From a similar post at a different forum I had a reply from Torsten:
"Just for the sake of completeness I'd like to note that another option for Debayer Y800 data would be the new standalone debayer tool in FireCapture. See screenshot here:
http://firecapture.wonderplanets.de/help/debayer.html
Based on comparisons Clif Ashcraft did it seems that the Bilinear and Adpative algorithms are producing a much better quality than the standard debayering (NearestNeighbor) in Registax.
Torsten"
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http://www.wonderplanets.de
http://firecapture.wonderplanets.de
I tried this method out last night on some old avi files and the results were quite strikingly better than anything I had previously outputted from Registax.