the active video. As you might imagine having a highly accurate time base is essential for keeping all of this together. This is the role of PTP ST 2059 that replaces Black Burst in IP systems, but we will live in hybrid facilities for a long time.
Kuhn explained how precision time protocol (PTP) is the heartbeat that keeps the entire system together and how every piece of equipment must be “PTP aware to maintain system stability.” This is especially true in large networks. While “grandmaster” clocks lock to a GPS derived reference—subsequent master and slave clocks lock to the grandmaster. He also explained the implementation concerns of transparent and boundary clocks to increase network resilience and stability.
The goal is always to maintain stability in the network. Every packet is needed and needed in time—or as Kuhn likes to say, “smooth is what you want.” Buffer overflow or underflow causes jitter and potentially dropped packets. Kuhn offered examples of how IP test and measurement equipment can keep you right on top of stream status and quality of service (QOS), the surest way to always keep yourself out of trouble.
While all forms of digital signal transmission (including IP) typically yield long term benefits in both cost and performance it is certainly not without its difficulties. Kuhn stressed this right out of the gate. By moving to IP we have added another layer of abstraction on top of the what we did when we left behind the analog world. We have added another layer to the digital cliff and we need new visualization tools to keep things running smoothly.
Staying current is our best approach to job security and having the right tools builds self-confidence. Kuhn shared his views on how technical people need to be able to better communicate with management in business terms to elevate their value toward being perceived as an asset focused on the success of the business.
The SMPTE New England Section also wishes to profusely thank WGBH and its Director of Engineering Emeric Feldmar for hosting this meeting. We thank Tektronix for providing ample food and beverage.
Marty Feldman, SMPTE New England Section Chair
Click here for writeups of other past meetings