You Can’t Just Swap Cables

In an IP Transport plant, if you have two sources reversed (like on your monitor wall) – swapping cables probably won’t work. More than likely, you have multiple signals muxed on that fiber or GigE cable and you have to open up a routing table to straighten it all out. Yes an IP-based plant gives you less wires, less weight and likely less cost but it also gives you new headaches.

Will TR-03 Stay In Sync?

Last week the Video Services Forum released its draft recommendation for “elementary stream” IP media (read that as non-embeded audio). While touted by some as a low latency, low payload transport protocol with video, audio, and ancillary data being transported separately, I think it once again opens the Pandora’s Box of “out of sync” audio and video. I know that Thomas Edwards of Fox Networks said: “…when every packet is time stamped accurately, we should have better synchronization between media streams than SDI solutions could provide.” I thought that audio & video packets in MPEG-2 transport streams were time stamped as well, but that hasn’t prevented them from becoming annoyingly out of sync.

I say if you have to implement IP transport now, plan to use SMPTE ST 2022-6. (‘Cause it’s nice when audio and video arrive together.) And let’s see what actually happens when someone else actually implements TR-03 in a control room near you.

SDI vs IP: Tale of the Switch

In the continuing battle between those newfangled “I only know IP” computer type people and us ole-time TV engineers, former ABC/FOX/Olympic/ATTC engineer Jim DeFilippis warns in an opinion piece in TV Technology that we should be skeptical of claims that IP transport is better/cheaper/faster than SDI. In the first part of the article, Jim points out that if you measure the total aggregate bandwidth (TAB) of both a comparably sized HD-SDI switch and a 10 GbE IP-based switch, you might find that the SDI switch is a better value in terms of TAB, power and size.

Also, let’s say you’re a company who has been asked to build a file-based multichannel playout facility for a major international video programming distributor. You wisely connect your IP-based equipment with fiber rather than with copper. Unfortunately “… UDP/IP … is not a reliable protocol. There is no built-in mechanism to guarantee arrival in the correct order, or even arrival of the packet at all. The order of packets can be restored through sequence numbering in the RTP layer, but packet loss remains a problem.” (EBU Technical Review – 2012 Q4) You may claim to have a managed network where packet loss does not occur, but that only holds true as long as you do not approach the available bandwidth limit.

And then gremlins might just strike and your program stream might be fine along one route, while in the air path you’re droppin’ packets left and right. Just sayin’.

Must SDI Die?

… or can it just retire in Florida? Recent moves by SMPTE to standardize IEEE-1588 for timing and sync may help the move to an IP-based plant. And the Joint Task Force for Networked Media is studying best practices for audio and video switching. Al Kovalick has written a comprehensive article titled SMPTE Looks at All-IT Media Facilities on page 26 of the December 18th, 2013 issue of TV Technology. He discusses some of the papers presented at SMPTE’s Annual Technical Conference in October 2013 and how they can make an all-IT based facility possible in the near future.

[With no apologies to Cinegy. SDI is not dead yet and neither am I.]

UPDATE – Feb. 2016: Mr. Kovalick updates us on PTP with “Time Transfer in Networked Systems”.

(Note to me: SMPTE 2059-1 and -2 are SMPTE’s version of IEEE-1588 V2 – PTP)

FOX News Rolls Out Election Wheels

And from Big Head DC, here is the companion story to my blog entry BOHRMAN’S BUS BEATS B’CASTERS W/ BGAN.