… The original avi file is 33 gb.
so, due to sheer size, my assumption is, this is a ~2.5h DV-encoded video/import from some miniDV-camcorder, right?
you then can use the free tool MpegStreamclip.
• open your avi
• go straight to 'save as'
• choose from drop-down DV as new media-container
=> this just 're-wraps' the dv-stream from avi to dv, without any conversion.
FCPX should handle that.