Hi John,
Very interesting and clarifying. It makes me wonder WHY all these different formats (envelopes) if codec and bitrate determine what is really going on. The only reasons I can think of are legacy and “my format is more important”. In any case, I find it extremely confusing to have all these formats like MTS, AVI, MOV and what have you while basically they are all just containers.
So, just to check if I get this right: I have an MTS file of 4GB, codec H.264/MP4 AVC and bitrate 9kbps. When I import this into iMovie it creates a MOV of 30GB with codec Apple Intermediate Codec and an average bitrate of 8Mbps. Would the massive increase in file size with a factor 8 be caused mainly by the bitrate difference ? And why this apparently very inefficient conversion in the first place ?