Well it's possible, but there's really no point. HD master>SD = Loss of Detail. SD SD>HD will not put that detail back in. Once it's gone, it's gone. The inordinate amount of time it will take is really not worth what minimal gain there may (not) be. If the source is a long movie, then the up conversion may well simply amplify any Compression artifacts that are not that noticeable at the moment. If the source is DVD then you'd be better just getting an up converting DVD player and leave it at that. If the source is DL'ed avi then [bold]really[/bold] don't attempt this.
