Yes, but if you use VirtualDub filters, there is a conversion to RGB, which was the point in my original post about not using VirtualDub for scaling (scaling is done via a filter).
You are right about your original point.
But if I have an avi in yv12 format and I open it in virtualdub and save it as an uncompressed yuy2 avi does virtualdub convert it from yv12 -> rgb -> yuy2? Or does it depend on using full processing mode or fast recompress? And what about direct stream copy, I assume it will stay in the colorspace of the original without being converted to rgb in between?
I'm using virtualdubmpeg btw but I don't think that makes any difference for this.