SIGMA is a system developed by the A.C. Neilsen company to make spots, VNR's and the like, trackable by automated systems for purposes of viewer ratings and confirming make-goods on commercials. Sort of a cousin of line-21 captioning, AFAIK, the signal lives in line 20 and 22 of the vertical interval, though I have no idea where it lives in a modern HD video signal - if anywhere. Maybe they use something different/better now? Do any of you have more up to date insight on using SIGMA or any competing technologies for tracking VNR's to see if any parts of them ran on-air anywhere? A client was curious about this, now I am too. What's it cost to get a report from Neilsen on how/where an encoded VNR got any airplay?