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’.