~9GB Footage = 42GB with iMovie import..

Question

I recently bought a Canon Vixia HF S20 camcorder which has a built in memory of 32GB. I took some footage on the camcoder for approx 41 minutes. In the quality of movie I am recording the 32GB gives me 2hours and 55 minutes of recording time on the camcorder. That would approximately take 9GB of space on the built in memory. I imported this into iMovie and the import files are 42GB. Why is it getting this high? Is it not a 1:1 ratio when storing it in iMovie? Am I missing something? Any pointers appreciated.
What is the best way to backup the video file from the camera instead of bloating up like this?

Answer 1

Hi
Your camera shoots and stores video in a highly compressed format that is excellent for shooting and storing, but is very, very difficult to edit.
To get around this problem, iMovie transcodes the camera files into a format that is edit friendly, Apple Intermediate Codec or AIC.
These files are much larger as the transcoding process essentially unpacks the video from the native format in which the frames are woven and chained together in as tightly woven package as possible and transcodes it, frame by frame into individual packages so that each frames is accessible and the points between each frame are easily found and accessible so that editing can be done.
These "unpacked" files are what iMovie will use to edit the your movie. There is little or no quality loss in the transcoding process as it largely a repackaging process and not a conversion one.
The best way to save your original files, in their native compression format is to use the ARCHIVE feature of iMovie '09.
To read all about this feature and to understand the workflow (which is quite simple) in iMovie go to the menu Help and select iMovie Help.
When the window opens, search for "Making a backup copy of the contents of your camcorder".
Hope this helps.