I have recently started using BCC Deinterlace in an attempt to convert from 29.97i to 23.976p, but I'm not having success. However, here is what i can do:
From within a Vegas project set to 29.97, I can nicely deinterlace 29.97i clips to 29.97p with the filter setting set for "Deinterlace only" and setting the properties of the Vegas clip with the plugin(not the whole project) to progressive even though the clip is interlaced. The quality of the deinterlacing process is very impressive!
From stand-alone RED I can load a 29.97 interlaced clip and render it as an uncompressed 23.976 progressive AVI clip (without even using the Deinterlace plugin). I then load the uncompressed AVI into Vegas and re-render it as a 23.976 DV AVI with 2-3-3-2 pulldown to reduce its size. I then finally load this into my Vegas "24p" project timeline as a new clip. This is currently my painful solution to the conversion process.
What I am NOT able to do is set a project in Vegas to "24p", load a 29.97 interlaced clip into the timeline, apply BCC Deinterlace with the "29.97i -> 23.976p" option, and get a result that is deinterlaced. Note that in Vegas the project deinterlace method is set to "None".
I have also played very extensively with all the combinations and permutation of the 2:3 pulldown simulation option, as well as the field order and framerate for all the other options in the filter with no success.
If someone has gotten this to work correctly with Vegas, please let me know how you did it.
After some additional experimentation last night I think that the problem lies with the way Vegas passes its frames to RED. If I apply BCC Deinterlace as a plugin but change the source from V1 to the video clip itself, all works well.
The problem seems to happen when I set my Vegas project to 23.976 non-interlaced. Apparently, Vegas does not pass the frames from the 29.97 clip in a raw form. By looking at the images in Red, it looks like Vegas averages/processes the fields even though the Vegas deinterlace method is set to None.